REFLECTOR: From IVO

[Jim Agnew]

Brian,

You wrote,

--- Brian Michalk <michalk at awpi.com> wrote: That's true for
the Franklin/IVO combination. 

"Maybe the Franklin works well with so many propellers is
because of the torsional damper built into the flywheel?
I'm sure you know, but maybe the others don't; the Franklin
has a damper which is a steel ring encased in a viscous
silicone type fluid, all housed  in the flywheel.  It's job
is to smooth out torsional pulses on the crankshaft."

It really acts to suppress certain harmonic torsional
vibration frequencies that may be destructive in the
engines normal operating range and not to smooth out the
torque pulses.  The real problem occurs when the crank, or
part of it, is turning one way when the other part
including the prop is turning the other.   Before any of
you say that isn't possible, I've seen computer simulations
of 1,000,000 pound Cat D-10s showing the frame twisting one
way as the engine twists the other way caused by the engine
torque.  At certain frequencies if allowed to continue the
frame will fail.  

Lycoming engines with the four or more character (I.E.,
C1D6)designations have internal harmonic dampeners that
perform the same purpose.

Engines without these dampeners are the ones that cause
problems with MT props.  

So I doubt that the Franklin has exceptional qualities
other than possibly lower peak torque pulses.  Since car
engines already have these dampeners an 8 cylinder should
be even better than a 6 cylinder.

I can still remember taking off a properly torqued IVO prop
on a Franklin after 3 hours of operation and finding all of
the through bolts bent and aluminum filings in the hub. 

Jim

=====
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying