CM 3 ton puller - how does it work?
 

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

http://tinyurl.com/69mhb

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

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

http://tinyurl.com/69mhb

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?


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...

http://www.cmindustrial.com/products/Hoists/h26.pdf


Ned Simmons

On 22 Dec 2004 15:28:43 -0800, "russell shigeoka"
wrote:

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

http://tinyurl.com/69mhb

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

Without a brake, they are not suitable for lifting, only for pulling.

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

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

remove ns from my header address to reply via email

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....

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

http://tinyurl.com/69mhb

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

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.

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