Hand vs electric winch: solo travelling

[Landi]

G'day. I have a couple of trips coming up that for the most part I'll be by myself. Now I already have a hand winch, but not yet used in anger. Just wondering if it's possible/safe to recover a vehicle on your own using a hand winch? I would imagine it'd depend on the recovery, but generally speaking I'd imagine it'd be impossible without a second person behind the wheel. An electric winch, on the other hand, seems like a better/safer option for the occasional recovery where I'm by myself. Does anyone have any tips or experience with this? If possible I don't want to have to get an electric winch if I don't need it, but have a feeling it's probably the best option for solo travelling

[rrturboD]

Most recoveries that involve winching, actually only need to move the vehicle a short distance onto stable ground or maxtracks etc. so you would manage with a hand winch.
Even if you managed to roll a vehicle, hand winch would work.
However, using a hand winch is not as easy as an electric, so you need to try it and decide if you can actually manage to move your vehicle, say onto a couple of bricks. If it is difficult, use a pully (snatch block) which will slow you down but double your power.

[BathurstTom]

Hi Landi, I understand what you mean - winching uphill and the winch breaks. Very Dangerous. Money allowing, I would have both. An electric/power winch on the front that could be controlled from the drivers seat and a hand winch for retrievals from the back or side etc.


Tom.

[Landi]

Yeh I understand hand winching is hard work, I've done a practice run before. I guess that doesn't bother me too much as I don't do tracks that get me stuck every half an hour. It's more for that long trip where I might need it once or twice and don't mind putting in a bit of extra time and effort. I've got a good set up with the hand winch: snatch blocks, 20m of synthetic rope, etc etc. Hence why I'm reluctant to put an electric winch on

[Landi]

Sorry I should clarify that obviously the synthetic rope isn't to run through the winch. Just as an extension to run through the snatch block if required

[AndyG]

If you don't intend to go on tracks where getting stuck is reasonably likely, i would stick with a hand winch and some maxtraks, if not for weight alone.

Saying that, i have a Tirfor hand winch, pick up my maxtraks next week (with rear wheel harness) and have a winch waiting for me at APT.
Why, no good reason at all except i tend to travel alone , and if it all turns **** i want options. And i was bored one day . :angel:

I have no plans of seeking out tracks where i am likely to get stuck.

[Scouse]

Get a hand winch.
Use it once in anger & I can guarantee you'll make sure you never get stuck again.
:)

[austastar]

Hi,
Yes, my hand winch has kept me out of more trouble than got me out of trouble.
I did relent last trip and bought a Runva, it is out of the way in the bullbar, not in with luggage storage.
So far, it has only got someone else out of trouble.
Cheers

[rangieman]

Get a hand winch.
Use it once in anger & I can guarantee you'll make sure you never get stuck again.
:)

Yep use it once in anger and then buy a electric winch;)
A electric winch will work longer and faster than you in the heat;)

[Landi]

Thanks for the tips. Think I'll have more of a serious look into getting an electric winch. Just to cover my ass I'll probably end up carrying the hand winch just in case as well. The Runva 11XP or avenger mako 9500 are prime candidates at the moment. I won't be adding a second battery any time soon so low current draw is my main criteria. Both seem pretty good in that respect, and lite with the synthetic rope

[rangieman]

Thanks for the tips. Think I'll have more of a serious look into getting an electric winch. Just to cover my ass I'll probably end up carrying the hand winch just in case as well. The Runva 11XP or avenger mako 9500 are prime candidates at the moment. I won't be adding a second battery any time soon so low current draw is my main criteria. Both seem pretty good in that respect, and lite with the synthetic rope

Runva:thumbsup:

[Adrian18]

Or step right up and get a pto winch and u can winch to u run out of fuel

Sent from my SM-N920I using AULRO mobile app

[Landi]

I don't tow or carry huge loads or anything like that, so I'm leaning towards the standard EWX9500 over the 11XP, keeping current draw in mind. Generally speaking would a 9500lb winch at its full capacity be drawing more amps than an 11000lb winch working at 75% capacity?

[barnfindseries3ffr]

I only have a hand winch, I've had to use it (first time too) uphill and all I was thinking was don't fail, don't fail! It didn't and worked a treat. I've used it a few times now and don't leave home without it. Having both would be the best as options are what you want when it goes a bit squiggly out with only the dog as company.

[AndyG]

I don't tow or carry huge loads or anything like that, so I'm leaning towards the standard EWX9500 over the 11XP, keeping current draw in mind. Generally speaking would a 9500lb winch at its full capacity be drawing more amps than an 11000lb winch working at 75% capacity?

I was advised by Ben at Apt to go up one size from 9500 for a fully loaded 110
If you don't have a tow bar have a look at Nugget s rear hitch

[alien]

Where are you going to be heading to?
This may be a factor in what you can do.
If your solo and using any type of which you need to be able to get out to set things up.
Not so easy if your half way up a steep track in the high country.
If your out in the desert sands you may not find it easy to access a anchor point.


An electric which on the front can only pull you forward, over or through the obstacle.
A hand winch can be used to pull you back out of trouble.
The other thing I've done is set a hand winch of the side to stop a rig falling over the edge of a track.


As has been said....
Hand winch's make you think about where you're going.
An electric winch can led to a false sense of security but are easier(and more dangerous) to use.

[alien]

I don't tow or carry huge loads or anything like that, so I'm leaning towards the standard EWX9500 over the 11XP, keeping current draw in mind. Generally speaking would a 9500lb winch at its full capacity be drawing more amps than an 11000lb winch working at 75% capacity?
Amperage draw will depend on the on the winch, some of the 11000lb jobs use bigger motors.
The load pulling power and speed of recovery will vary depending on how many layers of rope are on the drum.
Have a look at the different specs at the bottom of these links(chosen as popular choice only)..
http://www.warn.com/truck/winches/src/M1200.shtml
http://www.warn.com/truck/winches/95xp_winch.shtml

I'd be going for a slightly bigger winch(as I did on the last purchase).
Better pulling power with less rope out.
Covers you on any bigger trips when fully loaded.
You also don't know what or who you may be helping one day.


Don't forget if you go with an electric winch they do require maintenance.
It's also good to fire them up once a month to keep things moving.

[simmo]

Hi Landi, I'm sure you'll find the 9500lb winch adequate. if in doubt use your snatch block. I have dragged my defender along a track on the diff centers for a short distance, when the ruts were too deep to proceed. ( only have 32" tyres) and dragged a defender with trailer and 1500 kgs of wood up a slippery hill with a 9500 lb. Regarding batteries, I have only one battery in my car, its a big one though. (Truck King). I found as long as the engine is running I can get out of situations. Most winching is short distance so the battery has adequate reserve. IMV tough job is winching the car and a full trailer, ( about 4000 kg) for 100-150 m up a steep slippery slope with trailer etc. But even then the winch gets a break, because you have to re rig the winch every 20- 25 meters :). cheers simmo

[AndyG]

I was wrong, i was looking at 8000, but APT recommended 9500

With a Defender full of touring kit, it would be better to run a 9500lb winch. The M8000S comes in at 25Kg $1750, awesome performer, pushing its limits with a fully loaded 110 in harsh conditions. I have the following reliable options -
Warn Zeon 10S 34KG $2295
Warn 9.5XP S 30.8KG $2750

Avenger 9.5 TDS 27.5KG $1335

As far as a great touring winch goes, I can solidly recommend the Avenger. I fitted one to Roothy's truck about 6 years ago and I've had one on our 110 for around 3 years. Both have performed superbly time and time again. I run Warns on some of our more aggressive vehicles, these trucks are built for a different purpose though.

[Slunnie]

I would check the winches actually fit your bullbar too. For example, the Warn XD9000 winch just fits behind the bullbar with the motor very nearly touching the chassis rail. The Warn 9.5 is the same winch except with the bigger and longer 6hp motor which doesn't fit - so you won't actually get that one installed typically.

[Landi]

I've got a Rijidij tube bar which I've been assured will take almost any winch. 9500lb sounds like it'll be enough for me; now I've just got to decide if I want to stick with the cheaper Runva, or spend a bit more and get the Mako Avenger. Warn is out of my price range. My only concern with the Runva is that I want to run synthetic rope which I've heard doesn't go too well with the drum brake design sometimes. The lower current draw and external brake on the Avenger seem like a much better option, but at almost twice the price hmmm. Runva seems to have pretty good support here too. Not so sure about the Kingone winches. Thoughts? Would I really have any issues with heat build up damaging the synthetic rope on the runva if only used in anger occasionally?

[simmo]

Hi Landi, i checked ebay ( my price reference system:) Mako $1300, with synthetic rope, Runva an unbelievable $650 with synthetic rope. Warn XD 9000 with synthetic about $2000. Runva seem to stand strongly behind their product, and Mako talk about good waterproofing etc. I recall there was an in depth discussion on one of the threads earlier about the various winches, that would be good reference.

My old warn XD 9000 winch, (with a steel rope), has done a lot of work, it's been rebuilt once, and stripped down for cleaning at least one other time, it's reasonable quality, but there is something I don't like about it. No effort has been made to water proof or dust proof, where the drum enters the winch ends. The drum is just sitting on nylon bushes. So water, mud, dust etc getting into your winch makes more work for you. So any winch where an effort to seal it has been made is a bonus and worth paying for IMV.

I'll have to make decision soon about replace with a new winch, or refurbish my old Warn again. I like the idea of the Mako, but will probably end up refurbising and fitting a new dyneema rope. ($400 all up).

I chose the XD 9000 because it had a reputation for reliability etc, and it fits between the chassis rails of a land rover, so it can be closer mounted to the car. good luck with you project cheers simmo.

[Landi]

Yeh interesting point about the waterproofing. Runva are doing a "Premium 11XP" which they say has an IP67 rated motor. That's the only winch I've come across so far that doesn't just make vague claims about how tight the seals are.

[Blknight.aus]

electric winches re cheap and generally reliable but have a duty cycle can leave you with a battery thats too flat to start your car and will continue to winch for a short time after your engine is stopped

pro winches will winch for as long as the engine is running but can be a little abrupt on the control

hydraulic winches have the best of both worlds ,can be fitted with back upelectric boost pumps for when the engine has died but wont winch uside down.

all are a bucket load easier than a handwinch.

but a hand winch will work anywhere you can for as long as you can and it doesnt care about the orientation of the vehicle if the engine is running or the state of the batteries or even if its being used underwater.

just stand by to sweat for it.

If I was travelling solo, could only afford the one winch and set of reovery gear I would take the hand winch and send the leftover on adding more bits to the recovery kit.

[rangieman]

Yeh interesting point about the waterproofing. Runva are doing a "Premium 11XP" which they say has an IP67 rated motor. That's the only winch I've come across so far that doesn't just make vague claims about how tight the seals are.

Water proof is realy not a issue ;) All that has to be remembered is to operate the winch and get it hot not too long after a dunking with in a day or 2 to dry the moisture out of the winch;)
Plenty of winch`s have survived years with out being water proof just by doing this

[simmo]

I agree with rangieman, about water proofing, you can get by without it, its just extra work in maintenance.
But once the water is in there it is hard to get it all out quickly, some of it condenses again as the winch cools down.

The electric winches do work under water no problem, and drying them out is the go.
During my last overhaul, I drilled and tapped both ends of the winch/motor, and connected hoses to them.
I can blow air in one end and out the other, my plan at the time was to have a solenoid & pressure regulator connected to my air tank, to supply at at 2 psi via a canister filled with silca gel. ( a work in progress for 5 years :)).

Before a deep crossing I could open the dry air into the winch to reduce the amount of water entering, and then leave the air on for a few hours while driving to dry the winch out. Silica gel can be refreshed by warming in the oven, it's not hard to get or expensive.

If I could have only one winch it would be an electric one, just from the point of view its easy to use and will get you out of 95% of the problems. Sure you can't winch backwards, but that's the only advantage I can see for a hand winch. If you follow the makers advice regarding the battery capacity, you should be OK. It's hard to exceed the duty cycle of the winch, even in difficult situations because you have to be constantly re rigging the winch to different points as the recovery progresses, it gives the battery and the winch some recovery time, I never winch without the engine running.

I used to almost always be alone in the forest , because of my work pattern I had time off during the weekdays. I got stuck a lot because of the terrain and the trailer/ weight. I couldn't have got out of some of those situations with a hand winch because of the amount of physical work required. A couple of times it took me 2 hours of solo winching and re rigging to get out situations. I was very tired at the end of it. Have fun cheers simmo.

[AndyG]

That's why I pack my son with the recovery gear, to operate the hand winch :angel:

[Tank]

Trying to work out why most people think you can't winch backwards with an electric winch mounted on the front bar.
That bottom roller on the fairlead is not there for looks.
I have winched out of a bog and other impassable places by running the winch cable under the vehicle and attaching it to a tree behind and pulled my self free with no problems (another reason I don't use synthetic rope).
If I believe I may get stuck in an upcoming bog or I might need to pull myself back up a really steep downhill slope, I run my (wire) cable under the Disco and hook it up to the tow bar, a bit hard to run a cable under a vehicle that's bogged to the chassis and if I get stuck I just run out to an anchor point and winch myself out.
I use this method to pull a vehicle up onto a car trailer hooked up to the back of my Disco, never had a problem with catching or damaging anything underneath, will not work with Dyneema type synthetic ropes, for obvious reasons.
Snatch blocks are useful if used correctly, most have no idea of how to use a snatch block to give a Mechanical Advantage (MA), a stationary snatch block anchored to a tree will actually add up to 20% more load because of the friction caused by the pulley wheel against it's axle.
The only advantage gained by anchoring the SB to a tree, etc. is that you need to run out twice the length cable/rope, i.e. from the vehicle to the tree (snatch block) and back to the vehicle.
By doing this you reduce the number of layers of cable/rope on the winch drum and as we all know (or should know) max. pulling power of a winch is generated with only 1 layer of cable/rope on the drum.
For instance when you look at the specs. of a winches pulling power a 10,000lb rated winch will only ever pull that load at the drum, by the time you fill the drum to capacity your pulling power has dropped to around half the rated advertised pull.
So to get a 2 to 1 MA from a winch you will need 2 snatch blocks 1 attached to the anchor tree, the other to the front of your 4WD, the formula for working out the MA of winch and snatch blocks is: the number of parts of rope supporting the MOVING block. which is attached to the front of the vehicle, the lead rope which is the part of the rope from the winch to the stationary SB is not a supporting rope.
If you want to take MA of SB's buy good quality correct diameter (bigger the better) SB's from a rigging supplier, not some 4WD shop one that has one size to suit all. Kinks and broken wires are mostly caused by wrong size SB's, hope this helps, Regards Frank.









I agree with rangieman, about water proofing, you can get by without it, its just extra work in maintenance.
But once the water is in there it is hard to get it all out quickly, some of it condenses again as the winch cools down.

The electric winches do work under water no problem, and drying them out is the go.
During my last overhaul, I drilled and tapped both ends of the winch/motor, and connected hoses to them.
I can blow air in one end and out the other, my plan at the time was to have a solenoid & pressure regulator connected to my air tank, to supply at at 2 psi via a canister filled with silca gel. ( a work in progress for 5 years :)).

Before a deep crossing I could open the dry air into the winch to reduce the amount of water entering, and then leave the air on for a few hours while driving to dry the winch out. Silica gel can be refreshed by warming in the oven, it's not hard to get or expensive.

If I could have only one winch it would be an electric one, just from the point of view its easy to use and will get you out of 95% of the problems. Sure you can't winch backwards, but that's the only advantage I can see for a hand winch. If you follow the makers advice regarding the battery capacity, you should be OK. It's hard to exceed the duty cycle of the winch, even in difficult situations because you have to be constantly re rigging the winch to different points as the recovery progresses, it gives the battery and the winch some recovery time, I never winch without the engine running.

I used to almost always be alone in the forest , because of my work pattern I had time off during the weekdays. I got stuck a lot because of the terrain and the trailer/ weight. I couldn't have got out of some of those situations with a hand winch because of the amount of physical work required. A couple of times it took me 2 hours of solo winching and re rigging to get out situations. I was very tired at the end of it. Have fun cheers simmo.

[simmo]

Good point Tank, I never seem to have the for-thought to run the winch cable under the car. :). I never think my landy will get bogged :D.

