Description: 4 Span Deck Plate Girder Bridge
Prototype Information
Definition and use.
Engineering - nomenclature of girder parts and pic side and inside use micro 50 foot bridge as example with red lines and lettering.
girders are slightly wider in spacing than the rails
Multi-span deck plate girder bridges are not connected to each other. The rails and end bearings on the top of the bridge pier hold the bridge in line. The end stiffeners transfer the weight of the bridge and the train down onto the bridge pier. The end stiffeners are mounted on pedestals which are used to .....
Engineering - 60 foot plate girder bridge
The WWSL
Kitbatching
I have six Atlas Thru Plate Girder Bridges, each of them have 10 identically spaced steel plates.
- The prototype 21 panel plate girder bridges would be selectively compressed to 14 panels. To kitbatch this
bridge I need to add 4 panels. Total length of those two
bridges will be 25 inches.
- The 16 panel bridges would be selectively compressed to 10 panels. To kitbatch this bridge I need to shorten the height of the plate girders by approximately 1/3rd. Total length of those two bridges will be 18 inches.
Project Process
Tool List
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Materials
1 - 3/4 inch aluminum trim channel 48 inches long (Hillman)
10 - Atlas Through Plate girder bridges. I got mine at railroad swap meets.
2 - MicroEngineering Bridge Flex tie strips (36 inch each)
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Process Steps
Construction - 14 panel deck plate girder bridge.
The intent is to kitbatch four 10 panel bridges into two 14 panel bridges.
- Cut the through plate girder bridge apart. I used a 3 inch table saw. (4 bridges)
- Sand the back of each plate girder panel to remove the knee braces. I used an 18 inch belt sander (8 panels).
- Cut 4 plate girder bridge panels at the x panel from the center as shown in the example and sand the c panel cut lines smooth.
- Cut 2 plate girder bridge panels at the x panel from the center as shown in the example and sand the end panel cut lines smooth.
- Check for square then align and glue two end panels to both sides of each center panel.
- Add the rivet stiffener plate at the top using a piece of Evergreen Styrene.
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Construction - 10 panel deck plate girder bridge.
The intent is to kitbatch two 10 panel bridges by reducing the girder height relative to the 14 panel plate girder bridges (above).
1. Cut the through plate girder bridge apart.
2. Sand the back to remove the knee braces.
3. Measure the plate girder and mark a line 3/4 down the panel parallel to the base.
4. Cut the plate girder panel at the cut line and sand the panel cut line smooth.
5. Add the rivet stiffener plate at the top using a piece of Evergreen Styrene.
6. Cut the end plate from each end of the removed bottom section, sand and glue the end plates to the bottom of each end.
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Bridge Ties
1. Remove the sprue gates from each tie end and sand for smoothness.
2. Gently adjust the tie spacing as necessary. The Union Pacific Common Standard was 8 inches between ties.
3. Add initial tie detail.
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Channel Fabrication
1. Utilizing 2 14 panel girders and 2 10 panel girders, layout the girder locations on the side of the aluminum trim channel and mark the length of the 4 panel girders.
2. Mark the sides of the aluminum channel at the 10 girder panel locations for removing aluminum as necessary.
3. Cut the aluminum trim side channels to the depth of the 10 girder panels.
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Bridge Tie Painting
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Plate Girder Painting
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Bridge Assembly
1. Apply contact cement to top of aluminum channel. Center and attach bridge tie strip to top of aluminum channel. Clamp and allow to dry.
2. Apply contact cement to side of aluminum channel. Identify the edge of the panel that does NOT have the xxxx and attach 14 panel girder to the side of channel and along bottom of the tie strip. Align end of girder to the edge of tie. Clamp and allow to dry.
3. Repeat step 2 with a 10 panel girder. Ensure a gap between the 14 panel and the 10 panel the gap between two ties. Clamp and allow to dry.
