> The design is bad because a direct shear force is applied by design to
> stress a joint held only by friction. Failure of the joint has the
> potential to be catastophic because a slip could break teeth or fracture
> the ring gear. Pressing a bearing race into a flange is fine, almost no
> friction applied to stress the joint. But I would see a friction fit as
> a bad choice for the ring gear even if a failure never occurred in early
> production.
>
I have to agree with Randall on this one. Seems to me that just about every
LBC that I worked on in my youth (Ford, BMC, MG, TR, Hillman) had a ring
gear shrunk onto the flywheel. The possible failure modes you describe are
independent of the way the ring gear is attached to the flywheel. And
remember, this is a SHRINK fit, not a press fit. There is substantially
more interference in a shrink fit than in a press fit and hence a greater
torque required to move the ring gear relative to the flywheel. My Marks
Handbook tells me that for a class FN3 fit (defined as a heavy drive fit,
for heavier steel parts or shrink fits in medium sections), the interference
can be as high as 0.0098 ins for the diameter we are talking about, with a
corresponding pressure in the joint of up to 3,000 psi. That ain't gonna
move...
Michael Marr
Naperville, IL
1960 TR3A
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