I do like my snatch block though, but have never needed more than double the power of my XD 9000. I run the wire out though the block and back to my front recovery point (s). Its slow going and short pulling as you said. I was trying to get up a slippery hill once, it was so slippery my car and 2000 kg trailer slid slowly side ways due to the camber into the spoon drain full of clay and sank to the chassis. But the XD 9000 and snatch block got her & trailer out OK and back onto some firm ground so I could unhitch the trailer. I drove half a km up the track and turned around to winch the trailer to the top of the hill.
The most frightening time was the first time going down the hills with the full trailer, fortunately the track was rutted, the trailer and a car had almost no traction and we slid down the hill like a slot car past all the big gum trees. I never let that happen again, I welded a lug to the chassis of the trailer at the back and used my drag chain to connect to a log, and dragged the log down the hill. All in days wood gathering fun :). cheers simmo

[Blknight.aus]

Trying to work out why most people think you can't winch backwards with an electric winch mounted on the front bar.
That bottom roller on the fairlead is not there for looks.
I have winched out of a bog and other impassable places by running the winch cable under the vehicle and attaching it to a tree behind and pulled my self free with no problems (another reason I don't use synthetic rope).
If I believe I may get stuck in an upcoming bog or I might need to pull myself back up a really steep downhill slope, I run my (wire) cable under the Disco and hook it up to the tow bar, a bit hard to run a cable under a vehicle that's bogged to the chassis and if I get stuck I just run out to an anchor point and winch myself out.
I use this method to pull a vehicle up onto a car trailer hooked up to the back of my Disco, never had a problem with catching or damaging anything underneath, will not work with Dyneema type synthetic ropes, for obvious reasons.
Snatch blocks are useful if used correctly, most have no idea of how to use a snatch block to give a Mechanical Advantage (MA), a stationary snatch block anchored to a tree will actually add up to 20% more load because of the friction caused by the pulley wheel against it's axle.
The only advantage gained by anchoring the SB to a tree, etc. is that you need to run out twice the length cable/rope, i.e. from the vehicle to the tree (snatch block) and back to the vehicle.
By doing this you reduce the number of layers of cable/rope on the winch drum and as we all know (or should know) max. pulling power of a winch is generated with only 1 layer of cable/rope on the drum.
For instance when you look at the specs. of a winches pulling power a 10,000lb rated winch will only ever pull that load at the drum, by the time you fill the drum to capacity your pulling power has dropped to around half the rated advertised pull.
So to get a 2 to 1 MA from a winch you will need 2 snatch blocks 1 attached to the anchor tree, the other to the front of your 4WD, the formula for working out the MA of winch and snatch blocks is: the number of parts of rope supporting the MOVING block. which is attached to the front of the vehicle, the lead rope which is the part of the rope from the winch to the stationary SB is not a supporting rope.
If you want to take MA of SB's buy good quality correct diameter (bigger the better) SB's from a rigging supplier, not some 4WD shop one that has one size to suit all. Kinks and broken wires are mostly caused by wrong size SB's, hope this helps, Regards Frank.

umm...

not sure where to start with this but, would you like to have another go at it?

but for starters.. (and this is the simple version that doesnt deal with compounde/ing configurations)

MA is usually a theoretical perfect number. and if your going through an anchored snatch block back to the vehicle thats got the winch to self recover your at a theoretical MA of 2:1, you multiply the available pull of the winch (which for any drum winch you should always assume is the top layer for your actual pull and the perfect bottom layer pull when calculating safe working load) by the total MA of your rig and then multiply it by the loss factor of the rig so working with as a decimal percentage (.8=80% in your example of 20% above) using 8000b as the starting figure for your winch (as it'll have most of the cable out as its doing 2 runs)the math for your example would look a little like this

(MA)2x (winch pull)8000x (loss factor).8= 12800lb pull
12800 is still more than the perfect 10000lb pull of the bottom layer.

if you have the snatch block anchored to the tree and come back to the vehicle with the winch, as far of the physics of it go, the snatch block is effectively the moving part if you consider the winch to be the stationary what you're doing is moving the snatch block closer to the winch.

if your vehicle is not as badly mired in the planet as the tree is rooted into the planet then reducing the distance between the winch and cable anchor on the same vehicle and the sntch block on the tree has the effect of pulling the vehicle towards the tree.

[Tank]

Dave I don't know where you get your figuring from, mine comes from over 20 years as a Qualified Class1 Ticketed Rigger, Riggers guide and any reputable recognised source on the operation of pulley blocks, my ticket is recognised world wide.
I am telling you and anyone else interested, that to get a Mechanical Advantage (MA) from using pulleys or Snatch Blocks the formula is and has always been worked out by the number of parts of rope supporting the Moving block, the operative word here is the moving block.
A block or SB that is stationary is only re-directing the path of the cable, explain to me how you get any MA from a stationary block, and if you believe the stationary block attached to an anchor point is MOVING, well.....
A set of snatch blocks set up as in previous post is pulling to advantage, i.e. pulling motion is in the same direction as the load is moving.
A single snatch block anchored ahead of the load is pulling in the opposite direction, in other words to disadvantage.
Now if you want to argue this point further, first, go and read a Riggers Guide and come back and show me how a single grooved wheel sandwiched between two plates of metal riding on a solid axle can impart magic energy to the cable rolling over it.
An example, an industrial accident (true story), a worker on a building site was killed when a rope holding a snatch block broke while a load of around 300lbs. was being hauled up to a floor below the snatch block.
When the DLI inspector and Police arrived they were told by the dozen or so workers on the site that the man that was killed was pulling the load up by himself and when it was about 20' in the air the rope holding the snatch block broke and the load fell on the worker and killed him.
The DLI inspector told the police that the workers were lying, because if the load was around 300lbs. and the worker killed looked to weigh around 140 to 150lbs then it would take at least 3 men to lift that load. DLI inspector explained to the police that one man could not possibly lift that load(even with the magical single pulley snatch block, my comment, not DLI).
He explained that the rope attached to the load side of the pulley would've had 300lb on it while the lead rope being pulled would've had around 360lb pulling on it, so it was impossible for a 150lb man to haul 360lbs, the rope holding the snatch block would have been subjected to around 660lb. which was a higher load than the guaranteed breaking strain of the snatch block supporting rope, which resulted in failure of the rope supporting the snatch block.
The Foreman was arrested and he immediately confessed that he and 4 others were hauling on the lead rope when snatch block rope broke, dropping the load which hit the unfortunate worker.
Single pulley does not offer any MA whatsoever when pulling to disadvantage it actually increases load on lead rope to overcome the up to 20% friction of the wheel rubbing on the axle.
Please read the riggers guide or this will go on forever, Regards Frank.









umm...

not sure where to start with this but, would you like to have another go at it?

but for starters.. (and this is the simple version that doesnt deal with compounde/ing configurations)

MA is usually a theoretical perfect number. and if your going through an anchored snatch block back to the vehicle thats got the winch to self recover your at a theoretical MA of 2:1, you multiply the available pull of the winch (which for any drum winch you should always assume is the top layer for your actual pull and the perfect bottom layer pull when calculating safe working load) by the total MA of your rig and then multiply it by the loss factor of the rig so working with as a decimal percentage (.8=80% in your example of 20% above) using 8000b as the starting figure for your winch (as it'll have most of the cable out as its doing 2 runs)the math for your example would look a little like this

(MA)2x (winch pull)8000x (loss factor).8= 12800lb pull
12800 is still more than the perfect 10000lb pull of the bottom layer.

if you have the snatch block anchored to the tree and come back to the vehicle with the winch, as far of the physics of it go, the snatch block is effectively the moving part if you consider the winch to be the stationary what you're doing is moving the snatch block closer to the winch.

if your vehicle is not as badly mired in the planet as the tree is rooted into the planet then reducing the distance between the winch and cable anchor on the same vehicle and the sntch block on the tree has the effect of pulling the vehicle towards the tree.

[JoeFriend]

Dave I don't know where you get your figuring from, mine comes from over 20 years as a Qualified Class1 Ticketed Rigger, Riggers guide and any reputable recognised source on the operation of pulley blocks, my ticket is recognised world wide.
I am telling you and anyone else interested, that to get a Mechanical Advantage (MA) from using pulleys or Snatch Blocks the formula is and has always been worked out by the number of parts of rope supporting the Moving block, the operative word here is the moving block.
A block or SB that is stationary is only re-directing the path of the cable, explain to me how you get any MA from a stationary block, and if you believe the stationary attached to an anchor point is MOVING, well.....
A set of snatch blocks set up as in previous post is pulling to advantage, i.e. pulling motion is in the same direction as the load is moving.
A single snatch block anchored ahead of the load is pulling in the opposite direction, in other words to disadvantage.
Now if you want to argue this point further, first, go and read a Riggers Guide and come back and show me how a single grooved wheel sandwiched between two plates of metal riding on a solid axle can impart magic energy to the cable rolling over it.
An example, an industrial accident (true story), a worker on a building site was killed when a rope holding a snatch block broke while a load of around 300lbs. was being hauled up to a floor below the snatch block.
When the DLI inspector and Police arrived they were told by the dozen or so workers on the site that the man that was killed was pulling the load up by himself and when it was about 20' in the air the rope holding the snatch block broke and the load fell on the worker and killed him.
The DLI inspector told the police that the workers were lying, because if the load was around 300lbs. and the worker killed looked to weigh around 140 to 150lbs then it would take at least 3 men to lift that load. DLI inspector explained to the police that one man could not possibly lift that load(even with the magical single pulley snatch block, my comment, not DLI).
He explained that the rope attached to the load side of the pulley would've had 300lb on it while the lead rope being pulled would've had around 360lb pulling on it, so it was impossible for a 150lb man to haul 360lbs, the rope holding the snatch block would have been subjected to around 660lb. which was a higher load than the guaranteed breaking strain of the snatch block supporting rope, which resulted in failure of the rope supporting the snatch block.
The Foreman was arrested and he immediately confessed that he and 4 others were hauling on the lead rope when snatch block rope broke, dropping the load which hit the unfortunate worker.
Single pulley does not offer any MA whatsoever when pulling to disadvantage it actually increases load on lead rope to overcome the up to 20% friction of the wheel rubbing on the axle.
Please read the riggers guide or this will go on forever, Regards Frank.

I doubt that everyone, including Warn have gotten the use of snatch blocks wrong and how they work.

The example you gave is showing the force applied to a rope holding the snatch block, not the force required to lift said object.

I am no expert, and only going on HSC physics, but I am probably going to go with what the experts like the guys at Warn are prepared to put on their website in this litigious world we live in.

Sent from my SM-G900I using AULRO mobile app

[Tank]

Go for it, no skin off my nose, seems you didn't read the Riggers Guide, or are they all bull****, and Warn are the be all end all, before you make ridiculous statements do some research.





I doubt that everyone, including Warn have gotten the use of snatch blocks wrong and how they work.

The example you gave is showing the force applied to a rope holding the snatch block, not the force required to lift said object.

I am no expert, and only going on HSC physics, but I am probably going to go with what the experts like the guys at Warn are prepared to put on their website in this litigious world we live in.

Sent from my SM-G900I using AULRO mobile app


33






How to work out the load in a single part of a purchase








The greatest load on any rope in a purchase is the load in the lead rope to the winch. This is due to


the friction between the rope in the groove of the sheave and the sheave pin. Friction is estimated at


between 3 per cent and 5 per cent per sheave (ie up to one twentieth of the rope load that would occur if


there was no friction).


The effects of friction, acceleration or deceleration are not usually included when dealing with work of a


temporary nature unless a number of falls are used or the rope velocity is high, ie. 0.6m/sec.


When a load is at rest, suspended from the lower block, the becket load (the load in each part of the rope


purchase) is found as follows:






Becket load = Total load on lower block ? No. of parts of rope supporting load








Note: The total load on the lower block includes the load to be lifted plus packings, slings, shackles,












blocks etc.


For example – (including frictional effects)


Total load on the lower block = 10t including gear


Number of parts of rope = 5 supporting the moving block






Becket load (BL) = 10 + 5 = 2t








However as lifting commences friction causes the load in the rope falls to increase by up to 5 per cent for


each sheave the rope passes over, including lead sheaves (if any).


The load in the lead to the winch (given 5 per cent friction) may be calculated as follows:






Load in lead to winch (LL) = BL + (BL x number of sheaves x 0.05)


= BL + (BL x number of sheaves x 5 ? 100)


or for a given load in the lead, the maximum load that can be lifted is calculated as:


Load = LL x no. of parts supporting load


1t (number of sheaves x friction)


Example 1:


No. of sheaves in purchase = 5 (3 top block + 2 bottom block)


Number of parts of rope = 5 supporting lower block


Number of lead blocks = 2 (7 sheaves in total)


Total load on lower block = 10t


Becket load = 10 ? 5=2t


Load in lead rope to winch = 2 + (2 x 7 ? 20)


= 2.7t


Example 2:


Calculate maximum load for the above arrangement using a winch with a 2.7t line pull


Load = 2.7 x 5


1 + (7 x 0.05)


= 13.5


1.35


= 10t








The above calculations do not allow for sudden impact, acceleration and deceleration which can cause


very high loads in the rope. These should all be avoided.

[Toxic_Avenger]

https://www.youtube.com/watch?v=chZsmKZ9Rjw

[Blknight.aus]

I see where your crossed up.

MA is the total advantage which is different to rigged to advantage and rigged to disadvantage.

a single block rigged to disadvantage is only redirecting the rope real work gives you an overall MA (including losses) of about .85-.9

a single block rigged to advantage has and overall MA (including losses) of about 1.7-1.8

just as an additional...

why dont you, as a professional rigger get your hands on a set of strain gauges and do a youtube vid for us of how snatch blocks actually work...

just as a by-the-by what you're talking about as whats needed to achieve a theoretical MA of 2:1 is called "gun tackle"

[Toxic_Avenger]

Keep up the good talk, It's all over my head at the moment, but I'm absorbing it.
I like it when you talk nerdy...

[JoeFriend]

Right, figured this out - both sides are in fact correct.

You are right in that one pulley/snatch block does not increase or decrease the load, except for friction so it in actual fact increases the load.

The difference between a car and the situation above, is that the car (or pulling point) is both non static (which the other chap alluded to - sorry on the phone and can't be bothered scrolling) - the key point to keep in mind here is the winch drum, which in actual fact operates as a second pulley/snatch block in this situation, hence reducing the load. Because the drum is a cylinder, all pulling points are technically after a 180 degree point, hence giving you the mechanical advantage.

Sorry for saying you are wrong, its just we weren't comparing apples with apples.

Sent from my SM-G900I using AULRO mobile app

[Tank]

I see where your crossed up.

MA is the total advantage which is different to rigged to advantage and rigged to disadvantage.

a single block rigged to disadvantage is only redirecting the rope real work gives you an overall MA (including losses) of about .85-.9

a single block rigged to advantage has and overall MA (including losses) of about 1.7-1.8

just as an additional...

why dont you, as a professional rigger get your hands on a set of strain gauges and do a youtube vid for us of how snatch blocks actually work...

just as a by-the-by what you're talking about as whats needed to achieve a theoretical MA of 2:1 is called "gun tackle"


Dave, I am 68 years old I haven't worked as a rigger for many years, a "Strain Gauge" was used on a thread about this on 4WD action forum a few years back, but to find out how much load was being pulled by the winch the Gauge should have been placed between the snatch block and the anchor point instead of one side of the cable.
This stuff I am posting about is not out of the deep recesses of my brain, it is from Government supplied documentation from respective DLI depts. and NSW TAFE colleges, it is from Riggers guides supplied by Work Cover Authorities, research from years of rigging and actual work in the field, then we get some ...... coming along and saying that all these organisations and people are all totally wrong and that Warn is the one to listen to, this same company that sells winches rated at some ridiculous level which is higher than the Guaranteed Breaking Strain of the cable fitted to it and this bloke says he don't know much about it, the only sense he has spoken.
This issue has been around for years, because years ago some bright spark pulled his bogged 4WD out by using a snatch block when he couldn't budge it with a single line pull.
So the GOSPEL becomes a snatch block will make your winch pull harder by 2, not the fact that he was winching from the lowest part of the winch drum which gave him probably a 2:1 advantage over a single line pull which was pulling from near the top of the winch at about half the advertised load rating.
Remember the Earth was flat once, only because most believed it so.
If you want to argue this subject either read some correct info or go and annoy someone else, not you Dave, but those blokes that have NO idea of what they are talking about, Regards Frank.

[vnx205]

Have a look at page 31 of the 1995 version of Work Cover's Riggers guide.

http://www.riggingtraining.com.au/Rigging/rigging_guide_part_1.pdf

I think the reason for the disagreement is that none of the images there represent what normally happens with a 4WD recovery.

In fact I can't imagine a rigger needing to use the setup that a 4WD recovery uses, which I suppose is the reason it is not illustrated in the Riggers' Guide.

The example of the man in the seat on this page is close to a lot of 4WD recoveries.

Simple Machines -- Mechanical Advantage (http://www.edinformatics.com/math_science/simple_machines/mechanical_advantage.htm)


Here are examples where the fixed point is not obvious:

A man sits on seat that hangs from a rope that is looped through a pulley attached to a roof rafter above. The man pulls down on the rope to lift himself and the seat. The pulley is considered a movable pulley and the man and the seat are considered as fixed points; MA = 2.

