I have a curved section of track in HO scale under which passes another line. I need to bridge the curved section of track. My prototype is NYC transition era (cicra 1953). I would like a stone structure but it will need to be curved. Does anyone know a model scenery supplier who would have a product that I could put around a curve. I thought about tunnel portals because that is the approximate height of bridge that I need. This would work but I need to connect them with curved sections. Any thoughts?
There is a wonderful model of the Minneapolis Stone Arch bridge done in O scale at the O scale club in St Paul. It is curved. I think one of the regulars on this forum built it. He can give you some good advice. If you want something nice, it will take more than a simple kit.
I have made curved stone walls using a mold and Hydrocal. The mold is normally flat, but if you wait 10 to 15 minutes after pouring, the Hydrocal will set up enough that you can curve the mold around a form and then let it harden. To make the curve, I cut a form from a piece of 2-inch insulation foam and then added a thin piece of styrene (even thin cardboard would do) to get a smooth curve.
www.mrscenery.com has some nice stone walls. I like the “cut stone” one, which comes out about 3x8 inches.
A bridge deck which curves between vertical supports is structurally unsound, and you probably will not find prototypes suing the design. You can probaly get it to work on a layout as the weights are low in comparison with the spans, but even there you may have problems.
To illustrate, imagine a pair of two by fours nailed together to form an “L” shape with legs two feet long. Now stand up a pair of support blocks, lay the L-shape flat on the blocks and see what happens.
A trestle has very short spans between closely spaced suppots, and they appear to curve smoothly, but a stone bridge would need to become an “embankment” to manage the same technique.
In stone, prototype practice would either be a wide deck straight bridge, or several spans of straight decks between piers to approximate the curve.
Another option is to make the lower track into a tunnel, be sure to leave access holes if you go this route.
Do a Google search for ‘curved stone arch bridge’. You will get a lot of information on stone bridges, including curved ones.
One of the larger curved stone arch bridges was built in Minneapolis/St. Paul in 1883, crossing the Mississippi River. It has a large, graceful curve. Most bridge builders of the time thought that a stone arch bridge couldn’t be built with a curve.
The bridge still stands today, used as a pedestrian and bicycle bridge. For more information on this bridge, go to http://www.mrdbridges.com/stoneArch.php
In model railroading, you can do whatever you like. In all probability, there IS a prototype for what you want to do.
Darrell, quiet…for now
Check these out:
http://en.wikipedia.org/wiki/Glenfinnan_Viaduct
http://www.trekearth.com/gallery/Europe/United_Kingdom/photo341039.htm
http://www.fairbairn.pwp.blueyonder.co.uk/scotland/glenfinnan_viaduct.htm
It’s concrete, but it’s big and curved.
Model Railroad Mag had a 4x8 layout construction series 3 part that had a description of how to build a cuved viaduct.
Yes, there are exceptions to my earlier post, I was pretty sure when I wrote it that somebody would find one. If you notice in the examples though, the curvature of any given span is miniscule compared to the distance between the piers. This is because if the curved deck sticks out past the line connecting the edges of the piers, the deck wants to tip over when you load it. The same will apply to a model bridge, but you could easily get around that by attaching the deck to the piers and the piers to your benchwork.
This will work for a gentle curve where the piers are close together, but if they are well apart, it’s liable to look a bit strange. Not a dealbreaker, but it’s better to be warned upfront, before you put a lot of effort into something you might not like when you see it completed.
Sly and cunning prototypical trick for designing a curved stone arch: Curve the concave side to any appropriate radius. Make the portion of the convex side not supported by piers or abutments straight. Saves material by reducing the deck width to minimum at the center of the span.
Chuck
Hi maybe I misunderstood the post. You are looking for a supplier and not prototype information?
Check www.sceneryexpress.com I believe they have a flexible rock wall material you can use.
I made a simple curved viaduct in 2" foam. If you want something prototypical, try www.modelrailroadstoneworks.com
viaduct installed
in primer on bench
Good Luck, J.R.