Hi Group:

Is it possible to quantify the diminished smoothness of
the single rotor engine over the std. 2 rotor engine.
One of our helicycle builders group had some concern
that the power pulses of the single rotor could in time
degrade the transmission gears.  BTW, the transmission
is of very high quality and there would be a 6 vee belt
link between the engine and trans.

TIA

Ed Angell

The dotted line is the torque fluctuations of the one rotor.
Very severe to say the least.

Paul Lamar

The torque pulses of a single rotor Wankel are the same as a 3

cylinder

4 stroke engine, and a bit more severe than a 2 cylinder 2 stroke.

The

multi Vee belt will go a long way toward protecting the trans, and
I would expect it to be OK - Vance

Are you sure that is not a two cylinder four stroke Vance with one

torque

pulse

per revolution? The two rotor is the same as a four cylinder four

stroke

with

two torque pulses per revolution.  The one rotor is the same as a one

cylinder

two stroke engine with one torque pulse per revolution.
I think you still have not figured out the wankel :-)>

Paul Lamar

No! Paul! You are confusing your self by using the rotation of the

output

shaft, which does not have a one to one relationship with the

thermodynamic

cycle.

Paul Lamar responded:
The PSRU does not give a damn about the thermodynamic cycle or what you
claim
the thermodynamic cycle is. All the PSRU cares about and all the PSRU sees
is the torque pulse coming out of the output shaft.

One rotation of the rotor takes each face through all four "strokes "
of the Otto cycle - ie equivalent two two revoloutions of the classic
crankshaft engine, thus the shape, and duration of the torque pulses are
idistinguishible from a 3 cylinder, even firing 4 stroke engine, when
plotted on an equivalent time base. - Vance

Not true. We don't take power from the rotor. You seem confused about
that.
If we did try to take power from the rotor the size and weight advantages
of the wankel rotary would be totally destroyed. Perhaps then it might be
comparable in complication to your beloved Rube Goldberg piston engine :-)>

Paul Lamar

All I can add to this is, I looked at the geo 3cyl. The torsional vibrations
are not terribly bad, but not as good as the rotary (much more severe torque
spikes, plus negative values). What kills you is the out of plane 2nd order
moments that play hell with the prop hub or drive shaft. I'll take an inline
4 over a 3 cyl any day. As you can see there is a torque pulse every 240
degrees with the 3 cyl 4 cycle inline. The 3 cyl 2 cycle inline is the same
as a 6 cyl 4 cycle inline or opposed with regards to the torsional
characteristics, but you still have the 2nd order moments that kill you.

Monty

 
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