Harmonic balancer/damper dynamics...

[pishta]

Anyone have a link to a slow motion video of a damper in action? Ie how much does the ring move or is it more of a vibration damper as described? I'm curious as my slant 6 outer ring is being used as a 36-1 timing ring and I don't know if it's rigid enough for ignition timing. I'm going to install a 3 prong spider off the hub that will poke 3 90 degeee prongs into 3 drilled holes in the ring just to keep it from spinning. The hopes will be slightly oversized to allow a little movement but I'm not sure how much these actually deflect degree wise from rest?

 

[Plymouth 65]

The inertia ring will move based on the amount of hub input. Rubber also has what is referred to as a "magnification factor". Depending on the elastomer the mag factor will vary. Typically 4-5 to 1, hub input will be approximately 0.2 degrees single amplitude. You're inertia ring will have an amplitude of approximately 0.8-1.0 degree single amplitude. 65'

 

[pishta]

So if I make my spider holes big enough to handle 1 degree of deflection either way I should be ok? The outer ring was not ideal for the timing but it was available at the time. I can invest in a hub mounted 36-1 wheel if it will become an issue.

 

[Plymouth 65]

Yes, it would be best to use a hub mounted trigger wheel for timing if possible. The inertia ring will not move until it gets the torsional input from the hub. Once the ring starts to oscillate it may effect the timing. 65'

 

[67Dart273]

I'm not sure I'd do that, Pishta.........mount anything to the ring I mean. It is intended for a certain weight and dynamics, and adding anything much to it will change that completely

Also, with the longer, "spindly" crank in a 6, I'd bet the balancer is more important than ever

 

[pishta]

That's why I was thinking of a semi rigid "support spider" for the outer inertia wheel firstly to prevent a catastrophic timing ring slip. I can always replace it with a neutral 440 damper .....

 

[Plymouth 65]

The inertia ring is used to reduce the amount of torsional amplitude in the crankshaft. That inertia and spring rate of the elastomer is tuned to the resonant frequency of the rotating assembly. A slight addition of inertia to the inertia ring will effect the tuning frequency of the damper by slightly lowering it. How much will depend on the amount of inertia added. 65'

 

[pishta]

I guess I'll see what happens. Lots of info here!