Viscous Damper Design? 1

[Tiburontropic]

When constructing a Viscous damper, is there a set design clearence between the inertia ring and the case. Also what would the recommended senistoke of silicone to be used. This is my alternative design to the pendulum. It would be used on a 2.0ltr four cylinder. Is there a set sizing of inerta ring for this displacement.

 

[GregLocock]

As a first step I'd use the normal dynamic clearance +3 mm on the radius.

I don't know how to calculate a viscosity,I'd build 3 or 5 with different viscosities and fine tune by ear. You could construct a dynamic model to optimise this, but in my experience it would be indicative at best.

The inertia ring size should be related to the modal mass of the mode(s) you are trying to suppress. Practically speaking there is usually an upper limit that can be packaged, so design it to that and then hollow it out later. Again, this can be modelled, with some degree of success. There is a trade-off here - adding mass to the damper will reduce the bending frequency of the crank, which may hurt you more than the benefit from absorbing the torsionals.



Cheers

Greg Locock

 

[Gwion]

On a similar topic, I’d like to learn about the theory behind viscous dampers.

My particular interest is dampers suitable for the vibration control of large heavy machines, impact presses etc. Can anyone suggest any literature or reference sources?

With thanks in advance.

Gwion.

 

[EngJW]

The classic source about torsional vibrations and dampers are the handbooks by Ker Wilson.

 

[EHudson]

Clearances: The B.I.C.E.R.A. A Handbook of Torsional Vibration, Cambridge Univ. Press 1958, gives the formula:

Typical damper clearances = .010 + .010 x (outer dia. of inner mass/10)^(1/2) Units are inches.

The same reference will also give you the properties of silicone fluid as it varies with temperature plus all the formulas you need. Sadly this volume and Ker Wilson’s texts are becoming hard to find. Also try John C. Georgian’s paper, page 389-399 of the Transactions of the American Soc. of Mech. Engrs., 1949.

(Note: Professor Georgian told me the biggest problem was the distortion induced at welding.)

If you make a good faith effort and these avenues are not workable, advise and we can try to photocopy the design guide.

Regards,

Hudson

 

[GregLocock]

I've been looking for Kerr Wilson for fifteen years (on and off)!

Cheers

Greg Locock

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

 

[MGaberik]

Dr. Georgian from Washington University I presume!

 

[EHudson]

The same Dr. Georgian. I believe he turned 90 last December.

He was a torsional analysis for Nordberg back when they made large diesel engines.