Foam - does it need wood subroadbed?

"RL> The 2" extruded foam sheets seem very strong - if I had a 2' wide grid of "RL> benchwork, would I need a plywood subroadbed, or would the foam be "RL> sufficient with an frame of wood and stringers every 2' or so?
Generally yes. You might want make your 'stringers' as upside down L (or right-side up T) girders (made from 1x3s or 1x4s) to spread the support under the foam sheets. Note that you might NOT want to stand or jump on this benchwork, but it will be quite happy to support your trains, buildings, and scenery (esp. if the scenery is itself mostly more chunks of foam).
"RL> "RL> -- "RL> Frank Eva "RL> "RL> "RL> "RL>
\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu || snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

And I suppose to install under-layout switch machines, I could always glue a piece of wood to the underside, to give me something solid to mount the switch machine to... right?
Frank

Right - but remember to allow for the flex in the wire when it has to be 2" longer than it would with conventional roadbed.

Quite... in fact, you don't even need 2" foam for that. Lots of N-Trak modules are being built now with 1" foam. You _will_ want to make a _mechanical_ attachment to the foam, because while construction adhesives are fine for just holding it in place, I've found that if there's any kind of flex in the frame they'll let go over time. I use deck screws into the wood frame, putting them through 1/4" fender washers and snugging them down into the foam, then covering them with lightweight spackling.
-- Joe Ellis

The Flint Hills Northern is built on 2" foam, supported by 3/4"x3" slats every 18-20", and a 1x4" (equivalent) outside frame. No problems. I could have gone for 2', but chickened out. The biggest issue I've run up against is the problem of mounting switch machines under the layout to the foam. You can't use mechanical fasteners, since the foam is far too soft to hold. I have used two methods, both of which use latex foam adhesive to mount the machines. One choice is to mount the machine on wood, and then glue the assembly to the base. This works well when the machine design won't allow direct glueing (the other method).
When glueing anything to the foam from undeneath, you do need to rig some method of holding the item (switch machine, whatever) firmly up against the bottom of the layout until the glue sets up. I just use a couple of sticks clamped together and wedged between the item to be glued and the floor.
Good luck!

"RL> "Robert Heller" wrote in message "RL> news:af0c0$40dd911f$cb248f0 "RL> > "RL> The 2" extruded foam sheets seem very strong - if I had a 2' wide "RL> grid of "RL> > "RL> benchwork, would I need a plywood subroadbed, or would the foam be "RL> > "RL> sufficient with an frame of wood and stringers every 2' or so? "RL> > "RL> > Generally yes. You might want make your 'stringers' as upside down L "RL> > (or right-side up T) girders (made from 1x3s or 1x4s) to spread the "RL> > support under the foam sheets. Note that you might NOT want to stand "RL> > or jump on this benchwork, but it will be quite happy to support your "RL> > trains, buildings, and scenery (esp. if the scenery is itself mostly "RL> > more chunks of foam). "RL> "RL> And I suppose to install under-layout switch machines, I could always glue a "RL> piece of wood to the underside, to give me something solid to mount the "RL> switch machine to... right?
Yes, or you could cut a hold and mount a piece of plywood on top.
"RL> "RL> Frank "RL> "RL> "RL>
\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu || snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

"Gary M. Collins" wrote in message What brand of latex adhesive do you use? Is this what some folks are calling Liquid Nails for Projects?
Frank

