Originally Posted by NinerBikes
And yet galling still occurs in the gearbox, with metal on metal contact, with use of the specified oil, well before 2000 hours, in plenty of observed cases.
Should we point the finger at operator error?
Vendor failure for materials used and specified on the part?
Or oil failure? Rotax spec'd the oil... and gearboxes are failing, early.
Rotax has Qualitiy Control over all specifications except the end user, and operator error. Just like their Carb floats. Which they say is fine with Mogas up to E10, and they still keep failing. They've got a new part number out for the carb floats. Makes me wonder if it will ever happen for motor oil, too.
I'd love to see a failure analysis report as to the cause, because once that oil boundary layer is gone between the gearbox parts, the damage starts getting done. And there are fundamental differences in additive packages for motor oils, and in gear oils.
As to my Qualifications, let's just say I worked for the manufacturer of a bottle brush hone company that puts the final sealing finish on every single kind of sealing bore that you can imagine, both in the new and remanufactured engine industry. I've seen plenty of failures of surfaces that need lubrication, the metal finish our tools provided needs to work in conjunction with the tribologists concoctions. Failure isn't an option on hydraulic seals in bores when your John Deere is broken down and it's harvest time for the crops. We also worked closely with, back then, Parker Hannifin, with sealing surfaces compatible with their O ring products. So, I am aware of what causes seizures, and rebuilding and remanufacturing the surfaces, instead of just throwing all new parts at the failure. I also worked at a Fortune 50 aerospace company that made gyro and ring laser gyro guidance systems for the F-14, E2C and AWACS, before GPS, back when Fuel Injected motors were first coming into vogue for pollution control standards. Back then, for me, it was a profession, not a hobby.
So I apologize if I come across as condescending, this sounds like a project that could use some failure analysis as to the root cause. RV-12's are great planes, it's a shame they can get marred by Rotax part failures, long before 2000 hours on the power plant and drive train for the prop. Or it sounds like a great opportunity for an aftermarket parts manufacturer to offer replacement parts that don't fail so soon. Or an oil that works in it's intended application.
Because, something is under engineered, that the failures keep occurring. It could be something as simple as oil jets need to direct oil directly at the parts in question that keep failing, both for lubrication and boundary layer protection.
The good part is there are so many RV-12's already built and flying, with Rotax 912 engines in them, so there's a very large sample of Rotax engines to gather data from in one location.
Don't get mad, just because I think outside of the box. My lack of pilot experience has nothing to do with my experience in engines, and gearboxes, and lubrication issues. It's about how to prevent the failures... unless you enjoy more pulling gearboxes and sending them off to get them fixed and getting handed a bill, than you do flying your RV-12.