Somebody call Mythbusters or get those "Searching for Bigfoot" guys to do something worthwhile.....Saw that for the first time the other day....don't watch much TV....but what a bunch of idiots running around doing nothin'.....
The harmonics thing? maybe. Combination somewhat of both? Who knows?
The fact that BOTH happened directly under the pickup, almost completely different designs and manufacturing technique, I think is very important. And I can honestly beleive that suction/vacuum created by a HV oil pump through the pickup tube theory could honestly cause enough flex do this over a relatively short period of time. And probably your answer, completely feasible.
Back in HS, yes I know, back when Dinosaurs roamed the earth and Girls actually said "no", my Physics teacher showed us how vacuum worked by hooking up one of those little compressors (Older version and probably not as efficent) that everyone uses nowadays to inflate water toys or beds to a 55 gallon drum through a T fitting. Took about a half an hour before the first loud noise of something cringing from the strain, but in the end, about 2 hours, the thing looked like a smashed and squashed beer can. Those pumps only put out about, what, 10 PSI??? I couldn't get the side of an oil drum to flex without a LOT of effort either. Any cavitation, however unlikely, would cause extreme flex both ways if that theory proves true.
I would repair VERY carefully or replace the pans. Welding on them in this high stress area that apparantly showed it's ugly head doesn't seem like a very good idea to me. I would also make sure, next time, that the pickup is maybe a bit higher off the bottom than we would normally do. I think 3/8" is pretty much as close as any of us go, but I think after seeing this, I may just go to 1/2 inch or more on those types of pans.
Just thinking out loud.
Ray
