Foam as benchwork?

Discussion in 'Getting Started' started by Jim Cullen, Jan 14, 2004.

  1. Jim Cullen

    Jim Cullen Member

    I'm in the pre-planning stage of another n scale small layout and my mind is wondering. That's what we call thinking when you get up in age, but that's another story.

    Anyway, past layouts have been the traditional open grid with plywood sub-roadbed. Usually 1x4''s around the edge, 1x3 cross members, and 1/2" plywood for the top. This has worked well except for what now is a major drawback for me; weight and portability.

    Since I'm thinking about a 34x80 size, my initial thought was to consider a hollow core door with a foam top. But then the wiring and switch machines would hang below the bottom surface of the door and I want to be able to sit the layout on a flat surface if needed. I could build a 1x4 frame around the door but then why do I need a door to begin with when I could just mount 2" of foam on the open grid.

    I'm beginning to get a headache. The question I'm getting to is that I'm now thinking about making the entire benchwork out of foam: 1 or 1-1/2 inch foam cut into 4" and 3" strips for the grid, and a 2" thickness piece for the top. Small gussets of foam in the corners and elsewhere for bracing if needed. The layout will sit on sawhorses or cabinets, so legs are not really needed for now. Switch machines could be mounted on 1/8 masonite pads and glued to the bottom of the foam top.

    Anyone done this? Would there be too much "flex" or "twist" in a layout made with all foam benchwork?

    Jim Cullen
  2. MasonJar

    MasonJar It's not rocket surgery

    Hi Jim,

    I am seriously considering building some HOTrak modules, in which foam features significantly due to weight savings.

    I would say that the foam still has a little flex that you need to watch out for, especially over bigger distances. The other thing the wood will do is protect the foam if (when? ;)) it encounters something more durable...

    A sandwich construction is almost always stonger though, so if you laminated the foam with something as thin as 1/4 luan (the mahogony plywood used to build hollowcore doors) maybe you will achieve the strength you are looking for.

    If you are looking for table top modules, you might want to do a search on "TTrak". I used to have a link, but can't find it now.

    Here is another link to a step-by-step for building regular HOTrak modules. You could always leave off the legs, as Bob's design does leave some room underneath for wiring, etc.

    EDIT - forgot the link :rolleyes:

    Lastly, if you used a door, but cut through the lower (outer? bottom-most?) layer as required, you could mount wiring "inside" the door. If you don't need more than 1.5 - 2" of space for stuff, this might work. Don't know if Tortoises would be clear though.

    Interesting topic, I will follow this one!

  3. roryglasgow

    roryglasgow Active Member


    I've been pondering the exact same thing for my new layout.

    For a smaller layout, say 48" x 24", 1" foam all around would probably work just fine. My guess is that, with the proper bracing, you could make a rigid structure with the 2" foam on top like you suggested.

    The main concern I have with the idea is how to protect the foam from dings and dents.

    Check out my Copper Ridge Railway construction photos. I used a thin plywood frame, on top of which sat a sort of grid of 1" foam. The whole thing had some flex to it, but when sitting on a level surface, the foam did not bend or move. It was held together with white glue and toothpicks.

    My current plans are for a 36" x 24" layout, although I'm apt to change my mind on the trackplan in the near future. It will sit on top of an old computer desk, so like you I don't have to worry about legs. I have been debating on whether to make a light frame from wood like I did with the Copper Ridge, or go all-foam. I've been leaning towards the latter...
  4. jon-monon

    jon-monon Active Member

    If you make it like an upside down shadow box with lots of cris-crossed supports, I think it would be very rigid. Use of a glue that allows a little flex, such as liquid nails or silicone RTV/calk for no-foam items shuch as track and buildings may be benificial. Excluding use of plaster should minimize the ill effects of flex.

    You might also consider using 1 X 3's around the boarder, and 1 X 1's across. It will remain light weight and be perhaps more sturdy.

    A hollow foam mountain and/or a divider on top ads "I" beam effect and further strengthens it.

    As Andrew said, why not cut some of the skin off the wiring side of the board and keep the guts "inside"?
  5. Jim Cullen

    Jim Cullen Member

    Some good experiences/advice/suggestions already; thanks. Maybe I should have posted this in the Technical Q&A.

    I like the Tortoise switch machines and the "protected" space under the bench top would have to protect their depth. On the last two layouts I used 1/8" masonite as the facia. This give a smooth clean surface to the edges of the layout and helps to protect them.

    Interesting topic; will check out the references also. Jim
  6. shaygetz

    shaygetz Active Member

    Just finished reading an old MR that had an article on this very thing using 1/2" foamcore from a sign store. I'll see if I can't dig it out again.
  7. 60103

    60103 Pooh Bah

    I've just been adding foam to the sides of my spline section. I managed to bend the 1/2" stuff to a 36" curve without nticeable cracking.
    So ... you're going to need some bracing on it. maybe cut some 6" wide strips and glue them along and across -- that will give clearance for the Tortoises. (less than 6"?) -- like a big L girder.
    Somewhere there's a table or how much flexing it takes to crack plaster. (Linn Westcott article?) It was based on construction data for walls, but was applied to L girders to see where the legs could go.
  8. ddavidv

    ddavidv Member

    Another point to consider with will warp. I've noticed this just in the pieces I'm using to build scenery. Will vary with material thickness but if you check them at the Home Depot where they are stored vertically you can usually see warp setting in. Reinforcement would definately be needed I think.
    I used the hollow core door as a base with foam board on top. I was amazed just how light those doors really are. The benefit of using the door as a base far outweighs ;) any downsides. And I'd agree, there should be ample room in the door's "hollow" for the switch machines.
  9. Vic

    Vic Active Member

    I just want to point out that a hollow core door isn't really hollow. Inside of it is a cardboard "honeycomb" that gives it its rigidity. If removed the only support left is the sides and ends which is usually held together by some staples and it will flex and skew. The sides and ends are something akin to the thickness of lattice.

    The "honeycomb" is a bear to remove as its glued to the underside of the front and back door skins.

    But you can make something just as lightweight. You can buy just the door skins (cheap) and frame them using 1x2 for the sides and ends and a couple of cross braces. That way the underside is open for protection of your wiring and switch machines and attachment of legs if you want.

    If you can't find the door skins just get luan plywood...same thing just in 4x8 sheets.
  10. George D

    George D Member

    I read somewhere that running trains on a hollow door layout is noisy. Does anyone have any experience with this? I have an old closet door begging to be used for a switching layout.

  11. Fred_M

    Fred_M Guest

    If you cut openings in the bottom (for wiring and switch machines) and its mostly hollow it becomes a big sound box just like a guitar. It becomes a mechanical amplifier and the sound is like a room full of mad bumble bees. That was with cork roadbed on a door, with foam covering I don't know. DASH
  12. Lightbender

    Lightbender Member

    Hello DASH,

    The pink or blue extruded foam makes a very good amplifier. If you have a sheet try sticking a piece of coat hang wire in the edge and striking it. Fun eh? If used without cork roadbed you can hear where your trains are in the tunnels.

    Acoustic ceiling tile is useless for amplifying it deadens everything. It gets replaced when it becomes unattractive and can be had for free if you know anyone in the building maintenance business. I have used it extensively glued to pink foam with carpenters yellow.
  13. rsn48

    rsn48 Member

  14. Lightbender

    Lightbender Member

    Hello Rick,
    I have made some very strong load bearing structures (non-MR) out of this stuff and a hot glue gun. It is a godsend to the movie set builders and sign makers which is where you get used pieces free. It's a delight to work with and seem's quieter than plywood but doesn't deaden like ceiling tile. It is also a useful modelling material even down to small pieces. It's biggest drawback is the cost but as I said it can be found for free.
  15. fifer

    fifer Active Member

    My two cents

    I have built 4 modules using foam and have had no warping problems , even in the southwestern sun during transport.
    The lightest you will achive and strongest will be 1/4 luan panel cut into strips 5" wide for the outer box and then cut 1" strips for cross members and place every 10 to 12".
    We used a table saw to pre grove the front and back facias to accept the stringers. We also used 1X4 45% corner braces for strength.
    If you are connecting to other modules you may want make the ends from 1X4 select . Then use 1" extruded foam for the top.
    We also have taken some modules and faced them to the terrain contours with formica bonded to the facia ( very rugged but need a router and expensive). I think your tortoise machines will fit under at 5".
    Another tip I have used to mount tortoise's and turtable drives is double sided foam tape . REALLY!
    What ever you do GLUE EVERYTHING.
  16. Jim Cullen

    Jim Cullen Member

    Some interesting and creative ideas; thanks guys!

    I'm leaning to my first impulse of using a hollow core door with a 1" foam base on top for my next layout, but my mind changes as quick as the weather. Jim

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