Let's talk about foam...

In keeping with the all-foam theme, I made a cool discovery yesterday. I've been planning to use Woodland Scenics foam Track-Bed instead of the traditional cork roadbed, but so far I had only bought the 3/16"-thick, 2"-wide material that they make for HO scale. This comes with a 45-degree beveled shoulder and looks great for mainlines, but for my interchange track and the CV yard trackage, I wanted something with a lower profile. Woodland Scenics does make N scale Track-Bed in 1/8" thickness, but I wasn't sure how wide it was and didn't love the idea of trimming strips from the large sheets they sell. So, that's when I kicked into engineering mode, and here's what I learned...

The Track-Bed appears to be made from a closed-cell polyethylene foam, which is very different from typical open-cell polyurethane foam (think sofa cushions) or extruded polystyrene foam (think wall insulation). One of the more common uses for PE foam is flotation devices, since it's extremely buoyant, and it's also used in packaging for its firmness. I found some suppliers for it in black 1/8" sheets, but not really in the sizes or quantities (i.e. small) that I was looking for. Then I started looking at other uses of foam, and stumbled upon self-adhesive weatherstripping rolls sold in hardware stores. Not many of these were PE foam, but I did see a lot made from closed-cell PVC. I found several sizes (and colors!) that might be suitable for roadbed, and finally hit the jackpot with this pipe-wrap insulation tape from Frost King/Thermwell:

This particular roll is 1/8" thick by 2" wide by 15' long, and comes in a medium gray color with a self-adhesive backing on one side and a layer of aluminum foil on the other side. I was worried about the foil at first, but it turns out they also sell a black 30' roll without the foil. Since I didn't need that much length and didn't want to have wasted money if the foam was unsuitable, I bought the cheaper short roll ($3 at Lowes!) and set about peeling off the foil. Going slow and steady, it actually comes off pretty cleanly, although it tears often and you have to watch the jagged edges. Anyway, with that done (or unnecessary if you buy the longer roll) you get a convenient peel-and-stick roadbed that matches the Track-Bed nicely in width!

Comparison of the Track-Bed (black) and foam pipe-wrap tape (gray).

I will say that it's noticeably softer/squishier due to the different material, and I haven't found a good way to bevel the edges (hot-wire? Dremel saw blade?). But since I'm using this to represent less-maintained trackage, both of these issues pretty much go away. The softness isn't as apparent with track in place compared to direct fingertip pressure, and these tracks don't need crisply ballasted shoulders so I can just blend them in with putty or acrylic paste. The pressure-sensitive adhesive doesn't seem permanent, instead being more like the foam tape that 3M sells, but I think it'll hold fine (especially after gluing the track down and ballasting). It does have excellent sound-dampening qualities, which is important because extruded foam actually tends to amplify noises if track is laid directly on it.

By the way, I also bought some sheets of 'craft foam' at Jo-Ann that comes in various colors and thicknesses (2mm, 3mm, 6mm). This is a denser foam (neoprene, I think) that seems identical to what Atlas uses for protecting the handrails of their HO diesels. I plan on using strips of the 2mm to shim my roadbed up to meet the Track-Bed, and the other sizes could make nice level foundations for structures. It may have other scenic uses as well, since the black and gray colors do resemble asphalt and concrete, but I'm not sure how well it takes paint.

One more thing - check out this tool I made for marking the outside edges of where the roadbed should go, since the centerline won't be visible:

4 types of foam: expanded polystyrene beadboard (white); extruded polystyrene insulation (pink); closed-cell polyethylene track-bed (black); closed-cell PVC pipe-wrap (gray).

Wow, when did I become this obsessed with foam anyway?