portable electric winches

[Stuart02]

There seem to be quite a few reasonably priced 5000lb portable electric marine winches, and I'm wondering whether one with some synthetic rope and a snatch block could be handy for swapping between the work ute to the D4.
I think the weight would be similar or less than a Tirfor?

[Tank]

Unless you anchor the portable winch to a tree (anchor point) you will need at least 2 snatch blocks, Regards Frank.

[Stuart02]

Unless you anchor the portable winch to a tree (anchor point) you will need at least 2 snatch blocks, Regards Frank.

Sorry to be the novice I am and ask the obvious question Frank, but (and this may go for hand winches too), why can't you hook the winch to the car's recovery point? Thanks

[Tank]

No problem, but if you want to get a mechanical advantage (MA) of 2 then you need the snatch block attached to the vehicle and the winch anchored to a tree or anchor point. MA is calculated by the number of ropes supporting the MOVING block (snatch), so with the snatch block connected to the vehicle you are gaining a mechanical advantage. There is no MA the other way round, works good for tirfors as well, if you wish I can PM you the riggers guide, regards Frank.

[DT-P38]

I wouldn't mind a copy of that riggers guide Frank!

On the subject, I reckon its only a matter of time before portable winches get strong enough and light enough to add to a recovery kit and not cart around on the vehicle 24/7.

[Judo]

I wouldn't mind a copy of that riggers guide Frank!

On the subject, I reckon its only a matter of time before portable winches get strong enough and light enough to add to a recovery kit and not cart around on the vehicle 24/7.

x2 on both points!!

[RR P38]

No problem, but if you want to get a mechanical advantage (MA) of 2 then you need the snatch block attached to the vehicle and the winch anchored to a tree or anchor point. MA is calculated by the number of ropes supporting the MOVING block (snatch), so with the snatch block connected to the vehicle you are gaining a mechanical advantage. There is no MA the other way round, works good for tirfors as well, if you wish I can PM you the riggers guide, regards Frank.

Correction here.
If you put the snatch block on a tree and run your winch wire off and through the snatch block and back to the recovery point on your vehicle you gain a 2 x reduction. ie if you have a 5000lb winch in theory you have 10000lb pulling power.

[Didge]

:) From my readings it doesn't seem to matter where the pulleys are attached as long as the configuration is correct

[Stuart02]

No problem, but if you want to get a mechanical advantage (MA) of 2 then you need the snatch block attached to the vehicle and the winch anchored to a tree or anchor point. MA is calculated by the number of ropes supporting the MOVING block (snatch), so with the snatch block connected to the vehicle you are gaining a mechanical advantage. There is no MA the other way round, works good for tirfors as well, if you wish I can PM you the riggers guide, regards Frank.

Thanks Frank, I think I saw a link to the guide in another thread?

[Stuart02]

I wouldn't mind a copy of that riggers guide Frank!

On the subject, I reckon its only a matter of time before portable winches get strong enough and light enough to add to a recovery kit and not cart around on the vehicle 24/7.

These 5000lb marine winches weigh less than 20kg, apparently... It would be great.

[Tank]

Sorry double post, Regards Frank.

[Tank]

Correction here.
If you put the snatch block on a tree and run your winch wire off and through the snatch block and back to the recovery point on your vehicle you gain a 2 x reduction. ie if you have a 5000lb winch in theory you have 10000lb pulling power.
See you live in Balmain, I was born and bred in Balmain, still have a soft spot for tiger territory.
Now by what law of physics do you double energy by using a snatch block in the way you describe.
FYI to gain a Mechanical Advantage (MA) using a single sheave block you have to first be pulling to "Advantage", i.e. pulling in the same direction that the load is moving.
Second the single sheave block must be moving with the load.
The formula for working out the MA achieved using single/multiple sheave blocks is quite simple, MA= number of parts of rope SUPPORTING the MOVING BLOCK.
If your statement Quote: " Correction here.
If you put the snatch block on a tree and run your winch wire off and through the snatch block and back to the recovery point on your vehicle you gain a 2 x reduction. ie if you have a 5000lb winch in theory you have 10000lb pulling power."
is correct then if you sat your arse on the ground, tied one end of a rope around your waist (you representing the towed vehicle). Then ran the rope to a snatch block anchored to a tree (anchor point) and back down to your hands(representing the winch) and you weighed 100kilos. then you are saying that you would only require 50kilos of pulling power from your arms (winch) to drag your arse along the ground.
How does that compute, regards Frank.

[Chops]

These 5000lb marine winches weigh less than 20kg, apparently... It would be great.

