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I don't think many homebuilders could afford to fly you and your
equipment to them and then be there while they try different componants and adjustments to propellers over the evenings/weekends. So your business might be to buy the equipment, then rent it out to people to bolt onto their own hubs. Flyable instrumentation (recording) would be preferable to static thrust only tests. You might analyze the data collected (sent to you digitally after the fact) by the equipment for them and go over it with them by phone. Regards klehman wrote in message ... Garfield and company looked into this in some detail and concluded exactly what you have. He located a reasonble cost rf unit (a few hundred $) and planned to incorporate it into a short bolt on prop extension so it could be moved from engine to engine. (I understand that adding an extension is not ideal physics but I consider it a workable plan.) An IR or laser LED was also discussed to beam the info down the centerline of the shaft. Anyway, I would plunk down $1000. in a heartbeat for such a plot, probably more. Otherwise it will take me a couple of years to accumulate a couple of hundred hours to gain confidence in my engine system. Your location would be a factor. Multiple tests to let me tune the dampers in my psru might be desireable. Even a single test to tell me what (if any) rpm to avoid would be well worth $1000. in my opinion. Yes I think you could recover your costs. No I don't think you could make an ongoing business of it for a lot of reasons. An under $1,000. unit such as Garfield envisioned that I could rent (or build) would be wonderful. Even better would be releasing the details into the public domain. A user group would spring up quickly. My experience is that very very few people understand how important this is. Many might benefit hugely as combinations of common engines, psru's, flywheels, and props became known good (or avoid) combinations. Ken Dan Horton wrote: 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 |
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