4. Repeat 3 with second 10 panel girder. Clamp and allow to dry.
5. Repeat 2 with second 14 panel girder. Clamp and allow to dry.
6. Turn aluminum channel and complete other side in an identical manner as 1-5 above.
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Adding Final Track Detail
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Weathering
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Project Process
Bridges are a favorite scenic feature of model railroaders. The longer the bridge, the more dramatic, even spectacular, the visual impact becomes. As anyone who has attempted it can attest, installing even a simple, short, single-span bridge takes some forethought. But when a bridge or viaduct is lengthened beyond a span or two, construction and reliability issues start to arise. How do you keep all of the spans aligned as one continuous structure? How do you make them dimensionally stable? How do you install guardrails so they don’t buckle with changes in temperature and humidity?
These were questions I faced when a project in my custom building shop called for an almost scale length representation of the iconic bridges crossing the Potomac River in Harpers Ferry, W.Va. There are two bridges, one double track and the other single track.
The answer was using a length of lightweight aluminum channel as a core. Then I laid and fastened track to the top of the channel and attached girders to the side. In other words, I built the bridge around the core. Aluminum channel is inexpensive and easily found at hardware stores. Being relatively soft, it’s easy to cut with a hacksaw and drill through.
STEP 1 CUTTING THE CHANNEL AND ADDING GUARDRAILS
Begin by measuring the length of the bridge span. If the abutments are already in place, allow roughly 1⁄16" of clearance on the ends between the aluminum channel and abutment. The channel I used comes in 8-foot lengths. Mark the length on the channel and cut it with a hacksaw. Clean up any burrs with a file.
Because the span is relatively long, the risk of the guardrails buckling with changes in room temperature and humidity is significant. For each 3-foot section of flextrack, I removed three plastic ties and replaced them with Clover House printed-circuit (PC) board ties. After soldering the guardrails to the PC board ties, I applied thin cyanoacrylate adhesive (CA) to the rest of the length of the rail.
With the guardrails in place, I attached the track to the top of the channel. For double-track lines I used two aluminum channels laid parallel to one another, kept apart by a square spacer dowel every several feet. For this N scale project I used a 1⁄2" aluminum channel and a 1⁄2" square spacer dowel. Adjust the size of your channel and spacer dowels accordingly for other scales.
I used epoxy to secure the spacer dowels to the channel, forming the core. For a single-track bridge or viaduct, the process is much simpler; just lay the track on a single piece of channel.
For double-track spans, I aligned the outer railhead with the outside edge of the channel. For N scale, I use a 1" parallel track spacing. I didn’t want to rely solely on glue to attach the track to the channel, fearing it might loosen over time. I used a motor tool with a no. 69 bit to drill through the tie and into the aluminum channel every foot or so. I then set a Micro Engineering no. 30-104 medium spike in the hole and lightly tapped it down.
The spikes I used were .032" diameter; a no. 69 bit is .029". To find the exact drill bit size for your situation, experiment on a scrap piece of aluminum channel first. The hole shouldn’t be so small that it’s difficult to drive the spike in or so large that the spike isn’t snug. You want the hole to provide just enough friction to hold the spike.
The assembly of bridge track on aluminum channel is light, strong, and easy to move to the workbench for detailing. I attached the girders to the side of the channel with CA. Atlas Model Railroad Co., Central Valley, and Micro Engineering are among the suppliers of these parts. Then I added other details to match the prototype I was modeling.
I mounted the bridge in two steps. First, I supported the span with temporary blocks. Then I replaced the blocks with detailed piers. You can always reverse the order of mounting and detailing. Mount the assembly, run trains until you’re satisfied with its reliability, then remove it for detailing and painting.
When I was ready to install the bridge, I first set it across the span with each end resting on the abutments. I ran the bridge track an inch or so past the abutments. If you place the joint where the bridge meets the abutment, you run the risk of a bump at the joint. Then I temporarily supported the span with blocks of wood and made sure trains ran smoothly over it.
Finally, I took the finished piers, brought them up from the bottom until the bridge shoes just touched the bottom of the girders, and shimmed them into place from below. And with that, I had an exceptionally strong and stable long-span bridge that will provide stress-free operation without having to worry about dimensional stability or damage.
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