[Tank]

You posted this while I was typing my last post, all I ask is do some research before you make a statement and don't take it out on me, I'm only telling you what I learned from doing the Riggers ticket through a year at TAFE and the official books I had to read to pass my exam for my ticket, if you have a beef call them, regards Frank.





Right, figured this out - both sides are in fact correct.

You are right in that one pulley/snatch block does not increase or decrease the load, except for friction so it in actual fact increases the load.

The difference between a car and the situation above, is that the car (or pulling point) is both non static (which the other chap alluded to - sorry on the phone and can't be bothered scrolling) - the key point to keep in mind here is the winch drum, which in actual fact operates as a second pulley/snatch block in this situation, hence reducing the load. Because the drum is a cylinder, all pulling points are technically after a 180 degree point, hence giving you the mechanical advantage.

Sorry for saying you are wrong, its just we weren't comparing apples with apples.

Sent from my SM-G900I using AULRO mobile app

[Tank]

Allan, your "Quote is totally wrong and the easy way to prove it is to try it. Stick a snatch block on a tree branch, loop a rope through it, put a bowline loop in one end, put your legs through the loop and sit down on the ground. Using only your arms lift yourself up to the block.
If you can do that you must be very fit cause you are not getting any MA, to make it interesting put say double your weight in the loop and try lifting that, if you weigh say 150lbs you shouldn't have any trouble lifting 300lbs. with your magic snatch block that gives you a 2:1 advantage.
As far as using anything in the riggers guide in a 4WD scenario, the last time I winched you up Mongamulla I gained a 2:1 MA because my snatch block was attached to your front bumper, a bit slower, but much easier.
I have used Tirfors and multiple sheave blocks to drag loads of 100's of tonnes, a ships Diesel engine, about a 1000tonnes, the bow of a ship, forget how heavy, Rigging practices are the same as 4WD recovery and salvage and the same principles apply. I have used a bosun's chair more times than I can remember and I have NEVER seen one rigged with less than 5 parts of rope supporting the moving block (which is attached to the bosun's chair) I couldn't imagine what it would be like to haul yourself around in a bosun's chair with NO MA, just one pulley anchored (not moving) up above, can't and wouldn't be done in the real world.
When are we going to head bush again, got anything on, Regards Frank.
Quote below comes from same article yours came from:


Mechanical advantage

Consider lifting a weight with rope and pulleys. A rope looped through a pulley attached to a fixed spot, e.g. a barn roof rafter, and attached to the weight is called a single fixed pulley. It has a MA = 1, meaning no mechanical advantage (or disadvantage) however advantageous the change in direction may be.
A single moveable pulley has a Mechanical Advantage = 2. Consider a pulley attached to a weight being lifted. A rope passes around it, with one end attached to a fixed point above, e.g. a barn roof rafter, and a pulling force is applied upward to the other end with the two lengths parallel. In this situation the distance the lifter must pull the rope becomes twice the distance the weight travels, allowing the force applied to be halved. Note: if an additional pulley is used to change the direction of the rope, e.g. the person doing the work wants to stand on the ground instead of on a rafter, the mechanical advantage is not increased.





Have a look at page 31 of the 1995 version of Work Cover's Riggers guide.

http://www.riggingtraining.com.au/Rigging/rigging_guide_part_1.pdf

I think the reason for the disagreement is that none of the images there represent what normally happens with a 4WD recovery.

In fact I can't imagine a rigger needing to use the setup that a 4WD recovery uses.

The example of the man in the seat on this page is close to a lot of 4WD recoveries.

Simple Machines -- Mechanical Advantage (http://www.edinformatics.com/math_science/simple_machines/mechanical_advantage.htm)

[JoeFriend]

You posted this while I was typing my last post, all I ask is do some research before you make a statement and don't take it out on me, I'm only telling you what I learned from doing the Riggers ticket through a year at TAFE and the official books I had to read to pass my exam for my ticket, if you have a beef call them, regards Frank.

I looked at the riggers guides, and none of them showed anything about the situation of a winch recovery using a snatch block - or anything close.

I didnt mean any of this to **** on your experience, career or whatever so don't take it that way - but if you can't see the fact there are 2 pulleys in this situation and not the one because you aren't taking into account the winch drum, ain't my fault.

And while we are on the subject, the force involved in this you need to measure is not a pull, its a turning force. The measurement is the torque required for the winch drum (pulley) to turn. If it was a pull, then there would be an open end. It may be that the pull on the line may be the same, which is clearly shown by all your riggers knowledge, and clearly shown on the guide you have thoughtfully provided and I read, but the force we are talking about is not the pulling capacity of rope or wire, its the turning force required to reel in the line.

If you pull on your winch rope, straight pull. Stand near your car and pull on the line threaded through a snatch block, still a straight pull, you are just changing the angle, and putting added load on the snatch block. Stand near the snatch block, pull through the snatch block and back around the winch drum and that is what the winch is doing. Half the strength required. It is just doing the turning at the pulley.

I never said your information was wrong mate, you just didn't have the right equation.



Sent from my SM-G900I using AULRO mobile app

[vnx205]

Here is another way of looking at the situation.

Setup A is straight from the Rigger's Guide and is exactly as Frank says. It is pulling to disadvantage and all that happens is that the direction of the pull is changed and the frictional losses increase the effort required.

Setup B, which does not appear in the Rigger's Guide is the way some people use a pulley in a 4WD recovery.

Frank's statement about how to calculate theoretical MA is correct and again is taken from the Rigger's guide.


I am telling you and anyone else interested, that to get a Mechanical Advantage (MA) from using pulleys or Snatch Blocks the formula is and has always been worked out by*the number of parts of rope supporting the Moving block,*the operative word here is the moving block.

So the important question is how many parts of rope (are) supporting the Moving block?

The rectangle at the bottom, representing the vehicle surely has two ropes supporting it, therefore a theoretical MA of 2.

If you tie the end of the rope to another tree instead of back to the vehicle, you have setup A which as the riggers guide shows has a MA of 1.



Some of the things making it difficult for me to head bush recently are no longer a problem, so I'm hoping to be able to get out soon.

[bee utey]

... what fun...

[Blknight.aus]

Have a look at page 31 of the 1995 version of Work Cover's Riggers guide.

http://www.riggingtraining.com.au/Rigging/rigging_guide_part_1.pdf

I think the reason for the disagreement is that none of the images there represent what normally happens with a 4WD recovery.

In fact I can't imagine a rigger needing to use the setup that a 4WD recovery uses, which I suppose is the reason it is not illustrated in the Riggers' Guide.

The example of the man in the seat on this page is close to a lot of 4WD recoveries.

Simple Machines -- Mechanical Advantage (http://www.edinformatics.com/math_science/simple_machines/mechanical_advantage.htm)

three examples from the top of my head are gyn pole backstays, overhead gantry cranes and manual boom slew lines.. (I forget the current name for them)

the biggest issue as you've identified is that it is rare in the rigging world to have your winching line also be the same point as the anchor for the standing part of the rope.b

at a rough guess 80% of rigging world work is done at disadvantage. (im not counting gantry crane or pre-rigged tensioners that use a inbult rigged to advantage 2:! )

[vnx205]

Allan, your "Quote is totally wrong and the easy way to prove it is to try it. Stick a snatch block on a tree branch, loop a rope through it, put a bowline loop in one end, put your legs through the loop and sit down on the ground. Using only your arms lift yourself up to the block.

I bet I can. :)

In fact I think I could do it with one hand. Next time we are in Bendethera, you supply the pulley and I will supply the rope and the effort.

[Tank]

Read my last post above yours and see the bit about mechanical advantage.
As far as the winch drum is concerned, that is my point exactly, with a cable reeved through a fixed pulley and back to the point of origin (4wd Vehicle) twice the length of cable is wound off the drum placing the torque generated closer to the centre of the winch drum. Winches are rated for their pulling power (torque) at the closest point to the centre of the drum as they can get. Most winch manufacturers will supply at point of sale the max load for each layer of cable, the top layer usually coming in at around half the rated load of the first layer.
By running out twice the amount of cable over and above a single line pull you are gaining a near 2:1 advantage, but it has nothing to do with the snatch block. The same advantage could be achieved by picking an anchor tree twice as far away as the tree with the snatch block.
This topic was discussed extensively on 4WD Action Forum a number of years back, the topic got so hot that some of the *****s on that Forum got hold of my phone number and I and others that agreed with me were getting death threats, I eventually found out who they were and they were warned and that was the end of that.
But commonsense and Physics explains it all and I don't think Tafe and all the other Gov. depts. got it wrong.
I look at it this way, if you have a cable attached to a load at one end and a winch at the other and it is stretched tight, you place the wheel of a snatch block against the cable, does that halve the load on the winch, or do you have to have the cable being pushed into a 45 degree angle by the snatch block before MA applies, or is it 60 degrees or 90 degrees.
The snatch block does nothing except change the direction of pull when it is anchored and not moving, what if I ran the same cable through 1/2 a dozen snatch blocks anchored all in different locations, are they going to take half of the load each off the winch, of course not. If the theory that a single anchored snatch block will halve the load on a winch, then if I anchored another snatch block, say 6' to the side of the first block then I should require no effort from the winch, Doesn't work, does it?
If you didn't have a snatch block you could just throw your cable around a tree, more friction, but according to the believers in the magic snatch block, the same principle applies to the tree, change of direction only there is nothing inside a snatch block that allows you to pull 3 tonnes by only applying 1500kgs to one side of the pulley, Regards Frank.





I looked at the riggers guides, and none of them showed anything about the situation of a winch recovery using a snatch block - or anything close.

I didnt mean any of this to **** on your experience, career or whatever so don't take it that way - but if you can't see the fact there are 2 pulleys in this situation and not the one because you aren't taking into account the winch drum, ain't my fault.

And while we are on the subject, the force involved in this you need to measure is not a pull, its a turning force. The measurement is the torque required for the winch drum (pulley) to turn. If it was a pull, then there would be an open end. It may be that the pull on the line may be the same, which is clearly shown by all your riggers knowledge, and clearly shown on the guide you have thoughtfully provided and I read, but the force we are talking about is not the pulling capacity of rope or wire, its the turning force required to reel in the line.

If you pull on your winch rope, straight pull. Stand near your car and pull on the line threaded through a snatch block, still a straight pull, you are just changing the angle, and putting added load on the snatch block. Stand near the snatch block, pull through the snatch block and back around the winch drum and that is what the winch is doing. Half the strength required. It is just doing the turning at the pulley.

I never said your information was wrong mate, you just didn't have the right equation.



Sent from my SM-G900I using AULRO mobile app

[Tank]

Last time you tried it without the snatch block you did yourself an injury, the bets on when are we going, still got to get my stainless steel water tank in though, give us a call when you're ready, Regards Frank.





I bet I can. :)

In fact I think I could do it with one hand. Next time we are in Bendethera, you supply the pulley and I will supply the rope and the effort.

[Blknight.aus]

Allan, your "Quote is totally wrong and the easy way to prove it is to try it. Stick a snatch block on a tree branch, loop a rope through it, put a bowline loop in one end, put your legs through the loop and sit down on the ground. Using only your arms lift yourself up to the block.
If you can do that you must be very fit cause you are not getting any MA, to make it interesting put say double your weight in the loop and try lifting that, if you weigh say 150lbs you shouldn't have any trouble lifting 300lbs. with your magic snatch block that gives you a 2:1 advantage.
.[/SIZE][/FONT]


umm Tank,

Thats exactly how a single sheeve rigged to advantage works. excluding losses most people can only pull down 1/4th their body mass so most bosuns chairs are rigged in 5:1 advantage, 6:1 disadvantage or 6:1 advantage. to give you an effective MA equivalent of at least 4:1

getting someone who cant pull up their body mass in the first place to then attempt to pull up their body mass+100% (150lb body, 150lb load=300lb) with only a 2:1 MA wont work because it means their back to trying to pull 150lb before you have to deal with the extra work to overcome frictional losses

[simmo]

Well that was bit exciting :), I got lost in all the mathematics and calculation. It seems pretty simple to me.

There two wire rope lengths under tension connected to my car, one is connected to the winch drum, the other to my recovery point, via the snatch block connected to a large gum tree in front of me. ( hopefully)

Each wire rope has the same tension give or take a few percent, and is pulling me towards the snatch block, say about 6000lb for discussion. 2 x 6000 lb =12000 lb nominally. (5400 kg, but using the HP & running current for 6000 lb)

Normally when using the snatch block you have a fair bit of wire out, I think my Warn wire rope is about 30 yards, ( say 27 m), so you don't have a lot of wire to play with, only about 12 meters, (up and back). For that reason the last 1.5 meters of my winch wire is painted yellow, as soon as I see the yellow paint I know that's as far as I can use the winch wire under load, so I have to make snatch block securing arrangement to suit. The wire being close to bottom row of the winch drum, the winch can produce close to its rated pull.

I think in all the maths earlier the point is, while the winch is only pulling 6000 lbs, and having an easy go of it, the snatch block and its securing point/equipment is subject to 12,000 lbs, double that load.

That's the danger in my view, making sure the snatch block, tree trunk protector & winch extension strap is properly rated and secured. They could potentially be exposed to twice the rating of the winch. ( and the tree is a big one :)

I do have two snatch blocks, but only ever carry one because of their size and weight etc. I've never needed two yet, if i do I hope I have a well equipped mate along with me.
Its good to have a vigorous discussion and let the different ideas come out.

cheers simmo.:)

[Tank]

I try to avoid using a snatch block, especially if I can run out most of my cable to gain the same winch drum capacity as using a tree twice as close with a snatch block, does that compute, anyway. Snatch blocks are very hard on winch cables, as the cable travels over the pulley the wires on top are stretched and the wires closest to the bottom of the groove in the pulley are compressed.
This can cause kinking , esp. if it is against the lay (twist) of the rope and broken wires, all winch wire cable should be IWRC which has a wire core in the middle of the 6 outer strands of wire, it minimises crushing on the winch drum and wheel of the snatch block.
If snatch blocking is part of your life see if you can buy a decent snatch block, ideally for the 11mm cable that I use a 12" dia. snatch block wheel with the correct size groove for the wire cable used, too wide will break wires and cause kinks as it is not supported by the groove and allows flattening, too narrow pinches the cable and will break individual wires.


Running a cable or rope through a pulley one way then completely the opposite way through another pulley is the quickest way to destroy a cable/rope, so look for a decent snatch block, preferably 2 at a Rigging supply warehouse, not a 4WD shop where one size fits all, regards frank.














=simmo;2428575]Well that was bit exciting :), I got lost in all the mathematics and calculation. It seems pretty simple to me.

There two wire rope lengths under tension connected to my car, one is connected to the winch drum, the other to my recovery point, via the snatch block connected to a large gum tree in front of me. ( hopefully)

Each wire rope has the same tension give or take a few percent, and is pulling me towards the snatch block, say about 6000lb for discussion. 2 x 6000 lb =12000 lb nominally. (5400 kg, but using the HP & running current for 6000 lb)

Normally when using the snatch block you have a fair bit of wire out, I think my Warn wire rope is about 30 yards, ( say 27 m), so you don't have a lot of wire to play with, only about 12 meters, (up and back). For that reason the last 1.5 meters of my winch wire is painted yellow, as soon as I see the yellow paint I know that's as far as I can use the winch wire under load, so I have to make snatch block securing arrangement to suit. The wire being close to bottom row of the winch drum, the winch can produce close to its rated pull.

I think in all the maths earlier the point is, while the winch is only pulling 6000 lbs, and having an easy go of it, the snatch block and its securing point/equipment is subject to 12,000 lbs, double that load.

That's the danger in my view, making sure the snatch block, tree trunk protector & winch extension strap is properly rated and secured. They could potentially be exposed to twice the rating of the winch. ( and the tree is a big one :)

I do have two snatch blocks, but only ever carry one because of their size and weight etc. I've never needed two yet, if i do I hope I have a well equipped mate along with me.
Its good to have a vigorous discussion and let the different ideas come out.

cheers simmo.:)[/QUOTE]

[vnx205]

Page 25 of the Rigger's Guide that I linked to back in post #39 has more detail about the issues Frank has covered regarding the use of pulleys with wire ropes.

[ozscott]

Tank if you had a stuck vehicle and some trees and blocks available and wanted to get max MA how would you set it up? A diagram would be great because I have trouble visualising this stuff.

