torsional vibration

[terr]

Do the springs arrangedd radially around a clutch plate absorb or deturn torsional harmonic vibrations?

 

[GregLocock]

They definitely affect the TVs.

If you can make the travel long enough they can be made to isolate the driveline from TVs down to 80 Hz, but this is tricky. Another approach is to use a dual mass flywheel which allows you to put a low pass filter into the system.

Strictly speaking they detune the system - springs can't 'absorb' energy, as such, although they can certainly reduce the amplitudes of modes.

Cheers

Greg Locock

 

[ivymike]

yeah, what he said.

 

[terr]

GregLocock,
What's a TV; and, what's a dual-mass flywheel and a low-pass filer, and how is it inserted into the driveline? Are we talking mechanical driveliness here?
Terr

 

[GregLocock]

TV=torsional vibration, a low pass filter is a filter that removes high frequencies, a dual mass flywheel is one in which there are two flywheel discs, separated by a compliant system of some form (rubber would be good), which forms a low pass filter for rotational vibrations, and yes we are talking mechanical drivelines.

Cheers

Greg Locock

 

[terr]

Thanks for the education. I had been thinking I'd have to go to an expensive full-phase double cage sprag.
Eighty Hz is still 2400 pulses per minute....

1. I'm working with an 8-cyl 4-cycle input,and the idle speed about 600-rpm... that's 2400... so how do I figure how much spring I need? Or if that's too critical, can I buy a dual mass flywheel somewhere? (351-cu.in)
2. I'm also working on a problem with a 28-cyl 4-cycle engine, and wondered if it can be detuned with a simple spring plate. It drives through a 6-in. dia shaft, to a contra-rotating dual 4-blade prop, reduced to .381. Would it need a dual mass flywheel too, or could a spring plate detune it?

 

[GregLocock]

1 I don't know how to calculate it, we use suck it and see to tune spring rates. You should be able to buy a dual mass flywheel, I imagine Cadillac use them, even Corvette might.

2 Oh just the 28 cylinders is it? Sorry, way out of my experience, but given that you are talking about an expensive installation I would call in an expert. In England I'd talk to Holzer (spelling?).
Cheers

Greg Locock

 

[terr]

Greg,thanks for the info. I'll check out the Caddy and the 'Vette parts. Regarding the 28-cyl., that's for a fiction story I'm trying to write... about a WW II aircraft project. I just wanted to avoid saying anything really dumb... but maybe that's a lost cause.
Thaks again. T.

 

[Rob45]

On Corvettes the Lotus-designed (and Mercury Marine-built) LT-5 engine used in the ZR-1 had a dual-mass flywheel behind the ZF 6-speed.
Big drawback was of course the hugely increased mass of the flywheel, unacceptable to some sporting types!

 

[Rob45]

AHEAD OF! Make that "AHEAD OF the ZF 6-speed!"
Duh!

 

[GregLocock]

I tuned the crankshaft bending damper on that engine!

My boss at Lotus had a fixation with dual mass flywheels, shared by many NVHers at the time.

Cheers

Greg Locock