Most of the stress is near the surface of any shaft. Most of the stress in
the e-shaft is in the fillet area  between the main bearing and the
eccentric lobe. It does not need to be any bigger. Nobody has every broken a
properly balanced Mazda rotary engine E-shaft despite generating up to 800
HP so obviously it is over designed and can be hollowed out without
problems. The same thing cannot be said about piston engine crankshafts that
all crack sooner or later.

Paul Lamar ...No rotor no motor.


Don't mean to be a pest, but an alternative to hydro forming is laser
sintering, or DMLS.

http://www.eos.info/products/metal-laser-sintering.html?L=1
They have some amazing alloys developed. There is a machine in Ohio in a
contract fab shop.
C. Smith

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