CHRISMAN had a rear end break loose on him and resulted in very serious groin injurys. build it to stringent SFI or better spec's and inspect all tubes/welds after each weekend racing in especially critical areas. be safe and have fun.
bob
Hi,
New guy here. Just tripped over the place. This thread got me to thinking about an old friend and Bob's post triggered it.
This is meant to be a teaching moment so bear with me.
In the early 70s as a pup I raced a Jr Fuel car. The real version with 97% nitro. There were a lot of them back then with circuits everywhere. A friend of mine managed to lose his life in a grisly way to a rear end and it was senseless. There was a line of thinking that "light is right". This is cool as long as it doesn't become unsafe.
This took place at Motion Raceway in Assumption IL. We were running with the TF class. Yup, weekly TF shows were the norm then and we could run with them and win also but that's another story.
My friend was making his pass as I was sitting on the roller starters waiting my turn. I heard the car leave, the rpm climb, he pedaled then silence, then more rpm, more silence, etc. It was obvious something was wrong and then I heard a crash. My crew guy who was watching down track dropped his head, turned and signaled me to call it a day. This is not good he said.
The rear end had broken loose from the mounts and had rotated in the car over and over. I leave the image to your mind as to what took place.
Let's put it this way, this was a unique event for all concerned and afterwards the teams were in the tower deciding whether to go on or not. They did, I didn't as I was just too bummed out. While we were in the tower we all could see this wide swath of blood going down the center of the track. The track owner quietly said to me he wasn't sure how he was going to clean that up. Oddly enough a few minutes later a pop up rain storm rolled through followed by intense sunlight and the problem was solved. Come to your own conclusions on that.
Another friend that was the track go to guy and EMT was just a year back from Nam in country. He was the one that had to do the extraction and had that "look". He never went to a race track again.
End game: Remember I mentioned "light is right"? Let me add that "cheap is deep".
Well, what happened here is that the rear end was held in with not enough 3/8" bolts and the above go to guy found some of them later. Off the shelf stuff. When he lifted and got bite again the bolts gave up. That's all it took.
Now, the teaching moment and Roo will likely concur. We have pretty stiff rules for rear end mounting in place for this today but I don't think they mention the type of bolt used. You first thought is grade 8 right? Ok as far as it goes but not any old grade 8 will do. You need the NAS type bolts like the airplane guys use. These bolts come with different length shanks and short threads on the end. The rear end mounting must have a the shank portion engaging both the rear end and the mount. IF a threaded section of the bolt is in contact with the metal it will move and eventually give up. Those of you building your own cars will also want to make the holes a just fit, precision fit. A gnarly drill bit won't do. Also, no kidding, check the torque on these as part of your weekly maintenance program. Might even want to replace them on some kind of schedule. A double shear design is a good thing also.
Roo likely has these bolts on hand or maybe something even better.
I don't need to lose any more friends to stupidity.
Thus ends today's life lesson.