Cheers

[Landi]

Yeh agreed. A diagram would be great. Even university physics isn't helping me in understanding this one...I can definitely understand using a tree further away to un-layer more of the rope, but let's say there's only 1 suitable tree to use, 10-15m away, surely it would be better to use a snatch block at the tree, running it back to a recovery point on the front. Assuming of course you're using suitable and appropriate gear. Correct diameter snatch block, rope, rated shackles etc

[roverrescue]

Tank
First I completely agree that by running out cable to the first layer is a great way to increase pulling capacity. My winch only has 20m of dyneema on it but I carry lots of 50m lengths of extra dyneema to get length. This means the winch is generally always on lower wraps of the drum improving pulling power.

But now getting onto your rigging of winching riddle me this.

-Take a nice gantry crane with an winch rated to SWL 2T
-Take a cable down from a crane, to a 1T mass sitting on the floor and winch it up. Lets say the mass moves upwards at 1metre per second.
-Now place a block on the 1Tonne mass, send the hook through the block and back up to the crane and winch. Assuming it is a non load dependent constant speed hydraulic motor, how fast will the mass move upwards?

Obviously because the block is on the moving component you have your 2:1 MA which results in the mass moving 0.5m for every 1m of winching and as such the mass moves upwards at 0.5metres per second. And excluding friction etc etc you could say the load on the crane is halved due to the MA.

Now relativity is a bitch...

Have a read of this thread
MA debate and snatch blocks - Page 2 - Pajero 4WD Club of Victoria Public Forum (http://www2.pajeroclub.com.au/forum/showthread.php't=7020&page=2)

Mr Pajero did a winching experiment (using the well worn method of attaching the hook end to the vehicle) and found that winching 1m of rope equates to 0.5m of movement... Relatively speaking no different to the crane situation and as such there IS a MA when the cable is attached back to the bogged vehicle. The relative movement of the crane or the mass is irrelevant, it is that the load on the two cables is shared compared with a single cable.

If you disagree please explain how the pajero only moved 0.5m for 1m of winching?
If there is indeed no MA as you profess the pajero would have to move a metre for each metre of rope winching.

Peace

Steve

[Blknight.aus]

Sorry steve...you're very close but have made the same fopar in your descrpition as what Tank is making... but I know exactly what you mean and presume it was an expressive error. your original is in blue my corretion is in red, apologies for cutting the post down.

Tank

But now getting onto your rigging of winching riddle me this.

-Take a nice gantry crane with an winch rated to SWL 2T
-Take a cable down from a crane, to a 1T mass sitting on the floor and winch it up. Lets say the mass moves upwards at 1metre per second.
-Now place a block on the 1Tonne mass, send the hook through the block and back up to the crane and winch. Assuming it is a non load dependent constant speed hydraulic motor, how fast will the mass move upwards?

Obviously because the block is on the moving component you have your 2:1 MA which results in the mass moving 0.5m for every 1m of winching and as such the mass moves upwards at 0.5metres per second. And excluding friction etc etc you could say the load on the crane winch is halved due to the MA.



the total load on the whole of the crane is still 1T but the load on the winch is now halved, the other half of the load is born on the body of the crane from teh point where you have the cble anchore

Tanks been taught on the old school ways where you basically never do what you've just described because the winching limit is also the anchoring limit for that point so to gain additional lifting ability you need to incorporate a second anchor point.

unless hes also done plenty of shipping work he'll also be working off of the base that the winch is not able to move (closer to the load), the load must always come to the winch.

we had an instructor on one of my crane courses who had the same problem, 2:! hanging from a head of a crane works because the block is moving, 2:1 on the ground cant because the block is stationary. me personally I blame the following phrase.

"if the heaving line is coming from the moving pully the system is rigged to advantage, if it is coming from a stationary pully it is rigged to disadvantage"


as I'm about to get my replacement computer onlineif all goes well I'll do some drawings tonight I'm also due to do a service on a winch so I might even be able to demo and strain gauge some of the configurations..

[roverrescue]

yeah good point I wasn't clear in my wording (AND this topic does need to be accurately worded)
Your red is totally correct load on the crane is unchanged but load on the winch is halved.

As you state in the second scenario the load is half to the winch and half to the attachment on the crane - overall though the load(force) on the crane is a function of 1000kg x 9.9m/s/s.

s

[Tank]

First up, I thank you all for not threatening to kill me, like those clowns on that other Forum, if you don't agree with what I've written.
I used to be a permitted rigger, (under instruction) till I got the riggers job in the Boiler Shop and Turbine shop on Cockatoo Island in Sydney harbour, after working a number of years in the mining construction business all over Australia.
Now I thought I knew it all and wasn't pleased when Vickers Cockatoo asked me to do a 12 months TAFE course, because they had no ticketed riggers on the island and permitted riggers need to work under a Ticketed rigger.
So the first thing I learnt was that there was a whole lot of maths involved.
The first day at TAFE was a Maths exam, out of the 150 or so would be riggers only around 50 passed the Maths exam and went on to do the riggers course.
The course opened my eyes and mind to parts of rigging that I would never had known except by Accident, it IS a very dangerous business esp. with just a little knowledge.
I haven't worked as a rigger (except when 4WD recovering) for 30+ years and I do not profess to know or remember it all, as you may or may not have noticed I have wrongly claimed that friction on each wheel when using snatch block/s was up to 20% of the load, in fact it is 5%, so sorry there.
I would love to be able to illustrate with drawings different ways to set up cables, blocks, straps and other ways to extricate yourself from a bog or whatever, but I have no idea of how to get a drawing onto the forum, I have enough trouble with photos, Maybe Allan can come around and educate me, never to old to learn and he is a teacher.
There is a hell of a lot of writing to explain why certain things happen like winch a metre of cable thru a block and the vehicle only moves 1/2 a metre, to do with pulling to advantage or disadvantage, as I am a single finger typist it takes me forever to get my point across, maybe I'll write a booklet.
The simple explanation for MA using pulleys is to rig a pulley up to a rafter in your shed/whatever put a length of rope though and tie a bucket to each end and place an identical weight in each one, say a house brick.
You will find, of course that they balance each side out, which means if you have 10 kilos on each side you have you have 20kilos on the rope holding up the pulley. To move say the left side bucket up you will have to place more weight on the other bucket to overcome the friction generated in the pulley which can be up to 5%/pulley so you need to add that 5% to load on the rope holding the pulley, this equates to a MA of 1.
Do the same thing to yourself, make a loop in one end of the rope, sit your bum in it, your body is the load, your arms are the winch, with out using any other part of your body pull yourself up to the pulley, should be easy if you weigh 100ks. you will only have to apply 50ks. + 5% friction, if the pulley is giving you a MA of 2 as some are claiming, it has taken me over an hour to type this, so I'm taking a break for now, Regards Frank.













yeah good point I wasn't clear in my wording (AND this topic does need to be accurately worded)
Your red is totally correct load on the crane is unchanged but load on the winch is halved.

As you state in the second scenario the load is half to the winch and half to the attachment on the crane - overall though the load(force) on the crane is a function of 1000kg x 9.9m/s/s.

s

[Bytemrk]

Frank,

It's the shared knowledge that has accumulated in this place from those like you willing to share your knowledge and experience that makes this such a great place.

For sure not everyone will agree with everything... but the smart ones can spot those that know what they are on about.

Thanks for taking the time to help those that want to learn...;)

[roverrescue]

Frank.
First I don't want to bust your head. Honestly I just want the principles of physics to be seen. I don't discount your knowledge or experience but you are just wrong on this.

In the example I gave of a winch a crane a 1tonne mass and a block do you or do you not agree in the 2:1 MA. If so then the fact is that relatively speaking it is irrelevant if the load is moving or the crane is moving.

I think Dave needs to do some load testing using inline scales. Hell I was looking and can buy some PRC magic scales rated to 300kg that will do to prove this beyond reasonable doubt....

Dave if you can't I will just say the word.

S

[bee utey]

Do the same thing to yourself, make a loop in one end of the rope, sit your bum in it, your body is the load, your arms are the winch, with out using any other part of your body pull yourself up to the pulley, should be easy if you weigh 100ks. you will only have to apply 50ks. + 5% friction, if the pulley is giving you a MA of 2 as some are claiming, it has taken me over an hour to type this, so I'm taking a break for now, Regards Frank.

I was actually going to post this up as an example of MA, so I'll now finish my idea.

When I was younger I weighed 80kg and had no problems doing chin ups, therefore I could easily apply an 80kg downwards force with my hands. At that point my body was clear of the ground (zero weight on a scale) so I know that I can pull 80+kg. MA equals 1.

Now in my slightly more rotund middle age, chin ups are more difficult at a body weight of 100kg, I can just manage it. Now imagine me with a wooden rod under my feet tied to the rope that passes through the pulley above me. Now imagine I exert a 50kg pull on the rope, guess what, my body mass acting on the rod and rope is reduced to 50kg. Allowing for friction, I would now pull myself off the floor using a force approximately equal to half my weight. A spring scale on the rope on each side of the pulley would read 50kg. A spring scale on the pulley anchor would show 100kg. MA equals 2. :)

[Landi]

Me doing a recovery after reading this thread...

[Blknight.aus]

I have wrongly claimed that friction on each wheel when using snatch block/s was up to 20% of the load, in fact it is 5%, so sorry there.


The simple explanation for MA using pulleys is to rig a pulley up to a rafter in your shed/whatever put a length of rope though and tie a bucket to each end and place an identical weight in each one, say a house brick.
You will find, of course that they balance each side out, which means if you have 10 kilos on each side you have you have 20kilos on the rope holding up the pulley. To move say the left side bucket up you will have to place more weight on the other bucket to overcome the friction generated in the pulley which can be up to 5%/pulley so you need to add that 5% to load on the rope holding the pulley, this equates to a MA of 1.
Do the same thing to yourself, make a loop in one end of the rope, sit your bum in it, your body is the load, your arms are the winch, with out using any other part of your body pull yourself up to the pulley, should be easy if you weigh 100ks. you will only have to apply 50ks. + 5% friction, if the pulley is giving you a MA of 2 as some are claiming, it has taken me over an hour to type this, so I'm taking a break for now, Regards Frank.

Frank, you werent wrong, Ive got books that prove exactly what you're claiming provided you restrict yourself to the sections about rigged to advantage and rigged to disadvantage, I know I promised to do some pictures and experiement and I still will if I can get my hands on the scale sets but in the short term, the disconnect here is in identifying rigged to advantage, rigged to disadvantage on a single sheeve ppully and assessing its MA.

you're also not wrong with the reduction for a sheve its not a fixed percentage and the formula for a Fiber cored 6 lay rope with a 3/16th strand and a 6x9 lay construction on a minimum 8d turn has an swl reduction factor of 50% AND has an initial hauling loss of 50% decreasing to 30%

short version of all of that? using easy numbers, if that wire rope could hold 2 T and you reeved it through a minimum diameter block to lift a 2 T weight you would initially have to apply 2T worth of pull on a pully that was rigged to advantage you might as well just hauled the thing up on a single line and if you tried to lift the load using that pully rigged to disadvantage you couldnt. step ouut to a 15D pully and youre at 20% ste out to something like 40D a your back at 5%.

for those paying attention no you wouldnt use that construction rope as a winching rope, its a static line grade rope. think bridge stay not hauling line



Frank.
First I don't want to bust your head. Honestly I just want the principles of physics to be seen. I don't discount your knowledge or experience but you are just wrong on this.

In the example I gave of a winch a crane a 1tonne mass and a block do you or do you not agree in the 2:1 MA. If so then the fact is that relatively speaking it is irrelevant if the load is moving or the crane is moving.

I think Dave needs to do some load testing using inline scales. Hell I was looking and can buy some PRC magic scales rated to 300kg that will do to prove this beyond reasonable doubt....

Dave if you can't I will just say the word.

S
I was hping to get the strain gauges from work to do it sometime next week when I do a function test and service on dads winch. I cant afford to do it full scale but I might be able to get some 5 kg fish scales and lego it.

the laptop OS build is on hour 4 of one so far so the pictures arent going to hapen tonight so hopefully over the weekend....


Me doing a recovery after reading this thread...
nahh, this is the easy stuff...

wait till you see the math on some of the really advanced stuff, multiple winches pulling into different parts of a compound setup an the dynamics of the load in motion change the formulas part way through because the pull angles change...

[Disco-tastic]

This was what I was taught at school/uni (im a practicing structural engineer, if that makes any difference to the value of my opinion)

"The tension in the wire/rope is the same at all points along the rope (disregarding friction)"

https://www.dropbox.com/s/0gic152376b5z5r/20150930_091457.jpg'dl=0
pic link: https://www.dropbox.com/s/0gic152376b5z5r/20150930_091457.jpg'dl=0

In attached pic, situation A has one pulley but only 1 line of rope is supporting the weight (of say 100kg). Therefore the tension in the line is 100kg (or 1kN)

In situation B (similar to a winching 4wd) there is one pulley however there are two lines to the weight. In order to maintain equilibrium the tension in the line = 50kg (0.5kN). Increase the tension at the point of the arrow (ie by using a winch attached to the weight) past 50kg and the weight will move towards the top pulley.

In situation C there are two pulleys though the rope is anchored to a third point (similar to situation A). As there are two ropes fixed to the weight, the tension in the rope is 50kg (0.5kN). Increase this tension past 50kg by pulling on the rope and the weight will lift.

Disregarding the angles of the rope (please don't go there - this is just a diagram) the force in the top pulley equals the weight (100kg) in all situations. However in B and C the tension in the rope is only 50kg. My understanding is that is a mechanical advantage of 2.

Cheers

Dan

Ps. Sorry for the lousy photo link. I don't have photobucket or anything at the moment and don't have time to set one up!

[Disco-tastic]

Whoops.

Correction: the load on the pulley in case A is 2W, and the load on the top pulley in case C is 1.5W. (Once again ignoring angles)

Cheers

Dan

[AndyG]

So Landi, all clear now :D
Buy a HP calculator to run the numbers , then call Land Rover Assist

[Blknight.aus]

So Landi, all clear now :D
Buy a HP calculator to run the numbers , then call Land Rover Assist

close..
use the calculator app on your phone and then use the phone to call landrover assist.


of course if you're as lucky as I am when it comes to this stuff the battery will go flat in the phone so you'll have to do all the math from memory using a stick and the dirt on the ground then rig it all up do the recovery, pack it all up and then drive back to the campsite to grab the phone charger out of the goddies bag.

[ramblingboy42]

I have never had a winch on a vehicle and probably never will.

I have nearly always carried a 3t come-along with a 3-5mtr chain.

I also have never used it in anger but have exercised recovery just to practise.

It is the simplest thing to use, does not tire you out using it or carrying it (you can get them in aluminium).

You set it up wherever and to whatever your task is.

And on your own , incorporating your snatch strap , you can load the come-along right up . get in your vehicle and assist your recovery under the snatch strap tension.

When it goes slack just load it up again.

It works and doesn't have to go into the mud if you're in mud because you can set the come-along up wherever you want.

My favourite.....unfortunately now I will have to buy one because I'm retired and the big store in the sky is now closed to me.

[simmo]

When I first got my land rover i I was a believer that winches weren't necessary, I thought they were only for posing & decoration etc. I few long walks to the top of a high hill where my phone would work cured me of that delusion. :) . I started to think maybe there's a reason 50% of the 4x4 s have winches.

And I was amazed at how easy it is to stop a Land Rover, ( no prior experience) in muddy & hilly terrain, one front wheel slipping and one back wheel slipping & you're stopped. It's surprising land rover didn't use limited slip diffs or true tracks fitted to the car from the factory, I think toyota and nissan offered LSD in the back for that reason. Once I parked on a gentle grassy slope and could not proceed :(.

Fortunately there was a lot of good trees where I drove so a winch was on obvious addition, and not too expensive about $1000 for an unused 2nd hand Warn 9000. ( about the cost of set of good mud tires at the time)
It made bush driving more relaxing and gave some confidence i could take car of myself, if i got bogged.

But it didn't address the key issue of why I was getting stuck; 2 open differentials. I fitted the maxi drive myself, but if was fitted professionally it was 3 times the cost of the winch. I still got stuck but no where near as often, so the winching was reduced. To those who never need a winch I salute you :), dammed skillful driving and good vehicle preparation.

cheers simmo

[ramblingboy42]

Simmo, I have always had the thought that 4wd was to get you out of situations , not to drive you into them.

On that notion I have been known regularly to take the chicken track or the long way around.

On my last trip around the campfire a couple of weeks ago , I was attacked heavily by a Land Rover hater for taking the easy track up big red a couple of years ago.

I just could not see the point in large run-up engine screaming , kangaroo hopping up a more difficult track , and that's what the others were doing.

So , with me it's not so much skillful driving and vehicle preparation. just chicken ****!

[tact]

Tank, all your experience and all you write is absolutely correct for situations you are writing about. Eg The bosuns chair self lift thing. Sit in harness at one end of the rope, round a single pulley, pull the other end. No MA at all. Disadvantage only.

