Bridge Ideas?


H

hamltnblue

Active Member
Hello All

As I'm laying the foundation for my trackwork I have come across 2 sections that will require a curved bridge. I've looked around and haven't found anything that seems to fit so I think I'll try to build my own.

Layout is HO.

The first section is about 18 inches across and 3 1/2 inches High. The radius is 30 inches. 2 tracks will pass under the bridge leaving room for a support in the center.

IMG_0210.jpg


IMG_0211.jpg


The second section is 27 inch radius and about a foot wide:

IMG_0212.jpg


IMG_0213.jpg


Has anyone here done something similar and/or have ideas on the best way to go.

Also is there a source for girders material that can be shaped to a curve?

Thanks
 
Gee, the sky's the limit on these two. For the first, a wooden bent frame trestle or a steel trestle would be fine. For the second, a stone viaduct with one central pillar between two arches....or two deck girders or through girders with a central pylon or pier. The spans would not be curved, no matter which bridge types you use, singly or in combination, but the roadbed and tracks certainly could be.

You could have a lot of fun and skills-building here.

Here is my timber trestle. It is curved, but not really, the deck is laid out so that it conforms to the 33" radius, but it is really several straight sections, just like the real ones.

IMG_5145csharr.png


-Crandell
 
Thanks Crandell.
Is that kitbashed or something available? The limitation is the 3 1/2 inch height so What hangs underneath is my issue. The second pics are actually 3 inches. That's why I was leaning to girders. Are there sources for the raw girders or similar that can be used to make larger bridges?
 
Oh nice, you're making some great progress on that re-build project. I really like how you have the trackwork going around and up the incline!

I agree with Crandell, a nice rounded wood trestle would like nice with your layout.
Maybe you can kitbash this kit here: http://www.walthers.com/exec/productinfo/345-2016
 
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I forget by whom, but at least one outfit makes HO wooden bent frame trestle elements. You could google it as a query and see what comes up. In my case it was scratch-built. For a template I used the information here, particularly when laying out the timbers for the curved deck.

http://members.cox.net/sn3nut/trestles part 1.htm

-Crandell
 
This is in N-scale, but I kitbashed some Walthers through plate girder bridges into a gently curved bridge.

train_bridge_whole1.jpg


The bridge is strong enough to be used without any supports, but it looks strange. Here it is with a few supports temporarily in place.

bridge_w_supports1.jpg


I even found prototype photos of a curved bridge constructed more or less in this fashion.

- Jeff
 
hamltnblue said:
Thanks Jdetray. Something to definitely consider. How did you curve the bridges? Can you do a top down pic?
Click to expand...
Here's a drawing, looking down from the top. This drawing shows the side plates of the bridge segments in black. The abutments are shown in red.

curved_through_plate_girder.gif


In the drawing, the side plates are all the same length, but they are skewed to introduce a curve into the bridge. You have to modify the crossmembers and their attachment points, but it's fairly easy to do. This is a kitbash, after all, so some cutting and fitting is required.

Below is a photo showing a close-up of a portion of the bridge. You can see how the side plates of the rightmost span are skewed to introduce a curve.

bridge_overheadmed.jpg


To make the bridge stronger, I added a 0.125" (1/8" ~ 3mm) length of music wire on both sides of the bridge beneath the deck. The wire is bent to follow the curve of the bridge. In N-scale, 0.125" equals 20" scale inches, so the wire makes a fairly realistic representation of 20" water or sewer pipe that might logically be carried by a bridge.

- Jeff
 
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Blue, have you made any progress on your bridges and rebuild project?

Anxious to see how it's looking....
 
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