Clutch plate friction materials

[bob1111]

We are considering development of a new multi-plate wet clutch pack and curious what friction materials might be available to increase friction over an OEM type friction material? We will have the increase the power holding ability by 3x in this clutch. We cannot increase the diameter of the plate though. We can possibly decrease thickness to add more plates in the stack as well as decrease the ID to increase the friction surface area and will of course, raise the spring rates.

 

[GregLocock]

Let me guess - OEM friction materials run a mu of about 0.35?



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bob1111]

Yeah, we need more friction, as well as more surface area. what types of materials are there?

 

[GregLocock]

I don't know. The reason I put it that way is that all reasonably durable wet friction systems seem to run about that mu.

Can you take a tip from tire technology and think about removing the lubricant from the interface?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bob1111]

I don't think taking the wet clutch to a dry clutch will offer acceptable durability. Ducati has done it for years but they are well known for NOT handling abuse very well. They really need to stay in the wet zone.


I thought some carbon fiber or kevlar products had better friction but I guess if I knew, I would not be asking.

 

[drwebb]

Try a high traction fluid, like one based on Santotrac (Santotrack?).

 

[MikeHalloran]

Try Dexron ATF. If it doesn't grab like crazy with that stuff, you're screwed.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

viper6383,

The friction materials used in production AT clutch packs are designed to give consistent and smooth friction characteristics over the life of the transmission, as opposed to maximum grip. The OEM transmission designers are mostly concerned about shift quality. The materials used in wet clutch facings are usually classified as "papers".

http://www.wellmanproducts.com/D/D02/D02_FrameIndex.html

You need to be careful about putting more power through a wet clutch pack than it was designed for. The increased heat generated in the clutch plates during higher power shift events must be either absorbed or dissipated somehow. So unless you improve the heat conduction path away from the clutch facings or increase the effective thermal mass of the clutch pack, then you will likely exceed the flash/oxidation point of the transmission fluid and cause it to fail. Wet clutch power capacities are limited by the fluid properties, and not by the facing material properties.

Since wet clutch power capacity during shifts is primarily limited by the heat generated from slippage, making the plates thinner and increasing their number probably won't have much effect. Neither will increasing the axial clamping force on the plate stack. Increasing the number of plates/stators and increasing the axial clamp force will, however, increase the amount of torque the clutch pack can transmit without slipping, for what it's worth.

Good luck.
Terry