# Making a Bridge



## Aminnich (Nov 17, 2014)

Hey guys, 

I got some work done today on the water fall part of my layout. So I starting coming up with bridge ideas.... your talking to a future civil engineering, I know my bridges. 

At first I was thinking make it actually work (support the weight of the train) but then I saw a bunch of videos that show you dont really need the trusses of the bridge to support the weight of an HO scale train.... so im going for looks and not functionality. 

The bridge span is less than a foot, so i dont have much to work with. SO my thoughts are this;










EXCEPT, shorter in span, taller in arch, and double track.

Now here is my beginner question, would should I make this bridge out of. In my experience in building bridges and roof trusses for school projects, balsa wood was the go to material. But I am wondering if there is something better. 

If anyone has an idea, AWESOME. 

Ill post a picture of where the bridge will be going as soon as the area is ready to go. I still have to add some foam board to the area (need more liquid nails, time for another Walmart run)

Thanks for reading!


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## traction fan (Oct 5, 2014)

*Bridge Materials*



Aminnich said:


> Hey guys,
> 
> I got some work done today on the water fall part of my layout. So I starting coming up with bridge ideas.... your talking to a future civil engineering, I know my bridges.
> 
> ...


Aminnich;

Bridges should be strong. That's as true for models as for the real thing. Your right that the weight of a model locomotive is not a scaled down proportional version of its prototype. However our models have to deal with some pretty severe stresses of their own. A real bridge will not have a man 87 times its size bump any of his gigantic body parts into the bridge, but model bridges do! If your layout section is ever moved, that would create forces similar to those of a strong earthquake on
the real bridge.

For the bridge in your photo, my material of choice would be brass, soldered together. Second choice would be styrene
glued. Third would be basswood which is much stronger than Balsa wood. Balsa would be last choice for me, in fact, I don't recall building anything of balsa except a flying model airplane as a kid. Any of these materials will work. The first two have the added advantage of looking more like the steel that the real bridge would be made of. Wood usually needs a lot of sanding and sealing to look like metal.

Regards;

Traction Fan

PS. photos below show bridge models I have built from Basswood, and a modified styrene kit.


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## Aminnich (Nov 17, 2014)

thanks for the comments traction fan! Im thinking to use some styrene I beams, but im not sure how I could get the bend of the arch. 

I will be making mine pretty strong, as I move a lot as of right now. the "modular" section of the layout where the bridge will be is the smallest, so it would actually fit inside the truck when I have to move it again. 

Also, on your second picture, the trusses have a lot of detail, did you do all the cross sections, that looks really really good. 

For my bridge, I want to go with the more model steal bridge instead of the older wooden ones.


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## Lemonhawk (Sep 24, 2013)

Take a look at Central Valley http://www.cvmw.com/, they have a lot of structural beams in plastic. At the Sun Coast Model RR club they have bridges made from card stock. Amazing detail as the card stock is about the size of the steel plates that would be riveted together to make the beams of the bridge. My Father was a Civil engineer and I spent a lot of time going to bridge construction sites, the best was watching them throw hot rivets. Truly fascinating, they would catch them in a cup like thing that was only about 4-5 inches in diameter.


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## Lehigh74 (Sep 25, 2015)

Here is a double track bridge I made with plywood and rigid foam. The underside of the arch has plywood veneer. It’s modeled after the Manayunk viaduct. It is O scale and each span is 2 feet. You might be able to do something like it in HO using 5 mm luan.

The trestles look nice Traction Fan. So does the covered bridge


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## Aminnich (Nov 17, 2014)

I'll have to get a picture of the area the bridge will be going soon. It will give a much better idea of what I'm thinking.


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## CTValleyRR (Jul 26, 2014)

Central Valley and MicroEngineering make bridge pieces, Grandt Line and Tichy Train Group make detailed castings, and Plastruct and Evergreen make generic plastic shapes. Your hobby shop should carry one of both of the latter lines.

Traction fan is right innthat the bridge doesn't need to carry scale weight, but an unsupported 1' length of flextrack won't properly support a loco, either.

I would use styrene. To bend the long arch, use some of that math they forced on you in high school to calculate how long the beam needs to be, then create a jig to form it. Draw the arc on a piece of scrap wood, and insert some nails, screws or dowels to hold the beam on that arc. Use a hair dryer if necessary to soften the styrene and help it bend and hold that shape.


