Funnily enough my original design was set up to use the pinch bolt for clamping and retaining, however in-service I didn't feel it was the best solution.
The connection between the arm and the square end of the roll bar is great for torsional load, ie; it handles the up/down forces but it's not great as a clamping force stopping axial movement. I had the bolt running through a slot in the drive square (similar to a steering column UJ) with the idea that if it came loose the slot/bolt would still hold it in place, unfortunately during construction I made the bolt hole a fraction too big and probably a little too far back so the bolt only just interfered with the shaft which I wasn’t happy with. Considering the square drive is only 13mm across the flats, removing any material for a bolt slot could potentially leave a fracture point as its under significant load (although acceptable) for its size.
I had thought of pinning straight through the square end but again thought any hole through it would lead to it shearing off. The way I fixed it, with what I had, was to do a typical bolt through the interface faces as seen in the picture. In the new design I extend the shaft by another 15 mm and put M12 threads on the end with the addition of lock nuts thereby leaving the bolt and nut to do independent jobs.
Nice drawings you've done there