A situation we shall here call "apples".

The rig that is set up when a typical winch equipped vehicle runs cable out to a remote snatch block and back to the vehicle is not - apples. It's oranges.

The difference between these apples and oranges, is the that the apples bosuns chair set up has one pulley - the oranges setup has TWO pulleys in the system even if it's not obvious. The winch drum itself is the second pulley. A power driven pulley, not passive, both providing the "pull" and supporting a share of the load.

A bosuns chair arrangement that equates to "oranges" (vehicle mounted winch recovery incorporating a single snatch lock) is this:
Nice sit harness attached to a rope,
the rope passed around a remote pulley, back to ANOTHER pulley attached to the sit harness. The passenger/load pulling (awkwardly!) by extending his arms away from his body.

[Toxic_Avenger]

Everyone seems to love their tirfor winches.
I have a high lift jack and a jack-mate block to replace the base. With the addition of a few lengths of chain to my existing rigging, this can be used as a (slow) winching device.

What's peoples thoughts on this?

My reasoning for this route might be along the lines of the ability to lift vertically with the hi lift as well as horizontally. Electric winch is also available.

[tact]

[...]
I just could not see the point in large run-up engine screaming , kangaroo hopping up a more difficult track , and that's what the others were doing.

So , with me it's not so much skillful driving and vehicle preparation. just chicken ****!

Seems to me more like a case of a "mechanicals sympathetic" driving style.

A bit like you where, whilst I like testing limits and knowing capabilities and taking on a challenge, if it's likely to mean work afterwards - I'll prefer the easier path. So for me it's more a case of laziness than the more dignified "mechanically sympathetic".

[Blknight.aus]

Tank, all your experience and all you write is absolutely correct for situations you are writing about. Eg The bosuns chair self lift thing. Sit in harness at one end of the rope, round a single pulley, pull the other end. No MA at all. Disadvantage only.

A situation we shall here call "apples".

The rig that is set up when a typical winch equipped vehicle runs cable out to a remote snatch block and back to the vehicle is not - apples. It's oranges.

The difference between these apples and oranges, is the that the apples bosuns chair set up has one pulley - the oranges setup has TWO pulleys in the system even if it's not obvious. The winch drum itself is the second pulley. A power driven pulley, not passive, both providing the "pull" and supporting a share of the load.

A bosuns chair arrangement that equates to "oranges" (vehicle mounted winch recovery incorporating a single snatch lock) is this:
Nice sit harness attached to a rope,
the rope passed around a remote pulley, back to ANOTHER pulley attached to the sit harness. The passenger/load pulling (awkwardly!) by extending his arms away from his body.

careful with your wording...

if you are sitting in the in the harness and pulling the rope, you're rigged to advantage......

if the setup you're talking about is...
rope attached to an elevated point, the pully is supporting the chair and someone else pulls the other end of the rope thats rigged to advantage

if the setup is...

pully attached to a high point, you sit in the harness and someone else pulls the rope, thats disadvantage.

[Toxic_Avenger]

https://www.aulro.com/afvb/images/imported/2015/10/941.jpg
...with a defender for extra cool points.

[tact]

careful with your wording...

Watching wording indeed please. I never referred to "rigged to (dis)advantage" - the term with a specific technical meaning. Tried keeping all I wrote non-technical. Unless apples and oranges are in the riggers handbook too - then my apologies.

I wrote "no MA at all. disadvantage only." The disadvantage being frictional losses added to the load burden with no mechanical advantage to mitigate.

[vnx205]

Neil, if someone else is pulling on the rope, what you have said about no MA is true.

If the person sitting in the chair is doing the pulling, then it is exactly the same as a 4WD with a rope going from the winch, around a pulley and back to the vehicle. In that case there is a theoretical MA of 2 with some small loss caused by the pulley.

[tact]

Neil, if someone else is pulling on the rope, what you have said about no MA is true.

If the person sitting in the chair is doing the pulling, then it is exactly the same as a 4WD with a rope going from the winch, around a pulley and back to the vehicle. In that case there is a theoretical MA of 2 with some small loss caused by the pulley.

You are sitting in the chair. Rope up and over a pully back to your hands. You pull 1M of rope. How much higher off the ground is your bum in the chair? (1M)

You are sitting in the chair. Same chair. Same rope. Your mate standing behind you pulls in 1M of rope. How much higher is your bum in the chair now off the ground? (1M)

(All "apples")

Now it's time for oranges. You in the same chair. Same rope up and over the same single pulley. Difference this time, you feed the rope around a pulley attached to your harness/chair ... And you or your mate pull up towards the first pulley (above you). You pull in 1M of rope. Your bum goes up how far? (1/2M)

Oranges example is what you have in a normal 4x4 vehicle equipped with a winch and rope is passed through a remote snatch block and back to the vehicle. (Wind 1M of winch rope onto the drum and car moves forward 1/2m)

[vnx205]

You are sitting in the chair. Rope up and over a pully back to your hands. You pull 1M of rope. How much higher off the ground is your bum in the chair? (1M) Wrong

You are sitting in the chair. Same chair. Same rope. Your mate standing behind you pulls in 1M of rope. How much higher is your bum in the chair now off the ground? (1M) Right

(
Have you ever tried this? I can't believe how few people seem to have actually tried it. As a young teenager I used to regularly do it and the rope didn't pass through a pulley at the top. It just went over a wooden rafter. I had to overcome the friction of the rope passing over a square hardwood rafter and I could still manage it.

[vnx205]

In the diagram below, the total length of the rope (ignoring the little bit around the pulley) is 2 metres.

If the person in the chair pulls in 1 metre of rope as in the right hand part of the diagram, how long would X and Y be? So how much closer to the top pulley is the chair?

[tact]

Trying to work out why most people think you can't winch backwards with an electric winch mounted on the front bar.
That bottom roller on the fairlead is not there for looks.
I have winched out of a bog and other impassable places by running the winch cable under the vehicle and attaching it to a tree behind and pulled my self free with no problems (another reason I don't use synthetic rope).


On this I just gotta say, for the typical setup - that's evil! On so many levels! The purpose of the "bottom roller on the fairlead" (or any of the other rollers), in a typical front mounted winch setup, is most assuredly NOT for bearing high loads, nor for facilitating wire winch rope being deflected through large angles for loading! (180 degrees! Around a < 2" roller!)

Whilst it can work, can be done, please enlighten me on how you do that in a reasonable & safe, without inflicting damage to the wire rope?

Someone (was it you, Tank?) rightly wrote up how incorrectly sized snatch blocks can torture wire rope. Key points being decently sized pully diameter and right sized groove to support the wire rope properly.

How can the typical fairlead roller (less than 2" dia?, and not grooved at all) be anything but destructive to wire rope deflected more than just a few degrees!?

Got 12" diameter lower roller? Bottom edge gives line of sight clear pull underneath out to the rear? Maybe that's an order of magnitude less evil, but still is evil!

[Blknight.aus]

Watching wording indeed please. I never referred to "rigged to (dis)advantage" - the term with a specific technical meaning. Tried keeping all I wrote non-technical. Unless apples and oranges are in the riggers handbook too - then my apologies.

I wrote "no MA at all. disadvantage only." The disadvantage being frictional losses added to the load burden with no mechanical advantage to mitigate.

thats the point I was trying to get you to clear up.. whose doing the pulling, if the person in the chair isnt doing the pulling as well then you're correct, but if the person in the chair is doing the pulling then you're off the mark.


You are sitting in the chair. Rope up and over a pully back to your hands. You pull 1M of rope. How much higher off the ground is your bum in the chair? (1M)
no, you go up half a meter... 50cm of rope comes from the left side of the pully, 50cm of rope comes from the right side of the pully.


You are sitting in the chair. Same chair. Same rope. Your mate standing behind you pulls in 1M of rope. How much higher is your bum in the chair now off the ground? (1M)

(All "apples")

Now it's time for oranges. You in the same chair. Same rope up and over the same single pulley. Difference this time, you feed the rope around a pulley attached to your harness/chair ... And you or your mate pull up towards the first pulley (above you). You pull in 1M of rope. Your bum goes up how far? (1/2M)
33cms. assuming the rope starts at your chair, goes up to the top pully, back to a pully on the top of your chair, and then your mate lifts upwards, what you've constructed in this configuration is a 3:1 rigged to advantage.



Oranges example is what you have in a normal 4x4 vehicle equipped with a winch and rope is passed through a remote snatch block and back to the vehicle. (Wind 1M of winch rope onto the drum and car moves forward 1/2m)

how is this different to the situation in the chair above (i turned it blue)


Tank, all your experience and all you write is absolutely correct for situations you are writing about. Eg The bosuns chair self lift thing. Sit in harness at one end of the rope, round a single pulley, pull the other end. No MA at all. Disadvantage only.


which way does this work? as per your description I turned blue above or the way in your vehicle pulling itself on a snatch block? why does doing it vertically as a bosuns chair make it any different to doing it laid out on the ground




Everyone seems to love their tirfor winches.
I have a high lift jack and a jack-mate block to replace the base. With the addition of a few lengths of chain to my existing rigging, this can be used as a (slow) winching device.

What's peoples thoughts on this?

My reasoning for this route might be along the lines of the ability to lift vertically with the hi lift as well as horizontally. Electric winch is also available.

yep, I use the tirfor as an adjuster on anchoring gear and use chains, IF i carry the tirfor I carry 2 chains and a dog so that I can (in reality its usually just the extra chain and dog as I carry a drag chain anyway) use it as a winch/anchor tensioner as needed.



Now lets really set the cat in with the pidgeons...

whats the difference between 1:1 set to disadvantage, 1:1 set to advantage, 2:1 set to disadvantage and 2:1 set to advantage...

and I'll give you all a hint.... it all depends on which instruction I read....

I'll leave that there for a day and then give a wordy on how its all written up...

[tact]

Have you ever tried this? I can't believe how few people seem to have actually tried it. As a young teenager I used to regularly do it and the rope didn't pass through a pulley at the top. It just went over a wooden rafter. I had to overcome the friction of the rope passing over a square hardwood rafter and I could still manage it.

Fantastic! You try it again. Please.

Throw a rope over a beam. Tie nothing to either end. Pull a meter down on one side. The other side of the rope goes up how far? (1M)

Please physically try this. It's amazing.

Now - tie one end of the rope to yourself. Please. I insist. You must actually do this.

Now pull a meter down on the other end. You go up how far? (1m). Now pass the free end of the rope to your mate and ask him to pull in another meter. How much higher did you go up? (1m)

This is NOT the setup when a vehicle with a front mounted winch spools out wire rope which is run out to a snatch block and hooked back to the vehicle.

Proof : winch in a meter of wire rope. Vehicle moves 1/2 m

Let you figure out why. I have explained already.

[vnx205]

Fantastic! You try it again. Please. I have tried it. Have you?

Throw a rope over a beam. Tie nothing to either end. Pull a meter down on one side. The other side of the rope goes up how far? (1M)

Please physically try this. It's amazing. It isn't amazing. It is exactly what you would expect.

Now - tie one end of the rope to yourself. Please. I insist. You must actually do this. I have. Dozens of times.

Now pull a meter down on the other end. You go up how far? (1m).No. Now pass the free end of the rope to your mate and ask him to pull in another meter. How much higher did you go up? (1m)Yes

This is NOT the setup when a vehicle with a front mounted winch spools out wire rope which is run out to a snatch block and hooked back to the vehicle. Yes it is if you are the one on both ends of the rope.

Proof : winch in a meter of wire rope. Vehicle moves 1/2 m

Let you figure out why. I have explained already.
Have you looked at my diagram?

[tact]

Have you looked at my diagram?

Yes I looked. It shows a 1/2 meter pull.

If you pull in half a meter, the chair rises 1/2m .... (And yes there is a meter of rope below the chair.... But you didn't pull in a meter. You only pulled in half a meter, the other half meter of rope below the chair is because the chair moved up half a meter!)

Pull in half a meter, rise half a meter. 1:1

Pull in 1m and you rise 1m. (And amazingly there are 2m of rope below where the chair is now, but you only pulled in 1m!). Still 1:1

And it doesn't matter if it's you pulling yourself (intended) or your mate over there is doing the pulling... Pull 1m of rope down, chair goes up 1m. 1:1

Winch in a meter of rope when using a snatch block and hooking back to the vehicle. You move the vehicle 1/2 m. 2:1

[vnx205]

You started with the end of the rope in your hand. You pull enough rope down so that there is a metre of rope dangling below your hand. Yet you claim that you only pulled in half a metre? Surely a metre of rope passed through your hands.

[vnx205]

Yes I looked. It shows a 1/2 meter pull.

If you pull in half a meter, the chair rises 1/2m .... (And yes there is a meter of rope below the chair.... But you didn't pull in a meter. You only pulled in half a meter, the other half meter of rope below the chair is because the chair moved up half a meter!) You raised yourself half a metre by pulling in a metre of rope.

Pull in half a meter, rise half a meter. 1:1

Pull in 1m and you rise 1m. (And amazingly there are 2m of rope below where the chair is now, but you only pulled in 1m!). Still 1:1

And it doesn't matter if it's you pulling yourself (intended) or your mate over there is doing the pulling... Pull 1m of rope down, chair goes up 1m. 1:1It does matter. It gives quite a different result.

Winch in a meter of rope when using a snatch block and hooking back to the vehicle. You move the vehicle 1/2 m. 2:1

Have you actually tried to pull yourself up using this method? I have.

[NavyDiver]

I've pulled up a several tonne anchor with blocks and tackle on a ship. That's why I have an electric one:) Several hours of pain!

I do not have a hand one. When needed my mates have pulled from the electric bar mount under there trucks. :wasntme: Not such a great idea with wire but sounds feasible in an emergency.

With the low prices for good and often seldomly if ever used winches unless weight is an issue I suggest electric.

I do get to use mine a few times in the mountains but not at all often if MT tires are loaded. Not that I would like my MTs on for a long trip unless planning lots of mud or snow or very steep stuff.

[Tank]

To each his own, at least I understand what I'm doing is not 100% correct, BTW it is only 90 degrees not 180 degrees, this method has worked many times for me and have not had a problem, I'm aware of what is happening to the cable, but sometimes you need to compromise. What's the alternative, have 2 winches.
It is not an everyday occurrence and the winch cable has suffered no visible damage, unlike running it through a ****ty 4wd shop, one size fits all snatch block, bottom fairlead roller has no signs of damage either, horses for courses, Regards frank.









On this I just gotta say, for the typical setup - that's evil! On so many levels! The purpose of the "bottom roller on the fairlead" (or any of the other rollers), in a typical front mounted winch setup, is most assuredly NOT for bearing high loads, nor for facilitating wire winch rope being deflected through large angles for loading! (180 degrees! Around a < 2" roller!)

Whilst it can work, can be done, please enlighten me on how you do that in a reasonable & safe, without inflicting damage to the wire rope?

Someone (was it you, Tank?) rightly wrote up how incorrectly sized snatch blocks can torture wire rope. Key points being decently sized pully diameter and right sized groove to support the wire rope properly.

How can the typical fairlead roller (less than 2" dia?, and not grooved at all) be anything but destructive to wire rope deflected more than just a few degrees!?

Got 12" diameter lower roller? Bottom edge gives line of sight clear pull underneath out to the rear? Maybe that's an order of magnitude less evil, but still is evil!

[tact]

I've pulled up a several tonne anchor with blocks and tackle on a ship. That's why I have an electric one:) Several hours of pain!

I do not have a hand one. When needed my mates have pulled from the electric bar mount under there trucks. :wasntme: Not such a great idea with wire but sounds feasible in an emergency.

With the low prices for good and often seldomly if ever used winches unless weight is an issue I suggest electric.

I do get to use mine a few times in the mountains but not at all often if MT tires are loaded. Not that I would like my MTs on for a long trip unless planning lots of mud or snow or very steep stuff.

Completely agree that for simplicity & ease an electric winch looks good. The winch itself may not be so expensive but if you have to buy a winch bar as well as add on a decent installation it's not that cheap.

I had a winch on my hilux years ago and tackled a lot of hard HARD trails in the jungles. Sometimes solo. In 7yrs I used the winch to help myself out just once.

Maybe that means my definition of a HARD trail really means I am just not trying hard enough to get stuck properly. But to give example:
The Janda Baik trail is recognized by all Malaysian off-roaders in the know as a HARD trail. This is the trail that had me use my winch to save myself that one time in 7yrs.

One trip on that trail we started with my hilux, a long wheelbase LCII (troopy), a short wheelbase LCII, another long wheelbase LCII wagon, a jeep Cherokee, Nissan navara, and a Kia sorrento.

The jeep, Nissan, Kia all parked up after the first (easier) 1km. They jumped into the 4 Toyos. The next 6hrs we progressed 1.6km. Tough.