Fifteen years ago I started building modules for a portable layout that were 2' x 8' in size. The board frame is 4" wide x 1" thick pine on the four sides, glued and screwed together with 2" x 2" x 3 1/2" lg. blocks in the corners. 1 1/2" down from the top I glued and screwed on the inside of the frame, mounted vertically, 1" x 2" boards for 1 1/2" foams to sit on. 32" in from each end I pit a cross piece of 1" x 2" pine, mounted horizontally, to help support the foam. These were notched into the 1" x 2" vertical side members to make a flat frame surface to support the foam. All wood joints are glued and screwed together. Elmers wood glue is fine and cheap for this. The foam is glued in place with Liquid Nails for Projects. This will stal somewhat flexible since it is a latex adhesive.
In the period of time since construction, these modules have live in a house for a short time, and spent a lot of time in the trailer that is used to take the layout to shows. This trailer sits in the sun in the summer, at times well over 120 degrees F and at 30 degrees below zero in the winter with no ill effect.
As some one has pointed out, this is only a model railroad. How heavy is it? For practical purposes only build a layout a wide as you can easily reach. For most people 24" is good. If you can get to both side of the layout like a 4' x 8' table, put two 2' x 8' modules together.
The trrack is glued to the subroadbed, which is foamcore. The foamcore is easily cut with a sharp utility knife, with curves and bevels. The foamcore is glue to the foam. I use Future Floor Wax as a glue for the track and subroadbed. The subroadbed is glued down first and dried in place. Then the track and ballast are next, in one operation. I use round head pins to keep the track aligned until the wax is dry. Can goods make good weights to put ontop of the track while it dries.
This all has stood the test of time in Ohio. We have traveled over 9000 miles so far without failure.
Dave Decker
Digital Railroader LLC wrote:

Fifteen years ago I started building modules for a portable layout that were 2' x 8' in size. The board frame is 4" wide x 1" thick pine on the four sides, glued and screwed together with 2" x 2" x 3 1/2" lg. blocks in the corners. 1 1/2" down from the top I glued and screwed on the inside of the frame, mounted vertically, 1" x 2" boards for 1 1/2" foams to sit on. 32" in from each end I pit a cross piece of 1" x 2" pine, mounted horizontally, to help support the foam. These were notched into the 1" x 2" vertical side members to make a flat frame surface to support the foam. All wood joints are glued and screwed together. Elmers wood glue is fine and cheap for this. The foam is glued in place with Liquid Nails for Projects. This will stal somewhat flexible since it is a latex adhesive.
In the period of time since construction, these modules have live in a house for a short time, and spent a lot of time in the trailer that is used to take the layout to shows. This trailer sits in the sun in the summer, at times well over 120 degrees F and at 30 degrees below zero in the winter with no ill effect.
As some one has pointed out, this is only a model railroad. How heavy is it? For practical purposes only build a layout a wide as you can easily reach. For most people 24" is good. If you can get to both side of the layout like a 4' x 8' table, put two 2' x 8' modules together.
The trrack is glued to the subroadbed, which is foamcore. The foamcore is easily cut with a sharp utility knife, with curves and bevels. The foamcore is glue to the foam. I use Future Floor Wax as a glue for the track and subroadbed. The subroadbed is glued down first and dried in place. Then the track and ballast are next, in one operation. I use round head pins to keep the track aligned until the wax is dry. Can goods make good weights to put ontop of the track while it dries.
This all has stood the test of time in Ohio. We have traveled over 9000 miles so far without failure.
Dave Decker
Digital Railroader LLC wrote:

Wow! A floor wax as an adhesive? Is this an acrylic-based product that will not harden? My concern is to keep the materials from bonding together into a single piece, thus becoming a reverberation chamber when the trains roll over it. I want to be able to brush on an adhesive to hold my roadbed and track in place, but I want it to be a latex/acrylic based product for this reason. I discovered how acrylic matte medium kills noise when used as a substitute for white glue when ballasting...

I know a lot of people use it as an overcoat for homemade decals. Apparently it really isn't a wax, but an acrylic finish. Never heard of it being used as glue.

Apparently you guys didn't watch much television back in the 60s. Future "won't yellow because it is arcylic", the commercial said.
Regards,
DAve, the Professor and Mary Ann.

Hi, Frank!
I'm using something called "Nail Power Latex Panel & Foamboard Adhesive" by Sovereign Specialty Chemicals, Inc. of Mentor, Ohio. I got it at Lowe's. Liquid Nails for Projects would also probably work well.