I have a good spot for a bridge (HO). But suspect I’ll have to custom build or kit bash it. It needs to be about 18" long, about 4-5" high and the whole thing on a 24" curve. I model early 20th century so a steel or wood trestle will work fine. Sounds like a good magazine article - “How to stratch build a trestle”. Does anybody have any suggestions? Thanks - Bill
Curved bridges are actually a string of tangent spans that meet at a slight angle.
Which kind of bridge you will build is somewhat area and prototype specific:
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You model the early 20th century, but the bridge might be a masonry arch viaduct originally built in the second quarter of the 19th century - assuming you model hard coal country (think Starucca Viaduct.) The concave side can be a true curve, while the convex side will be a series of straight lines, with angles at the centers of the piers
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You model a recently built bridge in the far west - timber trestle now, but will be filled in (with a culvert at the bottom) as suitable fill material becomes available. The bents lie on the radius lines of the curve, perpendicular to the rails immediately above.
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Your railroad built with iron (or steel) to start with - think the high bridge at Georgetown, CO, or a modified steel viaduct kit (modified by shortening the inside-of-the-curve suspended girders, while keeping the towers rectangular.) The ties will usually be laid on short span deck girders.
My prototype would probably use deck girders on circular crosssection masonry piers, but that’s a Japanese thing (as is the oxide red paint job.)
The types of bridges you most likely will NOT see are pure steel arches and through trusses. They would have to be built wide enough to clear the rolling stock - probably twice as wide as needed for tangent track. Actually, for your 24" radius curve, almost any truss bridge would be overkill.
Hope this has been helpful.
Chuck (Modeling Central Japan in September, 1964 - with lots of deck girder bridges, most on curves)
There are several manufacturers of wood trestle bents. They’re not expensive, and look quite nice in the package. This would be an easy way to build the whole thing, if you didn’t want to construct them yourself. On the other hand, that’s not a difficult thing to do, either. Get some photos of real trestles to see how they’re put together. Go to a craft store and pick up a few pieces of balsa or bass wood, and give it a try.
What is this bridge going to span, by the way? A wood trestle is generally not something that would be built across a wide, strong river, unless the posts were set in solid, high piers.
A guy from Vestal isn’t doing the Starrucca Viaduct or Tunkhannock?
Or do you have them already?
They’re both WAY too big for my layout, even with selective compression. Also, since I grew up in NE PA, seeing the “Nicholson Bridge” (Tunkhannock) and “Kingsley Bridge” (Martin’s Creek) almost every day makes them kind of “normal” for me. I’m looking for something a bit unusual (for me). Either a wood trestle like DL&W turn of the century or a spindley early steel structure. It definitely should not be a through bridge. I like the precarious look of trains going over skinny open trestles. I model (loosely), early 20th century DL&W but am interested in the “spirit” more than prototypical authenticity. Thanks - Bill
Here’s a shot of the site. No scenery yet so there’s nothing to justify the bridge, but I will likely do it the other way around. The bridge will justify what ever I put under it. 
Ether go to Walthers.com or do a Google search for curved HO trestle bridges you’ll be amazed at how many you’ll find. I just got a quote of $500 for a guy to build a double track wooded trestle. His work is phenomenal some of the best I’ve ever seen but unfortunately thats about $450 past my budget so a couple of kits from Walther sare going to have to do.
Here is a photo of one that we are stratch building. Curve, incline, and a turnout. We used dowels,and scale lumber from the local hobby store. Once the ground goop set up, the bents became rock hard. The track is not down yet, but the structure is pretty tough.
Sue
Hi Sue, Wow. Very nice. And very similar to what I imagine for my layout. But where to start? Maybe some templates for the bents? I’d love to see a cross section of the top. I don’t need to be super accurate but am not artistic enough to go without guidelines. Thanks - Bill
Take a look at:
http://www.sceneryexpress.com/
or
JV Models curved bridge (link to a vendor with good picture) or
It is easy to make a template out of styrene. I will try to get you another view.
Sue
I’ve thought about the JV Models kit but it is probably twice the size that I can use. The old Campbell curved kit would be good too. Unfortunately no one will tell you the curve radius or the trestle height.