Wouldn't this testing have greater value if the builder could obtain data
before first flight? How about having him ship the complete power plant,
engine mount, and propeller to you, where it would be fitted to a stand?
This would:
1. Save him or you from flying or driving to the home of the new airplane.
2. Allow modifications or rework before fabricating cowling and the
remainder of the aircraft,
2a. ...maybe permitting mods while still on your stand.
3. Could you add other tests like thrust, etc. with a little additional
investment?

your questions Replied below...
baltobernie


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?
^^^^^^^^ Under $1k, including transportation. Maybe $100/hr. for
tinkering. What do shops presently charge to dynamically balance
propellers?

(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?
^^^^^^^ Don't think so, due to the huge number of variables in components.
PSRU manufacturer would need to list all internal engine parts and prop used
in test assembly. Data would be meaningless unless builder constructed an
exact duplicate of the tested assembly.

^^^^^ Many of your prospects would probably be builders of high-end
aircraft, who would pass the word. Perhaps not much of a market in
ultralights or Sport.