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Overall, this turntable bridge is a very robust structure. The stresses in all the main elements are very low. The primary limiting factor was deflection, which was governed by the longitudinal beams. The truss elements function to keep the loads on the perimeter rail and wheels near zero once the locomotive is centered. In fact if you look at some of the historical photos, there is only a partial perimeter rail. Finally, the bridge would still function without the truss, but it would be harder to turn.For the stress analysis, I used the biggest WW&F locomotive as the design load --the 26 ton #6. It was quite fun to look at the historical photos and analyze the changes from the Portland Co. drawing. Folks have noticed the tie rod between the queen posts so far. There are quite a few other differences, some of them subtle. Our turntable will be very much like the historical photos.