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## Aminnich (Nov 17, 2014)

The arch of the bridge is what could be a problem, that will definitely have to be homemade. But all the over parts of the bridge (that are straight), I can buy and cut for size. I'm leaning more toward plastruct and evergreen products. 

Thanks for the idea Ben. I think that will be the easiest way to get 2 of the same arches. The more nails I use for the jig, the more precise it will get.

I really want to take my time for this part of the layout, it is a small part, but it could really make the layout POP. I'm gonna do my research and planning, possibly even make a 3D model on Autodesk.... And maybe have it printed at school... How cool would that be.


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## DonR (Oct 18, 2012)

Many prefer Bass wood for modelling now. It
has a bit more structural strength than balsa
and comes in most of the familiar shapes and
sizes.

In addition to the already mentioned styrene
construction materials, there is Evergreen and
Plastruct at the hobby shops with a variety
of Beams and other parts.

You'll have to make your own arch. I'd suggest
a sandwich of flat styrene and one of the
structural beams. Perhaps heating the structural
beam with hot water will give it plastisicity for form the arch.

Don

Interesting project.


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## wingnut163 (Jan 3, 2013)

" your talking to a future civil engineering, I know my bridges."

i am glad you said that. i have been looking for some one (books ETC.) to find out how long can you make a truss bridge.
without any mid spend abutments. 
(pratt, bollmann, howe)


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## cid (Jul 3, 2014)

Hi wingnut, you might search online for "longest truss bridge" and find that it's 400 meters. Holy moly! That example in the thread is an arch bridge, not a truss bridge...anyway, you prolly don't need one as large as the prototype can be! Good luck!
I see there's also a "cantilever arch bridge" which gets even longer! One thing about MRR, you can learn something new every day!!


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## traction fan (Oct 5, 2014)

*Second (trestle?) picture*



Aminnich said:


> thanks for the comments traction fan! Im thinking to use some styrene I beams, but im not sure how I could get the bend of the arch.
> 
> I will be making mine pretty strong, as I move a lot as of right now. the "modular" section of the layout where the bridge will be is the smallest, so it would actually fit inside the truck when I have to move it again.
> 
> ...


 Amnnich;

The second picture is a modified Micro Engineering plastic kit.
The Milwaukee had many of these on their western, "Coast division." Following Milwaukee practice; I removed the horizontal bracing, as they used diagonal only. I also reduced the size of the box girders, which are HO scale, for my N scale railroad. Can't claim credit for any detail in these trestle bents, it was done at the factory. The other two photos are of scratchbuilt bridges, that I made from basswood.

Traction Fan

PS. You might try heating the plastic beams to gently bend them around a form. (Large can, wastebasket?) They will bend much more easily in their narrow dimension too.


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## Aminnich (Nov 17, 2014)

*here is what I got*

This is the area that the bridge will be going. As you can see the span is about 9 inches as of right now, it will be a bit longer once I get the foam shaped. The cliff is about 7 inches, 50.75ft scaled. 

I tried to draw my thoughts for the bridge, my drawing is VERY simple, but it gets you guys a pretty good idea of what Im thinking. 

shorter span, taller arch, double track


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## CTValleyRR (Jul 26, 2014)

wingnut163 said:


> " your talking to a future civil engineering, I know my bridges."
> 
> i am glad you said that. i have been looking for some one (books ETC.) to find out how long can you make a truss bridge.
> without any mid spend abutments.
> (pratt, bollmann, howe)


I'm assuming you mean real prototype bridges, not a model.

I once had a link to a cute little bridge builder program that was someone's Civil Engineering project. It basically allowed you to design a bridge using the provided library of components, and see if it stood up to a vehicle passing over.

I'll look around and see if I can find it.


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## Aminnich (Nov 17, 2014)

WEST POINT BRIDGE BUILDER, my best friend in 8th grade!!!!! oh the memories!!!! 

I was actually thinking about trying that out, just to get an idea of the load my bridge design could handle.


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## wingnut163 (Jan 3, 2013)

cid said:


> Hi wingnut, you might search online for "longest truss bridge" and find that it's 400 meters. Holy moly! That example in the thread is an arch bridge, not a truss bridge...anyway, you prolly don't need one as large as the prototype can be! Good luck!
> I see there's also a "cantilever arch bridge" which gets even longer! One thing about MRR, you can learn something new every day!!


thanks, but being in the US meters don't mean any thing to me. so i had to look it up and the 400 meters is 16" long.
i found a real bridge that is 190 feet long. (HO= 26 13/16")
at the moment i can t remember were it is but i'll look at my research and let you know.



