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Boom, straignt over my head and totally missed that! Sorry! :Rolling::oops2:
I have to admit, I also pulled out my Uni textbooks thinking I was going to get a metal rewrite and trying to work out WTF this was about because it didn't make sense to anything I learnt or had done either. :blink::lol:
Up an inclined plane due to the earths rotational forces? :lol2: OK, I shudup while I'm behind. :lol2:Quote:
Originally Posted by roverrescue
His quote, "Any day is a good day when you can use a snatch block"
He really should have added............
"An even better day is when you don't have the need to."[smilebigeye]
So if your typical ARB (for example) snatch block is rated at 8000 Kg (17636 lb) and your typical 4WD Supastore winch is rated at 12000 lb (5443 Kg) does this mean that when trying to move the immovable object (bogged to the gills vehicle) that the snatch block can be overloaded with a possible 24000 lb (10886 Kg) pull ?
I've noticed that some American snatch blocks have parallel lines etched into their side plates so that over load deformity around the 'eye' of the snatch block is easily identified.
It's worth noting that a common use of a snatch block is to easily change the direction of pull and that when doing this the 2:1 mechanical advantage ratio does not apply.
Deano :)
Snatch Block will have a SWL of 8000kg with a safety factor of 5
So ultimate limit of 40,000kg
Winches are “rated max pull” first layer of the drum.
So a 12,000lb with Dyneema will barely apply 5450kg of pull as dyneema you’ll need at least a few wraps on the drum to grip.
Soooo in short - winch will stall well before any risk to hardware
Snatch block anecdote, when the tojo 200 series first came out
Couple mates and I went chasing Barra in February on private property
To get to the waterhole we had to pass through a tea tree swamp.
130 defender and dual cab hilux both drove through fine
200 following was clearly too heavy for the swamp and went to the gills
Recovery took hours - in the end we had defender and hilux chained to trees at rear
Double line to cruiser and two winches just above stall dragging 200 through the crust.
Ended up cutting down about 20 saplings and built a road to hard ground
We did end up catching good Barra
After that incident I bought another 100m of Dyneema
Can never have enough string or blocks
S
Correct. (ish)Quote:
Originally Posted by DeanoH
the snatch block is rated for the max stress it can handle on the eye.
The ropes running to handle no less than half this
The winch (or line if you're doing a sneaky 4:1 by compounding snatchblocks) pulling on the block needs to pull no more than 1/2 the snatch block rated limit (this number goes down if you go past about 15 degrees off parallel)
Be careful with your snatck block SF, ones not rated for lifting will have a SF of 2, rated for lifting 5.
If you've set up the recovery properly ,the second weakest primary element in the whole system should be the winding force of the winch, the weakest element being the resistance of the object you're trying to move (and no I'm not going into compounding and multiple anchor points I'm only talking about a simple single line and double line pull)
In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]
Quote:
Originally Posted by Bigbjorn
Trust you to bring a bit of class to a thread.[biggrin]
I assume you didn't mean the ones on the Cargo handling gear either.
We can't unsee that now can we?Quote:
Originally Posted by Bigbjorn
So in theory with enough rope and enough blocks you could pull out a Tank?Quote:
Originally Posted by roverrescue
[tonguewink]
Steve