One section, maybe 100m long, took the short wheelbase LCII 45min and he had to break out his winch several times. (Seemed like every 10 meters!)

I was second vehicle. Cleared it in 38seconds. Still have the video of the "skippy run".
https://www.facebook.com/nwmclean/videos/10150150644042044/
(It was a little steeper than it looks in the video, and the slippery clay in the washouts isn't obvious...)

Not intending to fit a winch or bullbar to the defender I bought new 2yrs ago. Will be careful not to go solo at all. Have a decent recovery kit (straps, shackles, shovel, axe, pick etc) and will always travel in good (well equipped) company.

A lot of serious obstacles only need the first guy to have a front winch for safety. After that it's safer generally to use safety/tow straps to give the guy behind a tug if needed.

[Blknight.aus]

Fantastic! You try it again. Please.

Throw a rope over a beam. Tie nothing to either end. Pull a meter down on one side. The other side of the rope goes up how far? (1M)

Please physically try this. It's amazing.

Now - tie one end of the rope to yourself. Please. I insist. You must actually do this.

Now pull a meter down on the other end. You go up how far? (1m). Now pass the free end of the rope to your mate and ask him to pull in another meter. How much higher did you go up? (1m)

This is NOT the setup when a vehicle with a front mounted winch spools out wire rope which is run out to a snatch block and hooked back to the vehicle.

Proof : winch in a meter of wire rope. Vehicle moves 1/2 m

Let you figure out why. I have explained already.

yes and you contradicted yourself...

Ive just gone and done it, because yes, actually my life at this point in time is actually that boring and I have nothing better to do.

with my pully hanging from a tree tied a loop in the rope and lifted the loop about a meter, tied it off and knocked in a star picket as a height gauge. lowered the loop to the ground and knocked the star picket in to near enough 1m from the ground to the top.
went and stood next to the picket with the rope in my hand and using a pair of elastic bands and a meter long piece of string marked a meter on the rope. I pulled the rope down a meter. The chair was at the top of the picket (or near enough) so there we go, someone pulling the end of a rope through a single pully reeved 1:1 to disadvantage moves the other end of the rope 1m. Cool that works...

I stood in the loop.

I moved one of my elastic bands so it was at my eye height. I stepped out of the loop grabbed my bit of string from the first experiment and moved the second elastic band to 1m up the rope

I pulled the loop down and stepped in it again.
I put my belt on around me and the rope to help stop me from falling off.
I checked my first elastic band was at my eye height.
I pulled the rope until the second elastic band was at my eye height.
I noticed 4 things.
1. there was some weight being borne on my foot on the loop but it didnt feel like it was all of my weight
2. there was some weight being taken up by my arms, but it didnt feel nearly as much as if I was doing the flexed arm hang Im required to do for a fitness test at work.
3. It looked as tho the pully was getting closer to me but only at half the rate I was pulling on the rope.
4. The star picket was starting to **** me off because the top of it was banging into the soft part of my leg just under my knee cap.

I can only presume at this point that somehow, even though the pully is stationary it is now no longer rigged 1:1 to disadvantage it is rigged 1:1 to advantage. (ok, Im not presuming I know this for a fact, Im just pretending for the sake of the argument that Im trying to work this out for myself) and I'm thinking this because I only know 2 ways to use a single pully and a rope and thats either to advantage which the pretty picture in my rigging manual looks a bit exactly like the runner rig in this picture
from this website
https://www.aulro.com/afvb/images/imported/2015/10/794.jpg (http://www.globalsecurity.org/military/library/policy/army/fm/55-501/chap20.htm)
or its rigged to disadvantage which looks like the single whip configuration from the same page..

It is however the internet, people have been known in the past to be wrong on the internet and who knows, both my recovery mechanics pam and my rigging pam from the military and my rigging PDF and doggers PDF might also both be wrong so feasibly, this might not be right, I mean its not like its as accurate as say wikipedia or old lady May who lives next door so I thought Id better check it again.

https://www.aulro.com/afvb/images/imported/2015/10/795.jpg (http://www.hnsa.org/resources/manuals-documents/age-of-sail/textbook-of-seamanship/tackles/)

yep, same same.. so now Ive got 2 actual paper books, 2 pdfs and 2 websites showing me only 2 ways of rigging a single sheeve pully, and since for some reason I didnt go up a meter when I pulled the rope a meter while standing in the bight of the loop of the rope maybe I broke physics because the block didnt move and I didnt move up a meter but I moved a meter of rope past my eyes...

I then derigged all of this...

I took the rope and tied it to the top of the stairs banister rail.
I ran it though the pully and then took the other end up the stairs.
I called myself an idiot because I could have taken both ends of the rope up the stairs at the same time for either of 2 reasons. 1. the ropes long enough, I could have threaded it first and then taken both ends up together 2. its a snatch block I could have taken both ends of the rope up and then just opened the cheek plate to put it on the rope.
I lifted the rope until the pully just touched the ground. I grabbed my elastic band and string, marked the rope, pulled up a meter and tied it off. I swear, it looked like that pully only came up half the distance that I pulled that rope.

I measured the pully height.
40ish cms off the ground.
I turned the pully right side up.
50ish cms off the ground.

Its ok everyone relax, clumsy and oafish as I am, I didnt break physics, it still works exactly like it says in the pictures and in the interent and in the modern rigging manuals... If you rig up a single block from a rope hanging up high and then pull upwards, the pully only comes up half as much as the rope you pull up. Apparently if I wasnt so lazy I could also then use this to lift up either almost twice as much weight as I would normally be able to lift OR I could use a bit more than half as much effort to lift the same amount of weight as I would normally.. Id have to do it for twice the distance of rope tho...

now hang on...

I kind of remember that I had some weight on my leg and some on my arms when I was dangling from a tree and that for some reason the weight on my arms was less than when I do my static arm hang test, that missing weight must have been the weight in my leg.. so roughly that would mean that half my weight was on one side of the rope being taken up by my foot in the loop and the other half was in my arms then all of my weight must have been being taken by the pully up the top and the rope was simply balancing the tension out evenly...

I had another look at that picture from the historical navy site plate 32 and we have a look at fig 245 each end of the rope as a 1 on it and the P at the bottom has a 2 the number on one side of the rope added to the number on the other side of the rope is equal to the P number at the bottom of the weight. theres something fishy here... thats not how its written on the more modern page...

lets see here...
slide 32 fig 244 1=1, yeah i can see that whatever I put on one side of the rope happens on the other
slide 32 fig 245 1+1=2, yep got that. cool historic navy mathy type stuff still works.
single whip, P=W what no wait this isnt math any more its algebra... no fair, I have to take of my sarcasm hat a little to make room for some logicy thinky type hattery... ok so P=1 and W=1 so therefore 1=1 cool
runner P=1/2W so P=1/2x1 therefore p=.5 and therfore since P=W co... wait what i think I just broke maths thats not how the old navy did it surey i missed something obvious
Hmm
ahh
silly

in the runner there is 2 parts of rope supporting the pully and both have equal tension so 2x.5=1
ok relax i didnt break maths its just algebra versus simple addition...

so whats happening here? Im really confused (and if you believe that then mate, let me tell you about this bridge I can get you a deal on) when I stood on the ground and pulled the rope through the stationary pully the loop went up a meter. I mean thats simple but when I stood in the loop and pulled the rope it looked like for every meter of rope I pulled up the pully only came half as close to me... but the pully was tied to a tree it didnt move but the only way that works is like how it did when I had the rope in the pully tied off to the balcony and was pulling it up towards me it only looked like it came up half way too...

I mean in both cases the pully only looked to me like it came half a meter towards me for each meter I pulled in but when I had the pully in the tree the pully didnt move it just looked like it did and I had the top of a starpicket banging my knee because my feet were half a meter off

of the ground...

OF course, its relative... The pully looked like it was coming closer to me when it was up the tree because I was coming up off of the ground. and I was coming up off of the ground at half the rate I was pulling the rope Exactly the same as when I was pulling the pully up off of the ground, It came up at half the rate I was pulling the rope then too a single sheeve pully rigged to advantage will always relatively approach the pulling cable at one half of the rate that the cable is being heaved in at. The thing I hadnt worked out earlier was so easily explained by remembering one of the most annoying TV characters from my child hood and his pretty offsider before saying "upside down miss Jane, upside down." look at the single whip and look at the runner, now turn the page upside down.. you seeing what Im seeing... no?

ok Cut just the picture of the block and the ropes out of the picture (best print that first taking to your monitor with a knife and sissors wont do you much good) and then flip them around so that the same rigging through the block and the ropes can be switched between single whip and runner (that actually works if you use the simpler diagrams from fig 244 and 245) leaving the anchor, the load and the pulling indicators in their original positions


magic. Bet it looks and works the same as If I go and lay it down on the ground and tie it all off on the poles in the car port... Give me a minute (pause for dramatic effect here so people think Im out side doing something that I actually did about an hour ago while I had all the stuff out having planned this because after the stairs thing I realised Iwas too lazy to pack up unpack and pack up all this stuff again because someone is going to argue it doesnt or does work if you lay it all down have a coffee if you like, youre eyes could use the rest)

ok so.. IT works the same...

first I did the simple thing..

I tied the rope to the pole sat on the trolly and pulled a meter on the rope and the trolly moved a meter (made winching noises and all, old lady may is highly amused and thinks Ive gone nuts even offered me some of her medication)


http://www.trailersrless.com/images/single.jpg
If I tie the pully to the pole and the rope to the trolly and I stand beside it pull the rope a meter the trolly moves a meter ( in that poor little picture Im the winch the trollys the load

lets just use relativity and.. no, lets not.. I knew there was a reason I did this bit with the pully 3 ways...

lets pretend its the exact same situation but for some reason the load wont move and you dont have enough grip to resist the pull of the winch.

so I tied the rope to a pole ran it through the snatch block and pulled a meter and the trolly moved a meter happy with that if you pull 1 m of a rope through a pully and your not attached to both ends of the rope you move yourself or the load that far. makes sense, it looks like simple 1:1 pullys rigged to disadvantage and simple relativity as to which end of what is anchored or pulling.

now I tied the rope to the trolly, sat on it, grabbed the other end of the rope, made like a winch and pulled 1m of rope. only went half a meter...
thusly
https://www.aulro.com/afvb/images/imported/2015/10/796.jpg
all good so theres 4 ways to winch off the front of your vehicle using a single single sheeve snatch block.

1. direct pull without using the block. 1:1 (did I really need to put this here? maybe you keep the snatch block on the cable for some reason and its just dangling there incase you need it)
2. Direct pull using the block to redirect the rope to move a load. 1:1 rigged to disadvantage
3. direct pull using the block to redirect the rope to an anchor point and winch the vehicle 1:1 rigged to disadvantage (this actually gives your winch a break as you have more cable run out so its working on a lower layer)
4. Compound pull running the rope from the winch to the snatch block and back to another anchor point on the same vehicle. 1:1 rigged to advantage giving an MA of 2:1

so heres the simple bit..

if you can work out that going out to a snatch block and back to your vehicle gives you a 2:1 advantage and that for every meter you winch in your going to move forwards half a meter heres a simple idea to prove how hanging a pully from a tree (or a rafter) and sitting in a chair with a rope tied to it, going through it or standing in a loop of rope then pulling on the other while you're standing in the loop or sitting in the chair will only ever pull you up at half the speed that you take the line in at.

mark your winch cable every meter.
get a very tall very strong tree
get a very very tall ladder
have a tape measure handy
pay out all of your winch cable anchor one side to your recovery points and snap on your snatch block
put the snatch block way up in the tree and secure it tightly
power up the winch and let it winch in
as it winches itself up the tree antichrist style measure the movement relative to the ladder using your tape measure measure its progress for every meter of cable it winches in.
when its all done climb off the ladder, put everyting away, grab some old blue overalls, grow a beard (if you dont have one already) and say
aye i ia ia ia...

simple huh...

[Blknight.aus]

To each his own, at least I understand what I'm doing is not 100% correct, BTW it is only 90 degrees not 180 degrees, this method has worked many times for me and have not had a problem, I'm aware of what is happening to the cable, but sometimes you need to compromise. What's the alternative, have 2 winches.


https://www.aulro.com/afvb/images/imported/2016/02/886.jpg
nope, 3 snatch blocks

and a winch extension cable. and enough chain to let you position your blocks relative to your anchor points

and before you ask yes I do and yes, I have (Mostly just to prove you can safely and legitimetly winch backwards from the front) and a standard 30m usable winch cable using the above example rig with ideal anchoring points will permit about 5m of effective winching before the angles on the snatch blocks reduce the effective pull at he back to below .5MA go much futher and the MA drops off exponentially and you wind up with the winch stalling when the back angles hit around about 120-130 included angle on the rear recovery point. and thats just on grass using ground anchors.

[Tank]

Dave running a wire cable over 3 pulleys, all in different directions is the quickest way to destroy a wire cable you would cause more damage to a cable using those 3 pulleys than you would doing the "evil" thing of running the cable back under the car.
Would work of course, but you would need a lot of cable,
As the vehicle moves back you are creating a dangerous angle between anchor point 2 & 3, check out "Span Rope" tensions, can be lethal, using a single anchor point and pulley behind the vehicle would be safer and less damaging to the cable Regards Frank.










=Blknight.aus;2432659]https://www.aulro.com/afvb/images/imported/2016/02/886.jpg
nope, 3 snatch blocks

and a winch extension cable. and enough chain to let you position your blocks relative to your anchor points

and before you ask yes I do and yes, I have (Mostly just to prove you can safely and legitimetly winch backwards from the front) and a standard 30m usable winch cable using the above example rig with ideal anchoring points will permit about 5m of effective winching before the angles on the snatch blocks reduce the effective pull at he back to below .5MA go much futher and the MA drops off exponentially and you wind up with the winch stalling when the back angles hit around about 120-130 included angle on the rear recovery point. and thats just on grass using ground anchors.[/QUOTE]

[Blknight.aus]

Dave running a wire cable over 3 pulleys, all in different directions is the quickest way to destroy a wire cable you would cause more damage to a cable using those 3 pulleys than you would doing the "evil" thing of running the cable back under the car.
Would work of course, but you would need a lot of cable,
As the vehicle moves back you are creating a dangerous angle between anchor point 2 & 3, check out "Span Rope" tensions, can be lethal, using a single anchor point and pulley behind the vehicle would be safer and less damaging to the cable Regards Frank.



Sorry tank but maybe back in your day when cable was in its infancy and steel wire rope had only marginally more flex than a bar of steel anyway.

but I guess that given my statch blocks are all sized to suit my winch cable and all my snatch blocks are around the D20 mark in size and since the maximum permissable loading angle is 120 degrees and as I fairly clearly stated it pretty much self stops there from the winch stalling due to the increased loads and as my cables SWL is roughly 30% higher than my winches bottom row pull. And that I identified that you can winch back but only about 5m with a stock 30m winch cable that it cant be done without breaking my cable as compared to say running the cable over a dead flat roller, reversing the direction of the rope as soon as its coming off of the drum (assuming your winch like most is underwound). I think that given the option of setting that up, or doing what you'd do

I'll run three snatch blocks and not crush my cable into the bottom fairlead roller and having it do an immediate direction change off the fairlead roller or run the risk of rubbing the cable through things like diff housings

the other thing that I really like a lot more about using the multiple snatch blocks is this....

when the vehicle is bogged in water up to the door sills and mudded up to the chassis rails... I dont have to get anything more than my boots muddy to setup my method of recovery to make it winch backwards. But I digress

Its also not a span rope... they are static, and the setup and calculation of them require you to pretension the line and then increase it as you add load points to the rope. This is Dynamic and the maths is the other way around. You pull in on what you would call your "span rope" and you use it to move a load you do all of the math based on the maximum amount of pull the winch can provide, and then calculate out if you ever exceed the SWL of the rope (and unless mines damaged, I cant) on any of your pullys and anchor points and then you calculate how much pull you're going to generate to move your load.



Please go and get a more up to date set of documents.

and if you still want to insist that reversing a cables direction through a set of pullies is a problem you need to explain how anti twist rigging a 4:1 pully set works and why if it cant be done because it kills cables. and while your at it also explain why its an acceptable rigging method for fig 253. 254 traverse carriage dolly cranes, or using a leader pully to turn a disadvantage rig to advantage.

I will accept that there are specifications that identify what the minimum distance between changing the direction of the rope should be to prevent binding the cable. and that going inside these is not recomended because cable damage may result.

can you tell us what those specs are in a simple easy to express manner that a novice trying to rig something complicated can understand?

[simmo]

There's no reason to suppose the wire will be damaged by the snatch block provided the groove is a suitable profile for the wire, and the correct diameter relative to the wire diameter say, greater than 10:1, 15 or 16 to 1 is better.
A snatch block is kinder to our wires than the winch drum because the wire is usually better supported.

