I have heard good things about your newsletter and how persons interested in
rotary engine performance can share information.  I currently have a P-Port
Mazda single rotor and a Rotamax single turbo engines that I have been
dynoing in several off road configurations.  The idea of an aircraft
application intrigues me given the power curves available from these
engines.



Thanks and I look forward to my subscription

Bud Westerman

Your in luck Bud. I just came up with an idea to fix the Rotamax.
The problem is charge cooling. This SAE paper by Wankel will explain
what the Rotamax problem was.

There is a lot here based on years of research with charged cooled
rotary engines.


The home made water cooled hollow eccentric
shaft will fix the problem. It is machined in two pieces and welded
together than ground to final dimensions.

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

Bud, disassemble your Rotamax and if you see any discoloration
in these areas the engine has been run at excessive speeds or
continuous power levels beyond its ability to cool.

The shaft and bearings may be history. If not you are in luck
as you can increase the power and RPM capabilities at relatively
low cost. The current limit to what the engine can be run at IMHO
is about 4000 RPM. The limits the power to weight ratio.

The power out is directly proportional to the RPM so a small
increase in RPM will give you more power. Towards the end
of the Rotamax company they kept backing off on the claimed power
and RPM. I suspect this was typical charge cooling rotary
characteristics learned from various attempts to use it in
aircraft. At that time I was in close touch with an aircraft
company that attempted to use it. By June 2008 the HP was derated
to about 120 HP at 5700 RPM but I suspect that could not
be sustained.

One well known trick to improve charge cooled rotary engines is
to drill holes in the eccentric shaft in the indicated area to
better lube the rotor bearing. I learned this trick about charged
cooled engines too late to help Rotamax.

IMHO and I am guessing here this could increase
the continuous RPM to as much as 6500. That should increase the
continuous power out from around 80 HP to about 100 HP or more.
As I said I am guessing. In any event it will make the engine
more durable.

The second trick is to replace the rotor and main bearing
with expensive silicon nitride roller bearings.

This is the ultimate solution short of water cooling the e-shaft
and should further increase the RPM and continuous power out.
http://www.ceradyne.com/products/industrial/roller-bearings.aspx

Ceradyne, Inc.
3169 Red Hill Avenue
Costa Mesa, CA 92626
USA
Tel: 800-839-2189

Fax: (714) 549-5787
Email: info@ceradyne.com

Made out of the same stuff the best apex seals are made from.

There is no real reason why a water cooled e-shaft, p-ports and ceramic
bearings would not run to 10,000 RPM and roughly 200 HP in
a Rotamax based engine.

Paul Lamar

Bud and group,
What does your power curve look like for the Mazda single rotor?
It is looking like I have to develop a single and am hoping for
130hp @ 7,500 to 8,000rpm.  Don't really want to spin this high,
should I consider a turbo to cruise at a more realistic 4.500 to
5.000rpm?  And, don't want to add weight but what turbo is best
for an aircraft single rotor?
Dan F

Forget all you know about piston RPM.
A rotary thrives on RPM. 6000 is a good cruise RPM.
7500 RPM is a good take off RPM. My RX8 does not start
to go until 6000 with a 9000 red line.

Here is Richard Sohn's last HP curve on the one rotor P-port Mazda.

Turbo'a are a real pain in the butt. You need a lot of instrumentation
to monitor them like EGT, wide band mixture monitor and turbine RPM.

Turbo's are harder on the engine as one slip up on the mixture
and you can fracture an apex seal.

They make sense if you want to high speed  cruise long distance
at 12,000 to 14,000 feet.


So far a modified stock RX7 1990 to 1991 has been successful for two rotors.
For a one rotor it would be a whole new ball game and you would
be on the bleeding edge.

Paul Lamar