Wrathall Mark wrote:
"In previous attempts to use a highly tuned Mazda 13B engine in aircraft the
main obstacle has been the very large power pulses of the rotary engine
damaging the reduction drive. "
I thought it had been shown that the Rotary has a smoother torque delivery
than most engines? I heard through this forum that Powersport had a massive
failure on the test bench early on due to Torsional Resonance. But they seem
convinced the rotary is a really torsional beast, or is this just marketing
hype? Sounds like these guys have really done some serious analysis of this
aspect of the Rotary. I will never unstand why anyone would put anything but
a Planetary on a Rotary, unless you have a specific need for offset drive,
as low frontal area is one of the designs big advantages. Those big belt
drives that Wankel Germany uses really kill the shape.
Mark Wrathall
They are simply wrong about that Mark. What they have NOT done is compare it to
a four cylinder O-360 Lycoming. Now that is the world champ when it comes
to "very large power pulses". The Lyc O-360 chart below is from the Sky Ranch
engineering manual and the rotary verses the four cylinder chart from
Mazda's book, "Rotary Engine" by Kenichi Yamamoto. Unlike the four cylinder
piston engine, the two rotor rotary engine torque never goes negative.
I whole heartily agree on the planetary psru verses all other kinds.
The planetary leaves more room under the engine (compared to an up
offset) for a large rad which fits better in most stock cowlings.
Also, there is a tremendous weight advantage to the planetary compared to any
kind of spur gear, internal or external. When you add up the length of the
line contact between four or six pinions and compare it to any kind of
spur gear PSRU that becomes very obvious indeed. Line contact length is
almost the very bottom line of how much torque a gear set will transmit.
Paul Lamar
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