Support spacing for foam

[johncolley]

Here's a neat trick! I use 2" foam and Tortoise switch machines.
1. lay out the track centerlines and turnout, marking the turnout ends and the cross centerline of the throwbar.
2. from the centerline of the throwbar lay out a 3 1/8" square. offset to whichever direction forward or back 1/8", layout and cut through the foam a 2 1/4" square. This is clear for the tortoise.
3. cut the 3 1/8" square 1/4" deep and relieve the material just over 1/4" deep for the plywood.
4. take a piece of 1/4" plywood cut 3" square, layout and pre- tap threads for the 4 mounting screws. Turn over so the screw holes face down (you can even pre assemble it on the tortoise and drop in place) and glue into the 1/4" recess with silicone adhesive calk so the top is flush with the foam. You will see the 2 1/4"x 1/8" open slot for the operating wire. Cut a 1/16" to 1/8" x3/16" slot in both pieces of cork when you install the roadbed.
5. allow the turnout operating wire to extend 3/4" past the end of the tortoise, use a regualr power pack set around 8 to 10 volts and center the wire, install the tortoise.
Note: I use about 8" or so of connector wires to a 2 terminal block hanging down for easier connection or testing. A bit of work, yes, I have 13 of them on my 2'x8' yard throat module and they are great!

[Anonymous]

We built a 16' x 9' layout on 2' insulation foamboard using 1" x 3" pine boards around the perimeter and as joists spaced every 4'. We coated all of the tops of the pine boards with Elmers carpenter glue and placed the 2' x 4' foam panels on them. We sealed the seams on both sides of the panels with 2" wide, clear, packing tape. Legs for the table were made of 2" x 2" poles, drilled to accept 1/2" blinds nuts and bolts in the feet. The bolts allowed us to move the layout and re-level it easily. The legs were braced with 1" x 2" boards.

As we added additional pieces of foamboard to the surface of the layout for mountians, inclines, and such, we used carpenters glue as the adhesive. This technique added to the structural integrity of the layout.

Since we had no plywood underlayment, we could pearce the foamboard easily to insert track and switch machine wiring. We also found that wires could be secured to the bottom of the layout with a short piece of 2" wide packing tape. This method of securing wiring allowed us to add or move wires easily.

We had no problems with big guys leaning on the layout. The layout was solid, light, and held up well for the five years we had it on public display.

In my humble opinion, some of you guys might be over engineering the project. For doubters, I would suggest a simple test. Build a 4' x 4' box using 1" x 3" pine boards and glue 2" foamboard to the top of it. Stand on it, crawl on it, kmeel on it, and beat it up. You may be surprised how strong it is.

[Anonymous]

two inch foam in minnesota??? brrrrrr! pass me the ice tea and suntan lotion while i roll over.......... im done on one side. Actually i want two inch foam as well. What is the correct name for this stuff, so i can order some. It always has amused me how angst- driven people become over benchwork!!!!!!! Im from the 'overbuild' school of engineering. However, as age creeps up on me, I am attracted to light weight in large objects! How about a compromise? Say half inch ply, sixteen inch centers one by two l girder with one by two cross joists? Will this pass the sag test? Im thinking of a ten foot module about 30 inches wide...i cant quite shoe-horn enough spur length in eight feet. Of course, the sag of girders is affected by the number and spacing of legs or wall braces employed

[Eriediamond]

I'm going to jump in here with both feet and take a chance I won't make a fool of myself with this. First though, understand I haven't built a layout with a foam base as yet, but my future Erie will be. Also the layout will be partly an around the wall "self type" and a portion will be bench work about three foot in width spaning the distance between two walls accross the room. I have however, had a lot of experience with foam building and flying model R/C aircraft. I also realize that many people have different ideas and thoughts in what they want and I offer this as only possible solutions to problems you you may think you'll have by using foam. On the negative side of things, some paints and adhesives will "attack" foam and you need to be aware of this and as far as I'm concerned, that's the only negative I see to it. As far as attaching things such as switch machines, switch stands, signals or anything that needs to be fairly stable or ridged, the foam can be easily routed out and a small piece of 1/16" plywood epoxied in to attach what ever you need to attach with screws just as you would to a plywood base. As far as strength goes, that has been well answered above. I will be building the base for my layout with 1X3 frame work on 24" centers with the 2" foam screwed to it. I "think" that will be plenty stong for my puposes, if not I'll beef it up some as needed. Besides I'm modeling the 40's steam era so I won't have the heavy tonnage of today's trains running over it!! Thanks, Ken

[simon1966]

I only use 1" foam as this is what I got free from a siding job, so I stack it. One thing I have noticed. In all but one section of my layout, the foam is glued to a plywood base. The noise and resonance from the trains in the section that is just foam is far greater than the sections with wood.

