Pinion Mass Dampener

[forestgreen95gt]

So I was wondering if pinion mass dampeners that are found on some vehicles are to compensate for the harmonics generated due to pinion angles within a certain range. Am I wrong in thinking if the drivetrain were in perfect alignment for an independent rear suspension vehicle (ie zero angle between transmission tailshaft/driveshaft, and zero pinion angle) one would not need a mass dampener on the pinion?

 

[GregLocock]

No, you are wrong



Cheers

Greg Locock

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[forestgreen95gt]

okay...where do the harmonics come from? Why do certain vehicles need a pinion mass dampener? Front engine cars using torque tubes and rear transaxles don't use mass dampeners do they?

 

[btrueblood]

Every piston engine made has some torque harmonics. Wankel rotarys too. Turbines have them as well, but they're much higher. Electric motors have some.

And that's just the "source" end of things...

 

[MikeHalloran]

You're somewhat less than completely correct about the joint angles, too. If the joints never flex, the bearings within suffer false Brinelling and die.





Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

If the joints never flex, you don't need CVs or universal joints, just a flanged or splined coupling.

I imagine some vibrations are induced by CV joints in the axles if the diff centre is mounted rigidly to the chassis.

Also tyres might set up some reaction as they are never perfectly round with perfect side wall stiffness in all directions.

Regards

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[forestgreen95gt]

I was never implying the joints would not flex. Just the angles between them would be zero. I'm assuming universal joints would be used.

 

[patprimmer]

If the angle remains zero, why do you need universal joints

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[forestgreen95gt]

OK...lets just use the example of a front engine, rear transaxle vehicle connected via a torque tube like I've mentioned above. Like I asked above, does anyone know if this setup uses a pinion mass dampener?

If the engine, transmission, and differential were not connected rigidly, I would assume that the deflection in engine, transmission, and differential mounts would cause the angle to change slighlty (< 0.5 degrees for arguments sake). This is why I would use universal joints.

 

[patprimmer]

There we go.

The angle does change.

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[Fabrico]

You can't use a solid bar like most of the rest of the world?

 

[patprimmer]

I would think the less than 0.5 deg movement could be accommodated by the drive shaft flex if the drive shaft was not to thick or to short. I use a jack shaft in a speed boat to connect the motor to a V drive gear box. It is an old truck axle with the root dia. of the spline a bit over 1" dia. and the shaft was turned down to 1" dia. for most of it's length.

It is about 4' long. The boat flexes a bit (never measured) and the shaft never fails.

Regards

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[Fabrico]

Nor did they fail in the front engine/rear transmission Pontiac Tempests, a few Ferrari models, and the latest few years of powerful Corvettes.