Paul,
At this point my rotary engine options are better if I use a
horizontal engine and a right angle gear box (bevel) with a reduction
from perhaps 6,000 engine rpm to approximately 2,000 rpm. A near 1:1
ratio is also a possibility. It needs to be reliable, able to handle
about 75-80 hp for this application, but small and lightweight for
aircraft use. I think I know my personal limitations and gear box
design is one of them at this point. Any suggestions?

My thanks to you and everyone participating.

Regards,
John McEverett

Take a look at some quad four rear axles. As I recall some of
them have aluminum housings.


Paul Lamar

I could not find the live axle quad I was looking for.
I may have dreamed it :)

If you do decide to build a right angle gear box I can highly
recommend Arrow Gear. They have been around for a long time.
I worked on a land speed record car design and Halibrand (no longer in
biz I think) built a live rear axle for us using Arrow
gears. The Stock Gear Catalog is very helpful in designing
gear boxes.

http://www.arrowgear.com/downloads/downloads_documents.htm

Paul Lamar


Hello !

Several decades ago, there was a light helicopter called
"Djinn".
This helicopter was built by the company named SNCASE that
became later... Eurcopter.

Some "Djinn" pics can be found on the net.

The special feature of the "Djinn" was that it had no
transmission gearbox nor tail rotor.
The main rotor was moved by reaction : Compressed air outlet at
the rear of blade tip.
As there was no torque on the helicopter fuselage, there was no
need for tail rotor.
Except the rotating joint to prevent toobig air leakage, the
system was very simple.

The compressed air was produced by a single stage compressor
turbine powered by a small  gas turbine.
The fuel efficiency of the whole system was not good enough and
this solution was abandoned later.

The use of turbo-compound compression on a rotary engine could
perhaps be a better way to feed this sort of helicopter
rotor :
The idea is to use a rotary engine. The output power shaft woud
be used mainly to electric generation and supercharging
The exhaust gases fed through shortest possible pipes would
power standard turbochargers to compress air to the helicopter
rotor.
Of course, il there is remaining power on the engine shaft (I
haven't done any calculation yet),
it would be possible to use it to compress more air for the
helicopter rotor.

Does that idea make sense ?


        Philippe-Pierre DEJEAN

Yes, I'm familiar with the Djinn and other air pressure jet
helicopters as well. I went the Munich to see the little Dornier Do-32
in the museum there and have posted an archival video of it flying on
youtube. Please take a look at what can be done if you are interested:

http://www.youtube.com/watch?v=l2Oq1xmmIbg

Also look at the related video on the Voljet. I think inventor Bruno
Nagler was considering a Mazda engine at one point but stayed with the
available turbines. I saw a later modification of his at Sun-N-Fun in
about 1988 and it had a 13B if I recall correctly but it was coupled
to a turbine type load compressor. It has since disappeared and I've
tried to find it. It was located in a barn several years ago but I
can't find the gentleman that knew where it was located.

I've been working on building a similar one to the Do-32 for some
time. Not an easy task. The Do-32 used a turbine of about 90 hp with a
load compressor. I think a rotary engine could certainly supply the
necessary power better than a recip engine. I don't know about using a
wankel compressor however. Might work. They need about 50 psi and a
high volume too. Turbine air start engines will work. I have a
suitable turbine, but they are surplus engines and difficult to find.

I'm working on refining a "conventional" small helicopter and have
become increasingly interested in using a rotary, so much so that my
obsession with helicopters is about to give way to an obsession with
rotary power, but it needs either a vertical engine or a right angle
gear box. My project heli has flown sucessfully with a 65 hp 2 stroke,
but I recognize the less than desirable qualities of most 2 strokes
for the task. Helicopter requirements are different than airplanes. If
I find the right rotary solution there will certainly be a market for
them.

Thanks for the input. This a very helpful group. I hope I can add some help too.

John McEverett
Rotorlite Helicopters, LLC