Hi Paul i'd like to subscribe to the rotary newsletter as i am building the
airframe of my tango XR.
I was planning to go with the subaru EJ22 that i bought along with the kit
but i am busy gathering information on automotive applications for aircraft
to try and understand better why the reliability rate is less than aircraft
engines and to try and avoid the pitfalls and mistakes that have
contributed towards a lower reliability rate than equivalent aircraft
engines.
I am interested in the rotary because they appear to be robust, however
what is not clear and what i would really like to know is why with the
amount of expertise out there on rotary engine conversions, and the number
of years they have been in use in aircraft applications, why there are not
more successful rotary aircraft conversions seen on the flight line.
Hopefully a bit of research and reading will make this clear.
Thank you by the way for the excellent book "cooling your wankel", i have
no technical or engineering background but i found it logical and easy to
follow and i was planning to apply some of the principles of cooling to my
planned subaru setup.
regards
Alex Molteno
Welcome Alex.
Read the web site below and ask any question no matter how dumb it seems to you.
The main problem with auto engines is the duty cycle. An auto engine is only expected
to put out 40 or 50 HP indefinitely. An aircraft engine is 150 HP or higher
continuously. The main difffereces in the engines are the materials the moving parts
are made of. Things like powered metal rods and cast iron crankshafts are typical
for automotive engines. Of course these can be changed in some engines used for auto
racing but that gets expensive as a real aircraft engine. The rotary is an exception
as the stresses on the moving parts are much much lower. Nothing is stopping and
starting up again as happens in reciprocating piston engines.
The other thing is carbs and magnetos are intrinsically more reliable than
home installed EFI.
It takes more work to install a rotary. Many people just want to circumvent the FAA
3rd party maintenance rules for certified airplanes so they build an experimental kit
and install a certified aircraft engine. They just want to fly and the cost of an
aircraft engine is higher than a rotary but not more than about double.
The big rotary advantages comes with the ability of the rotary to run on low cost,
low octane, and less expensive auto gas. Also in the remote chance you wear it out
it is much faster and cheaper to overhaul it.
It is also very smooth so in the air it is far less fatiguing.
If you do go with the Soob you need to disassemble it and use helicoils in the head
bolt threads located in the aluminum block. These threads fatigue under the
continuous pounding and head gasket failure results. The corresponding rotary engine
tension bolts are threaded into the cast iron front end housing. Fatigue on these
threads are unheard of. Of course the Soob exhaust valves are not the same quality as
aircraft exhaust valves and that is also a weak link. The rotary of course has no
exhaust valves. Typcally exhaust valves are the weakest link in certified aircraft
engines as well.
Paul Lamar
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