I’ve built several structures out of foam core some backdrop structures and a few heavy industry buildings. They typically work out well and save some money being as many of them have been on the larger size. I have two spots on the new layout that will require a double track bridge. I was thinking along the lines of a concrete or stone viaduct bridge but am open to all ideas. I was wondering if anyone has ever applied the use of foam core or gator board and the like to bridge building.
Allegheney:
I don’t know whether or not this will help, but the entire elevation of my MR is built on WS foam core risers, which go from 0" to about 18" elevation at the highest point, and I’ve been running some pretty heavy trains (including heavy-duty brass articulateds) over it with absolutely no problems for the past eight years.
So I would think that if you were planning a stone or concrete viaduct with a foam core, you should have no problems at all. I assume you’re thinking along the terms of the Eastern arch viaducts, such as used on the Pennsy or Lackawanna, right? I should think that the foam would be pretty solid as a core. Just for safety’s sake, I’d use the pink Corning extruded type of foam over the beaded kind, though.
Besides, it will carve much cleaner. [:P]
Just my thoughts.
Tom [:)]
Well thats not exactly what I was talking about but it does sound like something that may work and work well. I was referring to the laminated board used for mounting pictures and such as you buy in ACMoore and other craft stores. It comes in 3/16" & 1/2" thickness and modelers typically use it for either mock up building or complete structures. I did notice a foam viaduct when I was looking at Scenic Expresses webiste I’ll have to check it out again…
As a cosmetic skin over a quick and dirty plywood subgrade with 1-by risers, there’s no reason why it shouldn’t work.
For my deck girders (on masonry piers) I’m thinking of using some 1/2" square stock and putting cosmetic faces of foam-core board on it, with appropriate angles and flanges to represent the reinforcing parts of the girders. The piers will provide solid (plaster) support on (approximately) 5 inch centers. Rail will be hand-laid on wood ties.
I have used some foam board as safety fences on tracks in the Netherworld.
Chuck (Modleing Central Japan in September, 1964)
Using the foamcore to build a viaduct type of bridge to my way of thinking would give you an extremely strong structure.I am asuming here that what you are planning would actually be an enclosed box structure.with the tracks running on top of it.The only problem I can foresee is curving the foamcore for the insides of the arches.
I think you should go for it and post your progress pictures on the appropiate forum(s)
As to the strength issue, might I suggest http://www.carendt.com/clinic/peekpike/index.html
From the Scenic Express Website “The massive viaduct is suitable for single track HO or double track N-Scale. The smooth back side allows two viaducts to be glued back to back for double track HO or single track O-Scale. Inside arch is same red block pattern as wall. Comes painted and pre-weathered. Made from urethane foam that cuts easily with most hand tools. Supports 60 lbs. Measures 21” L x 8"H x 2" Deep. Multi-Scale for N-HO-S-O Scales."
You might want to check out Mike Manes’ paper on " Foamcore Payload Construction" for a edge of space project. He covers cutting, holes and forming corners.
I think you biggest problem is that the material does not bend very well, so the lining the curved parts of a bridge or viaduct will be difficult.
Alan
I have a double arch cut stone bridge on my C&NW layout that I bashed using two Monroe Models plaster kits. To test out the area (and avoid too much handling of the plaster kits mostly due to Murphy’s Law concerns) i constructed a stand in of foam core, held together with hot glue from a glue gun. It was only a stand in, but it needed to be very precise. It is surprisingly strong. I did not bother detailing it in any way.
Years ago (January 1965) MR had a nice article on using foam to build a bridge but the foam used looked more like florist’s green foam, without a paper facing.
Dave Nelson
Your correct in your assumption Cat, What I have planned in my head and putting it on CAD today some time is a 4.5" wide top and the sides will be 32"Lx15" high all entirely one part. I have a foam cutter that cuts a perfect V groove hence when you remove the cut piece you can fold it at a perfect 90 degrees. So that adds to the strength, the arches would be cut by using a circle cutter I purchased and then cut two tangent lines on either side of the circle so when you remove the waste piece your left with the pier section with the arched tops.
The end walls of the bridge would be 1/2" foam core as opposed to the 3/16" used on the rest of the bridge. I would also gusset the inside corners with foam core wedges. In regard to the curved inner section of the bridge I had planned on using .040 styrene that I have 4’x8’ sheets of out in the shop. How ever in the book from Foamwerks (the company who makes the tools) and on their website they show how you can curve the inside corners by scoring the back side of the piece of foam about every 1/8" across the full radius of the curve so when you grab the flat pieces and pull them together the top will arc into a perfect curve.
I think that part may take a bit of practice.
I had planned on either painting it and using sifted sacrete like Ken McCorry did so you paint it with straight white glue and sprinkle on the sifted concrete leaving you with a real concrete bridge or option B: was that I was going to cover the outside of the bridge wit
Actually not as difficult as you would think. I don’t think you can do it with foamcore, but you can make a curve with Gatorfoam. There is a guy that sells this product at the Timonium, Maryland, train show and he demonstrated to me how to do it.
What he did was cut through the top face of the Gatorfoam and through the filling, but stopped short of the bottom face. Then you just flex the bottom face around to the radius you want. The face of the bottom face becomes the inside face of the arch. Obviously there is a limit to the amount of flexing, but the radius can be made small enough to become the inside of an HO tunnel.
The reason this can be accomplished with Gatorfoam is because the surface material is some sort of laminated or composite material, not paper like the cheaper foamcore product.