Sir,

I may be missing something here, If the maximum propeller rpm is
2800 . A single rotor engine with max rpm of 1100 with 37 KW @ 8750
rpm. With a reduction drive of 3:1 one could achieve maximum
propeller rpm of 2800.

Why can't this engine with low HP but with high rpm be used on the
Parsons auto gyro ( on YouTube https://youtu.be/QOwb8QRHrMY )which
is currently using the 12a Mazda rotary or can it ?

Best Regards Zahid Rahman

I 37 KW is only 50 HP. A Mazda 12A 2 rotor makes at least 150 HP.
Gyro's, like everything else, fly on HP. It probably takes a minimum
of 110 HP to fly a man carrying gyro.


Paul Lamar

We just need a modern version of the Hiller Rotorcycle :
https://en.m.wikipedia.org/wiki/Hiller_YROE

50hp would be more than enough!

-Dan G.

Actually, it wouldn't, if you want the helicopter to do useful things
besides hover in ground effect at sea level. Paul's number of 110 hp
for a single man carrying gyro is about right, and 150+ hp for a
single man carrying VTOL aircraft, 200 hp for a very light two-seater
like a Robinson R22. Yes, you can store a bit of energy to make a
jump takeoff in a gyroplane if you're lucky. The design boffins at
NASA Langley who are looking at all kinds of wild designs come up
with the same numbers. No avoiding the fact that if you want to hover
you need to produce as much thrust as it weighs, plus a margin to
allow for wind.

David Josephson


50 HP is the top power of the 294 cc per chamber Aixro kart engines,
liquid cooled housing, charge cooled rotor, however, this is a peak
power, not feasible for a sustained time, and no Wankel engine has
an FAA certification for aircraft use, few have a double
spark/ignition system system, that may be a minimum requirement for a
safer airplane use; glow plugs that would solve this issue are not
available in the market, and the producer of the engine in the light
Canard www.e-go.me warns that they sell only to this individual
airplane builder. Some other engine makers may be found, but it's
not clear at all if it are currently under production.

I've purchased an old KM-48 engine, fitted with a reduction gearbox
to move a concrete mixer, but with 10 HP it has little aviation
usefulness. 150 HP are close to the power of the early La Cierva
Autogyros, I can't imagine the reason why you may need 150 HP for a
Gyrocopter less than a 20% the weight of a full size Autogyro. I
asked in this forum about the reason for gyrocopters not having the
articulated blade roots that allowed first, autogyros, and then
helicopters to fly, but I don't remember any response, yes, latest
helicopters, starting by the Bolkow, had rigid rotors that left the
materials in the blades make the adjustment of pitch and incidence
that the articulated rotor had, but this is for helicopters, not for
autogyros/gyrocopters, and this is a RCE site, not an aviation one.
Does anybody offer for sale a single rotor engine, based in the
Mazda 13B housings?

Thanks, have a nice season, best regards, + salut Jose Gros-Aymerich


Alexander Schleicher has sold over 500 motor gliders with single
rotor 50 HP or 56 HP Austro Engines. The rotor is air cooled with
an external blower. The engine has no recommended TBO. In other
words it is intended to lasts forever.

It is FAA certified of course as otherwise AS would not be able to
sell it. Austro also has a 2 rotor version of this engine that is FAA
certified.

http://www.alexander-schleicher.de/en/flugzeuge/ask-21-mi/

Aixro have a prototype engine running with a pressurized oil
system. A oil cooled rotor will eventually be available. This will
solve the continuous HP rating problem and make it just like the
Mazda.

Paul Lamar


Here I am thinking I have flown many hours in gyros only to now find
it can't be done!Weary face I started out with direct drive 1800 cc VW, the
prop was 52 inch limiting rpm to under 3000, above that it was just
noise as the tips went transonic.

We built 1.85:1 tooth belt reduction allowing the rpm to go to 4500.
Performance was quite good. We reckon it had about 80 hp. The Subaru
EA 81 would have had similar hp.

Health problems brought an end to my ambitions of completing a
Tractor gyro powered by a turbo Mazda 12A rotary. It was to be jump
take off machine. We elected to run the drive shaft up to the centre
of the hub bar, but I couldn't find a suitable light gearbox, it
needed to handle 120 ft lbs to overspeed the rotor. The best rotor
rpm I saw was just under 200 before various gearboxes failed, we
were looking for about 550.

The rotor pitch change worked well so we could comply with Oz
requirements to only change pitch FOR flight not IN flight, although
I Thought it would be great to overspeed the rotor on approach by
partially de pitching it to store energy in it and then have control
over the amount of lift as you settle on. I'd love someone to finish
the project.

John Evans


Maybe I should have said plus or minus 20.

What did you weigh John when you did that?

What type of carbs were you using on the VW?

What did you do to the displacement?

The original engines were about 36 HP as I recall.

Paul Lamar



Sorry to be slow answering your questions Paul, we had a few problems
with Internet.
I guess I would have been about 95 kg (200lbs) .

The VW had twin Holley "Bugspray" carbs. Once I fitted the toothed belt
reduction it took a while to get it to cool properly with the higher
output, I had to scoop air from above my left shoulder with plastic
drainpipe fittings on the left, the airflow to the heads on the right
were less of a problem.

The cooling problems were investigated by using temperature sensitive
adhesive strips, they would show the maximum temp experienced by that
part of the head. Air cooled engines can be a pain to cool.

As far as I can recall we got the 1800 cc capacity by going to 92 mm
bore, longer stroke cranks were available to go to 2100 cc.

The EA 81 Subaru ended up with throttle body fuel injection from a
Holden Camira, it worked well but the engine would snuff on late final
if I didn't manually lean the mixture.


John Evans




FWIW, the direct-drive 2180cc VWs are putting out about 80 reliable hp these days (typically they max out at about 3600 RPM, due to prop pitch).  People have fitted them with redrives to let them rev higher, and with the right cam they can put out up to about 100 HP that way, but usually not for very long due to head temperatures--lot of tricks have been tried.  Sonex is now going full tilt with a turbo version of their Aerovee VW conversion that will give more than 80 HP, but boost has to be mild to avoid overheating the heads--I think people will primarily use it for turbonormalizing at higher altitudes.

Again, the exhaust valve brings limits the great plans--Felix Wankel's innovation clearly wins out in this regard.  But in hp per dollar, the well-explored VW is still bringing a lot of smiles to a lot of aviators.   I'm hoping the Mazda will someday become for the 160-200HP requirement what the VW is for the 60-80 HP world.  But there are lot of published guides and a few vendors specializing in VW aviation parts--its a lot sparser and more "experimental" in the Mazda world (something Paul knows very well).

Mark Waldron.

Maybe at 3600 RPM or above. You take a enormous prop efficiency hit at 3600 RPM
and the exhaust valves are still the Achilles heel right from the days of the 36 HP and beyond.
A geared VW makes more sense.


I went through SCCA race driver school back in the early 1960's in a split window.
The problem is the head design. The cooling fins are not near enough and long enough.

My O-470 goes through at least one exhaust valve per 500 hours
and it was designed from the get go to be an aircraft engine

It is a lot cheaper to cut down a 2 rotor eccentric  shaft than buy a forged
2100 CC VW crankshaft.

Paul Lamar


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