OK, I first want to mention my reason for involvement in ANY gearbox design. I want to use if for myself. I'm building an RV-10 which will require a safe gearbox with 300 HP (so there is some legitimate headroom on the 260 HP rating.) My siting of examples is relevant only because I want people to be aware that there are forces here that aren't obvious. Even good engineering requires scrutiny. Tracy's gearbox was a good effort, and designed to a lower price. Used within normal power ranges it is fine.
Powersport's earlier efforts had excellent design, but before they did pinion end support even their efforts had some failures. That is my POINT, not an obfuscation. Every time the car transmission example is brought up it totally muddies the waters. We don't know what power ranges or
RPMs the owner/pilot used to keep it running.
I have no concern whatsoever for who builds a gearbox. I would love to be able to buy one from someone. I have no concern which model, soft or stiff they use. I don't and didn't say a soft system wouldn't work. I only am saying that it requires just as much consideration of the forces involved as a stiff system. I also don't like to have the need to cross one of the resonance ranges every time I start or stop my engine. Look up the BD-5 they did a soft system that worked well in operation, but found that they could sometimes "hang" the system while turning it over on the electric starter! I HAVE ONLY 1 MOTIVATION HERE. I DON'T WANT PEOPLE DISCOUNTING TORSIONAL VIBRATION FORCES AND HAVING FAILURES THAT MIGHT CAUSE THEM TO CRASH. I have no profit motive as I may never find it practical to produce anything as a sideline to my "regular" job. If I did it would only be to defray the cost of building my own. I am hoping that I can be a repository for some of the Powersport knowledge for Steve so it won't get wasted or thrown away. Every time I discuss this stuff someone wants to discount it. Or say some guy just ran a car transmission locked in gear what's the big deal? At this point I am considering going silent and never commenting again. I would have far fewer problems to deal with.
Bill Jepson