"Bubba" PSRU


Well-Known Member
May 10, 2018
North Texas / South Bay
Before I drop about $500 to manufacture a prototype for something to do, has anyone tried making a PSRU out of quick-change gear covers and gears?
Something like this: https://www.summitracing.com/parts/wpp-3736

I have absolutely no idea what I'm doing. I just finished reading Finch's book on auto conversions and reflecting.
I don't plan to fly behind this thing any time in the near future. I was just interested in something to do and a quick project for CAD and machining.

The quick change gears are typically made out of 8620, and it's somewhat comparable (not quite as durable as 4140).
The housing is a fairly expensive piece to machine. Using two as a front and rear with two gaskets separating them from a 3D-milled centerpiece seems like it would bring down cost quite a bit.
The main part I would be concerned about is the bearing surface, but the helical gears are not as plentiful as the spurs, and the spur-type would not produce the axial load like the helicals would.
The big drawback would obviously be weight. These were not necessarily designed to be light.