[train18393]

My Dayton and Mad River layout is built of 2" foam and has 75' of double track mainline(150' total) and this is how I mount my switch motors. I have about 50 switches with Tortise Switch Machines. I cut out a 4" X 4" square through the foam where the switchpoints will be and mount a piece of 3/4" MDF with Liquid Nails Project & Foamboard adhesive. Just be sure it is flush with the top of the foam. I then lay my Woodland scenics foam roadbed right over the top of that, then drill the hole for the piano wire. I also have many switches in the yards with Caboose Industries Ground Throws, as I have found no way to secure them directly to the foam, plus you may want to add contacts later on under the switch with a link for the mechanisim.

Dayton and Mad River
Paul

[Roadtrp]

QUOTE: Originally posted by JPM335

Oh, never thought of that... Maybe Ill just glue a couple half inch sheets together...

Yes, I've read a fair number of posts on these boards from guys in warm weather locations who have trouble finding the 2" foam.

[Anonymous]

Oh, never thought of that... Maybe Ill just glue a couple half inch sheets together...

[Roadtrp]

QUOTE: Originally posted by JPM335

where do you get the 2" foam. All I can find at lowes is the 1/2" stuff

Come to Minnesota... we have it everywhere. In Texas no one NEEDS 2" foam insulation.

[:)] [;)]

[Anonymous]

where do you get the 2" foam. All I can find at lowes is the 1/2" stuff

[railroadyoshi]

Though I may not know much
(12 year old newbie)
isn't it reasonable to say that both methods are okay ways for benchwork
Plywood is a proven technique, but is becoming expensive and has its inherit problems
I use plywood for my 4x8 and havent had problems(except for a bloody lip)
Extruded foam is a new, less proven (not to say that i don't think it would work) technique that has promise but questions of ability to carry weight.

Also, hasn't steel been becoming more expensive?(though i probably wouldnt know)

-Siddharth

[wccobb]

Anyone bother to read the 05/05 Model Railroader, p.66 - 69 ??? "Weed-Tree Splinters" are probably part of a previous age & steel studs etc. are now of the 21st. century. For those who slept thru it: "Benchwork frames made with steel tracks and studs ... 1/4" plywood screwed to top of frame ... 2" foam insulation board scenery layer ... 1/8" hardboard fascia."

[grayfox1119]

No, your not going to dance on it, but you have a lot of time invested, and $$$ with all the track and equipment and structures. If money is an issue with your budget, you have to go with what you can afford, but if you can afford plywood, why not? I have my wife's dept 56 Christmas display on 6 4x4 3/4" panels. As this layout is against the walls, I need to crawl up on these panels to run HO gauge track, set houses in place, trees, etc at the far reaches of the universe. The plywood does not flex at all to my 185#. The spacing of the supports is 4' where the panels join.
I am not trying to convince anyone that this method is the last statement in layout construction, it is "me", I like things made strong, if I ever "have" to crawl up on the layout, granted, this should not happen often, I do not want to worry about it in "my" mind. Yes, plywood is not cheap, it is $27 for 3/4" 4x8 sheet, but I will buy it once, and never worry about it again...can I say that for foam with no under layer base? NO..sooner or later, there will be an accident, maybe not by you, but a friend or a curious youngster. I have seen it happen.

