Rotary firings

[Chris Rhodin]

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I'm not trying to throw gasoline on a fire here, but...

I have the book "Rotary Engine" by Kenichi Yamamoto that I got through =
the SAE.  This book tracks the history of rotary engines back to the =
year 1588.  It then goes on to detail the development of the modern =
rotary engine by NSU and Mazda.  on page 7 this sentence appears "In =
other words, the rotary engine undergoes one explosion while the output =
shaft rotates once, as in the case of a two-stroke reciprocating =
engine."  In addition to this there are a series of drawings on the same =
page (Fig. 1.28) that make it quite clear that the the eccentric shaft =
is only in position once every 360 degrees of rotation (of the =
eccentric) to allow an ignition event to occur.  From this I am lead to =
believe there is one power pulse every 180 degrees of eccentric shaft =
revolution on the Mazda two rotor engines.

Chris Rhodin


----------
From: 	Greg Hermann
Sent: 	Friday, September 18, 1998 13:04
To: 	diy_efi at efi332.eng.ohio-state.edu
Subject: 	Re: Rotary firings

>On a Wankel engine you get one power pulse per rotation of the =
eccentric
>shaft per rotor.
>On a Mazda 12a or 13b that has two rotors you would get roughly 2 power
>pulses per each eccentric shat revaluation.
>If you had a one rotor engine:
>
>3-360 deg turns of eccentric shaft =3D 1 360 deg turn of the rotor =3D =
3
>faces of the rotor coming into power pulses.
>			or
>1-360 deg turn of the eccentric shaft =3D 1 rotor face coming into a =
power
>pulse.
>
>Being you are talking about a Mazda 12a/13b engine you have two rotors
>the send rotor is set off of the first one. so you figure you would get
>2 power pulses per revaluation of the eccentric shaft.
>
>I can go out to my garage and double check, I have an engine torn apart
>right now waiting to be rebuilt.
>
>Dave S

Hi Guys---

Enough of this. There are two revolutions of the rotor for every three
revolutions of the eccentric shaft in a (three lobe rotor, two lobe
chamber) Wankel engine. The epitroichoidal chamber geometry will work =
for
any number of rotor lobes, so long as the chamber has one less lobe than
the rotor--and the ratio of shaft speed to rotor speed must always be =
the
same as the ratio of the number of rotor lobes to the number of chamber
lobes. ----OR THE FOOL THING WILL NOT TURN AT ALL!!!!----A 3:2
epitroichoidal geometry is what lends itself to use as a four stroke
engine, for reasons which I hope are obvious to all. There are plenty of
epitroichoidal design oil pumps out there which use a higher number of
rotor lobes (the oil pumps in old Jag twin cams, for instance).

If anyone doubts this statement--GO READ THE GODDAMN FELIX WANKEL =
PATENT!!
(Or count the teeth on the shaft and rotor gears on that disassembled
engine, and post the tooth count!) (I trust we all know how to divide, =
or
at least how to push calculator buttons.)

A two rotor Wankel motor makes 4 power strokes per output shaft =
revolution,
same as a 4 stroke, 8 cylinder piston engine { (3 lobes/rotor) x (2 =
rotor
revs/3 shaft revs) x (2 rotors) =3D4} .  PERIOD!!! (And a three rotor's =
power
stroke frequency is like a twelve cyl,, 4 stroke, etc., etc.)

Once upon a time (almost 30 years age) I actually got paid to figure out
the swept displacement of a Wankel--had a curious boss who was trying to
evaluate a similar idea. It was a fascinating exercise in calculus, and
turned out to have a rather simple looking numerical solution (which of
course I don't remember now) when all the integration was completed. The
swept displacement of a Wankel relates to rotor radius, eccentricity, =
rotor
width, and number of rotors, with (I think)  pi and some simple, =
integral
number fraction as multipliers.

Most of the other answers which are floating around out there as to =
Wankel
displacement are pure SNAKE OIL, and, I think,  the result of certain
individuals (and/or firms) having a vested interest in fooling the
mathematically and mechanically inept (such as members of race =
sanctioning
bodies and employees of the EPA and/or (foreign) vehicle taxing
authorities) (and apparently some members of this list, too) as to what =
the
real swept displacement of a Wankel is. Getting a handle on the real =
swept
displacement number for any given Wankel engine readily explains why =
they
perform so strongly (despite poor VE) and (together with poor VE) why =
they
get such lousy mileage.

I don't remember perfectly at this point, but I believe that it was an =
RX-3
motor that I measured, and calculated the actual swept displacement for
once upon a time, using my derived formula. Didn't Mazda claim that the
RX-3 was the equivalent of an 1800 cc piston engine???? The hard
calculation showed that it has more like the equivalent of 4.2 liters of
swept displacement, if memory serves!!!! Even if the number is off, the
difference between what Mazda claimed and what it really had was utterly
astounding!!!!

Regards, Greg




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