Sprung Centered Clutch Disk vs Solid 1

[apex944]

You guys were so helpful with my last driveline question that I thought I'd toss another one out to the collective group...

WRT racing clutch disks and a single mass flywheel...

This

vs This

Are sprung centered clutch disks primarily for the reduction of noise? (chatter)

There are some who say it will reduce the stress to the driveline (under power) but I'm skeptical of this. The springs in a disk dont appear to be strong enough to counter (soften) the torque and inirtia of the engine/flywheel... which make me think they are for noise or vibration reduction only...basically at idle and very low RPM/low power output.

For the purposes of answering this question lets disregard standing starts and concentrate on engagement where the engine is operating at or near it's torque peak after upshifts or at other RPMs on downshifts where the driver may be matching revs anywhere in the range.

Thanks!

 

[DennisP]

The springs in the center of the clutch disc are there primarily to soften the engagement of the clutch. This also serves to minimize the shock loads the driveline might see in normal use.

 

[Fabrico]

I can't help thinking they would also soften engagement of the gears while shifting. "Big rigs" have a similar spring arrangement. Even motorcycles have these, usually in the form of several rubber cushions in the clutch hub.

 

[patprimmer]

I thought the marcel (spelling ?) action. Wave type springs between the layers of facing material that compress under pressure plate load were to soften engagement.

Hub springs are to absorb drive line shock and slight misalignment.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[thundair]

Another reason to have the springs is to dampen harmonics generated in the crankshaft to protect the transmission.

Cheers

I don't know anything but the people that do.

 

[apex944]

OK, all good. Tis what I suspected. So it sounds as if they do nothing under full power. I'd imagine they would be fulley compressed under most conditions where power was being applied.

- Bill

 

[patprimmer]

It would be a fairly simple test to hold the clutch plate in a vice and modify an old first motion shaft by drilling and threading the end. Insert a bolt then test with a torque wrench to determine the torque required to fully compress the springs, then compare that to engine torque.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[tbuelna]

I always assumed the springs are in the clutch disc to help people that are "manual transmission challenged" smoothly engage the clutch without stalling the engine.

 

[IceStationZebra]

I agree with Dennis "The springs in the center of the clutch disc are there primarily to soften the engagement of the clutch. This also serves to minimize the shock loads the driveline might see in normal use."

For the springs to dampen harmonics they would have to operate in a slightly compressed state at all times. And for a simple spring to do this the engine would have to output a nearly constant torque at all times. The damper and flywheel mass are there to dampen engine harmonics.

ISZ

 

[Blitz94]

I would have have to agree with the majority of the remarks thus far.
I am in no way, shape or form a professional in drive-train technology. However, I have had the misfortune of running an un-sprung clutch in one of my own vehicles.
To the best of my knowledge, and the reason for my purchasing and installing said un-sprung clutch, is that un-sprung clutch's work better with drag slicks. They launch more consistently.
They do however also deliver 100% of the engines torque and vibrations immediately upon engagement.

I.E. un-sprung clutch's are far more likely to contribute to expensive repair bills than standard sprung ones. Just my 2 cents.

 

[Rob45]

In addition to the springs, there is frictional damping in the clutch center that counters torsional vibrations of various sorts; in order for this damping to work, there must be motion, which is where the springs come in.

 

[izzmus]

I spoke with an old drag racer on the subject after experiencing a rash of transmission failures with a solid hub clutch, and he pointed out that in the 60's, they used to twist the input shafts of their T10s until they switched from solid hubs to sprung hubs. The springs offer just enough give to reduce the initial shock to the system on launching and during (clutchless) shifts.

And then, he showed me a box full of trashed input shafts. It's hard to argue with experience.