[nfmisso]

QUOTE: Originally posted by rrinker

I don't know how Dow rates their foam, but the various Owens-Corning extruded foam products have product names that reference their compression stength in PSI. The common stuff I get at my Home Depot is FOmular-250, which is 250 psi compression strength - true this is against a solid immovable object, not unsupported. I've leaned on mine while trying to get a straight down view to align tracks, and it doesn't give. If I lean on my elbows it does. There is the next product up, either 350 or 450. The local HD doesn;t carry it, and it is likely to be very expensive. It's designed to insulate the OUTSIDE of a foundation and withstand the force of the backfill. If you could get 175 pounds on a 18" span of the 250, the better one would take well over 200 pounds.

--Randy

Hi Randy;

I just bought some foam at Menards' this afternoon; Dow Fomular 150, 2" thick. They also stock 250 in 2" thick, which he said was for under and on the outside of concrete foundations and walls.

Ray seems to be the only one here with any sort of engineering knowledge. I am a Registered Professional Mechanical Engineer. Strength and stiffness of anything like a table top or similar is proportional to the thickness of the material cubed. SO if you double the thickness, the strength and stiffness will increase by a factor of 8. Thus 2" foam is EIGHT times as strong as 1" foam.

If you insist on laminating something under 2" of foam, use the cheapest materials you can get. I used 7/16" OSB on my last model railroad project because it was here left over from some other project. If I had to buy new material, it would have been the thinnest and cheapest plywood Menards' had.

3/4" plywood, supported on 19.2" on center is sufficient for flooring in a house - and meets code - with people, refrigerators, beds, etc. Get real, you are not going to have a dance party on top of your layout.

[rrinker]

I don't know how Dow rates their foam, but the various Owens-Corning extruded foam products have product names that reference their compression stength in PSI. The common stuff I get at my Home Depot is FOmular-250, which is 250 psi compression strength - true this is against a solid immovable object, not unsupported. I've leaned on mine while trying to get a straight down view to align tracks, and it doesn't give. If I lean on my elbows it does. There is the next product up, either 350 or 450. The local HD doesn;t carry it, and it is likely to be very expensive. It's designed to insulate the OUTSIDE of a foundation and withstand the force of the backfill. If you could get 175 pounds on a 18" span of the 250, the better one would take well over 200 pounds.

--Randy

[bogp40]

The problem with using framing lumber for benchwork(crossmembers) besides major overkill and waste as compared to ripped quality 3/4" ply or pine 1x4s, is if one of the 2xs wants to bow, twist or warp it will usually take everything with it. If you still want to deck framing lumber w 1/2 or 3/4 ply, go for it but I feel it is too much. I personally prefer pine L girder and pine crossmembers for the majority of benchwork. Pine spline on risers, but this is my overkill.
Bob K.

[orsonroy]

QUOTE: Originally posted by mark_in_utah

I'm with grayfox. I'm currently building a new layout using 3/4" plywood. Why? I want it strong enough so that if someone lays across it it won't cave in,

I'm 6'2" and weigh 225. I walk and knee-crawl all over the lower level of my layout, which is a 2x2 box frame with 24" centers, 1/4" pine plywood and 2" foam. I've been doing this since the lower level was put in three years ago. It's more than strong enough for ANY modelling purposes, besides O and larger live steam.

QUOTE:
AND any vertical easements will become automatic as you cannot bend the stuff all that easily.

Personally, I'd WANT vertical easements to be flexible, so you can build them as units homogenous with the rest of the benchwork. I've got one area on my layout that has an area of track dipping below the main grade. I cookie cuttered it out of the pre-existing 1/4" Lauan plywood and 2" foam, and just bent in to the desired grade. With it flexing in an easy, natural way, it was easy to eliminate the REAL problem with vertical transitions, that of the sudden introduction of the grade. Instead of a harshly delineated line (which can cause havoc with derailments if it's done wrong) I've got a nice gentle slope to the grade.

QUOTE:
My benchwork is also 2X4 on 18" centers.

This is a HUGE waste, and I would strongly recommend to any newbie to NOT waste the time, effort or money on this sort of overkill. You've just built a loft structure, not a layout!

Once you factor in what you've just built (3/4 BC ply, 2x4x8' B or C grade studs, a 5lb box of screws, etc) versus minimalist layout technique (foam, 1/4" Lauan sheets, 2x2 legs, 1x2 leg supports, 1lb box of screws, 3-5 $1 tubes of caulk) you'll find that you could have saved a pile of dough by engineering the layout more carefully, versus brute forcing it.