I just fitted a TJM 9500 to my car last week, I'm not sure how much it weighs, but I reckon it's light enough to build a cradle for it and have it very portable,, you could make it so it fits either end of the car, or attatched it to a tree for use as well,

Chops

[steveG]

See you live in Balmain, I was born and bred in Balmain, still have a soft spot for tiger territory.
Now by what law of physics do you double energy by using a snatch block in the way you describe.
FYI to gain a Mechanical Advantage (MA) using a single sheave block you have to first be pulling to "Advantage", i.e. pulling in the same direction that the load is moving.
Second the single sheave block must be moving with the load.
The formula for working out the MA achieved using single/multiple sheave blocks is quite simple, MA= number of parts of rope SUPPORTING the MOVING BLOCK.
If your statement Quote: " Correction here.
If you put the snatch block on a tree and run your winch wire off and through the snatch block and back to the recovery point on your vehicle you gain a 2 x reduction. ie if you have a 5000lb winch in theory you have 10000lb pulling power."
is correct then if you sat your arse on the ground, tied one end of a rope around your waist (you representing the towed vehicle). Then ran the rope to a snatch block anchored to a tree (anchor point) and back down to your hands(representing the winch) and you weighed 100kilos. then you are saying that you would only require 50kilos of pulling power from your arms (winch) to drag your arse along the ground.
How does that compute, regards Frank.

It seems to compute simply to me..
there are 3 forces:
Rope A - between vehicle and pulley
Rope B - between winch and pulley
Rope C - between pulley and anchor

By simple physics the forces must balance. A and B both have force of 50kg on them, so C must have 100kg to balance.

Steve

Steve

[Tank]

It seems to compute simply to me..
there are 3 forces:
Rope A - between vehicle and pulley
Rope B - between winch and pulley
Rope C - between pulley and anchor

By simple physics the forces must balance. A and B both have force of 50kg on them, so C must have 100kg to balance.

Steve

Steve Steve somewhere on the forum there is an OH&S guide for riggers, go to P.30 and read all about it, then get hold of the writers and tell them they are wrong, or if you wish send me your email address and I will email it to you, Frank.Stanton@bigpond.com Regards Frank.

[RR P38]

It seems to compute simply to me..
there are 3 forces:
Rope A - between vehicle and pulley
Rope B - between winch and pulley
Rope C - between pulley and anchor

By simple physics the forces must balance. A and B both have force of 50kg on them, so C must have 100kg to balance.

Steve

Steve

The winch is still only seeing half the load was the point i was trying to make.
Half of the load is being supported by the tree and the other half is the vehicle.
So a 5000lb winch single line pull is 5000lbs
Double the parts (line) and it can pull 10000lbs

Sorry my mistake i should have made it more clear YES you need 2 snatch blocks, one on the recovery point on your vehicle and one on the tree.

Balmain aint what it used to be.

[Tank]

Yeh, the coffee latte set have taken over, I wish I still owned my old house though, the garage and back yard was subdivided and sold for $1mill., the front half would be worth $2mill. by now, right on the water, sigh, Regards Frank.

[goingbush]

I don't get it either, I know Frank would be right and even after watching the first part of this Video which explains it for the simpleton (me)

In my head I still think If I reel my winch cable out to a tree thru a snatch block and back to the car then the winch has to reel in twice the cable so it takes twice as long to get to the tree, isn't it going to be easier on the winch and the rope, Even if the MA =1 ???

or am I just wearing the winch out by making it go twice the distance

what am I missing ??

Mechanical Advantage (part 3) - YouTube

funny how the guy is talking about pulleys but he dosent know what an actual pulley is called so he refers to it as a disk :)

[Tank]

I don't get it either, I know Frank would be right and even after watching the first part of this Video which explains it for the simpleton (me)

In my head I still think If I reel my winch cable out to a tree thru a snatch block and back to the car then the winch has to reel in twice the cable so it takes twice as long to get to the tree, isn't it going to be easier on the winch and the rope, Even if the MA =1 ???

or am I just wearing the winch out by making it go twice the distance

what am I missing ??

