The axles tend to break where the threads begin. This is a stress riser
because of a fundamental design problem, so changing the manner of making
the threads (or the material) won't solve it. A threaded bolt simply is not
suited to take sideways stress at the the place where the threads begin,
and this is what happens in the axle, especially the cush drive version.
Best practices in aviation and other mechanical fields always have bolted
joints so any bending stress is on the unthreaded portion of the bolt.
Before I decided to convert to a one-piece axle, I mentally tried redesign
the two piece. The best solution would probably be matched tapers in the
axle and dummy axle, with threads only at the end of the axle to hold the
tapers together (some milling machine are designed to hold tools this way).
Steve Shiver's idea of redesigning the parts so the threaded section is
completely inside the dummy axle would also work, especially if the
unthreaded parts of the axle and dummy axle were a light press fit.
But it would be almost impossible to keep tapers or close-fitted
shafts clean enough in the environment of a motorcycle wheel axle.
Changing to a one-piece axle is the easiest solution, but there's not much
interest in it because people who ride sedately seldom have the problem,
and people who ride like hobot eventually tend to put on a different rear
wheel anyway, (as hobot did) because the stock one is so heavy.
Mike Taglieri
miket_nyc@verizon.net
