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



Paul,  Just a thought. For a helicopter installation you might mount the
coolers on a pylon above the engine under the big fan and not use any
ducting.Probably mounted at a 45 degree angle rather than flat since
down wash is not vertical.

George grimes


I don't know why one does not see that.
I think the problem with that is  helicopters spend a lot
of time going forward so perhaps the flow is sheared
off.  They all seem to use fans to cool
both air cooled and liquid cooled. Typically the engines
are de-rated by about ten HP as that much is going into
the fan.

Paul Lamar


Here is a picture of a Kamov twin engine (radial recip)
with the engine pods facing forward. I don't know if there
are any fans in there. Sorry about the file size, don't
have any photo editor on my net book yet. On much needed vacation.
C. Smith