Mechanical Advantage (part 3) - YouTube (http://www.youtube.com/watch?v=vSsK7Rfa3yA&feature=relmfu)

funny how the guy is talking about pulleys but he dosent know what an actual pulley is called so he refers to it as a disk :)
Goingbush, the simple formula is that if the block (snatch) is moving with the load then the MA = the number of parts of rope supporting the moving block, in the video drawings above where he went round the world to work out the MA the number of parts of ropes supporting the moving block was 2 therefore the MA is 2. In the first scenario the MA is one, because the block is doing no work, other than changing the direction of pull. The only advantage is that as you are retrieving twice as much rope it takes twice as long and you have less layers of rope on the winch drum, if you are using one, but you are pulling in the opposite direction that you want the load to move so you are pulling to disadvantage.
A simple way to remember, is that if the block is moving with the load it is doing work, how much is governed by the number of parts of rope supporting that moving block.
In rigging you would normally use multi sheaved blocks that have more than one pulley wheel, just look at large cranes with many parts of rope supporting the moving block.
In theory you could move a load weighing 100's of tonnes with a bit of string, if you had enough multi sheave blocks. But that theory in real life is not possible because of up 20% friction on each pulley wheel so the more pulley wheels the more friction.
For instance if you attatched a single sheave block (snatch block) from a beam in your garage and put a piece of rope say 3 metres long through the pulley and tied a bucket full of sand to each end and each bucket weighed 10kgs, they would balance out equally and support each other. Therefore you have 10kgs on each part of rope, to move one bucket up you would need to apply pressure of around 2kgs to overcome the friction generated (up to 20% of load) in the pulley bearing/shaft.
That means to lift 10kgs through a fixed single pulley you need to apply 12kgs to the opposite side, which means that the rope holding the pulley to the roof beam 10+10+2=22kgs, it is important that the rope holding the snatch block can support the weight which is double the original load, in this case no net gain and no mechanical advantage so it is MA=1, hope this helps, Regards Frank.

[steveG]

Your example of lifting a weight from a single pulley on a beam is a different scenario than a winch on a vehicle with the line anchor point attached to the same vehicle (which effectively is pulling in the direction of travel).

If you took the winch off the vehicle and anchored it to a tree - then you would have the same scenario as your beam lift. But that's not the case.
The winch on the front of the vehicle IS pulling to advantage - if you stopped the snatch block pulley from rotating the winch would pull the vehicle forwards.
With the pulley free, the tension from the winch is felt on the vehicle via the fixed end of the line - the same as it would if the winch was attached to another anchor point (not the vehicle).
So there are 2 forces pulling the vehicle forward. The winch pull, and the pull from the line coming back from the block.

Is that not correct?

Steve

[goingbush]

Thanks Frank

That explains it much better. So in effect the only advantage I gained by using a snatch block on the tree was the fact that the drum diameter was smaller , but that advantage was probably negated by the 20% friction from the snatch block.

So for the purposes of self recovery, using the vehicles winch, a Snatch block is a waste of time, Carrying two would be pretty useless too because of my 30m of rope I'd only end up with 10m (less a full single layer needed on the drum -synthetic rope)

But a snatch block is useful for winching another vehicle, Or If I was using my Tirfor attached to a tree & snatch block on the car.

Got it.

thanks ..Don

[isuzutoo-eh]

Frank is correct if the hook end of the winch rope was anchored to a non-moving object such as another tree. The snatch block would merely be redirecting the rope.

If the hook end of the winch rope is attached to the vehicle (load), then a mechanical of 2 is obtained. This is because both sections of rope are doing effort. This is what SteveG and RR P38 are saying. The snatch block does not have to be moving, as it doesn't care if it is attached to the fixed or moving anchor.

As with everything, you can't gain something without losing something else. In this case we lose out in the velocity ratio of ½, meaning the load only moves ½ the distance the effort does.

[goingbush]

Frank is correct if the hook end of the winch rope was anchored to a non-moving object such as another tree. The snatch block would merely be redirecting the rope.

If the hook end of the winch rope is attached to the vehicle (load), then a mechanical of 2 is obtained. This is because both sections of rope are doing effort. This is what SteveG and RR P38 are saying.
With this set up you do lose out in another area-the velocity ratio of ½ means the load only moves ½ the distance the effort does.

Noooooo,:confused: Thats how I thought it was too

I just got my head around it & now you throw a spanner in the works,
I'm pretty sure thats not what Frank is Saying.

The snatch has to be moving for there to be MA. If the block is on one tree it dosent matter if the Hook is on another tree next to the car, or fixed to the front of the car itself, there is no MA .

Thats why pulling myself out of a bog with the block on a tree & the hook back on the car seemed harder than I thought it should have,
And why pulling a scented gum out in the back yard with a block on it was easier than I thought it would have been !!

oh hang it, I'g going up the bush to have a play & find out for real.

[isuzutoo-eh]

The snatch block doesn't know which end it is on, whether it is on the fixed anchor or on the load. All it knows is the winch is at the other end. Hell, for all it knows, the winch is pulling the tree towards the 4WD. It just knows it has 1xload from the anchor it is fixed to, and two lots of ½xload pulling the opposite direction. The tension in each direction of rope is half the load as two ropes are supporting it in (roughly) parallel.

