Re: Torsional Vibration Testing

[B2431]

> (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?
>
>
I was unaware vendors hadn't done such testing. If I were me and was going to
sell such a thing at the very least I'd test to destruction and have a second,
independent, party do testing as he sees fit.

Your idea is a good one. I have no idea what a reasonable cost would be, but
keep going.

Dan, U. S. Air Force, retired

[baltobernie]

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 are:
>
> (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.

[Ernest Christley]

Dan Horton wrote:

> (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?

I've done enough study of the vibrational issues in PSRU construction to
be able to say, without hesitation, "Well, hell yeah!!"

I've considered long and hard about how I would test this. With no
obvious and practical test method other than maybe a strobe light, I've
concluded that I'd probably settle for running it 50hrs and declare
success if it survives. 8*) Off the top of my head, I guess I'd be
willing to come off of about $200 for 15min of test time.

> (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?
>

The typical homebuilder will assume that it has been done by the company
that they fork over $2000 to. They aren't likely to demand any
evidence. Like the companies that advertise how many chemicals are in
tap water in order to sell bottled water, if you want to sell your
services you'll have to educate the masses about the need. Note, I'm
not implying that yours is a useless service like the bottled water
vendors. I'm just pointing out that you'll have to use the same
marketing technique.

--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------

[klehman]

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 are:
>
> (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

[baltobernie]

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 ...


....Ken's comment raises another point. If Dan performs this testing,
evaluation and reporting, his name goes on the list of defendants should the
homebuilt project spectacularly fail. Renting the instrumentation (with a
well-crafted waiver) could save him a hefty liability premium.

baltobernie

[Jay]

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 are:
> >
> > (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

[Blueskies]

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 are:
>
> (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

[Ernest Christley]

Blueskies wrote:
> 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...
>
I'm listening, Blueskies, if you'd like to explain a little further.
I'm real good at following directions.

--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------

[Richard Lamb]

I dunno about x-y-z accleorometers "in a box".

Or are you talking about those little rate gyros used on model
helicopters? They are only a couple hundred bucks a pop...


Richard



Ernest Christley wrote:
>
> Blueskies wrote:
> > 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...
> >
> I'm listening, Blueskies, if you'd like to explain a little further.
> I'm real good at following directions.
>
> --
> ----Because I can----
> http://www.ernest.isa-geek.org/
> ------------------------