I'm new to T's but I've been a shade tree mechanic for more than 60 years and I haven't yet seen a bolt like this one. Probably I should get out more. The bolt itself has a double thread and is coarse. This makes the threads very steep. The nut has no flats, so the only way you can loosen it is with (gasp) vice grips. After the nut comes a coil spring, one end of which sticks into a hole in the side of the nut. Finally there's a stamped sheet metal hex thing which is held onto the end of the bolt with a cotter. It looks like you could wind up the spring a little bit to put a constant torque on the nut. I don't see any way to get the nut very tight. Can someone tell me the theory of operation? ( I tried to upload an image but I had too many kilobytes and I need to learn how to reduce them.)
It sounds like you have an aftermarket self tightening rod bolt nut. I have a set and the bolt threads are coarse and the "nut" is round. The spring that does the tightening is rather light weight. I don't think they were very successful.
Thanks, Jack. What you're saying makes sense to me. I guess its an interesting piece of failed invention. Glad to hear that Henry Ford didn't invent it.
The kind of thing that you hang on a nail or place in a showcase just to show to visitors!