If you compare it to a crane, the boom is the vehicle as that is where the winch is fitted. The snatch block is on the load. free end of the winch rope is attached on the boom again. This has the snatch block moving with the load, giving a mechanical advatage of 2. Load and effort are switched compared to 4WDs, but the bits in the middle are all the same.

[steveG]

Thanks Mark - that's a better example than my garble.

Steve

[goingbush]

Steve & Mark

this concurs with what you are saying,

How to Use a Winch Snatch Block « « ProMark Offroad Blog ProMark Offroad Blog (http://blog.promarkoffroad.com/2010/02/11/how-to-use-a-winch-snatch-block/)
(the middle drawing is the scenario I'm interested in)

Of course the winch dosent know the tree is not moving, As far as the winch is concerned the Snatch block IS moving, The winch does not necessarily know its bolted to the front of a car. so the MA would be 2

So now I'm back at square one.

Which brings up back to the original post, the portable boat winch - with snatch block on the tree !!!

I think I'll still take my Tirfor 15kg plus rope 15kg vs 20kg boat winch , might not always have 12v in a recovery situation

[Tank]

Your example of lifting a weight from a single pulley on a beam is a different scenario than a winch on a vehicle with the line anchor point attached to the same vehicle (which effectively is pulling in the direction of travel).

If you took the winch off the vehicle and anchored it to a tree - then you would have the same scenario as your beam lift. But that's not the case.
The winch on the front of the vehicle IS pulling to advantage - if you stopped the snatch block pulley from rotating the winch would pull the vehicle forwards.
With the pulley free, the tension from the winch is felt on the vehicle via the fixed end of the line - the same as it would if the winch was attached to another anchor point (not the vehicle).
So there are 2 forces pulling the vehicle forward. The winch pull, and the pull from the line coming back from the block.

Is that not correct?

Steve
Steve I have explained it to the best of my ability, you seem to think that all this is my idea, it's not.
I was taught this basic setup by ticketed riggers, TAFE college teachers, and it is available for all to read and digest in the many Tafe text books or the OH&S riggers guide available through Google or send me your email address and I will email it to you.
I don't want to argue with you, so have a look at the references available and argue with their authors, sorry I can't explain it better to you, Regards Frank.

[NavyDiver]

Reading this thread took me back to seamanship school. Rigging to advantage or disadvantage is another concept Rigging or reeving a tackle to advantage when the hauling part comes away from the moving tackle. Conversely when the hauling part comes away from the fixed tackle it is reeved to disadvantage.
What you use, how you use it rig and how you reeve all impact to some extent.

Single Whip (fall through a single fixed block)- no MA
Runner (rope through a single moving block)- MA 1.82
Double Whip (two single blocks cannot be rove to advantage)– MA 1.67
Luff (double and single block) - MA 3.08 or 2.3 depending if rigged to advantage or disadvantage.
Two fold purchase (two double blocks) MA 4.37 if rigged to advantage or 2.86 if disadvantage


Did MA just get a little more confusing? “Admiralty Manual of Seamanship Volume 1” page 238 on would match the riggers guide fairly well I guess and I guess as every sailor got one for donkeys years they should be as cheap as chips if you can find one. Mine is a 1979 version.

[steveG]

Steve I have explained it to the best of my ability, you seem to think that all this is my idea, it's not.
I was taught this basic setup by ticketed riggers, TAFE college teachers, and it is available for all to read and digest in the many Tafe text books or the OH&S riggers guide available through Google or send me your email address and I will email it to you.
I don't want to argue with you, so have a look at the references available and argue with their authors, sorry I can't explain it better to you, Regards Frank.

I'm not arguing with the theory Frank, just that I believe you have applied it incorrectly in this case.
I've read a number of rigging references, but failed to find one that shows the line anchor point on the winch. I emailed you earlier for a copy of the rigging guide but haven't received it yet.
I don't have your experience or knowledge, but that doesn't mean you're correct all of the time.

Firstly, you're giving conflicting information. You say that there is no mechanical advantage to using a single pulley with a winch, but you give a scenario with the 10kg bucket that shows a 10kg line pull over a single pulley results in a 20kg beam loading. That transposes horizontally to the winch situation and gives a pulley anchor point loading of double the line pull - which goes against your no MA statement.

To test for myself, I've just been out on my sloping driveway with a spring balance, some rope, a snatch block, my garage creeper and my fat ass.
With a direct pull on the rope, it takes about 13kg to get/keep me moving up the driveway, but if I tie the rope around my waist and pass it through the snatch block and pull on the free end it only takes about 8kg. Plenty of variables there, but if you were correct the line pull through the snatch block would be the same or slightly higher then a direct pull as there is some additional pulley friction. The reality is that its closer to half the load.

