bob wrote:
This is where I beg to differ. That lug welded to the chassis is being hammered in just about every plane. Under braking with the torsional twisting and over bumps, it`s failure in my eyes is inevitable. Having the lug hanging off the side of the chassis like that is a failure waiting to happen and believe the outside portion of the lug should be braced back to the chassis. I think that the bracket has work hardened to the point of becoming brittle and sheared of when the car hit the pothole. Hence the clean break, its not torn off its a fracture.
Bob
The fracture happened at the event on the day of. In fact, there were two fractures to the LH mount that day; both the front and rear tabs of the mount fractured simultaneously. Post-accident analysis aside, I know this to be the case because my car receives (by me) a thorough inspection prior to the first HPDE for the year. The TWS event was the first such event for the year for me. Aside from fluid changes, checking and re-torqueing fasteners, etc., every component on my car received a visual and tactile inspection; this included all suspension components and mounts. In seven years, and almost 9,000 miles of driving, there has never been a single issue with the mounts. I reiterate, there was no damage to LH mount prior to impacting the pothole, and there was no damage to the RH mount prior to the car going airborne and impacting the ground. For the sake of discussion, it may well be better to refer to the fractures as tears, because the initial failure (tearing of the mount) was caused by excessive force being applied to the mount, not fatigue. Impacting the pothole exceeded the shock and spring compression travel limits which, in turn, exerted an outward and upward force against the mount; this force exceeded the structural integrity of the mount and was the cause of the tears. The pothole impact was very solid, and even hard enough to bend the lip (and the rim, slightly) on the inside rear wheel.
The photos below reveal clean (fresh) breaks running the full length of the section of mount still welded to the frame as well as fresh breaks running the full length of the tabs. The edges of the breaks are jagged and the tabs deformed (bent) indicating the tabs were forcefully torn away in a pulling, twisting motion (such as that which occurs during braking) following the initial damage. Once the primary damage was done, the integrity of the mount was compromised to the point that it was only a matter of time before complete failure would occur; this happened 5 minutes and 32 seconds after impacting the pothole.
Bob, to echo your concern, tabs that extend beyond the edge of the frame rail absolutely do need to be braced back to the frame. My new chassis (currently being built) will have additional bracing in this area. I dare say that had my chassis had such bracing, the pothole may have very well ended up being nothing more than a very hard hit that left me with a bent wheel.
Again, what I shared initially in my USA7’s post was for the sake of safety with the truest of hopes that some may learn from my tragedy and avoid serious injury or death to themselves or someone else. Perhaps it will prevent some one’s wife from getting a phone call from a stranger telling her that her husband has been involved in an accident, and she’s a minimum six-hour drive away. As for those of you who want to go on debating whether or not my mounts were damaged prior to the accident, that’s your prerogative on this forum. For me, it’s a moot point; sixteen weeks in a back brace has left me with a slightly different perspective and more pressing concerns, some of which may have long-term effects on my profession and my family’s livelihood. Bottom line is this; the accident happened and I can’t change that. But hopefully, there’s something positive to be learned here. And just maybe, what I’ve shared, will prove useful to someone else. For me, it’s not about any one person being right or wrong about metal fatigue, or about proving someone else’s viewpoint wrong or mine right. It’s about what can be learned here and moving forward with it; it’s about preventing another accident such as mine from happening in the future.