Thread: Will they ever learn?

no pulleys needed


truckpull.jpg

Originally Posted by vnx205

I think some of the problem has been the fixation (pun intended) on the word "fixed".

Should that be "fixed in relation to the position of the sun", "fixed in relation to the winch" or "fixed in relation to something else entirely"?

Almost all of the diagrams and videos illustrating a single pulley don't have the end of the cable attached to the same object as the winch. So it is understandable that most people get the impression that there is no advantage when the pulley is attached to the tree.

It becomes quite a different situation when the cable is attached to the same object as the winch.

True. Where I've been at odds with this discussion is exactly that. If the pulley wend on a tree, and the other end comes back to another tree, then the pulley would be deemed to be 'fixed', and no MA is there. When it comes back to the car doing the winching, then it would be deemed to be moving, in an engineering sense, and MA is present.

AM's vid showed that, and maybe one less glass of my favourite and I'd have seen it, but personality got in the way.

My take on this, if you've got yourself into a situation where you need to do all this, then you should have not been there in the first place, the fact is not what they should have done, but what they shouldn't have done to get themselves in the situation in the first place.

The only time you should need a snatch block is if you need to change the direction of the winch rope!!

Originally Posted by Redback

My take on this, if you've got yourself into a situation where you need to all this, then you should have not been there in the first place, the fact is not what they should have done, but what they shouldn't have done to get themselves in the situation in the first place.

The only time you should need a snatch block is if you need to change the direction of the winch rope!!

Spoken like a true Weekend warrior

Brian, this info is from a magazine that shows readers that you should use a shackle with the eyes of the strap anchoring it pulling on one side of the shackle with the snatch block on the other side of the shackle , doing it's best to spread the shackle apart, as you know a shackle should only be loaded in the bow and on the pin.
The Formula for determining the MA of a pulley system is: The number of Parts of rope Supporting the MOVING BLOCK.
Diagram 2 below receives no MA from the block, BUT as there is twice the length of rope/wire wound off the winch drum (compared to the straight pull) there is a MA due to the fact that the winch is pulling from a point closer to the centre axis of the winch drum, you could gain the same MA by doing a straight pull over twice the distance, (without the magic snatch block) again pulling from a point on the winch drum closer to the drums centre axis.
The diagram described by these dicks at this particular magazine IS NOT a triple line pull as described, the lead rope from the winch to the pulley DOES NOT support the moving block, there are 2 ropes supporting the moving block so it is a MA of 2, Regards Frank.

Originally Posted by BMKal

Another way of showing it .....................

Wouldn't doubling the amount of force on the pull exceed the rating on the "D" shackles used?.
The Maximum pull on a 12,000lb winch is over 5 tone and most of the "D" shackles we normally carry are only rated at 4.7 tone, So if we double the pulling power from the winch then there has to be the possibility that somewhere in the setup the 4.7 tone rating will be exceeded.

That second one down in the pic with one pully block,very handy when using the capstan on the front of the series 1.

But no tree protecter in those days...

Originally Posted by scarry

That second one down in the pic with one pully block,very handy when using the capstan on the front of the series 1.

But no tree protecter in those days...

That wouldn't work with a capstan as you are not decreasing the diam of the drum wich according to tank is the only MA you are going to get

AM