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[FOT] Crank dampener and harmonic vibration

To: fot@autox.team.net
Subject: [FOT] Crank dampener and harmonic vibration
From: "SHANE Ingate" <hottr6@hotmail.com>
Date: Mon, 12 Jun 2006 12:42:10 -0400
Amici,

Most (all?) reciprocating motors develop some harmonic vibration in the 
crank.  I
specifically address the 2.5 liter 6-cylinder harmonics at around 6,200 and 
7,000+
rpm.

The theory of using a dampener on the nose of the crank is to reduce these 
harmonics.
Given all the stories I have heard about the TR6 motor, it seems to me that 
either the
dampener does a poor job, or that the cast-iron TR6 crank really is a wet 
noodle.

The dampener weighs a lot and I could free up a lot of rotational mass by 
replacing
it with a smaller diameter alloy pulley which would have the additional 
benefit of
underdriving the water pump and alternator.

Track work calls for extensive time spent at killer-rpms, especially down 
straights.
My street motor is not a dedicated racetrack motor, but also does yeoman's 
service at
auto-X,  hill-climbs and 1/4-mile sprints.  As such, I do not spend a lot of 
time at the
killer-rpms, and I try to buzz through them very quickly

Question: Would I significantly reduce the life of my motor by removing the 
dampener?

If so, are there better dampeners than the stock Triumph unit?

Shane Ingate in Maryland
"Anyone can restore a car. It takes a real man to cut one up".



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