QUOTE:
I can crawl around on it without damaging it.

Heck, you could pogo stick on it! My first "real" layout was built out of 3/4" plywood, 1x4 L girders, and 2x4 legs. Four of us 150 pound teenagers could root around on top of the thing without shifting it. The layout was so overbuilt that when I moved out of my parent's house, I left it in place. Thankfully, my dad's a N scaler, and he took it over for the base of his new home layout. 18 years later, and the supports STILL haven't shifted any, but I hate to think what it would cost me today to build!

QUOTE:
Unless you're going to have a very narrow layout, I'd put down some plywood.

I actually agree with this, but plywood doesn't mean 3/4", 5/8", or even 1/2". You only need to build enough layout to fully support what will USUALLY occur on the layout. 1/4" ply and 1" foam is more than enough for most typical layouts. I "overbuilt" my lower level with a 2x2 box frame, because I knew I'd be crawling around on it to get to 65% ofd the layout during construction. 2x2s cost a THIRD of what 2x4s cost these days, and they do the job just as well.

QUOTE:
You can easily span long distances with the foam, BUT the foam cannot support much weight before it starts to give.

True, but 16" OC isn't a "long distance". We're talking the length of two hands, not two bodies.

And you'd be surprised at just how strong 2" foam really is. We did a test (OK, we were bored) with a 4x8 sheet of 2" foam, where we experimented with the foam to see how much weight it would take before breaking. 18" without support would hold a 175lb buddy of mine. True, it broke once he started bouncing up & down, but it did hold him until then. Foam is much stronger than it looks.

QUOTE:
When you look at all the cost of what you'll put on top of the foam, as well as the value of your time, plywood is CHEAP.

Not really. Plywood prices have skyrocketed over the past 10 years, and the availability of things like Hydrocal, Homasote and metal screen wire has made traditional layout construction methods a rich retiree's endeavor. Modern materials, techniques and adhesives are cheaper, less expensive, faster to use and generally more user-friendly than the old ways. It's the 21st century, not the first third of the 20th.

[Anonymous]

I'm with grayfox. I'm currently building a new layout using 3/4" plywood. Why? I want it strong enough so that if someone lays across it it won't cave in, AND any vertical easements will become automatic as you cannot bend the stuff all that easily. My benchwork is also 2X4 on 18" centers. I can crawl around on it without damaging it. Overkill, maybe, unless someone by "accident" down the road puts their weight on it. Picture some dufus (me) falling through the benchwork. Now picture yourself falling through your benchwork. Get the idea? Unless you're going to have a very narrow layout, I'd put down some plywood.

You can easily span long distances with the foam, BUT the foam cannot support much weight before it starts to give. When you look at all the cost of what you'll put on top of the foam, as well as the value of your time, plywood is CHEAP.

Mark in Utah

[orsonroy]

QUOTE: Originally posted by Lovelady

There is no way to attach under table switch machines such as Tortise, or for that matter any other under table devices to foam.

Absolutely untrue. With a little ingenuity, you can do ANYTHING with foam that you can with "traditional" layout construction techniques. Model Railroader has run at least three articles in the past ten years about mounting switch throws (manual and automatic) to foam-based layouts, and they work. I've operated on Bill Darnaby's Maumee Route layout, and all his homemade, hand throw switch levers are glued to his 2" foam, NO PLYWOOD, layout. Some have been in and working for ten years without a single failure. And with Tortise machines, all you need to do is mount the motor to the underside of the switch, carve out a hole in the foam to accept the switch machine, and drop it into place.

QUOTE:
Use the foam but support it with at least 3/8" plywood min, thickness, 1/2" is better, then you have more support for under table wiring and switch machines. You can then support it with a 2 foot grid spacing. If nothing is under the table, 16 inch centers will work.

Again, wholly untrue. Some of the largest operating layouts in the country (see above) are built out of 2" foam base with NO underlayment plywood, and with only 16" OC 1x3 supports. If you DO decide to go with a wood underlayment (not a bad idea in my judgement) you only need 1/4" Lauan plywood (door veneer; the cheapest plywood on the market). My own three level layout is built out of 1/4" ply and 2" foam, supported off the layout room's studwalls with metal shelf brackets. It's been up for three years, and I have had zero benchwork problems.