That sounds about right, my snatch block is about 150 mm, and the wire is about 9 mm. Given our winches don't do much work compared to industrial winches or cranes, (some working about 20 hours or more a day), the likely effect on their life or strength is not significant. But the down side is our wires don't have the big safety factor of industrial equipment. I think my 9000 lb winch wire has a breaking strain of about 15,000 lbs. some reading attached from the internet. cheers simmo

[Tank]

Dave, from the "Riggers Guide";
Reverse bends


Avoid reverse bends because they cause much greater fatigue than if all bends were made in the


one direction.


A rope running in one direction over one sheave and then in a reverse direction (ie ?S? fashion) over


another sheave will suffer early fatigue and deterioration. As the rope passes over a sheave it is bent, and


as it leaves the sheave it is straightened, two distinct actions causing fatigue. This is made worse if the


rope after being bent in one direction is then straightened, and again bent in an entirely opposite direction


over another sheave after which it is again straightened.























Sorry tank but maybe back in your day when cable was in its infancy and steel wire rope had only marginally more flex than a bar of steel anyway.

but I guess that given my statch blocks are all sized to suit my winch cable and all my snatch blocks are around the D20 mark in size and since the maximum permissable loading angle is 120 degrees and as I fairly clearly stated it pretty much self stops there from the winch stalling due to the increased loads and as my cables SWL is roughly 30% higher than my winches bottom row pull. And that I identified that you can winch back but only about 5m with a stock 30m winch cable that it cant be done without breaking my cable as compared to say running the cable over a dead flat roller, reversing the direction of the rope as soon as its coming off of the drum (assuming your winch like most is underwound). I think that given the option of setting that up, or doing what you'd do

I'll run three snatch blocks and not crush my cable into the bottom fairlead roller and having it do an immediate direction change off the fairlead roller or run the risk of rubbing the cable through things like diff housings

the other thing that I really like a lot more about using the multiple snatch blocks is this....

when the vehicle is bogged in water up to the door sills and mudded up to the chassis rails... I dont have to get anything more than my boots muddy to setup my method of recovery to make it winch backwards. But I digress

Its also not a span rope... they are static, and the setup and calculation of them require you to pretension the line and then increase it as you add load points to the rope. This is Dynamic and the maths is the other way around. You pull in on what you would call your "span rope" and you use it to move a load you do all of the math based on the maximum amount of pull the winch can provide, and then calculate out if you ever exceed the SWL of the rope (and unless mines damaged, I cant) on any of your pullys and anchor points and then you calculate how much pull you're going to generate to move your load.



Please go and get a more up to date set of documents.

and if you still want to insist that reversing a cables direction through a set of pullies is a problem you need to explain how anti twist rigging a 4:1 pully set works and why if it cant be done because it kills cables. and while your at it also explain why its an acceptable rigging method for fig 253. 254 traverse carriage dolly cranes, or using a leader pully to turn a disadvantage rig to advantage.

I will accept that there are specifications that identify what the minimum distance between changing the direction of the rope should be to prevent binding the cable. and that going inside these is not recomended because cable damage may result.

can you tell us what those specs are in a simple easy to express manner that a novice trying to rig something complicated can understand?

[Tank]

[QUOTE=Tank;2433156]Dave, from the "Riggers Guide";
Reverse bends


Avoid reverse bends because they cause much greater fatigue than if all bends were made in the


one direction.


A rope running in one direction over one sheave and then in a reverse direction (ie ?S? fashion) over


another sheave will suffer early fatigue and deterioration. As the rope passes over a sheave it is bent, and


as it leaves the sheave it is straightened, two distinct actions causing fatigue. This is made worse if the


rope after being bent in one direction is then straightened, and again bent in an entirely opposite direction


over another sheave after which it is again straightened.

[Fast Freddie]

I read this entire post very thoroughly up to about page #7.
Something more interesting may have happened in the last 3 of 4 pages, but it doesn't look like it at first glance.
Here's my summary, for what it's worth:

Dave is correct in every detail.
Everyone else except Frank understands pretty much what Dave is saying.

Frank's not exactly wrong, he's just been confused by what may have been a too literal, and perhaps a too rigid, understanding of the education he was offered 50 years ago.
To be fair, I got my education not long after he got his, and rigid and literal was pretty much how it was served up to me too.

[Tank]

I read this entire post very thoroughly up to about page #7.
Something more interesting may have happened in the last 3 of 4 pages, but it doesn't look like it at first glance.
Here's my summary, for what it's worth:

Dave is correct in every detail.
Everyone else except Frank understands pretty much what Dave is saying.

Frank's not exactly wrong, he's just been confused by what may have been a too literal, and perhaps a too rigid, understanding of the education he was offered 50 years ago.
To be fair, I got my education not long after he got his, and rigid and literal was pretty much how it was served up to me too.
So in the above post #94 Dave is CORRECT and the RIGGERS GUIDE is WRONG, guess everything I learned is all wrong, I should have consulted all the EXPERTS on this FORUM, Regards Frank.
Quote: Riggers Guide, "Avoid reverse bends because they cause much greater fatigue than if all bends were made in the one direction.
A rope running in one direction over one sheave and then in a reverse direction (ie ?S? fashion) over another sheave will suffer early fatigue and deterioration. As the rope passes over a sheave it is bent, and as it leaves the sheave it is straightened, two distinct actions causing fatigue. This is made worse if the rope after being bent in one direction is then straightened, and again bent in an entirely opposite direction over another sheave after which it is again straightened."

[Tank]

There's no reason to suppose the wire will be damaged by the snatch block provided the groove is a suitable profile for the wire, and the correct diameter relative to the wire diameter say, greater than 10:1, 15 or 16 to 1 is better.
A snatch block is kinder to our wires than the winch drum because the wire is usually better supported.

That sounds about right, my snatch block is about 150 mm, and the wire is about 9 mm. Given our winches don't do much work compared to industrial winches or cranes, (some working about 20 hours or more a day), the likely effect on their life or strength is not significant. But the down side is our wires don't have the big safety factor of industrial equipment. I think my 9000 lb winch wire has a breaking strain of about 15,000 lbs. some reading attached from the internet. cheers simmo
Did you read that pdf file esp. p.30 to p.34, maybe Dave and fast freddie should read it before putting their feet in their mouths, Regards Frank.

[Blknight.aus]

heya frank...

maybe you should look at whats actually happening.

tell you what, go setup your "rope under the vehicle" recovery and then grab some photos of the rope under tension as it goes off the drum, around the fairlead roller then as it rubs across the bottom of your barwork.

measure the effective radii of those "bends" and let me know how they compare to the minimum reccomended radii for SWR through a pully also check the width of the support flanges on those 2 points and compare it to your winch rope diameter for us.

then measure the relative deflection directions of the rope coming off the winch and then going over the failead roller unless youve got your winch incorrectly wound (or correctly wound but incorrectly mounted) and have it overwound and not underwound then you're doing a completely opposite direction bend with an effective distance between the 2 of just a few inches.

If you look at the included angles and direction of angle in the diagram I have 2 of the bends are the same direction and none of them run over an under diameter unsupported roller but all of them sit in the appropriate size pully. All of the pullies are placed at sufficient distance to negate the issue unless you were doing something silly like using older style rope thats prone to walking its lays.

Additionally, I dont even need to get into the rigging book to dispute your understanding of the facts in play here...

I try to avoid using a snatch block, especially if I can run out most of my cable to gain the same winch drum capacity as using a tree twice as close with a snatch block, does that compute, anyway. Snatch blocks are very hard on winch cables, as the cable travels over the pulley the wires on top are stretched and the wires closest to the bottom of the groove in the pulley are compressed.
This can cause kinking , esp. if it is against the lay (twist) of the rope and broken wires, all winch wire cable should be IWRC which has a wire core in the middle of the 6 outer strands of wire, it minimises crushing on the winch drum and wheel of the snatch block.
If snatch blocking is part of your life see if you can buy a decent snatch block, ideally for the 11mm cable that I use a 12" dia. snatch block wheel with the correct size groove for the wire cable used, too wide will break wires and cause kinks as it is not supported by the groove and allows flattening, too narrow pinches the cable and will break individual wires.


Running a cable or rope through a pulley one way then completely the opposite way through another pulley is the quickest way to destroy a cable/rope, so look for a decent snatch block, preferably 2 at a Rigging supply warehouse, not a 4WD shop where one size fits all, regards frank.

Which is all nice enough right up untill


Trying to work out why most people think you can't winch backwards with an electric winch mounted on the front bar.
That bottom roller on the fairlead is not there for looks.
I have winched out of a bog and other impassable places by running the winch cable under the vehicle and attaching it to a tree behind and pulled my self free with no problems

which reads like you're reccomending to do exactly what it is that makes you baulk at using snatch blocks in the first place.

or is there something magic about fairlead rollers that prevent the bit highlighted in blue from happening?

I guess now all thats left is to wait for the pics of your setup.

actually its not, heres an edit for ya tank...

its not that either of us are 100 correct in the way that we winch backwards off the front mounted winch.

its just that because I'm only

going against a single recommendation that says "avoid" by having one reversing bend in the setup

where as you are

doing the same thing (reversing bend between winch drum and fairlead) as well as
taking at least one bend (your fairlead roller) thats massively under the reccomended radius,
thats on a flat roller with no grooving to support the rope,
then taking another one over a static surface (the bottom of your barwork)
which is also not designed to support the rope

I'm doing a lot less wrong than you are.

or do you actually want me to go and read the 22yo riggers guide thats been quoted from by you previously and actually provide the book and verse on the extra 4 things you're doing wrong are wrong.

[Tank]

heya frank...

maybe you should look at whats actually happening.

tell you what, go setup your "rope under the vehicle" recovery and then grab some photos of the rope under tension as it goes off the drum, around the fairlead roller then as it rubs across the bottom of your barwork.

measure the effective radii of those "bends" and let me know how they compare to the minimum reccomended radii for SWR through a pully also check the width of the support flanges on those 2 points and compare it to your winch rope diameter for us.

then measure the relative deflection directions of the rope coming off the winch and then going over the failead roller unless youve got your winch incorrectly wound (or correctly wound but incorrectly mounted) and have it overwound and not underwound then you're doing a completely opposite direction bend with an effective distance between the 2 of just a few inches.

If you look at the included angles and direction of angle in the diagram I have 2 of the bends are the same direction and none of them run over an under diameter unsupported roller but all of them sit in the appropriate size pully. All of the pullies are placed at sufficient distance to negate the issue unless you were doing something silly like using older style rope thats prone to walking its lays.

Additionally, I dont even need to get into the rigging book to dispute your understanding of the facts in play here...

Which is all nice enough right up untill



which reads like you're reccomending to do exactly what it is that makes you baulk at using snatch blocks in the first place.

or is there something magic about fairlead rollers that prevent the bit highlighted in blue from happening?

I guess now all thats left is to wait for the pics of your setup.

actually its not, heres an edit for ya tank...

its not that either of us are 100 correct in the way that we winch backwards off the front mounted winch.

its just that because I'm only

going against a single recommendation that says "avoid" by having one reversing bend in the setup

where as you are

doing the same thing (reversing bend between winch drum and fairlead) as well as
taking at least one bend (your fairlead roller) thats massively under the reccomended radius,
thats on a flat roller with no grooving to support the rope,
then taking another one over a static surface (the bottom of your barwork)
which is also not designed to support the rope

I'm doing a lot less wrong than you are.

or do you actually want me to go and read the 22yo riggers guide thats been quoted from by you previously and actually provide the book and verse on the extra 4 things you're doing wrong are wrong.
Dave if you're in a pinch and there is no other way then do it for christs sake, I have done it 2 to 3 times in 30+ years for ****'s sake. Most times I only had to winch a couple of feet to get out of trouble, your idea of running over multiple snatch blocks one way then another is MORE damaging that running backwards over a roller.
Now it seems you are all experts when it comes to rigging and you consider what I say on the subject to be my idea of how it should be.
WRONG any statement I make re: rigging here is straight out of the Riggers handbook and if you wish to argue that you know more than the people that publish these books, well go and argue with them.
From now on when there is a query, you can put your years of experience and study together and solve all of the forum posters problems with your " he said that and I heard from someone that the world is flat experts, cause so and so said so" theories, just don't ask me, I don't give a ****, Regards Frank.

[PhilipA]

Boy has this thread got off topic,although it is interesting and AFAIR is a rerun of the same arguments about 10 years ago. Creates lots of passion but good to see good nature prevails.

I have had experience with Tirfors about 20 years ago when I was off-roading a VW type 3. Aside from the hard work, I found that the wire ropes frame for the winch took up lots of roomand weighed a lot .

About 20 years ago I bought a Warn 6000lb winch which came in a steel box with a receiver and fittings for 2 bow shackles, so it can be mounted on the tow bar or front recovery points with a cradle, or to the chassis for a sideways pull for that matter. Or you can fab up a receiver on the front as I had with my RRC.

You cannot buy that exact thing any more but you can buy cradles with receivers for winches up to 10,000lbs. If you welded a couple of mount points for shackles on, then you could use front or back. The warn also came with a kit of cable to reach the back bumper with an Anderson plug.

The winch fits neatly in the rear floor of the D2so is not exposed to the weather or UV on the synthetic rope, and can be removed when not needed. Downside is that it takes longer to set up.

It always confuses me a bit when people compare Tirfors to electric winches as Tirfors usually have quite a low capacity 2000kg? And you would have to use quite a few snatch blocks for a difficult recovery and still risk breaking shear pins.
I have been involved in several recoveries over the years but haven't had ever to use my winch to recover myself.LOL

The latest time I was recovered was on the ott when I got stuck towing my 1000kg camper trailer out of cannibal creek, and someone waiting at the top did a single line pull with his 9500lb, for what was a serious load of an RRC towing a 1 tonne camper with the drawbar in the mud.but it did it easily, although I did assist.
So single pull is most likely and often adequate anyway.

Regards Philip A


BTW some 11000lb winches are the same physically as 9500 lb but are lower geared. AFAIR Kingone are like this .

[Blknight.aus]

It always confuses me a bit when people compare Tirfors to electric winches as Tirfors usually have quite a low capacity 2000kg?
.

Ive got a 5000KG one, (and a 2t...) the largest one I've ever seen (thankfully never used it) was in the order of 15T.


Trying to work out why most people think you can't winch backwards with an electric winch mounted on the front bar.
That bottom roller on the fairlead is not there for looks.
I have winched out of a bog and other impassable places by running the winch cable under the vehicle and attaching it to a tree behind and pulled my self free with no problems (another reason I don't use synthetic rope).
If I believe I may get stuck in an upcoming bog or I might need to pull myself back up a really steep downhill slope, I run my (wire) cable under the Disco and hook it up to the tow bar, a bit hard to run a cable under a vehicle that's bogged to the chassis and if I get stuck I just run out to an anchor point and winch myself out.
I use this method to pull a vehicle up onto a car trailer hooked up to the back of my Disco, never had a problem with catching or damaging anything underneath, will not work with Dyneema type synthetic ropes, for obvious reasons.
Snatch blocks are useful if used correctly, most have no idea of how to use a snatch block to give a Mechanical Advantage (MA), a stationary snatch block anchored to a tree will actually add up to 20% more load because of the friction caused by the pulley wheel against it's axle.
The only advantage gained by anchoring the SB to a tree, etc. is that you need to run out twice the length cable/rope, i.e. from the vehicle to the tree (snatch block) and back to the vehicle.
By doing this you reduce the number of layers of cable/rope on the winch drum and as we all know (or should know) max. pulling power of a winch is generated with only 1 layer of cable/rope on the drum.
For instance when you look at the specs. of a winches pulling power a 10,000lb rated winch will only ever pull that load at the drum, by the time you fill the drum to capacity your pulling power has dropped to around half the rated advertised pull.
So to get a 2 to 1 MA from a winch you will need 2 snatch blocks 1 attached to the anchor tree, the other to the front of your 4WD, the formula for working out the MA of winch and snatch blocks is: the number of parts of rope supporting the MOVING block. which is attached to the front of the vehicle, the lead rope which is the part of the rope from the winch to the stationary SB is not a supporting rope.
If you want to take MA of SB's buy good quality correct diameter (bigger the better) SB's from a rigging supplier, not some 4WD shop one that has one size to suit all. Kinks and broken wires are mostly caused by wrong size SB's, hope this helps, Regards Frank.


