Vance, I am going out of town for a few days, when
I return I will look into
the "math" with more rigor. One thing to think
about intuitively, however, is
that each rotor and eccentric serves as a
"counterweight" for the other in a
twin. Also, in a single, the rotor / eccentric
mass is 180 deg opposite both
counterweights, so the single rotor crank is in
the worst possible bending
situation -- simply supported beam with a
concentrated load approximately at
its center. In a twin, the counterweights are 180
deg away from each other.
The twin crank tries to bend in an "S", but the
stiffness of the gooseneck
restrains the deflections considerably.
This is not to say that a single rotor engine is
"bad," it just needs to be
understood and designed properly, and mating
equipment designed to suit. (You
may recall some discussions a while ago where I
was defending single rotor
engines against an individual who had a bad
experience, either because the
engine was not made correctly or it was
misapplied.)
Jon Lauter
Rotary Power Marine Corporation