In writing this email I am assuming that none of you in the
rotaryengine group have made any studies of torsional resonances that
might occur when operating Tracy Crook's redrive with an NA Mazda 13B
(if such a study has been made,  please let me know).
I am considering making such measurements using the laser-based
Rotational Vibrometer system developed by Polytec (http://
www.polytec.com/int/158_423.asp).
I can rent the device for $500/day, and it appears to be made exactly
for this sort of measurement. I would do this with my son + classmate
studying engineering, possibly in conjunction with a member of the
faculty at the college that they attend. It would be great to have
various propellers to try out as part of the system.

If anyone has any suggestions as to how best this might be done,
please let me know.

Thomas Lowell


Well when you get it set up on an airplane with a gear box and
prop you can soon find out what it is by idling the engine at
various speeds. As soon as you hit resonance all hell breaks loose.
The system shakes rattles and rolls.

Typically this happens about 1800 engine RPM. Tracy claims he can lower
the frequency (RPM) by going to softer rubber bushings in the torque pulse isolator
plate.