>  > Me too on the mold. I was thinking a spinning on the bell housing part

 > and welded aluminum tubing on the rest of it along with some machined
 > aluminum plate (ribs with draft). All tig welded up. I think a
 > six pinion ring gear held stationary with power out of the planet carrier
 > on a A4OD 2.17 gear set will yield a 3.15 over all gear reduction
 > for an RX8 based motor. 8500 takeoff RPM divided by 3.15 is 2700 RPM.
 >
 > Lycoming should give up now.  Resistance is futile.
 >
 > Paul Lamar

 Paul do you think the EVOLV engine offers great advantages over the 13B in
 aircraft application. The little I have read seems to indicates that most of
 the HP increase comes from operating at a higher RPM. It is my understanding
 that rebuilding a 13B for operation up to 8200 RPM is not that difficult or
 expensive. Also could taking the exhaust through the sideplates increase the
 cooling load in that area and the overall system.

 Graydon Woods

I think you mean the RX8 or Renesis engine. Yes most of the HP increase
does exist from operating it at higher RPM. However we must get rid of the
subconscious bias against high RPM engendered in most of us by the
fact that piston
engines blow up at high RPM. No such thing happens in a rotary. The
minimum bearing load in the RX8 motor probably occurs somewhere around
7000 RPM. This is where the centrifugal loads on the rotor bearings
are exactly balanced by the combustion loads. In the current 13B engines
this number is about 6000 RPM.

This point occurs in the majority of piston engines at 3600 RPM.

The rotor bearing loads are the limiting factor in the max RPM
of the rotary engine. The main bearing loads are only a function
of the combustion pressure.

How then do we get the potential power out of an RX8 engine? We use
a 3:1 gear box
and run the engine at 8500 RPM (HP peak) for takeoff. Prop RPM is still only
2800 RPM. The other advantages of the RX8 engine are less fuel burn for
a given amount of power and a cooler and quieter exhaust.

Cruise RPM can be anything you want it to be. Particularly if you have
a variable pitch prop.

Paul Lamar

Ken Welter wrote:

   The Ross gearbox that I had was a 3.17 to 1 and I don't think they
were the same gear set as the 2.17 to 1 but cant be for sure.
  That was the best ratio that I have run, much better than the 2.95
that I am currently running but its not practical get any lower with
the cog belts I am running.

  Ken Welter

The 2.17 takes the power from the ring gear. I think if you take the
power from the planet carries and hold the ring gear fixed you
will get 3.17 out of the same planet set. This is also how the 
2.85:1 works but that is an entirely different planet set.

The one on the left is the 2.17 planet carrier and the one on the
right is the 2.85 planet carrier. The sun gear shown fits both.
So the sun gear diameter is smaller for the 2.17 giving a greater
reduction when power is removed from the planet carrier.

Paul Lamar
 
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