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Curved trestle bridge

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  • Member since
    September 2021
  • 6 posts
Curved trestle bridge
Posted by psgivenjr on Thursday, September 30, 2021 7:41 AM

I need to fabricate an HO scale curved (28" radius) trestle bridge over an industrial area.  What are the best materials to use to accomplish this?

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Posted by maxman on Thursday, September 30, 2021 11:31 AM

Wooden or steel trestle?

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    October 2008
  • From: Canada
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Posted by cv_acr on Thursday, September 30, 2021 12:00 PM

As usually mentioned whenever this topic comes up, keep in mind that you will not be trying to actually make curved bridge spans, but a series of straight spans at a slight angle to each other that "curves" the whole bridge. The rails on top are then laid in a continuous curve across the individual spans.

I assume you are looking to build a steel trestle/bridge if there is going to be stuff under it...

You can also mix and match types of spans in the same bridge... short trestle-supported girder spans on either side of a truss span over a larger opening for example.

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Posted by doctorwayne on Thursday, September 30, 2021 1:30 PM

First, a big "Thank You!" to our unaddressed Forum-flaws for deleting my post as I attempted to reply here.

I have a couple of curved trestles on my layout, but in the photo below, the one in the background is considered a trestle, while I'm guessing that the one in the foreground is not, due to the "concrete" supports.

For the background bridge, I used mostly Micro Engineering kits and parts, modifiying them because the track is on a 2.9% grade. 
The "concrete" bases are stacked pieces of .060" sheet styrene, cemented together, then shaped, using a coarse mill file to create the sloped tops.  Each of them have a short piece of .039" piano wire projecting from their top, allowing the assembled trestle to be "clipped" in place, and also removed as a one-piece assembly when I finaly get around to adding "water" to that plywood "riverbed".

I used both 30' and 50' Micro Engineering girder bridges, as the curve is on a 32" radius.  For your 28" radius, the 30' girders might be a better choice.
I also used M.E. bridge track, which has thicker and more closely spaced ties, along with the guard rails used on such bridges.  Pretty-well everything you'll need is available from Micro Engineering.

I did have a wooden trestle on a much earlier layout, built by my father, using strip balsa wood, but can't find a photo to add here.

I am planning to build a "wooden" trestle on the upper portion of my layout.  It will not be operational, but rather a "scenic feature", mostly for taking photos.  Rather than using balsa or basswood, I'll be using strip styrene, which, when done properly, will not only look more like wood than will wood, but will be stronger, too.

I do have another trestle on my layout, also with a curve, but it's a much broader curve, allowing the support towers to be connected with longer deck- and truss-girders...

...and it's also in a more "finished" state...

Wayne

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    February 2005
  • From: Vancouver Island, BC
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Posted by selector on Thursday, September 30, 2021 4:39 PM

The answer depends on the construction of the bridge, and to a smaller extent what era of railroading.  Modern times, say post 1908, would almost certainly be steel on a Class One.  But on smaller operations, even into the early 1900's, you might see more wooden construction.  So, which is it?

You'll only want the roadbed to afford a curved path.  The underlying support will almost certainly be a series of girders or stringers, and they'll be dead straight over a distance.  For a wooden trestle, you lay the foundations of the bent frames at slight angles so that the bents will help to support the roadbed of stringers, themselves laid in a pattern of support which I can provide you if you're interested.

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Posted by psgivenjr on Friday, October 8, 2021 11:07 AM

looking for steel, not wood (early 1900s to 1960s).  Looks like Wayne had some great ideas - using Micro Engineering bridge components to fabricate  a series of short straight sections that ultimately bend around a curve.  That's the plan for now!!!  Thanks all for your responses - exactly what I was hoping for.

Peter

  • Member since
    September 2021
  • 6 posts
Posted by psgivenjr on Wednesday, November 17, 2021 10:08 AM

I finally purchased several Walthers "90' single-track through girder bridge" kits, cut blue foam board into a 28" radius arc, cut to thickness (held my breath the entire time), then glued the girder pieces to the sides of the foam with compatible construction adhesive.  The girder pieces are thin enough to bend and held with clamps until the adhesive dried.  Adding all the gussetts (?) helps with strength.  The piers are made from blue foam, cut using a band saw so the striations once painted look like a cement form was used.  I'm happy now!  Peter

Tried putting in a photo but software not cooperating ... oh well

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