Blue foam board layout

On 7/29/2007 12:05 PM David Starr spake thus:

Might oughta work.

The trick here is to achieve balance between too low a resistance that will overload the xfmr (with smoke coming out of it instead of the cutting wire), too high a resistance that won't generate enough heat, too small a wire that will vaporize, and too thick a wire that won't heat. Just play around with different wire (and you needn't use nichrome, although that's nice if you can find it, maybe cannibalize an old toaster) for short bursts, ready to pull the plug if you see "magic smoke" coming from the transformer.

Music wire (e.g., old guitar strings) works pretty well here.

Magic smoke detection is fairly straight forward. Look at the transformer rating (volt/amps or watts) If your junkbox transformer lacks a rating, estimate one based on the size and weight of the transformer.

Let V = open circuit transforment voltage P = power in the transformer secondary Rt = resistance of the secondary Rload = resistance of nichrom cutter wire

P= V**2 / (Rt + Rload)

Solve for Rload.

Rload = V**2/P - Rt

Wire tables from the net or the CRC Handbook of Chemistry & Physics will give the ohms per foot of various sized wire. Check your work by firing it up and checking transformer temp. The transformer should remain cool enough to lay the BACK of your hand on it. Use a momentary contact switch for a trigger to prevent leaving it "on" when you put the tool down.

David Starr

Any 'foam friendly' glue will work. Liquid Nails for Projects is highly recomended.

I use Homasote roadbed

1) Glue the homabed to the foam with Liquid Nails for Projects (I get it in the caulk gun cartridges and use a caulk gun). The homabed comes in straight sections (two halves) and 'curved' sections (same as the straight stuff, except it is notched to allow bending) and larger sheets (for yards) and special pieces for switches (turnouts). I use either track nails or push-pins to hold the homabed in place while the glue dries (24 hours). (I use heavy SciFi anthologies for large areas (yards).)

2) Tack the track to the homabed with track nails. The homabed will easily take the nails, which can be pushed in (use a screwdriver blade rather than a hammer). 3) Spread the ballast (I have a ballast spreader). 4) Use a 50/50 white glue (eg Elmers) / water mix (with a drop of dish soap) to soak the ballast to glue it to the track/homabed.

(You can skip 3 and 4, esp. if you might be thinking of re-arranging your layout at a later time. It is not hard to even 'peel' the homabed off the foam and re-use it.)

Inset a 1/4" or 3/8" piece of plywood just under the homabed in the top of the foam. Cut a square hole smaller than the plywood with a

1/4" lip all around for the plywood rest on. Glue the plywood into place. Mount the switch machine on the bottom of the plywood, with a 1/4" hole through the plywood and homabed for the control rod/wire.

I'd suggest using a 'bread' knife instead. Avoids the *nasty* (and harmful) fumes. A 'Sureform' tool is also usefull for final shaping.

On 7/29/2007 12:56 PM David Starr spake thus:

[...]

So are you actually using nichrome wire? If so, where do you get it?

On 7/29/2007 1:36 PM Robert Heller spake thus (regarding cutting foam):

That's "Surform", in case anyone goes looking for one.

On Sun, 29 Jul 2007 15:05:02 -0400, I said, "Pick a card, any card" and David Starr instead replied:

A brushing of white glue and water (5:1 Glue:Water) mixed with fine sandy ballast works well. If you use a spreader and build up about

1mm of ballast and spike the track when the glue is tacky (about a 3

- 4 hour window) it's easiest. Every foot or so, use a "T" pin instead of a spike. Gives it stability. You can paint them black or brown to match your ties later. The 25mm ones are perfect.

See above for one step ballasting. You can add a wriggly bead of white glue to the track bed as you lay your rail. If you ever need to pull up your track, a blow drier or heat gun will soften things.

Use small pieces of MDF or Masonite(tm) glued underneath. Thinner is better. You can pre mount most of the electrical stuff before you glue it saving that work being done upside down.

The model airplane guys have worked this one to death. Here's a good source for you. Instead of the hot wire bow which is used for airplane wings, build one that looks like a wooden coping saw and another that can be used as a scoop. Also, consider making one that uses an old band saw blade segment bent into a "U" shape to dig trenches in the foam. I've played around with old plastic disposable razor blades with great success but the bandsaw blade works best. Use the dull side to cut and the toothy side to scrape the surface. Makes bonding with paper mache easier.

Use wood to hold the hot wire blades for obvious reasons.

Also, a bread knife is good but even better is an electric carving knife. There's much less foam dust from that. The best brand to use is the Black & Decker which is no longer made. You can still find them at thrift stores and garage sales. It has the toothiest blade set. Or, you can have a set from almost any brand ground into a more toothy setting by any saw sharpener.

-- Ray

wrote:

[...]

If you use plaster-cloth over the foam, you don't need precise shaping. I use a small kitchen knife to cut bits off the foam layers, just poke near the edge at an angle and twist, and you get a nice rock effect. Use a shallower angle for gently rolling hills. Reasonably smooth is all you need, the plaster cloth is very forgiving, especially after ground cover has been applied. The Surform rasp makes a _lot_ of dust.

