This page describes two versions of the same bridge type I built for my S-scale layout. Their primary components are the girders, so I'll start with that first. The first version was completely scratch-built from very basic styrene pieces. I built the plate girders from 0.030" thick styrene. I carefully cut and glued scale 7-inch strips of 0.015" styrene, and glued them to the tops and bottoms of the plate (perpendicular). I then simulated the L-shaped brackets with thin strips glued to the inside corners. The profile is shown in the photo.
Here are the two girders in their approximate location. I misjudged their location so the bridge's pedestals were initially glued in the wrong location (too wide). I cut and glued new ones in place, which you might be able to make out under the girders.
The remainder of this project uses only 0.015" styrene. The next step is to install the vertical L-brackets. These provide support for the steel plates. Since I didn't have any angle brackets, I made each of mine from two strips of styrene, meticulously glued together.
And now we are ready to start building the frame work between the two girders. Because of the fact that this bridge sits on a curve and that the two sides are offset from each other, I decided to glue some temporary strips on the bottom of the girders while they rested in their approximate positions. I could then move the whole bridge to the workbench and continue to work on it there, knowing that the two sides are in the correct position. I held them down with some metal weights while the glued set for the two strips.
The cross braces have been installed in the next photo and half of the lateral braces are in place, too.
The next photo shows the remainder of the lateral braces installed. The gusset plates on the bottom were cut and glued next.
I then glued some L-brackets to the top of the bridge. These need to match up exactly with the ones I installed in the bottom, because there will be vertical cross braces installed between them.
The vertical cross braces have been installed. The cross braces in the bottom were made to match the prototype exactly, including gusset plates. However, I got tired of doing that, and the space within the framework is getting quite tight and crowded. I decided to just overlap the two strips of styrene and then glue them in the center. The truth of the matter is that most of this will not be visible once the ties and track are in place. The point of this construction technique is to make sure the bridge is strong and stable enough. I believe I can achieve that for the model with this construction method.
The next photo shows the completed structure. I finished the lateral braces on the top, and added the gusset plates on the top. Like the vertical lateral braces, I just used simple strips of styrene. I didn't bother to make them L-brackets. The whole structure is strong enough. I also didn't put the gusset plates on top of the lateral braces, like I did in the bottom. I was worried about them interfering with the ties that will go on top of the bridge.
Off to the paint shop we went! Actually, I just spread some newspaper on the garage floor, grabbed a spray can of "flat aluminum" and added several thin layers to get all the nooks and crannies of the bridge.
And here is the finished structure. After the flat aluminum had dried, I used Floquil "Rail Brown" with a small, flat brush to paint the whole structure. The brush had most of the paint removed from it so that it didn't go on too heavy. I used deliberate vertical strokes to show aging of the steel plates. The inside of the bridge (as well as the back) were just crudely painted with Rail Brown to hide most of the aluminum color. Most of that will be hidden once the ties go on. The front girder received most of the attention, because, as you can see, it will be very visible. I did leave some of the aluminum color visible. This seems to add to the effect. After that dried I used a dark rust color of the Bragdon Enterprises weathering chalks to really create the dark, rusted, red color I wanted. This seems to match the prototype photos I have found. I also added some black chalk along the bottom of the structure and down the middle of the top (to represent engine oil leaks). This completes the first version I built.
I decided to build another copy of this same bridge for the other gap in my layout. Although the prototype used a truss bridge in this location (near Canonsburg, PA), such a tall bridge seemed out of place for the scale 40-foot span that I have. This gave me an opportunity to build another one and improve on my work of version 1 above. I studied the first bridge to see what is really visible once I had added the ties, rails, and guard rails/timber. It turns out that a lot of work I did on the first bridge is not really visible on the final model. Using that information, I decided to build this one differently. I also had had an opportunity to stop by a hobby shop and improve my supplies. This allowed me to build the model quicker and easier than version 1. I used .040" thick styrene sheet for the girder plates (Evergreen part #9040), two packages of .060" angles (Evergreen part #291), and one package of .010" x .040" strips (Evergreen part # 102). The angles come out to just under 4 inches which is about the right size.
The first step was to measure the height of the plate girders and transfer that dimension to the .040" sheet. Using the score-and-snap method, I created the two parts. I also cut 8 sections of the angles to the same length.
These angles were glued to the top and bottom edges of the plate girders. The next photo shows the setup I used to make sure these strips (which are quite flexible) actually aligned with the edges of the plate girders. Here the top one is being glued in place.
The vertical angles were cut next. These will be notched to sit flush on and against the horizontal angles already installed.
After these were installed, I placed the plate girders on the abutments, held them down with some weights and glued two temporary strips on the tops to ensure proper separation between them. This will then allow me to take the whole setup to the workbench and continue assembly there.
The angles make very quick work of this. I installed them between the plate girders, and, after sufficient drying time, I carefully removed the temporary strips (which required some filing).
The thin strips of styrene I listed are now used to make the "X" cross braces using two of those strips. This makes the structure very strong. In "version 1" I used gusset plates to hold these. I also made angles for the cross braces. This was a lot of work and overkill for the model. This system for "version 2" is plenty strong. The gusset plates are not visible in the final model, so they were omitted for this one.
Next, I installed the angles at the top of the bridge, followed by the vertical cross braces.
To wrap up the construction phase, I installed the cross braces on the top.
Here is a photo of the side profile of the completed bridge. Painting will be done exactly as I did "version 1", because I was very happy with the result.