Dave if you're in a pinch and there is no other way then do it for christs sake, I have done it 2 to 3 times in 30+ years for ****'s sake. Most times I only had to winch a couple of feet to get out of trouble, your idea of running over multiple snatch blocks one way then another is MORE damaging that running backwards over a roller.
Now it seems you are all experts when it comes to rigging and you consider what I say on the subject to be my idea of how it should be.
WRONG any statement I make re: rigging here is straight out of the Riggers handbook and if you wish to argue that you know more than the people that publish these books, well go and argue with them.
From now on when there is a query, you can put your years of experience and study together and solve all of the forum posters problems with your " he said that and I heard from someone that the world is flat experts, cause so and so said so" theories, just don't ask me, I don't give a ****, Regards Frank.

I actually cant tell if you're being serious, or taking the **** and stiring the pot. so lets try it another way...

hey frank, can you show us in the riggers book (include the link, chapter, page and if possible fig numbers) where it teaches how to run a rope over a fairlead roller and then over a bent steel plate, maybe even the edge of one of those plates and then how to calculate the SWL, MA and the expected life of the rope. Also which particular build of rope it recommends for doing this?

oh also, try getting a more modern rigging book. If you're being serious I bet one of the pictures in one of the many from early this decade for calculating anchorage values is going to make your head go wibbely.

[Tank]

Ive got a 5000KG one, (and a 2t...) the largest one I've ever seen (thankfully never used it) was in the order of 15T.





I actually cant tell if you're being serious, or taking the **** and stiring the pot. so lets try it another way...

hey frank, can you show us in the riggers book (include the link, chapter, page and if possible fig numbers) where it teaches how to run a rope over a fairlead roller and then over a bent steel plate, maybe even the edge of one of those plates and then how to calculate the SWL, MA and the expected life of the rope. Also which particular build of rope it recommends for doing this?

oh also, try getting a more modern rigging book. If you're being serious I bet one of the pictures in one of the many from early this decade for calculating anchorage values is going to make your head go wibbely.
Dave, I guess you don't know it, but the laws of physics haven't changed since JC played fullback for Israel.
You have NO idea of what you're talking about and YOU are having a shot at me for quoting the Facts from the Latest OH&S Riggers Guide.
Don't blame me because you are to lazy to check the facts for yourself, you pick on the fact that I ran a cable under my Disco to get myself out of trouble a few times.
Yet how many on this forum, including you think that having a recovery point under the front of your vehicle is the way to go. Any idiot can see that the rope or cable is in danger of the bottom of the bullbar is likely to crush the rope/cable when the front end drops into a hole or comes up against sheer rock. Not to mention that you all think it is OK to pull a shackle sideways when it is fitted to one of these ridiculous recovery points
with the shackle pin hole orientated in the horizontal plane.
Your ridiculous setup with all those snatch blocks which will stuff a cable real quick to pull a vehicle backwards is a joke, yet you have a shot at me for suggesting a last resort and not the right thing to do by running a cable underneath my vehicle, Don't like, Don't do it. Before you go shooting your mouth off making out your the know it all guru, check that you're not living in a Glass House, OH, and yes I could show you where in the riggers book, as I have on NUMEROUS occasions, which you have totally ignored as Above in this post. Maybe Dave you can show us in "Daves Riggers Guide" where you get your so called facts from, can I get it down at the local library, like the Riggers Guide, last word on this Dave, Regards Frank.

[Blknight.aus]

Yet how many on this forum, including you think that having a recovery point under the front of your vehicle is the way to go. Any idiot can see that the rope or cable is in danger of the bottom of the bullbar is likely to crush the rope/cable when the front end drops into a hole or comes up against sheer rock.

Really?

explain



If I believe I may get stuck in an upcoming bog or I might need to pull myself back up a really steep downhill slope, I run my (wire) cable under the Disco and hook it up to the tow bar




given that the only riggers book listed in this thread is from 1995 and you've quoted it every time... I kinda suspect you ought to prove your references, preferably with something from say, this century. Id hate to think that I wasnt playing the game on your playing field.

https://www.aulro.com/afvb/images/imported/2016/01/180.jpg
https://www.aulro.com/afvb/images/imported/2016/01/181.jpg

https://www.flickr.com/photos/skumroffe/6952813630

https://www.aulro.com/afvb/images/imported/2016/01/182.jpg
https://www.aulro.com/afvb/images/imported/2016/01/183.jpg
https://www.aulro.com/afvb/images/imported/2016/01/184.jpg
Dunno, but I reckon the guys who design the cranes that use the "tank says dont change direction over sheeves it'll root the cable" method of reeving,are probably a hell of a lot more knowledgable than you and probably have more recent set of docs as well. Kinda reckon I'm going to trust them a hell of a lot more than your circa 1960 learning and the 1995 edition of the rigging book.



Probably doesnt help your case all that much when one of the original patents for the container handling crane layout date back to 1962 and theres a link to one thats as far back as 1926 (https://www.google.com/patents/US3207329)

[AndyG]

My 1.6 tonne tirfor has a 11mm cable, but is rated to a standard, somebody?
My electric 9500 lb/ 4300 kg winch, 10 mm from memory, is rated by a marketing dept and not to any standard I can find.

[Blknight.aus]

the SWR should be compliant to AS 2759 or 3569 or and have a tag to reflect that its been tested.

The winch cable should be the same but if you read the fine print you're likely to find that there'll be a disclaimer that provides the winch is marketed on that, not the strength of its cable.

If you know the construction of the rope its possible to work out its theoretical strength by measuring its thickness grabbing the look up chart to suit and doing some math.


the rough and ready formula is.... 8*(inch fraction*inch fraction)=WLL(t)

which means...

if your rope is half inch accross (measured so its widest) the formula becomes

8*(1/2*1/2)=8*(.25)=2

[Tank]

My 1.6 tonne tirfor has a 11mm cable, but is rated to a standard, somebody?
My electric 9500 lb/ 4300 kg winch, 10 mm from memory, is rated by a marketing dept and not to any standard I can find.
Quick way to calculate SWL of a cable on a winch is Dia.x Dia. x10 and if it is (as it should be ) 7 Strand wire rope add 12% for the 7th. centre strand.
The winch manufacturer calculates the pulling power of the winch with only 1 layer of rope/cable one the drum, by the time you have wound on 30 metres of rope/cable onto the drum the manufacturers rating will have dropped to near half of the rating at the drum. A 10mm dia. 7 strand wire cable will have a SWL of around 1120kgs., so remember a winch is no stronger than the rope/cable it is fitted with, Regards Frank.

[bob10]

This bloke seems to have winching backwards worked out.

https://youtu.be/_4tI3HtgdCY

[bob10]

This, perhaps is a better example, and better explanation. You need to enhance the sound.

https://youtu.be/P0j_9mRB5g8

[Tank]

This bloke seems to have winching backwards worked out.

https://youtu.be/_4tI3HtgdCY
Bob the bloke with the jeep got it right, except he said he used a Snatch Strap for a tree protector. bad blue, otherwise good.
The bloke with the Toyota was wrong, he claimed that the first block attached to the tree in front gave him a MA of 2, WRONG. If that was the case the next block (2nd.) in the line would have also given him a MA of 2, which it didn't, it merely changed direction of the rope.
But the angle that the 2nd. block was set at had an angle of the rope at over 90 degrees, doubling the load on the rope and the tree protector.
The 3rd. block attached to the tree was also redirecting the rope/pull and had NO MA,
the 4th block attached to the Toyota (which was overkill) is the only moving block and as it was Supported by 2 parts of rope it has a MA of 2.
The simplest way requires 2 snatch blocks (Sb), one SB in front, cable (only) through and back under your car or beside, whichever is the most convenient to a SB attached to a tree behind your vehicle and then attached to the back of your vehicle.
In the video with the Toyota the angle of the rope between the 1st. and 2nd. block and onto the third block was excessive and puts undue strain on ropes/cables/SB and tree protectors.
I seen the result of a person using a Snatch Strap(SS) as a tree protector/SB anchor rope. He had to wrap it a number of times around the tree with layers overlapping one another.
After some really tough winching the SS had stretched so tight tat it had melted itself together into one messy lump, one more good pull and it would have failed and god knows where that SB would've ended up. Don't ever use a SS as part of rigging up a Winch recovery, ever, and just for Dave, even easier is to run your cable down over the bottom fairlead roller and underneath the car and hook up to an anchor point and drag backwards, not recommended or approved but it works when you're in a pinch and bereft of 2000m of rope/cable and half a dozen SB's, Regards Frank.

[bob10]

Yeah, I thought the snatch strap was a bad idea, but for the reason it would be springy, and not give you a solid pull. But, if I was stuck on my own, I would use what I had. I'd even wrap a chain around a tree, if that was all I had. You do what you have to do.

[Disco-tastic]

Haha i loved it when i saw this thread was still going. Thanks for the videos bob, id never seen that before - hopefully I'll never need it!


The 3rd. block attached to the tree was also redirecting the rope/pull and had NO MA,
the 4th block attached to the Toyota (which was overkill) is the only moving block and as it was Supported by 2 parts of rope it has a MA of 2.


Heya frank,

As you say, that 4th block was the one giving the mechanical advantage, and hence allowed the car to be pulled backwards. Im not sure what you mean when you say it was overkill? Without it the truck wouldnt have moved. Can you please clarify? (Not having a go, just wanting to know what you mean).

Cheers

Dan

[Blknight.aus]

This bloke seems to have winching backwards worked out.

https://youtu.be/_4tI3HtgdCY


This, perhaps is a better example, and better explanation. You need to enhance the sound.

https://youtu.be/P0j_9mRB5g8

Hey, I see what they did there....


https://www.aulro.com/afvb/images/imported/2016/02/886.jpg
nope, 3 snatch blocks




Bob the bloke with the jeep got it right, except he said he used a Snatch Strap for a tree protector. bad blue, otherwise good.
The bloke with the Toyota was wrong, he claimed that the first block attached to the tree in front gave him a MA of 2, WRONG. If that was the case the next block (2nd.) in the line would have also given him a MA of 2, which it didn't, it merely changed direction of the rope.
But the angle that the 2nd. block was set at had an angle of the rope at over 90 degrees, doubling the load on the rope and the tree protector.
The 3rd. block attached to the tree was also redirecting the rope/pull and had NO MA,
the 4th block attached to the Toyota (which was overkill) is the only moving block and as it was Supported by 2 parts of rope it has a MA of 2.
The simplest way requires 2 snatch blocks (Sb), one SB in front, cable (only) through and back under your car or beside, whichever is the most convenient to a SB attached to a tree behind your vehicle and then attached to the back of your vehicle.
In the video with the Toyota the angle of the rope between the 1st. and 2nd. block and onto the third block was excessive and puts undue strain on ropes/cables/SB and tree protectors.
I seen the result of a person using a Snatch Strap(SS) as a tree protector/SB anchor rope. He had to wrap it a number of times around the tree with layers overlapping one another.
After some really tough winching the SS had stretched so tight tat it had melted itself together into one messy lump, one more good pull and it would have failed and god knows where that SB would've ended up. Don't ever use a SS as part of rigging up a Winch recovery, ever, and just for Dave, even easier is to run your cable down over the bottom fairlead roller and underneath the car and hook up to an anchor point and drag backwards, not recommended or approved but it works when you're in a pinch and bereft of 2000m of rope/cable and half a dozen SB's, Regards Frank.


Just to be really picky, in the video of the toyota, counting from the winch its the second pully that is the redundant one its the only one providing a non essential redirection that makes the whole system work. I dont have a top down layout of exactly how it was done but I can easily envision it being done to get the rope clear of the side of the vehicle.

Also agree with the snatch strap round trees thing and if you do have to do it you very carefully lay the strap on the tree so it doesnt cross over itself and if you can you dont just wind the strap around the tree but you pass it through shackles so each "turn" around the tree helps support the load.

[Tank]

Haha i loved it when i saw this thread was still going. Thanks for the videos bob, id never seen that before - hopefully I'll never need it!



Heya frank,

As you say, that 4th block was the one giving the mechanical advantage, and hence allowed the car to be pulled backwards. Im not sure what you mean when you say it was overkill? Without it the truck wouldnt have moved. Can you please clarify? (Not having a go, just wanting to know what you mean).

Cheers

Dan
What I mean by overkill was that he could have just hooked directly to the rear of the toyota, for the demo, unless he was bogged to the chassis there is no need for the last block, who carries all that gear, maybe if you are with a bunch of people who you could borrow a couple of blocks off, but if you're on your own you're not likely to have several snatch blocks.
Bob10 the only reason I don't use a chain around a tree is the damage it will do, but in an emergency, use what you got, except a snatch strap, Regards Frank.

[Blknight.aus]

What I mean by overkill was that he could have just hooked directly to the rear of the toyota, for the demo, unless he was bogged to the chassis there is no need for the last block,

You're taking the mick right.

if your not.. when you flip your rigging ticket over does it have some fancy fonted text on it that says something like coco pops, cornflakes, wheat bix or kellogs?

without the final block on the back of the vehicle providing at least a 2:1 the system cant work. you'd just wind up stretching the vehicle, stalling the winch or snapping something.

[austastar]

Hi

https://www.aulro.com/afvb/images/imported/2016/02/868.jpg

Cheers

[vnx205]

I just thought of another way to try to explain why a single snatch block attached to a tree can give a MA of 2.

I think we all accept the calculations associated with this diagram if we ignore frictional losses for the sake of simplicity.
https://www.aulro.com/afvb/images/imported/2016/02/863.jpg
I believe that we all also accept that the mounts for that green pulley have a load of 20 kg.

I think everyone accepts this one too.
https://www.aulro.com/afvb/images/imported/2016/02/864.jpg

Now for the fun part! Does anyone dispute the calculations in this diagram?
https://www.aulro.com/afvb/images/imported/2016/02/865.jpg

How about now? Still accept the calculations?
http://www.aulro.com/afvb/attachment.php?attachmentid=105223&d=1454472257

How about now? Still happy with the calculations?
http://www.aulro.com/afvb/attachment.php?attachmentid=105224&d=1454472669

Still accept the calculations?
http://www.aulro.com/afvb/attachment.php?attachmentid=105225&d=1454474276

I could add a couple more pictures, but you can probably see where all this is heading. The top pulley is now effectively the winch drum and the 5 kg force in red is being applied by the drum on the winch. Since the drum is round, surely that 5 kg force applies regardless of the angle at which I rotate the arrow.

So if you aren't happy with all the calculations, why not? Feel free to add 10% or 20% for friction, but it is still roughly a MA of 2.

I know others have tried to explain the situation in similar terms before, but I thought the series of pictures might make things clearer. :)

There is another way of looking at it that I don't think has been mentioned. MA is usually calculated by counting the number of ropes supporting the moving pulley and as far as I know, everyone accept that.

I read an article recently that said that the MA was equal to the number of ropes that are getting shorter. Can anyone show a situation where that description is not correct? If people are prepared to accept that it is always true that the MA is the same as the number of ropes getting shorter, then that might be an easy way to explain why a single snatch block on a tree would give a MA of 2 if the end of the cable is attached to the same vehicle as the winch.

[Safari]

Hi all, I could be very confused with all this technical talk so to save some confusion I can give a simple example. I own 3 winches, 2 tirfors and a warn. I have used the tirfors for over 30 years. I have 2 different sizes a small one and a bigger one. (750kg & 1.5 I think ) The small one is a lot easier to lug around. When pulling tree stumps out if the little one gets too hard I put a snatch block on the the stump and return the other end of the cable back to the anchor point. Guess what the effort required on the handle is halved (approx) but it is slower to move the item. I may add that in over 30 years the tirfors get used more than the warn as they are used for moving other items around, power poles, lifting motors, steel beams, etc flying foxes etc. So to answer the initial question I would buy a tirfor first unless I was really old or was going looking for trouble regularly. Cheers Rob

[Tank]

Hi all, I could be very confused with all this technical talk so to save some confusion I can give a simple example. I own 3 winches, 2 tirfors and a warn. I have used the tirfors for over 30 years. I have 2 different sizes a small one and a bigger one. (750kg & 1.5 I think ) The small one is a lot easier to lug around. When pulling tree stumps out if the little one gets too hard I put a snatch block on the the stump and return the other end of the cable back to the anchor point. Guess what the effort required on the handle is halved (approx) but it is slower to move the item. I may add that in over 30 years the tirfors get used more than the warn as they are used for moving other items around, power poles, lifting motors, steel beams, etc flying foxes etc. So to answer the initial question I would buy a tirfor first unless I was really old or was going looking for trouble regularly. Cheers Rob
This is how this argument/discussion over MA came about, I posted in another thread about using a snatch block attached to the load (or stump) with a Tirfor with the cable hooked back to the anchor point to get a MA of 2, i.e. 2 parts of rope SUPPORTING the MOVING block.
This said post was in another forum of a popular (don't know why) 4WD magazine and the flat earthers denounced me and I even had death threats, so I was out of there, much better treatment on this Forum, Thanks, Regards Frank.