You lot seem to have been taking this a lot more seriously than I intended, but if you can.... Not having a full size wagon to hand, I've had a look over a few mineral wagon drawings and its not clear to me if a hanging door would remain in contact with the stops or not. The door hinge is about the widest part of the wagon, and given the way the hinge is arranged so the door falls vertically clear of the wagon floor, it must hang well outside the line of the hinge pin and if it actually did hang vertically, almost certainly clear of the stop. However it I would not hang vertically as the hinge is to one side of the door not directly underneath it, it would hang with its centre of gravity directly below the hinge pin so I expect it would lean slightly inward. Question is would that be enough to put it in contact with the stop.
I don't think the weight of the door is any bar to them at least swinging gently when in motion, quite the contrary. I agree the concept of them flapping does contains an element of hyperbole. Their weight would ensure any movement was relatively slowly, but if would also overcome any stiffness in the hinges. I would speculate that any "normal" siding is going to be rough enough to ensure the door does loose contact with the stops at some point and that the motion of the vehicle is more than enough to start them swinging a bit.
jim s-w wrote: It seems to be the nature of the finescale mindset that we over think things and get theoretical when sometimes its easier to just ask someone who actually knows.
Absolutely I expect I'll catch up with Don Roland in the next month or two I'm sure he'll put me right.
P.S. I am also aware that, given the physics of systems driven by the weight/mass of an object doesn't scale well, if you did model a hanging door that could swing, it wouldn't swing like the real thing under gravity and you'd back to the same problem as to how you make a signal arm seem to bounce. but as I said I wasn't being entirely serious...