In answer to several inquiries about the 5/8" wobble I found on the TR-6
while on the dyno and using a scope and sensors on each side of the wheel:
Yes it was .625" ( approx, memory) but that is total from deflection "A" to
"B' or fore and aft
not a figure in each direction. As I was no longer working on the 4 cylinder
TR's at that time I do not have a number the Spitfire or the 3's and 4's.
But the 3's and 4's do not have anywhere near the problem due to the better
crankshaft stiffness. By the same token the GT-6 is not as bad as the TR-6
as the GT-6 has a lot more overlap on the journals and thus is stiffer also.
As the first resonance with the 3's & 4's is about 2800 to 3000 rpm and
second about 5200 you shouldn't expect the terrible third until about 7000
or a little more. The third cycle on the TR'6 was so bad the pen went off
the page. This is dead stock now, not a modified and special unit. In the
end I increased the weight of the crank throws with brass plates and all the
heavy metal the throws would hold and this raised the resonance level to a
point of the rpm range and we were then looking good.
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