Pendulum Absorber Design?

[Tiburontropic]

Is there any design criteria for building a pendulum torsional absorber, as far as pendulum weight and number of pendulums. I am working on a design for a 2.0ltr four cylinder.

 

[GregLocock]

What are you trying to absorb? I've never seen one of these things, just read about them in books, many years ago. The rule of thumb is that an absorber has to be at least 10% of the modal inertia, at the point of absorption, to be at all effective, and often a lot more than that.

You might try and find some literature by Holtzer, who have been interested in wacky crankshaft absorbers for many years.

Cheers

Greg Locock

 

[EngJW]

Ker Wilson wrote the bible on pendulum absorbers. It is a large book and may be difficult to find. Engineering schools may have it or perhaps your local library could get it on interlibrary loan. I think there is only one long chapter that you would need. Equations and practical information are given.

As I understand it, they cancel out torsional vibrations of a particular order across the rpm range, instead of responding to a particular frequency as others do.

These originated (I think) in aircraft radial engines since there is only one crankpin and they don't take up much room. They are still used in Continental 6 cylinder aircraft engines. There is also an aftermarket torsional damper that uses the principle. Adding them to an existing engine would be very difficult.

John Woodward