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Scratch build a bridge

6K views 24 replies 6 participants last post by  D&J Railroad 
#1 ·
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This is my layout. As you can see, there is a bridge that is a focal point of my layout. It is at the highest point, and will be seen when entering the room. I want to make it special and something eye catching. Behind it, the circle will be a mountain with part of the circle being in a tunnel.

So, what kind of bridge and approaches would you suggest? There is a twist, literally. The track curves at each end of the bridge. The board currently used is 17 inches long.
 
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#2 ·
Where's the bridge?

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This is my layout. As you can see, there is a bridge that is a focal point of my layout. It is at the highest point, and will be seen when entering the room. I want to make it special and something eye catching. Behind it, the circle will be a mountain with part of the circle being in a tunnel.

So, what kind of bridge and approaches would you suggest? There is a twist, literally. The track curves at each end of the bridge. The board currently used is 17 inches long.
swimmer_spe;

I'm not sure where the bridge will go from your photos. However since the elevated track is virtually all curves, the bridge will need to be curved as well. Trestles, wood, or steel, are most commonly used on curves. Most other types of bridges will not work (AKA collapse!) if built on a curve. That's assuming we are talking about one, continuous bridge. Curved track can be supported by a series of short, straight bridges, laid out to form a curve. The steel trestle in the top photo is built this way. It is a kitbash of two Micro Engineering "Steel Viaduct" models.
Wood trestles are also commonly used on curves, often as approaches to another type of bridge. The center photo is a scratchbuilt, N-scale model of a small coal dump trestle that has a short deck truss section. The bottom photo shows a larger deck truss, wooden bridge. It is also scratchbuilt in N-scale.
If you can straighten out a section of your curved high track then you can use a truss bridge, or plate girder bridge, with trestle approaches at each end. Note: If you want to be realistic, make the truss, or plate girder bridge a straight, "deck type" bridge. That is a bridge with all it's main structure under the track instead of over it. Through bridges, with the bridge structure above the track, were only used when clearances below the bridges required them. Railroads strongly preferred deck bridges because they were cheaper to build, and maintain. They also made life easier for the track maintenance people, since all parts of the track could be reached easily.

good luck, have fun;

Traction Fan :smilie_daumenpos:

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#4 ·
swimmer_spe;

I'm not sure where the bridge will go from your photos. However since the elevated track is virtually all curves, the bridge will need to be curved as well. Trestles, wood, or steel, are most commonly used on curves. Most other types of bridges will not work (AKA collapse!) if built on a curve. That's assuming we are talking about one, continuous bridge. Curved track can be supported by a series of short, straight bridges, laid out to form a curve. The steel trestle in the top photo is built this way. It is a kitbash of two Micro Engineering "Steel Viaduct" models.
Wood trestles are also commonly used on curves, often as approaches to another type of bridge. The center photo is a scratchbuilt, N-scale model of a small coal dump trestle that has a short deck truss section. The bottom photo shows a larger deck truss, wooden bridge. It is also scratchbuilt in N-scale.
If you can straighten out a section of your curved high track then you can use a truss bridge, or plate girder bridge, with trestle approaches at each end. Note: If you want to be realistic, make the truss, or plate girder bridge a straight, "deck type" bridge. That is a bridge with all it's main structure under the track instead of over it. Through bridges, with the bridge structure above the track, were only used when clearances below the bridges required them. Railroads strongly preferred deck bridges because they were cheaper to build, and maintain. They also made life easier for the track maintenance people, since all parts of the track could be reached easily.

good luck, have fun;

Traction Fan :smilie_daumenpos:
From the pictures I posted, the current piece of wood is what will be replaced by a bridge. The straight section will be different than most of the rest.

Transport Track Railway Train Vehicle


Transport Bridge Railway Girder bridge Mode of transport


These are 2 bridges that are on the line that I like. The straight section is what I want to have over the lower track. The curved section, I want to have the truss on the rest of it.
 
#3 ·
If the lower track is inside a tunnel, the bridge wont be very high.
So a trestle would look a bit strange on the top of a mountain.
Building a trestle on a curve and grade gets time consuming since each bent wil be a different height.

IMHO, I'd reroute the curves to get a straight bridge, and get it away from the lower track.
 
#6 ·
I have built a few bridges for my empire.
This series of pictures shows the progress of a trestle that I built a couple years ago.
This first picture is where the trestle will go.
Second picture is the section of the layout cut out for the trestle.
Third picture is the trestle being built, upside down so the top deck will be perfectly flat.
Fourth picture is trestle placed in the opening with the landscape developed using foam board and plaster.
Fifth picture is the ground cover painted, ballast applied and the fascia in place.
This is a video of trains running over the trestle.
 

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#8 ·
A couple other bridges on the layout.
The first one is a Campbell Truss bridge kit that I built back in the late 1980s.
The second picture shows a few bridges that I built from scratch to span an Orroyo on the layout.

The last one is in progress. It's a scale model of the Canyon Diablo bridge on the BNSF mainline that is a few miles west of Winslow, AZ. The model is about 84" end to end, double track.
 

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#10 ·
Your bridges look amazing.

Here are examples of what I would like:
Transport Track Railway Train Vehicle


Transport Bridge Railway Girder bridge Mode of transport


Basically, I want to combine them with the part that crosses one track to have the over arch, and then where it just keeps going, to have the truss under it.

I am trying to figure out how to build it. Any tips?
 
#13 ·
So you are looking for a curved truss type bridge. I've never seen curved versions of them. That would compromise the strength of the bridge. Either earth embankment or separate trestle bents would be more appropriate for that kind of application. The part of the bridge that goes over the lower track would have to be supported by a wider support system that straddles the lower track because of the lower tracks footprint under the upper track.
 
#15 ·
Steel bridges, even when the rails laid on them are curved, are composed of a series of straight segments. Generally, there is a pier or trestle at each joint between segments.

Stone viaducts are not so limited -- they can be (and are) built in curves.

You might be able to kitbash a double-track truss bridge kit to give you room for curved rails, although clearances would likely be an issue if the radius was tight. Each span also has to be long enough that it doesn't need a support too close to the lower track.

For materials, you can look at Central Valley Gems. They have a lot of good bridge construction pieces. Basic old Evergreen Styrene I or H beams would also work.
 
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