View Full Version : Harmonic balancers/dampeners

03-02-2003, 11:45 PM
Ok, so I know what they are, and where they are, but exactly what/how does the physics and mechanics of them function? Does the fan and extension really work as a dampener? Are there dampeners that fit a TR3's crank? Is there a need for one if the revs are kept below 4500? Does the flywheel act as one at the rear? Where are the stresses of an undampened crank? Please, just give me the details! Thanks

03-03-2003, 08:57 PM
A TVD (tortional vibration damper) is used to stop HARMONIC resonance inherent in a gas motor. Every time the ignition fires, and forces the crank down, a resonance is built up in the motor. Think of hitting a pipe with a hammer, it rings. But when you touch the pipe, it may sting, but the ringing is dampened. The rubber ring in the balancer acts the same way. It absorbes the harmonic virbrations generated in the crank from the hammer blow of the ignition firing.

Running an engine without one can be deadly. The resonance never gets stopped, and... kinda like the fat lady busting a glass by singing.

But don't panic. I think the reason 3's don't have one is based on the low rpm range, bore*stroke characteristics, metalurgy, and the heft the engine was built with. (ever see the size of the bearings in that motor?) All these things have to be taken into account to determine the frequency something will vibrate at and when.

I don't know if somebody makes one or not, i'd guess so, last vintage race I was at, I know that motor was revving higher than 4500.

Hope this helps.

03-05-2003, 11:14 PM
I have been trying to find just such a beast for my tr4. The motor was setup for and tested to 7000 rpm.At these revs it could certainly stand a little dampening, but as yet we have struck out. I may have to have one custom made at an expense my wife will greatly dislike.........Oh well...
MD(mad dog)

03-15-2003, 12:24 PM
Hi read in a book by graham robson,that reg woodcock of tr3 fame uses a harmonic from a 3 main mgb don't actually know never tried.