CM 3 ton puller - how does it work?

Question

I just refurbished a CM 3-ton puller. Does anyone know the purpose of the "Weston brake system" on these pullers?

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From what I can see it really has no purpose on the load itself, it's

only purpose seems to be to provide enough friction so that when the puller is in freewheeling mode the chain doesnt start coming out of the hoist on its own by gravity and bonking you on the head. However, the sales literature seems to imply it has more function that that - "positive load control". What is that?

Aloha, Russell

Ned Simmons · Accepted Answer

Presumably it's the brake that requires that you crank the load down as well as up. Something is wrong if yours doesn't operate this way. I have a 3/4T puller/hoist that also has this feature--there's a cutaway here...

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Ned Simmons

MP Toolman · Answer

While I am not familiar with the term "Weston brake system", I have several larger CM hoists that have a very effective brake system for lowering loads. Without a brake system that requires the operator to ratchet loads down as well as up, the load would not be held in a raised position (without some sort of ratchet lock) and would simply fall as soon as one tried to lower it. I have seen cheap cable pullers that worked like that. Without a brake, they are not suitable for lifting, only for pulling.

Mill

Don Foreman · Answer

It's an important safety feature preventing the load from freewheelingif you let go of the chain.    Boat lifts like Shorestation  also useWeston brakes.   They are interesting mechansims.

russell shigeoka · Answer

Looking at some patents and studying the puller a little more I guess I have a clearer picture of how the "Weston brake system" operates. Mines has a 4" diameter ratcheting pawl that is not keyed to the shaft. Surrounding the pawl are two friction discs, this assembly is pressed together by a cam system which is keyed to the shaft.

I was initially surprised that such a small surface area could control

6000# of weight, but when I thought about it some more I guess thats about the same surface area on the front disc brake pads on a small car.

It's a pretty neat mechanism.

Aloha, Russell

Old Nick · Answer

On 22 Dec 2004 15:28:43 -0800, "russell shigeoka" vaguely proposed a theory ......and in reply I say!:

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I know this has nothong to do with your question, and somebody may correct me. But my problem with the lever style puller/lifters is that while they get rid of the pesky chain, you have to up with the lifting device in order to lift anything....

Old Nick · Answer

On 23 Dec 2004 09:49:38 -0800, "russell shigeoka" vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

It has an enormous mechanical advantage. If the lever is replaced by a chain on these units, to lift 1 tonne takes maybe 50lbs of force on the pulling chain.

That's how that little bit of friction works. car brakes are somewhat different, in that they use an enormous amount of pressure.

CM 3 ton puller - how does it work?

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