Paul Yaw wrote:

Paul wrote:

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.

snip

This is not the way the Mazda Wankel rotary engine works
so whatever displacement you care to assign to this
engine is purely academic.

Paul Lamar

Boy, I don't know where to go with this.  First off, displacement alone
is not at all useful for comparing power output of engines because it
doesn't consider rpm.  As I said in an earlier post the power potential
is related to an engines ability to move air.  If this argument is for
the sake of making valid comparisons from one engine to another, the
intended rpm range of each engine must be considered.  Let's say for
instance that we have two racing engines, one being a 13B, and the other
being a 240 cubic inch V6, which Vance claims is the four stroke piston
engine equivalent. Both engines run with an upper rpm limit of 9,000
rpm. which is common for race engines.  A 13B at 9,000 rpm, 100%VE will
displace 416.7 CFM.  The V6, or 8, or 10, as long as it is a 240" engine
at 9,000 rpm, 100%VE will displace 625 CFM.  Using this "rating system"
the piston engine has a 50% advantage.  There is clearly no point in
building a rotary to compete in this class. A 160 cubic inch four stroke
piston engine on the other hand will have the same airflow potential for
a given rpm as the rotary, and these days piston engines ARE running in
the same rpm range as rotaries.

In the old days, the rotary had an advantage, even being rated at 2
times its displacement because of its superior breathing ability.  It
could easily rev much higher than a piston engine, and so had a greater
airflow potential.  At one point, IMSA considered rating it at 2.3 times
its displacemnt to even the field.  These days piston engines have come
a long way in the airflow department with multi head valves, the
popularity of flow bench development, (General Motors has ten of them.)
and improvements in material technology which allow them to rev higher.

If any valid comparison is to be made, swept volume, AND rpm must be
considered.  As Paul L points out above, Vances direct to rotor
arrangement limits the output rpm to one third, but the engines ability
to move air has not changed. This effectively turns the rotary into a
low speed high displacement engine.

So I guess what I am saying is that you can call a 13B a 240 cubic inch
engine if you like, as long as you don't ask me to seriously compare it
to a 240 cubic inch four stroke piston engine running in the same rpm
range.  I do believe that your idea has some validity, but NOT for the
sake of comparison to piston engines.

Paul Yaw

 
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