Hi Paul, I am new to the area of Rotary Engines, but have
been trying to educate myself on them. I currently have
an experimental helicopter with a solar turbine engine.
I have been considering converting to a piston engine,
and was wondering if the rotary engine would be a good
fit. The engine needs to be able produce a max hp around
100 to 120 and turn constant 3150 rpm at the pulley with
the average hp use of 65 hp. The engine with reduction
gear case and accessories need weigh no more than around
150 lbs. I would be very interested in your thoughts.

Thanks

David Lyons
N3722T

The HP is a piece of cake for a Mazda based rotary but
you will need an additional 2:1 gear box as the engine
produces power at 6000 RPM and up. Mostly up.

The weight is in the ball park with aluminum center and end
housings from Racing Beat. An all aluminum Mazda based two
rotor would weigh about 110 pounds and have as much as
300 HP at 9500 RPM. At 6000 RPM it would be about 180
HP. To get a lot of HP at 3150 RPM one would need a super
charger or a turbo charger. The engine is only 2.6 Liters.
or 160 cubic inches. Forget all you know about internal
combustion piston engine RPM. Rotaries are not affected
in the same way. They are more like turbines.

Tracy Crook builds a 40 pound
gear box with a 2.85:1 reduction ratio. It is also possible
to buy some early Tracy Crook and Ross gear boxes used that have
a 2.17:1 ratio. These are easily overhauled as they use Ford C6
auto tranny parts.  The GB could be ten pounds lighter with a bit
of custom machining. Mostly on the gear case.

Read the complete web site http://www.rotaryeng.net

The BSFC is twice as good as a small turbine at around
.47 to .52 so fuel burn per hour would be about
half.

Does your helicopter have a  right angle drive to the
main rotor shaft? The engine needs to be mounted horizontally.

Paul Lamar

Yes, the helicopter does have a right angle
rotor gearbox. The helicopter is called a helicycle,
and uses a 6 belt pulley with a tensioning system.
Is the rotary engine a complicated installation?
David Lyons
N3722T

Other than liquid cooling no different. You will need
a fan to cool one in a helicopter so plan for that.

Do you have any dwgs on the turbine?
Here are some on the Mazda for comparison.
They look pretty much the same size.

Paul Lamar


I think there might be some drawings of the turbine without the gearbox, I will see if I can find them and send them to you. Do you by chance know were the  CG is located on the engine with 2.17 Reduction gearbox installed. I am curious if the weight would be more to the rear or not than the turbine installation. I know that there was one helicycle with a Hirth engine installed in it without any problems as for as CG was concerned. Also would you have an idea as to what the cost of a complete 13b engine would run including the gearbox.

David Lyons


It is about here David with wood prop.
As I said think 10 pounds can be removed
from gear box.

Paul Lamar