# Scratch build a bridge



## swimmer_spe (May 3, 2016)

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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## traction fan (Oct 5, 2014)

*Where's the bridge?*



swimmer_spe said:


> View attachment 411161
> 
> 
> View attachment 411169
> ...


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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## Dennis461 (Jan 5, 2018)

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.


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## swimmer_spe (May 3, 2016)

traction fan said:


> 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.
> ...


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. 

















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.


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## swimmer_spe (May 3, 2016)

Dennis461 said:


> 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.


I am not changing the lay of the track. I have nothing but time, so, I welcome the challenge.


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## D&J Railroad (Oct 4, 2013)

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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## D&J Railroad (Oct 4, 2013)

This is a video of trains running over the trestle.


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## D&J Railroad (Oct 4, 2013)

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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## D&J Railroad (Oct 4, 2013)

Video of the Orroyo crossing on the D&J Railroad.


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## swimmer_spe (May 3, 2016)

D&J Railroad said:


> 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.


Your bridges look amazing.

Here are examples of what I would like:
















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?


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## D&J Railroad (Oct 4, 2013)

swimmer_spe said:


> 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?


I'm kinda lost on what you are trying to achieve.


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## swimmer_spe (May 3, 2016)

D&J Railroad said:


> I'm kinda lost on what you are trying to achieve.


Here is the place I want a bridge:








Over the part that is the lower track, I want something like this:








Over the rest, I want this:


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## D&J Railroad (Oct 4, 2013)

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.


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## swimmer_spe (May 3, 2016)

D&J Railroad said:


> 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.


Which is perfectly fine. I am not sure of even how to start to build it. What materials? Where do I take measurements. How long does each piece need to be?


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## CTValleyRR (Jul 26, 2014)

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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## swimmer_spe (May 3, 2016)

CTValleyRR said:


> 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.
> 
> ...


Link to Central Valley Gems?

I would rather not kitbash anything and build from scratch.


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## traction fan (Oct 5, 2014)

*Two bridge types*



swimmer_spe said:


> Your bridges look amazing.
> 
> Here are examples of what I would like:
> View attachment 418913
> ...


swimmer_spe;

The photos of prototype bridges that you posted, show an arched through truss, a deck truss, and some steel trestle approaches. What you want then is very much like what a real railroad would do. Use the arched through truss where clearance under the bridge requires it, and use deck trusses and/ or steel trestles elsewhere as you choose. Several companies make models of through, and deck, truss bridges in HO-scale. Central valley models makes a beautiful through truss bridge model that could be adapted to use as a deck truss. The model has a straight top , not the arched one shown in your photo. I think I saw an ad recently where they were coming out with an arched version. I don't know if you would settle for a straight top, or want a curved one. If you really want to accurately duplicate the two truss bridges in your photos, you might consider scratchbuilding them from commercial plastic, or brass, shapes. If you want to build the steel trestle sections Micro Engineering makes them in HO, and N scales.

good luck;

Traction Fan:smilie_daumenpos:


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## swimmer_spe (May 3, 2016)

traction fan said:


> swimmer_spe;
> 
> The photos of prototype bridges that you posted, show an arched through truss, a deck truss, and some steel trestle approaches. What you want then is very much like what a real railroad would do. Use the arched through truss where clearance under the bridge requires it, and use deck trusses and/ or steel trestles elsewhere as you choose. Several companies make models of through, and deck, truss bridges in HO-scale. Central valley models makes a beautiful through truss bridge model that could be adapted to use as a deck truss. The model has a straight top , not the arched one shown in your photo. I think I saw an ad recently where they were coming out with an arched version. I don't know if you would settle for a straight top, or want a curved one. If you really want to accurately duplicate the two truss bridges in your photos, you might consider scratchbuilding them from commercial plastic, or brass, shapes. If you want to build the steel trestle sections Micro Engineering makes them in HO, and N scales.
> 
> ...


I would rather build it myself then to order kits.


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## CTValleyRR (Jul 26, 2014)

swimmer_spe said:


> Link to Central Valley Gems?
> 
> I would rather not kitbash anything and build from scratch.


Google worked: http://www.cvmw.com

They sell pieces for construction in addition to kits. But really, if you take a box of parts intended to be used for one structure, and build something completely different out of it, isn't that scratchbuilding? Unless you're submitting a qualifying project for MMR certification, I would say so.


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## swimmer_spe (May 3, 2016)

CTValleyRR said:


> Google worked: http://www.cvmw.com
> 
> They sell pieces for construction in addition to kits. But really, if you take a box of parts intended to be used for one structure, and build something completely different out of it, isn't that scratchbuilding? Unless you're submitting a qualifying project for MMR certification, I would say so.


I would like to go to a hobby store pick up some wood and cut it to lengths and build my own bridges.


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## DonR (Oct 18, 2012)

swimmer_spe said:


> I would like to go to a hobby store pick up some wood and cut it to lengths and build my own bridges.


While at the hobby store look also at their stock of
styrene construction pieces. They'll have beams and
girders of various sizes and designs that may work
with your project.

Don


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## CTValleyRR (Jul 26, 2014)

swimmer_spe said:


> I would like to go to a hobby store pick up some wood and cut it to lengths and build my own bridges.


Suit yourself. I would say styrene is much better suited to building steel bridges than wood is, because of the availability of parts that have the correct basic shape (and whether you pull these parts from a kit or buy individual pieces doesn't seem to me to diminish the craftsmanship involved).

Personally, I would go crazy trying to carve a piece of steel lattice out of a piece of wood, but that seems to be the only option you're interested in. Your layout, your rules. Good luck.


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## swimmer_spe (May 3, 2016)

CTValleyRR said:


> Suit yourself. I would say styrene is much better suited to building steel bridges than wood is, because of the availability of parts that have the correct basic shape (and whether you pull these parts from a kit or buy individual pieces doesn't seem to me to diminish the craftsmanship involved).
> 
> Personally, I would go crazy trying to carve a piece of steel lattice out of a piece of wood, but that seems to be the only option you're interested in. Your layout, your rules. Good luck.


When I say a hobby shop, I do not mean one that sells model trains or even any other model stuff. I mean one that has a lot of various craft stuff.

So, i want to work with what I have here, and not have to order things and wait.


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## swimmer_spe (May 3, 2016)

I think I now know enough to begin building the bridge. 

I have one simple question... How do I attach it to the layout? 

Is it as simple as just gluing it to the foam board I am using?


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## D&J Railroad (Oct 4, 2013)

Yeah, just make sure it aligns with your track and then glue it in place. Apply ballast to cover the glue points and it will have a natural setting look.


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