[rebel-builders] Rebel/Subaru/Ross Aero Drive

[ray.mason]

For those looking at a subie, Maxwell Propulsion
http://www.maxwellpropulsion.com/ has almost or just finished testing all
the components for their EJ25 FWF. I have seen the PSRU and it does look
good. I believe it is the only one out there that is designed by an
aeronautical engineer.

Ray


On 9/26/2007 2:11 PM, im_planecrazy@yahoo.com wrote to rebel-builders:

-> I purchased a damaged Rebel that has a Formula Power Sub engine that
uses the Ross PRSU. I have not run the engine as I had originally intended
to rebuild the plane. I talked to the gentleman that built this Rebel and he
relayed that he had ZERO problems with the engine or the redrive. It had
303 hours on it when I purchased it from the insurance sale. I am thinkling
of selling it though since I highly doubt I will ever have the time to rebuild it.
->
-> Keith R661
->
-> mdb1225@comcast.net wrote:
-> Ken,
->
-> EPI makes a strong case for not using a subaru engine.
->
-> The Vans forum comments run 50/50.
->
-> What does Murphy Air have to say about this?
->
-> Mike
->
-> -------------- Original message --------------
-> From: Ken
->
-> > In general any significant time in this region destroys the psru and it
-> > can do so in minutes. The forces can multiply to several orders of
-> > magnitude higher than the engine could ever deliver. Think opera
singer
-> > shattering the wine glass. No psru is immune to destruction if operated
-> > in the resonant range. If they are aware of the issue, most folks use a
-> > light prop and idle their psru above typically 1200 to 2000 rpm to
-> > attempt to stay away from the first destructive region. It seems that
-> > some units are OK above above 1000 rpm. A heavy flywheel usually
also
-> > helps. My slightly soft Marcotte (small amount of rubber coupling)
-> > seems happiest if I avoid below about 1700 which is effortless except
-> > during warmup. Ross (google sdsefi) idles his above 2000. Torsional
-> > resonance is the big risk with an uncertified engine/prop. Most of us
-> > just don't have access to torsional testing equipment although some
-> > estimates can be calculated if the effort is put in to measure
-> > components. Sadly the safest thing for most of us is still to use an
-> > engine/psru/prop combination that has been successfully operated by
-> > others for a significant time which probably means the next harmonic
was
-> > avoided. A soft element in the drive will reduce the magnitude of the
-> > forces but mostly they are used to attempt to tune the resonant
-> > frequencies out of the normal operating rpm range. As I indicated
-> > previously there are also assembly issues with the Ross psru that must
-> > be addressed. Scary stuff but aircraft engines don't do much better;
-> > even when pampered (and fed with a highly leaded diet) they still fail,
-> > just for different reasons IMO.
-> >
-> > http://www.epi-eng.com/BAS-TorVibInt.htm
-> > http://www.vansairforce.com/community/s ... hp?t=19030
-> >
-> > Ken
-> >
-> > Drew Dalgleish wrote:
-> >
-> > >At 01:28 PM 9/25/2007 +0000, you wrote:
-> > >
-> > >
-> > >>I am thinking about buying a used Rebel with a Subaru engine and
a Ross
-> > >>
-> > >>
-> > >drive.
-> > >
-> > >
-> > >>I would appreciate anyone's thoughts on the what to watch out for
and any
-> > >>
-> > >>
-> > >personal experiences.
-> > >
-> > >
-> > >>The owner discussed a problem related to "sympathetic vibrations"
causing
-> > >>
-> > >>
-> > >chattering in the Ross drive at prop rpm's below 1000. Has anyone
else
-> > >experienced this?
-> > >
-> > >
-> > >>Thanks,
-> > >>Mike
-> > >>
-> > >>
-> > >
-> > >Hi Mike I don't have any experience with ross or subaru ( other than
my
-> > >car ) but 1000 prop RPM is slow enough that unless you're
considering
-> > >putting the plane on floats you could always avoid the harmonic
range.
-> > >Drew
-> > >
-> > >
-> >
-> >
-> >
-> >
-> >
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