CTValleyRR said:


> I'm assuming you mean real prototype bridges, not a model.
> 
> I once had a link to a cute little bridge builder program that was someone's Civil Engineering project. It basically allowed you to design a bridge using the provided library of components, and see if it stood up to a vehicle passing over.
> 
> I'll look around and see if I can find it.


thanks CTV. real or model it still would work out the same, right?
i think i saw that project. quite a surprise on what it did hold up.


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## CTValleyRR (Jul 26, 2014)

wingnut163 said:


> thanks CTV. real or model it still would work out the same, right?
> i think i saw that project. quite a surprise on what it did hold up.


No, this would be for the REAL ones! Our scale building materials and the vehicles which use our bridges do not have the same mass as the real ones (a 200 ton locomotive, scaled to HO, should weigh 2.3 tons... and what DOES it weight, 1.5 pounds?) Likewise with a plastic girder.

We build our bridges the way we do because we want them to look like the real thing, not because they need to be built that way. I had a bridge on my old layout that was a 9" segment of Atlas Code 83 Sectional track. It worked great for years before I finally got around to building "structure" underneath it. Even then, the structure was for show. The track piece carried the weight of the train.


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## ED-RRR (Jun 4, 2015)

*[HO] Scale --> Deck Arch Bridge..*

From my past experiences, I would highly recommend you build the *"Bridge" *first..
The "Bridge" will determine what required mounting scenery is required..
It will also be much easier for final scenery assembly..

*A Custom Built Bridge:*
Here are (x2) well know parts suppliers..
- http://plastruct.com/ 
- http://www.cvmw.com/bridges.htm

In [HO] Scale: (0.140") = 12" in real life scale..
You can use balsa wood but it will not result in a fine detailed bridge..
To build a custom made bridge using custom plastic parts may/will become very costly ($'s) requiring many different plastic parts.. 

Maybe have a look at "Faller" [HO] scale deck arch bridges..
In Europe they are called "Viaducts".. (Metal Bridges)..

*Faller (B-548):*
- [HO] scale
- Vintage Item (Still Sold On Ebay)
- No actual sizes now available









*Faller (120541):*
- [HO] scale
- 355.MM (14") long
- With (x2) straight track beds <-- For (x2) Tracks
- Can be assembled in (x2) different ways
- Track bed elevation from 117.MM (4.6") high, down to 91.MM (3.6") high

*Special Notes:*
Modify this bridge into a (x1) track bridge by adding (x2) safety walkways..
- OR-
Use both (x2) tracks on the bridge to enlarge the train operations.. <-- --> (Both Ways)..









......


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## Aminnich (Nov 17, 2014)

Thanks ED-RRR, 

Those look really nice, my problem is that it has to be custom built to fit in the area. Plus, a custom bridge I gonna be very cool to have on the layout. 

The length of the bridge is not going to be long, but the height of it will be substantial. 

Im lending more towards using styrene to make my bridge, but I wanna find where I can get some for free/cheap to test out a jig to bend it to shape. 

This project is definitely going to be the most challenging.


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## wingnut163 (Jan 3, 2013)

CTValleyRR said:


> No, this would be for the REAL ones! Our scale building materials and the vehicles which use our bridges do not have the same mass as the real ones (a 200 ton locomotive, scaled to HO, should weigh 2.3 tons... and what DOES it weight, 1.5 pounds?) Likewise with a plastic girder.
> 
> We build our bridges the way we do because we want them to look like the real thing, not because they need to be built that way. I had a bridge on my old layout that was a 9" segment of Atlas Code 83 Sectional track. It worked great for years before I finally got around to building "structure" underneath it. Even then, the structure was for show. The track piece carried the weight of the train.


i understand were you are going with this. i was not saying that the weight is the same , but the length. i would not want to build a bridge 3' long ( ho) when in 1 x 1 its impossible.


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## CTValleyRR (Jul 26, 2014)

wingnut163 said:


> i understand were you are going with this. i was not saying that the weight is the same , but the length. i would not want to build a bridge 3' long ( ho) when in 1 x 1 its impossible.


I knew exactly what you meant, and we are in violent agreement. My point is that we make bridges look like the real thing because we want to (so they look right), not because we have to for structural reasons.

Aminich is right, the tool is the West Point Bridge Designer, which you can download here: http://www.softpedia.com/get/Others/Home-Education/West-Point-Bridge-Designer-2011.shtml


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## wingnut163 (Jan 3, 2013)

thanks CTV.


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