shopping for a snatch block

[firefox]

3DAngus, That is close, but I think the one I have is even beefier than that. I will try to get some pictures made of it. Thanks a lot for the help!
Bruce

 

[stumps]

Ty, I cannot get my mind right. A 10k winch pulls 10k. Doubling the line back to the vehicle performing self recovery doubles the pull power but it is still the 10k being leveraged.

In the above situation the snatch block will see 10k, and the truck front bumper will see about 20k..... I think.

Rick

I believe that you have heard somewhere that for every action, there is an equal and opposite reaction... should be a familiar phrase to most people, even if they don't know what it means.

In short, when you stand on the ground, your weight is pushing down on the ground, and at the same time, the ground is pushing up on you the same amount (If it isn't, you're sinking ). If you have two feet on the ground, then each foot is pushing with 1/2 your weight on the ground.

When your snatch block's hook is pulling on a load with 1000 lbs force, the cables attached to the snatch block are pulling on the snatch block with 1000 lbs force.

If your snatch block has a single sheave, then each cable will have half the pull in it. If your snatch block has 5 sheaves, then each cable will have 1/10th the pull in it. The cable tension can be found by dividing the hook tension by twice the number of sheaves. The total of all of the tensions in the cables equals the tension in the hook.

If a snatch block is rated for 10,000 lbs, that means the hook is rated to pull 10,000 lbs. If it has a single sheave, then the rated maximum cable tension is 5000 lbs. Regardless of what some towing company has gotten away with. Be thankful that a quality snatch block has a 2 or 3 times safety factor built in. Don't count on a Chinese snatch block even meeting its rating.

-Chuck

 

[3dAngus]

Bruce,

ok. You probably have a twenty ton then. If the wheel is greater than 6.5 inches, it is probably 20T. And of course, that is all based on it being made by Skookum, who makes some of the best.

 

[firefox]

Forth attempt with this camera.
Notes: shieve is 6 1/2" valley to valley.
designed for 5/8" cable
Hook opening is 2"
Hook pin is 1"
Hope this works,
Bruce

 

[3dAngus]

Firefox, that one looks like it came out of WWII. Manly! for sure.

 

[firefox]

Thanks, but somehow I don't think so. There was a NSN type bar code sticker on it but it was too mangled to read. It came from one of the bases up in Washington, but I don't know which one.

What is your guess as to the rating? I suspect the limiting factors are the 6 1/2" diameter shieve size and the 5/8" cable size, but I don't know enough to guess.

Thanks again for all your help!
Bruce

 

[3dAngus]

OK. Well, I didn't know that for sure. Bar codes are put on everything now, old and new. It just looked a little manly and prehistoric.

My guess is, and I'm the last person to ask, is between 10 and 20 ton. This is based on size and cable width of 5/8" which is a tad bit bigger than the recommended 9/16" on my 12 ton at the same pully size. Of course, mine can take 5/8" as well, but the normalized recommended size is 9/16". Either way, you have a ten tonner for sure. I would hoist up a bank a 5 ton truck with it in a heartbeat.

 

[firefox]

Talk about weird luck...I was following a reference from Kenny in regard to the cable size for a M108 winch and stumbled across the following in:
TM 9-2320-209-34P
fIG 267
Sheave assembly
M756A2 Truck Pipeline Construction

Haven't looked up the capacity yet, but that is definetely the snatch block I have less a few of the extra parts.

Thanks again,
Bruce

 

[timntrucks]

that snatch block is close to the one i have i was talking about.. it is to small for the duece in rating. i dont know exactly what that one is for.

 

[rchalmers3]

Rick, think about what the hook of the snach block is hooked to that you are trying to move. If you agree that you can pull 20,000lb with using a snach block you can't look past the fact that there will be 20,000lb on the snatch block hook. If you are pulling 20,000lb there will be a 20,000lb load on everything between the object and the winch vehicle. Of course you will have a 2 part line so each line will take half the load. Hooking as you described, there would be 10,000lb on the bumper (where the dead end is attached) and another 10,000lb on the winch (where the live end is attached).

That helps! Now what didn't you explain this sooner when you were jousting with that other feller?!!!

The warn snatch block in my Land Cruiser confirms your explanation and understanding. It says right on it it is for winch loads 1/2 of the block rating.

appreciate the learning,

Rick

 

[jesusgatos]

What snatchblock is this? Think it's military, but doesn't seem to have any identifying markings on it. Not sure how these are measured, but the pulleys looks to be about 6-6.5" in diameter (to the valley of the cable-channel, not the centerline diameter), and the opening at the widest part of the cable channel on each pulley is about 7/8".

 

[jesusgatos]

Anybody?

 

[3dAngus]

I can' tell from the pics if the pulley easily opens up to accept a cable. If not, it is NOT a snatch block but a hoist instead. Does it have a lever to open up the pulley assy for quick cabling?

 

[jesusgatos]

I can' tell from the pics if the pulley easily opens up to accept a cable. If not, it is NOT a snatch block but a hoist instead. Does it have a lever to open up the pulley assy for quick cabling?

Yes, both sides open up quickly/easily and without any tools. The first two pictures show a tab that's bent over 90-degrees. If you align that tab with the slot (perpendicular to a pulling load), that allows the gate to be opened.

 

[3dAngus]

OK, thanks. The other issue is there is no hook. Most snatch blocks have hooks on them. No?

 

[jesusgatos]

No idea. I just got this with a big pile of mil surplus parts from that yard I posted about a while ago, that was getting cleared-out. Looks like it's set-up to be used with a clevis or something, but I don't have any idea what I've got here. Was hoping it would be a useful winching accessory.

 

[73m819]

Its a double pulley(4 part) shackle termination snatch block.

It would look good hanging off the front bumper of MY m819 (hint,hint)

 

[jesusgatos]

shackle-termination, huh? So is there a part that I'm missing that would allow me to mount it to a shackle-mount?

 

[jesusgatos]

I'd like to be able to use this with a winch, but can't foresee many occasions when I might need to have a double-pulley attached to my bumper. Much more likely that I'll just use one pulley attached to whatever I'm pulling from. Would also like to hang it from the gin-poles I'm building out of my tow-bars though. Got an extra set of towbar legs that I'm going to cut-up to extend my towbar, and I'm planning on making some type of simple bracket that will attach to the lunette-eye, that I can hang a snatch-block from. If there's a better snatch-block to use for the applications I've got in mind, I wouldn't mind trading with someone that could use the one I've got.

 

[3dAngus]

Its a double pulley(4 part) shackle termination snatch block.

It would look good hanging off the front bumper of MY m819 (hint,hint)

Ron's the man. His depth of knowledge of this stuff amazes me.