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CI am constructing three truss bridges. Two are 21-1/2 inches long and the center one is 54 inches long. I am going to build the two small bridges first. I am using Plastruct H and I beams. The main columns are 7/16 inch H beams. The diagonal bracing is 7/16" I beams. The top cross beams are 1 inch I beams and the bottom cross beams are 1-1/8 inch I beams. The top beams are 7/16 inch H beams constructed from ABS sheet. Each beam is three pieces. 

Here are some pictures.


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Last edited by Alan Graziano
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The beams are made from gray abs. The flanges are .060 and the web is .030


The customer sent a couple of pictures of bridges with arched tops and a truss frame. I have not seen one like this anywhere in New Jersey.


i am using bondene. It is supplied by plastruct for gluing similar materials. This bridge will be constructed completley of abs to hopefully avoid a potential failure in the glued connections.


alan graziano

I completed the second bridge and have a photo of the two bridges together. I fabricated the parts for the 54 inch span bridge. I was going to use an 80 inch radius for the curved beams on this bridge but felt there was not enough arch in relation to the two 21 inch bridges. Based on that, I calculated the radius based on the 18 inch radius of the small bridges. I came up with a 45 inch radius. This makes the center of the 54 inch bridge about 15 inches tall. I think it will look much better with a higher arc.


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