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


Just read your e mail  my 2 cents check with k.i.s.engineering in California
they use a mini sprint car rear from Speedway Engineering in a Rotorway
exec with a turbine  its been around for years. They have a complete kit out.
Good luck.

Bobby c


Good work Bobby! Thanks. I suspected a midget sprint car rear end but
I could not find the source.

Here you go John. You wont find a better right angle gear box as these
are light weight, rugged and well tested. Typically they use hollow output
shafts.

http://www.1speedway.com/
http://www.1speedway.com/Center_Kits.htm

------------------------------------------------

With the right quick change gear set you can get up to a 8.65:1
reduction so 8000 engine RPM would be 925 rotor RPM.


Paul Lamar