"This gear box is stunning in it's simplicity. Since we are proposing using the A/C proved Ford eight pound A4OD six pinion planetary in a differential mode the total gear reduction is 6.34:1. See http://www.rotaryeng.net/psrus.html. The ring gear is rotating in one direction and the planet carrier is rotating in the other. As long as both props have the same drag the RPM's of each prop will be equal. With an engine RPM of 8000 the rotors will be turning 1262 RPM for take off. I would use a 13 foot diameter rotor at this RPM."

"There is a possibility that the gear box could start up with both blades rotating in the same direction. One blade would be going backwards so that might be sufficient torque load difference to force the unit into counter rotating mode."

"The over all diameter of this gear box is only about 6.5 to 7 inches. It should have it's own oil supply as it is on the very front of the airplane and the engine is at the very rear for weight and balance reasons. A simple mechanical pitch change design is used. The size of the aft shaft is the same size as the ring gear. Namely five inches. A simple butt weld is all we need. One of the results of this is the gear case now becomes a simple piece of thick wall aluminum tubing about six inches in diameter and eight or ten inches long. This will allow increasing the diameter of the front shaft connected to the planet carrier to four inches. A front shaft needs a lot of torsional and bending stiffness as it is cantilevered a fair distance out of the gear box."

"I would use plain bearings, oil filter and an oil cooler with a dedicated high pressure stock Mazda 13B automatic transmission oil pump driven off the input shaft. The remaining problem would be high speed shaft seals."

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BTW this concept was conceived before we had a 200 pound turbo 2 rotor
putting out 650 HP making this project more than doable.

Paul Lamar