x-y-z accelerometers 'in a box' attached to the engine; pick up RPM; feed it all into an excel sheet then plot the
results. It does not need to be very expensive to be effective...

--
Dan D.



..
"Dan Horton" wrote in message om...
RAH Gang,
Have not posted here in a while. Hope all are doing ok.

I'm considering the purchase of some very expensive equipment for
the live measurement of torsional vibration. The methods are industry
standard; apply strain gauges to the shaft, connect to a telemetry
radio transmitter, beam the signal to a receiver, then output to a
variety of analysis/recording devices.

The typical result is a plot of vibratory torque amplitude by RPM.
Any critical (resonant) RPM range is obvious. The point is to
determine vibratory behavior and loading while the airplane is safely
tied to a post. Unacceptable vibratory torque amplitudes are cause
for a redesign. This sort of work is a big part of what you pay for
when you choose a certified engine/propeller combination.

The homebuilt world has a lot of interest in alternative engines,
propeller speed reduction units, etc. To date, very few are subjected
to actual measurement. The usual program is to fly it and hope it
doesn't break. If it doesn't break in 50 hours or so, the builder
declares it to be a success. If the builder is also a vendor, the
next step is an advertisment in Sport Aviation. There are obvious
shortcomings to this system.

RAH is a great place for opinions, so I would like to hear yours.
The questions a

(1) Would individual homebuilders pay money to have their
self-designed engine/drive systems checked for torsional amplitudes,
determination of frequency, etc? If yes, how much money would it be
worth to an individual builder?
(2) Would homebuilders eventually demand evidence of such testing
from vendors to the experimental market? Or is it likely that the
average homebuilder would never become aware of the need for such
testing?

Please, no soapbox stuff. This is not an invitation for another
debate about "certified vs auto conversion" and the like. This a more
of a market survey. Is there a market for a currently unavailable
service that would make the use of experimental engines and drive
systems safer?

Thanks,
Dan Horton