If anyone's interested in seeing pics of my layout under construction, email me offlist and I'll be more than happy to send ya a few (I'm too cheap & lazy to post them online!)

[grayfox1119]

BTW, nice website Randy, I like what you have done !!!!

[grayfox1119]

I am using 3/4" plywood as the base and 2" foam on top of that for easy scenery and layou construction. When you consider the value of what you will have on TOP of the table/benchwork, "why" not spend the few extra bucks and make yopur layout bullet proof for strength. Yes, there are those that will say that 3/4", even 1/2" plywood is overkill, but after 66 years, I have learned to error on the side odfstrength and security for a few extra bucks "once". You will always have the plywood, lean on the foam with no support underneith in "that" area just once too hard, and you will have your answer.
My [2c] worth,

[rrinker]

Mounting them underneath is so old-fashioned [:D][:D][:D]

Check my web site. I don't use plywood, and I'm not going to start.

--Randy

[Anonymous]

There is no way to attach under table switch machines such as Tortise, or for that matter any other under table devices to foam. Use the foam but support it with at least 3/8" plywood min, thickness, 1/2" is better, then you have more support for under table wiring and switch machines. You can then support it with a 2 foot grid spacing. If nothing is under the table, 16 inch centers will work.

[rrinker]

I built my 2' wide sections with 16" spacing for the crosspieces. I'm pretty confident I could use 24" spacing instead and it would still be plenty strong. Probably even 1x3's instead of 1x4's - I have a lot more benchwork to build so for the next pase I may experiment a little.
The problem with 18" centers, it doesn;t come out evenly over an 8' long sectiion. But if you aren't making sections... My idea is that if I ever move, I cna cut through the track and roadbed at each section joint, unbolt them all, stack them up,a nd go. Probably wishful thinking, because I will never have a basement with this same shape anyway.

--Randy

[twhite]

I'm using 1x3 support bracers every 18" for my extruded foam base, and it's worked out just fine. Also, if you layer the foam for scenery, each layer tends to strengthen the foam extremely well. I'm amazed at how strong the foam actually is. One thing, though, if you run out of extruded foam (it's hard to find here in California any more) and have to resort to the 2" beaded foam insulation, you'll need to change the bracing to 12" or even 10" spacing, as the beaded foam has only about 1/3 the tensile strength of the extruded. But either way, the foam bed allows you to use much lighter bracing than if you were using plywood. I find it much easier to work with, also.
Good luck.
Tom [:D]

[nfmisso]

QUOTE: Originally posted by Blind Bruce

Hello folks,
I have begun constructing benchwork for my 4X8 layout. I would like to know how large a span will be needed to support 2" extruded foam. I was thinking of 18". Will this be enough?

Bruce;

18" is plenty, increasing the spacing to five supports over the 8ft length is more than enough.

As mentioned above, make sure you protect the edges all the way around. I am using 7/16" OSB underneath, and around the edges, no other supports. I used the OSB because I had it left over from another project. If I had to purchase new stuff, it would have been the thinnest, cheapest stuff I could find.

[MisterBeasley]

I'm using 16-inch spacing, and no plywood. My frame is 1x4, and I use 1x3 supports for the foam, aligned with the bottom of the frame. I put 1x2 supports in a few places around the outer frame so I could have support for the foam while still having it inside the frame. That way the frame protects the foam's edges. I glue it on with Liquid Nails for Projects.

I'm sure 18 inches would work, too. 2-inch foam is pretty stiff and doesn't sag.

[orsonroy]

Standard construction supports of 16" OC should be fine. Of course, you really only need two 1x4 boards running down the long axis of the foam for support. Shok absorption along the edges of the foam will require some sort of wood sheathing (1/8" Masonite or 1/4" Lauan should do).

[Blind Bruce]

Hello folks,
I have begun constructing benchwork for my 4X8 layout. I would like to know how large a span will be needed to support 2" extruded foam. I was thinking of 18". Will this be enough? (There is no pluwood under the foam.)
Thank s,
BB