Paul, is this engine giving us a 3 to 1 ratio?
Seems to be.
Royce

 Reduction gearboxes fitted as an integral part of Mid West rotary

engines and

incorporating torsional dampers, allow the propeller to turn relatively

slowly.

The reduction ratio of the twin-rotor GAE100R unit, for example, allows

the

propeller to experience six power impulses per revolution. That sort of

power from

a conventional direct-drive would require a twelve cylinder four-stroke

engine to

achieve the same smoothness of delivery. Similarly the single rotor

GAE50R can be

equated to a six cylinder, direct-drive engine. Any vibration which may

be felt

from a Mid West engine can almost certainly be attributed to imbalance

in the

propeller.

Sounds like it.

Paul Lamar

"Smoothness" is not a function of pulses per minute - that only sets the
frequency of the vibration
torque overlap or the lack of it, is the primary drive for vibration. The
single rotor has
torque reversals, the shape and spaces based on time are identical to a 3
cylinder
four stroke engine. The 2 rotor has continously positive torque with the
same time
signature as a 6 cylinder 4 stroke, or a 3 cylinder two stroke. Vance J.

I think what they are claiming here is what the prop feels.
With a 3:1 box the prop feels 3 pulses per rev. So in a sense
they are comparing it to a direct drive six cylinder 4 stroke engine.
True these are discrete pulses with no overlap and torque reversals
unlike the overlap of the six cylinder 4 stroke engine. 

On the other hand no telling how much of that torque reversal gets 
by the flywheel and the large rubber device the Midwest engine has 
between gear box and engine. This rubber device is normally used
as a U joint in the final drive shaft of an english race car.

If it were a direct drive one rotor the prop would have some
serious problems no question about it.

BTW Vance I found a HP curve for a 13B for you.
Looks like 155 at 6000 RPM and 187 HP at 7000 RPM.
Very modest porting from the looks of it.

Paul Lamar
 
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