BTW I just got a video on John Vlake's Ford based PSRU. The one in the
video removed power from the ring gear
reversing prop rotation and limiting the reduction ratio to 2.17:1.
Unsuitable for the RX8 engine or any rotary running at 7500 RPM for takeoff.

The rubber coupling was the BMW type drive shaft U-joint. Probably
too stiff for a rotary however. It might work fine for a four cylinder
piston engine. Unlike Tracy's torsional isolator it can't be adjusted
for torsional resonant frequency.

Apparently the designer did not understand or was unaware of gyro prop torque
loads as two very large and heavy ball bearings weighing in the neighborhood
of 3.5 pounds each are mounted back to back. Given the weight of the planetary set is about 8 pounds alone that is a total of 15 pounds right there with no shafts or housings. Consequently the box appears to be very heavy indeed. Old man Lou
Ross did it right with widely separated, very light weight, needle bearings
accepting gyro torque loads. His design was around 30 pounds total.

For more info check out  http://www.rotaryeng.net/psrus.html

Paul Lamar ...No rotor no motor.

I just noticed a note in the package with the CD.
Apparently this is a real old video and Vlake changed the bearings.
Also the shaft is 45 mm and not 55 mm as I had guessed.

That would make the bearings lighter than I estimated probably around
a pound or so for each bearing but the shaft will be weaker.

BTW the crankshaft shaft on a Lycoming is about 60 mm or around 2.3 inches
in diameter.

Attached is the formula for a hollow shaft under torsional loads.
Note: the strength of the shaft goes up as the fourth power of the radius.
a 60 mm shaft would be 810,000 while a 45 mm shaft would be
256,289 or about only 32% as strong. This is a very rough calculation
your actual millage may vary somewhat depending the wall thickness
of the two shafts and the exact evaluation of the formula. There
is a high bending load on the shafts
as well due to prop gyro loads. At 60 degrees per second pitch
or yaw and a CS prop it amounts to 650 foot pounds which is just
about enough to bend the flange on a Lycoming crankshaft.

This is one of the rationals behind my advanced design PSRU.

Paul Lamar

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