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RE: >>The earlier ring gear was pressed onto the flywheel (what an

To: "Richard Alexander" <RALEXANDER@smail.umaryland.edu>, <triumphs@Autox.Team.Net>
Subject: RE: >>The earlier ring gear was pressed onto the flywheel (what an
Date: Thu, 14 Oct 2004 13:57:11 -0500
> 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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