Since this is the recovery section, I can't sit back and let something go if I feel its wrong as I consider it my responsibility to point it out (as I know you would ).
If someone were to take your advice that there is no mechanical advantage, and uses a double line pull with an 8000lb winch, proceeds to anchor the block with something rated to 8000lb its likely that the anchor would break. I'm not comfortable with that.

Steve

[Stuart02]

I think I'll still take my Tirfor 15kg plus rope 15kg vs 20kg boat winch , might not always have 12v in a recovery situation

Haha, that's a scenario I don't want to contemplate! :)

[Stuart02]

I just fitted a TJM 9500 to my car last week, I'm not sure how much it weighs, but I reckon it's light enough to build a cradle for it and have it very portable,, you could make it so it fits either end of the car, or attatched it to a tree for use as well,

Chops

Yeah there's cradles you can buy, but I thought fixed winches were more in the 45-50 kg? I'll check out the TJM, thanks

[steveG]

Yeah there's cradles you can buy, but I thought fixed winches were more in the 45-50 kg? I'll check out the TJM, thanks

Warn state the weight of an XD9000 as 35kg including wire. I weighed the wire from mine and its about 8kg, and the equivalent synthetic rope is about 2kg.

Their portable XD9000i complete with cradle and wire is 47kg:
Warn Industries - Jeep, Truck & SUV Winches: XD9000i Portable (http://www.warn.com/truck/winches/src/xd9i_multimount.shtml)

Steve

[Didge]

..........
FYI to gain a Mechanical Advantage (MA) using a single sheave block you have to first be pulling to "Advantage", i.e. pulling in the same direction that the load is moving.
.........
Frank's comment here agrees with the diagrams I posted earlier. You need two snatch blocks;one connected to your car and one to the stationary point (tree, etc). An alternative scenario to what Frank described earlier about sitting on the ground - you have a single snatch block connected to the roof frame of your garage. A rope runs up and through it. Your mate weighs 100kgs (exerts a force of approx 1kN) and you weigh 60kg ( a force of approx 0.6kN). He's connected to one end and you to the other. Can you pull him up to the roof? Short answer is NO!.It's the same principle as the old see-saw where the heaviest person could sit on the ground and keep you up in the air until you decided to bail. :)

[Tank]

I'm not arguing with the theory Frank, just that I believe you have applied it incorrectly in this case.
I've read a number of rigging references, but failed to find one that shows the line anchor point on the winch. I emailed you earlier for a copy of the rigging guide but haven't received it yet.
I don't have your experience or knowledge, but that doesn't mean you're correct all of the time.

Firstly, you're giving conflicting information. You say that there is no mechanical advantage to using a single pulley with a winch, but you give a scenario with the 10kg bucket that shows a 10kg line pull over a single pulley results in a 20kg beam loading. That transposes horizontally to the winch situation and gives a pulley anchor point loading of double the line pull - which goes against your no MA statement.

To test for myself, I've just been out on my sloping driveway with a spring balance, some rope, a snatch block, my garage creeper and my fat ass.
With a direct pull on the rope, it takes about 13kg to get/keep me moving up the driveway, but if I tie the rope around my waist and pass it through the snatch block and pull on the free end it only takes about 8kg. Plenty of variables there, but if you were correct the line pull through the snatch block would be the same or slightly higher then a direct pull as there is some additional pulley friction. The reality is that its closer to half the load.

Since this is the recovery section, I can't sit back and let something go if I feel its wrong as I consider it my responsibility to point it out (as I know you would ).
If someone were to take your advice that there is no mechanical advantage, and uses a double line pull with an 8000lb winch, proceeds to anchor the block with something rated to 8000lb its likely that the anchor would break. I'm not comfortable with that.

Steve
Steve, Quote: "You say that there is no mechanical advantage to using a single pulley with a winch", I don't say anything of the sort, the text books say it, along with TAFE teachers and the laws of physics, this is why I am loathe to explain things of this nature, it falls back on me to justify what is a known fact.
Steve I havent recieved an email from you, send me your email address and I will send you a copy and you can dispute the facts with the authors of the Riggers Guide, Regards frank.

[steveG]

Steve, Quote: "You say that there is no mechanical advantage to using a single pulley with a winch", I don't say anything of the sort, the text books say it, along with TAFE teachers and the laws of physics, this is why I am loathe to explain things of this nature, it falls back on me to justify what is a known fact.
Steve I havent recieved an email from you, send me your email address and I will send you a copy and you can dispute the facts with the authors of the Riggers Guide, Regards frank.

