> Back to the point - the heavy mass of the stock flywheel coupled with
> harmonic motion characteristic of the design (only 4 main bearings!) leads
> to lots of crank _flex_. If you can reduce the mass of the flywheel (and
> clutch assembly, BTW), you will reduce the amount of rotational and
> tortional forces on the crank and therefore reduce the potential for
> cracks or worse.
I saved a long-ago post from Kas Kastner, where he talked about measuring
flywheel wobble on a TR6 (stock crank and flywheel) : he found the wobble
could reach 5/8" !! This was at 5800 rpm, the third resonance point of the
crank, which of course most street motors will never see.
Curiously enough, his solution was to add weight to the crank, to move the
resonance up above the speed they were trying to turn (which was not
revealed). He also made the point that the flywheel-to-crank bolts get
heavily loaded in tension, in this situation, and that he found the
clutch-to-flywheel bolts would usually let go first.
Randall
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