Snatch block question

[cranetruck]

The snatch blocks can be used in various configurations to gain mechanical advantage, however the type needed for "Gun Tackle" set-up seems hard to find. Has anybody spotted one of these, with the extra feature marked in the diagram below?
Should be for 5-ton truck winch (5/8" dia wire rope).

Thanks.

 

[Boatcarpenter]

snatch block

Bjorn, I don't mean to get too technical on you here, but those don't look like "snatch blocks" by definition. They look to be just regular blocks as one would find in a rope block and tackle setup. Pics illustrate what they look like to me. Maybe yes, maybe no
BC

 

[cranetruck]

RE: snatch block

Agreed, the illustration may not show snatch blocks, but the principle is the same.
The result is a 3 to 1 advantage.

 

[timntrucks]

RE: snatch block

i am thinking your just have to use two regular blocks and anchor the line else where to a tree or back to truck.... just not to the shacles TIm

 

[Boatcarpenter]

RE: snatch block

So you are looking for a block with a thimble. I'll keep my eyes open while I'm searching around for other good MV must have stuff
BC

 

[rizzo]

RE: snatch block

I thought that it is a 2:1 ratio because the top block is not moving.

 

[doghead]

RE: snatch block

here's a good calculator/example of 1,2 and 3 part lines. http://www.thecrosbygroup.com/productcatalog/Calculators/Calculators/snatchblockrigcalc.htm

here's a few more interesting load calculators, http://www.thecrosbygroup.com/productcatalog/Body_calculators.htm

This info is all from the Crosby. http://www.thecrosbygroup.com/productcatalog/maininterface.htm

 

[cranetruck]

RE: snatch block

Good links Doghead, thanks.
We can make it easy on the winch, but one block will have to take the full load.

 

[m16ty]

The easiest way to figure max lift with a block and tackle is to count the lines between the blocks or winch. The picture is a 2-part line. Whatever your line pull is you multiply by the number of parts (lines between the blocks) and that is how much you can lift/pull. In the picture you could lift 100# with a 50# line pull. You will loose a little from friction in the rigging but not a lot.

 

[rmgill]

Attaching back to the block means you have ALL that force on that one attachment point. You're better off spreading it over several points if you can.

Between my truck and another truck, I'd prefer to have two blocks on the pulled truck and one on mine with the last line going to my other front clevis. That gives me three attachment points on my truck and 2 on the pulled truck with the load spread across several points. A double sheave block allows more dense rigging, but your attachment point needs to be up to snuff.

 

[rizzo]

Attaching back to the block means you have ALL that force on that one attachment point. You're better off spreading it over several points if you can.

Between my truck and another truck, I'd prefer to have two blocks on the pulled truck and one on mine with the last line going to my other front clevis. That gives me three attachment points on my truck and 2 on the pulled truck with the load spread across several points. A double sheave block allows more dense rigging, but your attachment point needs to be up to snuff.

I agree

CT: is there a certain reason you want this type of block? any back story? You always have interesting projects going on. Whats up ?

 

[cranetruck]

........
CT: is there a certain reason you want this type of block? any back story? You always have interesting projects going on. Whats up ?

Nah, just like options, in any case way too much money at this time.