that’s a beautiful door- I don’t know about the Diebold/HHM question, and I don’t think I’ve seen that design before, but to me at least, it seems the most common sense way of doing it.
Same principle as the others, but here it’s in it’s most basic and obvious form- solid connecting rods linking the drive ring to each individual bolt.
It seems a bit of a mystery why all the other doors, including Britain’s Chatwood, always made threaded adjustment on these rods- the doors were machined to such tight tolerances in the frames, that making the extension distance of each bolt individually adjustable seems pointless. On this door they all extend by the set distance and that’s it, no studs with locking nuts to work loose and nothing to cause lock-outs or future problems.
If the door drops and gets tight, it’s adjusted on it’s hinges anyway- returning it to it’s original position-
seems the more practical of the designs to me, although some of the others are perhaps more visually attractive with the additional parts and bushings. I think there was often an element of pushing ideas to sell, impress, and intimidate with the designs of a lot of these old doors- that one proves a simple fixed ‘piston’ action is all you need- love all the pattern work on the steel
