Re: Friction (clutch) lining

moray wrote:
"ChrisQuayle" <nospam@xxxxxxxxxxxx> wrote in message news:k3Sgi.17574$3j1.11851@xxxxxxxxxxxxxxxxxxxxxxx

moray wrote:

Thought this would be the best place to ask, as people here seem to have answer for everything.

I may (depends on if the required components will fit in the given space) be making a winch that will need a reasonably substantial/hard wearing clutch, but I can't seem to find anything suitable via google.
The clutch will be single sided, so I'm looking for some kind of material that can be rivetted or possibly bonded on, and suitable spec sheets, so I can figure out if I can fit the clutch where I want it, and have it transmit the required amount of power (guessing about 30-40hp, but low speed so fairly high torque is needed).

Anybody know of any possible sources?

thanks
Moray

Diving in the deep end here and may be making it more complex than it needs to be, but 40-50hp sounds like a lot of torque at low speeds, though no mention of speed range. I would first look at the torque required at expected speed. Then use this in frictional coefficient sums for the material (clutch plate / brake lining ?) chosen, to get some idea of surface area required. All the math will be on the web somewhere, as will friction plate mnaterial characteristics. Ideally, run the clutch at the high speed end of the geartrain to minimise the torque, as this is really what defines the surface area required.

Looking at car or m/c clutch components might be a good start, similar bhp. Alternatively, use a dog and / or sprag clutch, which would have no problem handling that sort of power...


It's for a forrestry winch/dozer blade to be mounted on the front of a tractor driven from the PTO (rated at 540rpm, or possibly 1000rpm if extra speed would be needed).

Inital figures for a 3500kg pull (dead pull, not rolling), with a reel centre diameter of 100mm, gives a torque of 1746Nm at the reel.
Now reeling speed is still to be figured out, but probably looking at something in the region of 100 rpm, so with a 5:1 ratio, I'm still looking at 350Nm if I can fit the clutch on the input shaft. Having the clutch on the input shaft is the key to this winch, as I want to minimize stack height of the winch drum/clutch.

The commerical winches have the clutch working directly on the reel, and is a disc of friction material rivetted to the driven sprocket, with the other side pressing directly on the underside of the winch reel.

My main issue is finding the frictional co-effcient figures so I can work out what size of clutch plate would be needed, aswell as a source of suitable material. Dismantling a commercially available clutch is one option, but I still need figures as the torque transmission is going to be pretty critical, as it also acts as a slip clutch for overload protection. The whole lot is going to be hydraulically controlled, so adjusting the pressure of the thrust ram will be done to fine tune the clutch slip point, but I still need to get in the ball park in the first place.

thanks
Moray


You're going to use hydraulic pressure to engage the clutch?
Not very good idea from a safety point of view.
If pressure falls or the engine stops for any reason, the winch
lets go.

BTW MH gives the a co-efficient as .4 for brake type material on cast iron.
The formula:
Power Transmitted by Disk Clutches. -
The approximate amount of power that a disk clutch wi]] transmit may be
determined from the following formula, in which:

H = horsepower transmitted by the clutch:
p = coefficient of friction;
f = mean radius of engaging surfaces;
F = axial force in pounds (spring pressure) holding disks in contact;
N = number of frictional surfaces;
S = speed of shaft in revolutions per minute:

prFNS
H =-------
63,000

BTW p was not strictly "p" but an open topped "p"

Tom

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