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<< Lancair Builders' Mail List >>
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In a message dated 6/6/01 10:39:41 AM EST, MIAMICONCRETE@aol.com writes:
<< In addition, forward thrust
forces between a 180 and 200HP was not my major concern (or should it be my
major one?) Torque, asymmetrical thrusts, hard landing forces with added
weight of the varr.pitch prop, and CG did come to mind. A 58 lb. vari pitch
prop more firewall forward with the ext. mount seems fwd heavy. >>
Vic,
I believe you are correct in worrying about the added weight of the
engine/prop combination.
I have a buddy who works stress analysis on the engine mount beams for Cessna
business jets (I work wing stress analysis). He tells me that the critical
load case for engines/mounts is typically a gust condition. Now these are
turbofans rather than pistons, so pistons may have some other critical load
case. I can imagine that the torque load at engine startup is fairly high.
This may be what sizes the engine mount structure or perhaps it may be the
impact load of a hard landing. Who knows.
Guessing about this sort of thing is rather dangerous. For example, I know of
one airplane where a sharp turn at taxi speeds puts more side load on the
landing gear than a crooked touchdown in a crosswind. Certainly not intuative.
I would not consider putting more bending load on the "triangular chocks"
and engine mounting structure than the stock configuration. I would try to
figure out the heaviest stock engine/prop/starter/exhaust/alternator/etc.
combination and not exceed this. I would also contact that factory and ask
them if there is any structural difference between the 320 and 360 airframe.
I would bet there is - same molds with just a few more plies of fabric here
and there.
Paul Klusman
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Please send your photos and drawings to marvkaye@olsusa.com.
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