My dream engine is
still a 3-4 liter two rotor Wankel with a built-in prop bearing
and aircooled, designed to run at about 2800-3000 RPM.   No
danger of getting it, sadly.  HMMM??

Is there any real possibility of designing one of these here and
getting a prototype built?  Jeff has done a lot of this and could
guide us, plus there is a lot of design and engineering talent
out there.   Pipe dream or mere insanity?

David Doshay wrote:

Well, there are dreams and then there is engineering reality.
Here is my opinion:

It makes no sense to design a diesel engine for use at 9,000 rpm.
It makes no sense to design a wankel for high power use at
2800 rpm. The design of each, and all practical examples of each
to date, has characteristics which lead quite naturally to one being
a low rpm engine, and the other being a high rpm engine. Rotary
engines spin fast ... it is inherent in the design.

David

The main attraction of the Wankel for aircraft is no valve gear, extreme
mechanical simplicity not necessarily the RPM capability.  Gearboxes are
relatively expensive and all certified geared motors have had difficulty
with the
gearboxes. The certified engines were built with gearboxes for a while, but
they
have almost totally gone to direct drive with more displacement.
I really think this is the sweet spot (low RPM direct drive) if you had a
funding
source to do a clean sheet of paper design.  If Wankels live well at
6500 RPMs just *think* how well they would live at 2800 RPMs!

Bill
Long EZ builder & pilot
BSME, MSME

The big problems would be rotor weight and combustion chamber size Bill.
Twice the displacement for the same HP.

Paul Lamar
 
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