Not sure what happened to the email I sent yesterday but I've just PM'd you my email address for a copy.

Steve

[steveG]

Frank's comment here agrees with the diagrams I posted earlier. You need two snatch blocks;one connected to your car and one to the stationary point (tree, etc). An alternative scenario to what Frank described earlier about sitting on the ground - you have a single snatch block connected to the roof frame of your garage. A rope runs up and through it. Your mate weighs 100kgs (exerts a force of approx 1kN) and you weigh 60kg ( a force of approx 0.6kN). He's connected to one end and you to the other. Can you pull him up to the roof? Short answer is NO!.It's the same principle as the old see-saw where the heaviest person could sit on the ground and keep you up in the air until you decided to bail. :)

Didge, hook up a snatch block in your shed with a rope through it.....
Tie a big loop in one, then stand/sit in it. grab the other end and try and pull yourself up and get a feel for the force required.
Repeat the test with just the rope tied to a beam in the roof and try to pull yourself up.
Report back what you observe in regard to how heavy each scenario feels.

Steve

[NavyDiver]

Runner (rope through a single moving block)- MA 1.82

“Admiralty Manual of Seamanship Volume 1”

A single snatch block and winch is a probebly a "Runner". It doubling the cable and halves the pull lenght and halves the velocity or speed over a single straight pull. it may then have a MA of 1.82. It is not double the capacity but it is an improvement of .82.

I wonder if the Winch itself could be considered a block giving a "double whip"? If so the MA would be reduced to 1.67. I will ask some crusty old salty people for us. Bet that discussion will be heated unless I can take it to a pub near Garden Island:D

Edit do not ask winch manufactures- Looked at two and both claimed a single santch block doubles your MA. http://www.gowarn.com/warn-winches/winch-tips.aspx

this link below also mucked up MA but at least points out that as line comes onto the drum the pulling power is reduced for each layer added

http://www.innovation-engineering.co.uk/theory.htm "As a guide for each layer of wire rope on the drum deduct 10% off the rated line pull. e.g. A winch with a line pull of say 6,000 lbs.. will have a line pull of 5,400lbs.. on the second layer, 4,860 lbs.. on the third layer and 4,374 lbs.. on the fourth layer, etc."

That is a issue well worth considering as is the roughly 10% reduction caused by friction on the snatch block.

[steveG]

A single snatch block and winch is a probebly a "Runner". It doubling the cable and halves the pull lenght and halves the velocity or speed over a single straight pull. it may then have a MA of 1.82. It is not double the capacity but it is an improvement of .82.

<snip>


That's my view also.

Steve

[isuzutoo-eh]

Mechanical Advantage is the force applied to the load, divided by the force applied to the apparatus.
In a simple lever, pulley or geared system, it is the inverse of the:
Velocity Ratio (VR) is the distance the load moves divided by the distance the effort moves.

(The majority of pulley diagrams I have found don't show the free end of the rope anchored back to the effort (winch) as in a double line pull, perhaps because it seems counter-intuitive to be pulling a rope back towards itself. Thankfully the rope doesn't care which direction the tension comes from it will still exert equal force upon its ends, ie pulling towards its centre.)

https://www.aulro.com/afvb/images/imported/2012/06/995.jpg

An easy way to calculate mechanical advantage is to count the number of parallel ropes in tension between the load and the effort. For my diagram above, the ropes to count are red. Count through where the MA and VR are listed.



Weakestlink's figures do account for friction in the system whereas my physics based diagram is a 'perfect' friction free environment.

[goingbush]

I thought I was right, then I was wrong, then I thought I was originally right now I know what I always thought should be right is right,

Jury is out, Bush Rats =1 Riggers Manual =0

I did the pulley on the shed roof test, scientific measuring device results show that I should put a Snatchblock on the tree & winch hook back on front of car.

Image below Snatch Block attached to truss, with Telecom rope, And also single line Telecom rope tied to Truss.
http://www.goingbush.com/landy/pulleytest1.jpg


Scientific Measuring device (bathroom scales)
http://www.goingbush.com/landy/pulleytest2.jpg


Ok Standing on scales my fat arse is 100KG, Pulling with all my might on the single line rope With my gloved hand thru the rope loop the Scale comes back to 40KG so I can exert 60KG downward force on the rope.

Now putting one foot through the loop in the bottom of the telecom rope & pulling on the other end of it I can EASILY lift my fat arse completely off the scales, with plenty to spare. So I'd say somewhere in the range of 110-120 KG,
http://www.goingbush.com/landy/pulleytest3.jpg

So Myth Busted !!

