Rotary displacement verses piston engine displacement:

Here is a chart from the R.F. Ansdale book that says it all.

What is a bit controversial about this is the area under the
displacement verses shaft angle curves. As Ansdale said
on page 53:

"it ought to be reiterated that the displacement volume
of any positive displacement engine has no direct bearing
upon power output."

The rotary changes its displacement 0 to max over 270 degrees while
the piston engine changes it displacement in only 180 degrees.
However this has absolutely nothing to do with the equivalent
displacements. Displacement is displacement. Displacement is defined as
max volume of the working chamber.

If the bureaucrats and racing officials are dumb enough to tax or handicap
engines based on displacement there is always the possibility someone will
figure out how to get more power out of a given displacement. It can be
done in many ways. Up the compression ratio is one way. Improve the
volumetric efficiency is another. Power of course is a product of
torque times RPM of the output shaft.

The previous unheard of way was to change the mechanical way displacement
is varied. That is exactly what Felix Wankel did. In other words he did
not use a crankshaft to vary the displacement and Vance is crying foul
or unfair.

This, I think, is where Vance is going wrong.

The 13B is indeed equivalent, displacement wise, to a four cylinder 2.6 L

four

cycle piston engine or a 1.3 L two cylinder two cycle piston engine with 2

power

pules per output shaft rotation. Just because it can generate up to 800 HP
has nothing to do with its exact displacement :-)

This is my version of Ansdale's style rebuttal Vance.

Paul Lamar

Paul - Ansdale's own curves show that a Wankel has three working
chambers/cylinders.
Output shaft rotation is not a valid way to rate displacement, Other engines
have an
indirect relationship, usually in the opposite direction, since lower output
shaft rpm
is generally desired, Most cam driven engines , such as the dynacam have one
turn
of the output shaft for the entire 4 stroke cycle - much like a 2:1
reduction without
gears. A simple way to rate displacement, for any form of positive
displacement
engine is to take the charge volume of a single chamber/cylinder, and
multiply by the
number of power expansions that occur during that cylinder/chamber being
taken through it's
complete cycle. This method will work with geared engines, two stroke
engines,
and even with engines that have no output shaft, (free piston)  and if you
insist that it
does not apply to a Wankel engine, you are atributing magic powers which it
does not posess.

The Wankel develops 800 hp in 3.9 liters, the same way a top fuel engine
makes
3000 hp out of 400 cubic engines, and a 0.15 cu inch F1 model airplane
engine
makes almost 7 hp per cubic inch  (normally aspirated) by turning 30,000
true rpm
 on nitrated fuel. As we both agree - displacement is not an issue for our
airplane
application, but I tend to be adament about engineering integrity.
Vance

Up until Vance Jaqua nobody has accused Ansdale of lacking integrity :-)

There are sixteen cylinder engines with the same displacement
as two cylinder engines. If you don't take into consideration
output shaft rotations the concept of displacement is meaningless.

Another point you are missing is ignition intervals.
With out ignition there are no expansions. 

You are also still thinking crankshafts. As I said before:
"The previous unheard of way [to increase power per cubic inch] was to change 
the mechanical way displacement is varied." 

The combination of eccentric shaft and phasing gear is a whole
new way of changing I.C.E. volume. This is the key difference.

BTW the tooth contact is not a fulcrum as the pressure on the face
of the rotor is considered perpendicular, uniform and centered over the eccentric. 
The measured tooth loads confirm that tooth load is totally unrelated 
to anything but RPM. I have some charts of tooth loads in case you
are interested.

The 800 hp rotary is not running on nitro methane which
has it own fuel and oxidizer. Nitro methane is more like liquid dynamite.
The top fuel 400 cubic inch 3000 HP engines are running on nitro methane.
There is a huge difference between nitrous oxide the 800 HP rotary is running
and nitro methane. I am sure Archie can fill us in on the differences.

Paul Lamar
 
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