I am responding with regard to Mark Hull's letter. As he stated, Kudos to
Kitplanes for allowing people to express their viewpoint.
I am a 30 year auto and heavy duty mechanic with instrument mechanic for 10
years.
Mark, I congratulate you on a 30 year career. How ever I think you should do
a little more research on this topic.
First, log into the rotaryeng@earthlink.net web site and read who Paul Lamar
is. While there you can also read some of the articles on there. There is also
articles by other writers expounding the rotary engine.
Two, Paul is not expressing the idea that rotary engines are infallible. It
is the stresses on reciprocating engines that is a concern. No, rods do not
get shot out of the crank case regularly, and Paul is not saying that. It is
the low stresses in the rotary he is trying to explain.
Three, a lot of the article is aimed at auto engine conversions. Certified
engines are heavy duty engines on the vein that highway truck engines and
large industrial engines are. They are designed with a high duty cycle
engineered in. These engines run for thousands of hours before overhaul. Auto
engines run at low duty cycles with brief blasts of full power. When subjected
to aircraft use and 75% power for hours, the TBO is going to be reduced.
With regard to the tuner racers blowing rotary engines, yes they do. But they
are pushing the boost and tune envelope. Log into Mazdatrix site and they show
some destruction that testing develops.
Four, if you are going to quote, please get the whole sentence in. The
sentence should read,"If the wear of seals and sliding surfaces can be reduced
to low levels the, the life of the rotary could be 10,000 hours or more. This
is not an admission of rotary reliability issues when taken IN CONTEXT. It is
a statement that with more development what we MAY expect.
Five, with respect to exotic rotor materials; Paul presents a possible
advantage. If you subscribe to the news letter, you will find out Paul has
advocated staying with the cast iron rotors for aircraft use. The reason is
twofold. First is cost and second is that at the RPM required the exotic pats
are not required. For racing that is a different story; according to Paul. If
you read the article on the Le Mans 26B engine, they used Cermet coated side
and rotor housings but kept the RPM down to 9,000 for engine life. There was
minimal wear in the engine at the completion of the race.
Six, balance. Rotaries are very smooth as compared to a recip. engine. They
do not have the other frequencies propegated by the reciprocating motion. A
horizontally  opposed engine is well balanced for the mechanical balance. It
is the dynamic balance with respect to torsional vibration that large bore
engines suffer from. The vibration you refer to in the turbine can be
illustrated be an example of a car with a slight wheel balance imperfection.
All tires have a slight difference in circumference. If a few of the wheels
are out just a bit, you will not notice it if they are out of phase. But due
to the circumference difference they will all come into phase and out. The car
will have a vibration when they are in phase. The turbine with segments at can
rotate at different speeds does the same. And as you stated, no balance is
perfect which produces the harmonic.
Thank you Kitplanes for letting me vent my spleen.

Dale Davies

Good job Dale. Thanks.

Paul Lamar