VERY helpful Eric, I have some long spans, like 6 to 12 feet, and maybe I need something that looks more like a truss bridge… also then I can have cross bracing above the locos and cars.
It would seem to me that trying to keep the sides from pinching in above would be very hard with any bracing below, unless it was longitudinally stiffening…
I would welcome a separate thread on the bridge and what can be learned…
Greg