[goingbush]

Mechanical Advantage is the force applied to the load, divided by the force applied to the apparatus.
In a simple lever, pulley or geared system, it is the inverse of the:
Velocity Ratio (VR) is the distance the load moves divided by the distance the effort moves.

(The majority of pulley diagrams I have found don't show the free end of the rope anchored back to the effort (winch) as in a double line pull, perhaps because it seems counter-intuitive to be pulling a rope back towards itself. Thankfully the rope doesn't care which direction the tension comes from it will still exert equal force upon its ends, ie pulling towards its centre.)

https://www.aulro.com/afvb/images/imported/2012/06/996.jpg

An easy way to calculate mechanical advantage is to count the number of parallel ropes in tension between the load and the effort. For my diagram above, the ropes to count are red. Count through where the MA and VR are listed.

Weakestlink's figures do account for friction in the system whereas my physics based diagram is a 'perfect' friction free environment.

Hey Mark, For some reason I can't see your diagram on my computer, Its ALL BLACK with text faintly visible as below, other people can obviously see it as you have been thanked for your post. Below is a screen cap of how I see your diagram.

http://goingbush.com/landy/aulrowinch.jpg

Really Weird, but when I put it thru photoshop I can see it clearly,

Any one else have this issue, or is it just me , or a mac vs windows thing ??

http://goingbush.com/landy/WinchMAdiagram2.jpg

[isuzutoo-eh]

Hi Don, it is probably a legacy of the program I used.
Hopefully the following is better
https://www.aulro.com/afvb/images/imported/2012/06/995.jpg

[goingbush]

Hi Don, it is probably a legacy of the program I used.
Hopefully the following is better


Yes I can see it now, thanks. I wonder if I was the only one that could not see it, :eek: BOTH, the drawing & the way the block worked :D

[ramblingboy42]

well, all that convo is enlightening, but the topic was portable winches. I now carry with me a 6 ton come a long with a long chain. It can be carried with one hand , is simple to use, takes up little room, uses no electricity. On a long recovery may have to be reset more than once. I havent had to use it yet but may have to on my next trip. It seems a really easy answer to me as I dont want to have an electric winch hanging off the front of my vehicle.

[goingbush]

well, all that convo is enlightening, but the topic was portable winches. I now carry with me a 6 ton come a long with a long chain. It can be carried with one hand , is simple to use, takes up little room, uses no electricity. On a long recovery may have to be reset more than once. I havent had to use it yet but may have to on my next trip. It seems a really easy answer to me as I dont want to have an electric winch hanging off the front of my vehicle.

Understood, but I don't think that 6 Ton come along will be any good, I suppose its better than nothing (but not by much) You should go and get stuck within walking distance of home, Then practice getting yourself out with that, you'll either bugger it up or chuck it over the nearest fence. I don't think Electric Winches are much use if you get stuck either, you will usually want to be pulling yourself out backwards, not further into the quagmire. You need to invest in a Tirfor style hand winch especially if you go offloading on your own.

[NavyDiver]

well, all that convo is enlightening, but the topic was portable winches. I now carry with me a 6 ton come a long with a long chain. It can be carried with one hand , is simple to use, takes up little room, uses no electricity. On a long recovery may have to be reset more than once. I havent had to use it yet but may have to on my next trip. It seems a really easy answer to me as I dont want to have an electric winch hanging off the front of my vehicle.

LOL sorry. Most post get off target as did I.
Lewis Winch snatch block demo, huge log skid. Double the pulling power of a portable winch. - YouTube uses a portable winch but it does again claim the MA of 2 which is wrong.

Portable gives you the ablity to winch from front or back which would be great if running solo with out a mate to help pull you back. The 6 tonne would seem a little light if belly deep in muck as I seem to end up rather often:D. A Luff or double block and a single block on your portaable giving MA 3.08 (or 2.3 if reeved to disavantage) would give your 6 tonne more than enough ommps but may mean several pulls given the 2 to 3 times reduction in pull lenght.

This is about portable winch and still on M.A. and advantage. :cool: I will skip the friction resulting by the Luff rig:D.
Found a neat site on the other stuff ( not just about portables again)
http://www.btinternet.com/~fourthgill.seascouts/tackle.htm (http://www.btinternet.com/%7Efourthgill.seascouts/tackle.htm)

[Didge]

In diagram bt3, imagine the 100lb weight is the tree with the snatch block and the pulley at the top of the drawing is the winch. The point at the top left is the recovery point on your car to which the winch cable hook is attached. Half the load is taken by the winch and half by the recovery point.

