Recovery - The Fundamentals

[Silver]

lol silver i have no idea, i dont have a winch and im not too sure about all the math equations. i can change it if you want, but someone suggested to make a PDF outta the thread, so i did for the forum. let me know which part you want me to change and ill do so gladly

Crikey Nic, 2nd form science was a long long time ago for me!

The PDF says

The snatch block is a rated piece of equipment that allows the cable to run over a pulley and change direction too another tree or back to the winching vehicle. The awesome power of the Snatch Block is that as soon as you introduce a pulley within the line you HALVE the weight on the line!! Add 2 Snatch Blocks and you reduce the weight to 25% of the line weight at the hook!

Maybe it could say:

The snatch block is a rated piece of equipment that allows the cable to run over a pulley and change direction to another tree.

The cable can also run to the block and back to the winching vehicle.

The awesome power of the Snatch Block is that as soon as you introduce a pulley within the line that goes back to the winching vehicle you HALVE the weight on the winch!! Add 2 Snatch Blocks and you reduce the load on the winch to 33% of the actual load! There's a way to work out this mechanical advantage. One line from winch to anchor - winch is pulling 100%. Line from winch to anchor, through block and back to winching vehicle, winch is pulling 50%. The line is twice the distance to the anchor point - and the load is 1/2. Introduce another snatch block at the winching vehicle and run the cable back to the anchor - 3 times the distance, and the winch is doing 1/3 of the work.

There is a trap to this. If your winch is at max load of 3.6 tonnes, because the GU above is bogged to the chassis with a camper trailer, with the two snatch block set up above, then the anchor is bearing 3 x 3.6 tonnes - close enough to 11 tonnes. That 11 tonne load is also spread across the attachment points on the vehicle. Beware failing anchor points and make sure the shackles, tree trunk protectors and anything else that is carrying the full load is up to the job.

The other thing is that there is little or no mechanical advantage where the snatch block merely changes to the line of pull between winch and load a bit. The maximum effect is where the winch line does a 180 and goes back to the winching vehicle.

I'm sure someone could improve on this :-)