Trestle Bridge Diorama
06/24/2005
I was in between layouts, but I still wanted to continue to do some modeling work. I decided that a fun project might be to build a small diorama that featured a large trestle bridge. I started off with a design and then built the basic box that is the diorama. Using 3/4" plywood, I used my router to cut a groove near the bottom of the two sides, into which the bottom of the diorama was installed.
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I installed a backdrop using 1/4" plywood, put a decorative edge along the front, stained the exterior of the diorama, and painted the interior with black latex paint (just to protect the wood from moisture).
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It was now time to work on the interior of the diorama box. I had made some designs to plan out this project. These printouts show the overall shape of the scenery.
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The track in the diorama was fairly simple, so I glued the boards forming the basic "benchwork".
Trestle_Bridge_Diorama
Next, I set off to build the trestle bridge bents. The bridge is 150 scale feet long and 120 scale feet tall. The design follows the practices of the Pennsylvania Railroad (or at least that is what I was shooting for). The measurements and overall design came from diagrams found in the book "Trackside on the Pennsylvania, Volume 2" by Jeff Scherb, published by Highlands Station, Inc. Years before I built this bridge, I had attempted a real-world 4-foot long trestle bridge in N-scale. I eventually got so bored with it that I abandoned the idea and switched to a different type of bridge. What I had lacked then was not having a jig with which to make the trestle's bents. I was building it by applying board after board waiting for the glue to dry. The photo below shows a bent assembly jig I made based on the design I picked to follow. It was made from a sheet of Plastruct ABS, and individual thin strips of styrene that fit the scale wood I used. Since I built the bents out of wood, the jig needed to be made out of something to which wood glue doesn't stick. A jig made out of wood would not work!
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The next photo shows a close-up of one of the bents. I started applying nut-bolt-washer simulations by making a tiny dot with an ink pen. It worked well. However, I stopped doing it after a while, because I realized that most, if not all, aren't going to be visible when the whole bridge is finished. Note that the bent has already been weathered using the famous india ink and alcohol mixture.
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I built the various bents for the bridge using the jig. I didn't take any photos of the actual construction of these bents in the jig. The basic flow was to line up the vertical posts in the jig. I made small marks on the jig to identify where the horizontal boards were to go. I glued them to the vertical posts using yellow carpenter's glue (a very thin amount applied with a toothpick). When those were dry, I applied cross braces on the one side. After those were dry, I trimmed the bent on the bottom, installed the bottom boards, and removed the bent from the jig. I flipped it over and installed the cross braces on the other side.
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The bents at the end of the bridge have planks glued to them. These are supposed to act like bridge abutments, holding back the dirt and rocks from the surrounding surface.
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With the bents done, my next focus was on constructing the bridge platform. The platform had to be perfectly straight. Strip wood has a tendency to warp a little, so I made this temporary jig which would hold the long boards in the right location. I placed spacer strip wood pieces in between the two sets of support boards I am gluing up here. Various weights, clamps, and metal bars were used to hold the whole thing together while the glue dried. The support boards are the ones that are stained already. Note that the unstained boards are not used; they are just there to prevent the two sets of stained boards from accidentally being glued to each other, while still allowing all the be straight in this jig.
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Next, I glued bridge ties to the boards. Special long ties were used for the area that will have the fire prevention water barrel. Then two boards were installed that act as the outside guard rails (to help prevent a derailed car from falling off the bridge). I also applied additional weathering under the area where the rails will sit to represent the soot and dirt deposited by the engines and cars.
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After the platform was finished, I glued the bents to the bottom of the platform. After that I installed the cross braces on both sides to hold the bents apart at the right distance. The final result is shown below (the curving is due to the photography, not the bridge's construction). Code 40 rail sections were glued to the top of the ties using 5-minute epoxy.
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I removed the section of the benchwork where the bridge was to sit, and applied cork sub-roadbed. The bridge could then be lined up in place. I used the location of the bents as the guide for installing 1/4" balsa wood supports for the bents.
Trestle_Bridge_Diorama
The bridge is still removable at this point so that I could work on the scenery without damaging it. I painted the tops of the bent supports a gray color to represent concrete footings. Next, I used my favorite scenery base method, cardboard strips, to form the basic shape, using my diagrams as a guide. The yellow pieces of paper were there to represent tunnel portals. This was an idea I was experimenting with, but decided not to pursue.
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Here is a top-down view of the diorama with the Woodland Scenics plastercloth applied.
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I then started applying various washes of paint to stain the plastercloth to look more like rock.
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I spent quite a bit of time working on the creek itself. After painting it and putting some twigs and rocks in there, I poured some Envirotex epoxy to represent the water.
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This was the only last "overall" photo of the nearly completed diorama I took. I glued up some code 40 rail sections on either side of the bridge using five-minute epoxy, and added some greenery.
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