-----Original Message-----
Subject: RE: Flying: Performance: Speed kit.
Hi Duncan-
Whoever said that geared reductions are free from resonance's? On my
Avid Flyer I have a 3.2:1 reduction driving a 60" prop. I have had
two (2!) crankshafts break on me in flight due to torsional resonance.
The last one occurred even after my implementing a torsional vibration
isolator, with an added flywheel. I believe that geared reductions can
exacerbate torsional resonance problems by multiplying the inertia of
the prop by the gear ratio. I, for one, would love to have knowledge
of which rpm ranges to avoid!
Pops
A036
-----Original Message-----
From: owner-europa@post.aviators.net
Subject: Re: Flying: Performance: Speed kit.
The necessity for all that would be for direct drive engines. But always
nice to confirm that geared reductions don't have resonances.
Duncan McFadyean
----- Original Message -----
From: <ptag.dev@ukonline.co.uk>
Subject: Re: Flying: Performance: Speed kit.
> Hi! Mike.
> MT Propellers ,in my case supplied the propeller
> kit fully balanced, however they insisted that to
> maintain warranty conditions it must be supplied
> back to them within 50 hours for strain gauge and
> dynamic balance tests with the particular engine
> combination to identify any resonant RPM's over
> the full range of operation.
> This now completed a "non-flying" peak resonant
> range between 2150 rpm and 2400 rpm has shown to
> be present, and they are recommending not to
> cruise in that range if possible.
> I guess if I can't live with that it means
> another trip back to the factory for flight
> testing to try to narrow the non- useable range.
> The point about this is that simple balance isn't
> the full story and further strain gauge testing
> needs to be carried out to do the job in a
> professional manner. Only with that test can it
> be established what crankshaft oscillation is
> taking place, allowing you to select the most
> engine /propeller friendly flying.
> Best regards
> Bob Harrison
> G-PTAG Europa MKI /Jabiru 3300
>
>
> Quoting DuaneFamly@aol.com:
>
> > Please excuse a dumb question.
> >
> > How do you know you have an out of balance
> powerplant setup? If it is
> > "really" out and you start the engine, can you
> do damage before being
> > able to
> > shut it down?
> >
> > Mike Duane, San Jose (soon to be Redding)
> California
> > Lurking for a long time but hope to build soon.
> >
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>
>
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