snips.....
Of course I jest. But the PSRU still does not care about all this.
All it cares about is the torque pulse. One per e-shaft rotation
for a one rotor just like a two cycle one cylinder piston engine.
Two pulses per rotation just like a two cylinder two cycle piston
engine and a four cylinder four cycle piston engine.
Paul Lamar
The "roughness" of the output, and severity of the pulsation on redrives
etc,
is not just the number of pulses per revolution, but the duration, and peak
levels of the pulse (as you have shown in the famous picture of overlap
and no reversal with the two rotor). In a single cylinder 2 stroke, the
theoretical duration of the expansion power pulse is 180 degrees out
of 360 degrees of cycle rotation - actually a bit less because the exhaust
port opens and scavanging starts before bottom dead center. With a 4 stroke
single, the pulse is closer to the 180 degrees, and thus is 180 degrees
out of 720 degrees for the cycle. The single rotor Wankel shaft (getting
it's power from the expanding gases on the face of the rotor, where this
expansion theoretically extends over 1/4 turn of the rotor) turns 3/4 turn
(3 to one) during this power stroke or 270 degrees out of 360. Thus the
the pulse extends over 75 percent of the time ( no overlap and some
reversal). An even firing 3 cylinder 4 stroke has 3 180 degree pulses
(540 degrees) out of 720 (two turns) for 75 percent (son of a gun!).
The 2 cylinder 2 stroke has almost 360 out of 360 = almost overlap.
By the way - if you took power directly off the rotor, it would not
be any bigger - just 3 times the torque for 1/3 the rpm - same
horsepower - I am sure that Herr Wankel would have liked to do that,
but the complexity outweighs the advantage. - Vance J.
Vance and Emily Jaqua wrote:
Enclosed is the concept sketch as you requested -
not a developed design by any means. With a single
rotor the direct U joint is pretty clearly putting
the output shaft direct to the rotor. The U joint
will follow the the rotor center describing the
same circle as the eccentric, and adding it's
unbalance loads to that of the rotor.
This movement by itself does not turn the
out put shaft, but the
actual turning of the rotor does ( at 1/3rd ecc
rpm. The eccentric is overhung, which is not a good
thing, but can be handled structurally. Adding
the second rotor clouds the ?purity? of this
concept since the the power from the front rotor
gets transferred by the eccentric shaft. This was
not proposed as a workshop project, but an effort
to get you to step outside the "box" we all live
in, for a fresh look at displacement defination.
The five sided Wankel is in the same vein - if
it is sized such that one flank has the same
displacement as the Mazda with the out put shaft
travelling at the required 5X speed - the defination
would say that it is the same size engine in spite
of the greater physical size and each flank firing
twice per rotor full turn.
Obviously all this is trivia compared to a goal of
adapting the Masda to an aircraft but I feel that
mental exercise in the goal of increasing the
understanding of the device you are working with
is seldom wasted - Vanc
I'll let all this speak for itself :-)>
Paul Lamar
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