Thread: Winch on a winch!

Originally Posted by bacicat2000

Just to add to the confusion a bit - there is some talk here of a double line pull. Did the result of this conversation yield any result from previous discussion? I thought that running a cable through a snatch block back to the rig halved the speed, but didn't provide and mechanical advantage - what was the result of all that...?

A snatch block is quite literally a text book example of a mechanical advantage

Originally Posted by Didge

Can't agree with you bacicat2000,
Imagine you are hanging off an overhead beam by one arm- all your weight is transferred through your arm to the point of attachment (your shoulder aka winch). Now if you have a piece of rope looped over the beam and you hang from both arms, half the weight of your body is distributed to each arm (one shoulder - winch, other shoulder - recovery point). The anchor point (beam, tree, rock, etc) still supports the full load.

The argument is not what is happening in your anchor point but what is happening at each shoulder and clearly with two shoulder each shoulder is "shouldering" half of your weight. If you do not believe this then time yourself hanging from a suitable point by one hand and then time yourself hanging by two hands and I am sure you will be able to hang on a lot longer with the two hands thus proving the point beyond further argument that a snatch block will halve the load on your winch if you run the block off an anchor point back to your bull bar.

I think the hanging from a tree example doesn't demonstrate a mechanical advantage because there is no motion. It's merely sharing the load - concurrent forces.

If half the weight is carried by the winch and half by the recovery point, then the load on the winch is half of whatever it is. I can't see a logical argument against that. So if the winch is only carrying half the weight, when it is operated it is only retracting half the weight, hence the mechanical advantage.

Woops - seems like i've opened the can of worms again here - sorry for the thread hijack.

I thought maybe this had been worked out definitivley - just wondered whic way it went... apparenty the jury is still out.

Looks like some members did some actual tests which seem to support the mechanical advantage side of the coin.

Cheers from (the still confused) - Gav

Originally Posted by bacicat2000

I thought maybe this had been worked out definitivley - just wondered whic way it went... apparenty the jury is still out.

No, the jury is in, the verdict has been read and everyone has gone home!

If I ever have to do jury duty, I hope the case is similar to this.

Originally Posted by bacicat2000

Woops - seems like i've opened the can of worms again here - sorry for the thread hijack.

I thought maybe this had been worked out definitivley - just wondered whic way it went... apparenty the jury is still out.

Looks like some members did some actual tests which seem to support the mechanical advantage side of the coin.

Cheers from (the still confused) - Gav

the Jury may be out, but that does not change the result, the facts and physics.....