When using foam is there a favored thickness on top of plywood or does 2" take the prize?
Thanks for the help.
Charlie
Assuming your benchwork is solid, and the plywood a reasonable thickness the depth of your foam is more dependent on the features you want to carve out of it or build up.
I did not use plywood - just foam on top of L-Girder benchwork. I could only find 1" so in most places doubled up, but if I had plywood I would only use the depth of foam I needed to achieve my topography requirements.
That is a good way to go.
I used one inch foam on a Luan top. If I were not going to use any plywood, I would go with two inch foam at a minimum.
2" foam is quite ridgid. A simple frame with 16" or 24" centers is sufficient to support it
I like working with the foam, easy to carve, if you goof, glue a replacement piece in. I used inexpensive latex caulk to “glue” it together. Whatever you decide to use, make sure it is foam compatible,
One drawback to foam is, that if you are carving or shaping it with a knife or Surform tool, it can be messy. I use a can of anti-static spray to keep it from clinging to me or other things. Keep a shop vac handy.
Another drawback is that if you are cutting it with a hot knife cutter, it gives off fumes. Good ventilation is highly recommended.
Good luck,
Richard
I am just about ready to start my benchwork for the layout. It will be 4’ x 11’. My thinking is that I will frame in the benchwork with 1"x4" on about 2’ centers. I am fortunate that I have access to foam board that comes in a 4’x8’ sheet and is 4" thick. This should be plenty deep for any streams or creeks. If not. I could always go 8" thick. In any event, this foam is incredibly strong.
My layout is 2" foam on a frame of 18" centers. No plywood. I can lean on it easily. I could probably climb on it, but that would wreck my scenery.
I’m really hung up with this one. I’m building a significantly sized second model railroad to replace the small 4x8’ I had years ago. Spent the last several years completing my basement so “the empire” would have a solid future. Entire foundation was re-mortared, and Drylocked. Walls are done, ceiling done, recessed dimmable lights installed. Time for 19x32’ benchwork!
I’ve settled on the L girder design and was planning 1/2" plywood with 2" foam on top to do small streams, etc. I really wanted to go with some Tortoise switch machines on the mainline but all this talk about drilling them out to replace the wire with heavier gauge has me concerned, especially going through 1/2" ply, 2" foam, and then cork roadbed on top of that.
I’ve read a pile of articles over the past year regarding cutting the foam out and mounting the machine to hardboard and dropping it in, but like everything else, half the people say that’s not a good idea, half the people say it’s worked fine for them. Then there are those who say just go with heavier, longer piano wire and you’ll be fine, never had any problems, etc. etc. while others warn against doing it. I’m really, really up in the air with this. Has anyone else ever struggled with the decision and how did you fare? I’ve gone so far as considered 1/2" ply and 1" foam but even that is debatable and won’t give me as much carving room as I’ d like to have.
Any advice? Many thanks in advance!
~Kris
I also use 2" foam, but I am a believer in rigid/ strong benchwork, so it gets a 5/8 to 3/4" plywood top over the 1x4 frame, before the foam. In my opinion the plywood also helps quiet the noise a lot.
The main drawback I ran into using a sheet of plywood, was when the track was on top of more than 2 or 3 layers of foam. It was a real pain to drill holes for the feeders. Now, I just glue the foam to the open grids, and I made a “wire needle” to feed the wires through the foam. It’s a wire hanger with a sharp point on one end and an “eye” on the other. Twist the wire through the “eye”, push it through the foam, then pull it through.
I had started a shelf layout about 5 years ago which was just 2 layers of 1.5" foam over L girders. The idea was that the foam was stiff enough to omit plywood, that it made it easier to make penetrations, and that the upper layer could be cookie-cuttered to make roadbed elevation changes. Those concepts were all valid. However after neglecting this layout for years I went back the other day and found that the track had buckled. The conclusion I reached was that the foam had shrunk over time. When I measured an 8 foot length of it I found it was 3/16" short of 8 feet. Since I hadn’t gapped the rails enough for that much shrinkage, they buckled.
In rebuilding this thing I am going to put down 3/4" plywood as the base and then 1.5" foam glued to that. But I am going to cut the foam every 2 feet or so such that the shrinkage is controlled.
FYI this was Owens-Corning pink foam called ‘Foamular’ purchased at Home Depot.
Of course, many will reply to this post saying something like ‘Well I’ve been building with foam for 20 years and I’ve never had a problem!’. Maybe so. Maybe such folks use big rail gaps. Maybe their foam is cut in small pieces. Maybe their roadbed isn’t rigidly attached. Maybe putting plaster on the foam holds it in place (no plaster for me). All I’m saying is be careful and don’t assume this stuff is dimensionally stable.
George
If you accept the fact that the included wire with the Tortoise is too light from the get-go, then the almost mandatory change to heavier wire is just one of those thing you have to do. Just like accepting rail joiners don’t conduct electricity from to rail to rail in the long term, and you have to put in feeders.
2nd issue with Tortoise is that the conventional mounting scheme does have its issues as the distance from Tortoise top to turnout throw bar reaches 3 inches or more. A feasible alternative for long vertical reaches is a version of the old Anderson link. A wire rotates within a vertical tube. Arms (90 degree bends) in the wire move the throw bar, and are used at the bottom to link to the switch machine. The Anderson link can be used with virtually any switch machine. And there are still commercial versions available.
Kris,
It seems to me that you don’t need the foam everywhere, or at least not the same thickness. For example, suppose your track is on 1/2" plywood bottom with roadbed directly on that. The foam could be 4" thick next to the roadbed and wouldn’t make a switch machine issue.
In other places where you might wish more scenic carving ability you could drop the plywood several inches and make up the difference in foam.
Alan
I used one inch foam pink board on 16 inch centers and it has held up well for 12 years or so in a garage layout. For scenic purposes I feel 2 inch foam offers more flexability.
Gale
Previous layout I used 2" foam laid directly on the 1x4 frame. Never had a problem, it wasn’t loud, and it wasn’t goign anywhere - I even bumped my head unerneath several times and never did it come unglues from the edge of the 1x4s.
This time I have 2 layers of 2" foam and put a layer of 1/3" plywood under it. I use servos for switch motors but they install exactly like a Tortoise, and with .037 piano wire they work just fine through the 4" of foam, 1/4" plywood, and cork roadbed.
I have an area where I want to carve away the top layer of the foam to make a road that goes under the tracks. I haven’t worked up the nerve to start cuting, but the actual height of the bridge comes out to be nearly 2" in HO, so goign down to the bottom layer of foam will be perfect, and yet still give me plenty of base below. I started with the 2 layers of foam when I initially planned just a small shelf switchign layotu that was to include a coal trestle, scale height woudl require the track to be about 3" above the base level, so the idea being with 4" of foam I could carve out 3" and still have a base underneath.
–Randy