[ramblingboy42]

Understood, but I don't think that 6 Ton come along will be any good, I suppose its better than nothing (but not by much) You should go and get stuck within walking distance of home, Then practice getting yourself out with that, you'll either bugger it up or chuck it over the nearest fence. I don't think Electric Winches are much use if you get stuck either, you will usually want to be pulling yourself out backwards, not further into the quagmire. You need to invest in a Tirfor style hand winch especially if you go offloading on your own.

Not sure where you're coming from here. The come along is much easier to use than a tirfor and for the same capacity is about 1/4 of the weight not counting necessary cable, and is also a dam site cheaper. I carried 35m of cable with me for years gave it away just a few months ago to Harry(hope you're getting some good use out of it mate).aluminium bodies are available for come alongs now making them lighter again. They pull as fast as a tirfor and tuck away in a nice small parcel.Why will I bugger it up? I have used them often in my job and find them very user friendly.I certainly wont chuck it away. You must have had some bad issues with them.

[PhilipA]

I have had a Warn 5000Lb portable winch for almost 25years.

Warn then made them in a steel box with a plastic lid, with provision for a receiver , and two shackles which are stored inside the box along with the power cable.So it can be used on either end of the car, or even off the chassis on a rollover, using the shackles as remote mounts .

I have fitted a towbar under the front bumper to enable front recovery and I have a heavy power cable to the back bumper with an Anderson plug to use the rear towbar.
In all the time I have owned it , I have used it once in anger to recover a car that had two wheels over a precipice on a RRNSW club trip to the Watagans.

I had another opportunity on The OTT but it was faster to use the winch on another car waiting to cross the creek to recover my car and trailer, as I would have had to get it out and rig it before use.

I still think it is a great solution , as it can be stored on the rear seat floor area and is clean and regular in shape so that stuff can be stacked on it and if I am really stuck somewhere it can be utilized.
I have 2 snatch blocks , 30 metre extension strap, tree protector, and spare shackles.
It weighs about 24Kg including box and Dyneema cable.
I also carry a "bullbag" as I have found that if you are really stuck, you need 2 recovery methods eg bull bag to lift out of mud, then winch maybe rolling over the bullbag, which I have actually done, or shovel etc .
Regards Philip A

[Stuart02]

I have had a Warn 5000Lb portable winch for almost 25years.

Warn then made them in a steel box with a plastic lid, with provision for a receiver , and two shackles which are stored inside the box along with the power cable.So it can be used on either end of the car, or even off the chassis on a rollover, using the shackles as remote mounts .

I have fitted a towbar under the front bumper to enable front recovery and I have a heavy power cable to the back bumper with an Anderson plug to use the rear towbar.
In all the time I have owned it , I have used it once in anger to recover a car that had two wheels over a precipice on a RRNSW club trip to the Watagans.

I had another opportunity on The OTT but it was faster to use the winch on another car waiting to cross the creek to recover my car and trailer, as I would have had to get it out and rig it before use.

I still think it is a great solution , as it can be stored on the rear seat floor area and is clean and regular in shape so that stuff can be stacked on it and if I am really stuck somewhere it can be utilized.
I have 2 snatch blocks , 30 metre extension strap, tree protector, and spare shackles.
It weighs about 24Kg including box and Dyneema cable.
I also carry a "bullbag" as I have found that if you are really stuck, you need 2 recovery methods eg bull bag to lift out of mud, then winch maybe rolling over the bullbag, which I have actually done, or shovel etc .
Regards Philip A

That's pretty much exactly what I envisioned - does anyone still sell anything like that? Wanna sell yours, Phil? Haha :D

[PhilipA]

You can buy receiver cradles , as I have seen them advertised in 4WD Australia.
The cradle can take up to a 9000Lb winch, but it is just a square tube ,baseplate plus handles so the winch would need to be wrapped in something if in the car , which is not such a big deal.

I hold mine down with HD rachet straps attached to the driver's seat base and to loops rivetted to the floor near the seat mounts with HD rivets. A winch flying around in a rollover would not be funny.

You could easily weld some loops on the baseplate for shackles. You would need to buy a winch where the contactor box could be attached to the crossbars.

The cables could be easily done by doing what Warn does, about 2 metres attached to the contactors, and an Anderson plug with a short length with matching anderson plug on the battery. The Warn rear anderson plug screws to the bumper and there is a short earth, which is attached to the body and a heavy welding type cable to the battery. I leave mine unattached as it is not fused LOL . Whenever I want to test, all I do is tap the + on the battery +. No sparks = good .

If I were doing it today , that is what I would do.
Regards Philip A