[OhBuoy]

I thing it is primarily vibration. For my installation, I used a carriage bolt through the slotted side pipe hanger on the frame. I put the top peice without the metal washer on top of the bracket that is on the side pipe. I then put the bottom part on the bottom and tightened up. The trick is getting the the bottom nut to stay. I am tring a nylock washer this time. I may revert to two nuts tightened against each other as a jamb nut arrangement.

Tom