Post 490 and 49 pages - whew - made it finally.
Edit: 492 & 50 by the time I got it posted geesh
First I have no budges or cracks, moderate wheeling, slow & steady - only as fast as necessary.
After reading the first 20 some pages I began to see a pattern with the lifted rigs. From what I can tell the vast majority have after market bumpers with 886 (or equivalent heavy) front springs.
Totally unrelated to the bulging (not knowing about it) but because of one curve I drive around ever day from work I swapped out my 886's with 885's to eliminate some tire hop issues. Now the whole vehicle responds instead or the front end feeling like a pogo stick.
I have a Road Armor bumper with Warn 9.5 winch and I have too small scrapes at either corner where the bumper meets the fender. If the flexing of the frame/body/bumper combination were causing enough stress to budge and crack the structure I would expect to see some deformation of the fender in that area on any vehicle. So far no-one has mentioned any and mine is only paint scraping which can be resolved by cutting back that corner.
Also you should see a crack in the lower lip of the fender but I haven’t seen any pics of that area from any affected rigs. If someone can take some that would help.
I borrowed someone's pic to illustrate some directional forces that are occurring.
At first glance this is a compression of the structure. There could be some extension pointing to cyclic stress but the only thing I can think of that would cause this activity would be bouncing across a washboard surface which would repetitively flex the front clip independent of the rest of the structure. Whether the duration is long or short I cannot determine. But again there should be equal cracks elsewhere. Whenever we find a crack in an airplane we look for its mirror (in the structure not side to side).
I am going to get one of my AOG engineers to look at these pictures to see if he can give an idea where these forces are coming from. So far I haven't seen anything that definitively points to the cause. I will be doing some forklift flexing at the hanger tonight to see if I can determine any other contact/stress points but I’m not leaning toward a flexing problem but more of the repetitive annealing issue BellyDoc is referring to but I'm not a stress engineer. I'll post up what he has to say.
