Peter's Model Railroading - Structures

Plate Girder Bridge

For the CrystalCreek module I needed several bridges that could go below the subroadbed. The plate girder bridge seemed to be right type of short, but sturdy bridge for this module. This page shows how I made them. They are fake plate girder bridges because I simply attached the sides to the subroadbed, thereby providing the look of the bridge, but yet keeping a solid support for the track.

Design

To speed up the overall process of creating seven of these bridges, I decided to make them all the same length. Most of the bridges are skewed over the two creeks on the module, so the longest bridge came out to be 20 scale feet. I consulted the book "Bridge and Trestle Handbook" by Paul Mallery to find out more about plate girder bridges. It has design diagrams and a couple of prototype photos in it.

Construction

I built these bridges out of 0.040" styrene. I used a knife and a small file to cut them to size. Styrene can be snapped once a score mark has been made on its surface.

	Taking a large enough piece of 0.040" thick sheet of styrene, I measured and marked a 20 scale foot section. Then I used a metal ruler and a knife to score this section. After I snapped it off, I marked 5.5 feet sections and snapped those off. The side panels are shown in the photo on the left.

	A popsicle stick made just the right template for the curves some plate girder bridges have. I used that to trace the curve out and using a knife and a file I finished both top corners of each side panel.

	Here's the final shape of the side panels. The curves are probably a bit too much, but it still looks nice.

	The prototype has a thin railing over the top of the side panels, so I cut these from strip styrene.

	I then put the side panels in an alligator clip stand and held the strips in one hand, while applying glue with the other hand. I prefer Testor's plastic cement for gluing styrene.

	Next, I needed to curve the styrene strip around the corners and hold them to apply glue and to give them time to dry. I did all this work on a sheet of glass, and I used weights to hold the styrene strips in place.

	I wanted some distance (clearance) between the trains and the side panels of the bridge, so I glued these square tubes to the inside of the panels. In the real world this would have been part of the bottom of the bridge.

	There are triangular pieces of plate used to hold the sides panels in place in the prototype, so I cut these. I got a rough measurement of the height and width needed. I first cut rectangular pieces from 0.010" styrene. Then I cut those diagonally, by eye. I glued them in place by eye. I placed one in the middle, one on each end, and one in between these. It seems to look right.

	In the real world the side panels are made out of steel panels that are bolted together. To simulate these bolt flanges, I simply glued some 0.010" strip styrene to the outside side and trimmed them to length. They probably should be thinner, but it looks good enough.

	And here is the finished product. They are not glued in place yet, because I need to paint them first. It took me two evenings to build these while watching TV.

Painting

I painted the side panels with a cheap spray paint bought at Walmart. It makes the panels look like stainless steel. After the module is further along, I will come back and weather these down a bit.

Conclusion

This was a fairly straight-forward project. I enjoyed making them, and will use this technique in future layouts. Below is an updated photo showing the bridge in action with track and ballast installed.