[Plane-Eater]

JtD:

Sorry to dig out an old thread. From a quick search in a few places online I vaguely remembered, the AVG had repeated issues early on with thrust bearing failures in their engines. I think it was Molesworth's Sharks Over China as well as Clemmon's book on the AVG that mentioned a field-modified oil recovery and sprayer system was devised to sump extra oil and deliver it back onto the bearing.

That kind of failure in the reduction gear case, from my understanding, is a symptom of higher power loads over a significant period of time than the reduction gears are rated for. I'm not an engine expert, though, so somebody who knows the old war engines better than me might be able to elaborate.

The AVG-vintage pilot manual on Dan Ford's site mentions 41" Hg as max boost at sea level. I've seen a multitude of sources, including my brief contact with Mr. Shilling before he passed, that indicated 41" was... we'll call it highly conservative. 41" was routinely exceeded by a notable margin.

Dan Ford has updated some of his research since I was last involved heavily, and his work is extensive and exhaustive. I'll need to brush up before I try to speak authoritatively on too many more specifics. : )

EDIT: Like I mentioned above, I'm not an engine expert, but wouldn't closer tolerances also allow (at least to some extent) higher loads than the design rating without the same level of wear or failure? IE, you could run the engine at - for example - 115% rated output without as much / as many of the corresponding wear and problems that would cause on a stock engine? So along those lines, by the time you did finally start getting high-load related failures, you'd be running at WAY more than just 5 or 10% above max rated output?