A friend in the construction business gave me 3-1/2" and 4" thick foam boards used for insulation (between the wall studs). Very light, very rigid. I just glued the pieces together along their edges, and glued strips of 1/4" ply about 4-6" wide crosswise underneath. You don't need that 1x4 frame at all - it just adds weight.

For under-track switch motors, try a standardised switch-mounting pad of plywood and cork (or plywood and Homasote), with the switch machine underneath. If they are uniform, it's easy to build them at the workbench, and plug them into the layout where needed. Just cut a suitable sized and shaped hole first... ;-)

HTH&HF

Ok, nice, how does this translate to FOAM?

I glue the 1/4" thick Homasote roadbed to the foam. I then attach the track (flextrack, turnouts, etc.) to the Homasote roadbed with track nails and then ballast the track.

I explained this in my followup post, but you only quoted one line of my post, totally losing the complete context...

>

Robert Heller wrote:

Been thinking and talking about this project. The road bed issue is partly one of looks. Real track is laid on a bed of coarse gravel (ballast is the railroady word) to let the rainwater drain off and prevent the wood ties from rotting from contact with moist dirt. The ballast raises the track about a foot above the terrain, with sharply sloped edge, very characteristic. The track doesn't look right to my eyes unless it is raise up on a ballast bed. Starting with a flat piece of blue foam, one way of getting the ballast bed is just lay it down. Either the traditional cork road bed, or the homabed, which does the same job, except it's made out of Homasote instead of cork. Both materials take track nails, which makes tracklaying straight forward. The blue foam is too soft to take nails, or fasteners. With a nailable ballast, you can lay track with just nails, or use latex caulk as a stickum and the nails to hold the track in place while the stickum dries. Without a nailable ballast, stickum does all the work of holding the track in place, and you weight the track down with books or cinder blocks or anything heavy till the stickum dries. You gotta have the track aligned just right while the stickum is soft, once it dries, you can't move anything. If you have a kink or bump it's there for good. One cheapcut roadbed is artist's foamboard. It comes in sheets, in white, and cuts with a utility knife. You cut it straight up and down and stick it down to the blue foam base with latex caulk. Careful layout and a steady hand are needed for good results. You get the 45 degree slope on the side of the ballast by applying latex caulk and smoothing it with a putty knife. The track goes down with the same latex caulk 'cause the artist's foamboard doesn't hold nails either. I'm thinking in terms of a narrow around the walls layout in the guest bed room, leaving enough room for guests and beds. Anticipated guests are mostly grand children, who think trains are cool. I'm thinking of making frames out of 1*4 pine with 1/4" plywood bottoms to stiffen up the frames, and give something to attach switch machines and electrical terminal blocks too. I have a power saw so I can put a 1/4" dado in the frame boards to acept the plywood bottom. I am leaning toward legs, as opposed to wall brackets. The legs are stronger, my stud finding abilities are week. Legs might be 2*2, attached with carriage bolts so the train can be taken down, folded up and put away, or moved, if necessary. Diagonal braces to prevent wobble. Some lift out sections to give access to the room, closet, and bathroom doors.

David Starr

On 8/17/2007 9:11 AM David Starr spake thus:

Actually, as I'm sure you've figured out, there are a bunch of ways to skin this particular cat. Something similar to what you just described, but maybe better in some ways, is to use illustration board instead of foamcore board. (This type of board will take nails, for one thing.) Since it's thinner, you'll need (at least) 2 layers, so it's a bit more work cutting the roadbed pieces out. However, by making only straight cuts, you can make the underlying pieces larger than the top ones, therefore creating an automatic tapered profile, albeit a stepped one:

|--- | |--- |

Has anyone ever tried N scale cork on an HO layout? I realize that the width wouldn't be right and you would have to space them apart some, but I think I'd like the lower profile. And I was thinking that if you were gong to ballast the track, simply fill the gap between the pieces of cork with ballast.

My current layout was built with four inch side boards and three inch underframing. These were all cut from plywood at the lumber yard. For $.50 a cut, it was a lot cheaper & better than if I would have cut them myself. The process went like this... I built a grid of the three inch pieces, then used the four inch pieces for the outside frames. I lined these up at the bottom with the grid work. Then, I used a sheet of 1/4" luan plywood on the grid and then glued 3/4" blue foam on top of that... and it all fit perfectly within the four inch frame.

Don't know what kind of track plan you have in mind, but in a tight space, i might suggest a bookshelf layout only about 16" wide. I built one of those a while ago and put it on bookcases made from 3/4" plywood... extra storage under the layout for lots of different things. Just a suggestion.

dlm

[...]

MR used it one of their project RRs recently. Used three strips, and yes, they did so because they wanted a lower ballast profile. Looked good when it was done.

HTH

I plan to use N scale cork roadbed for sidings and secondary tracks on my upcoming layout, with HO scale for mainline tracks - saw the suggestion somewhere a couple of years back, and like the idea. Should provide a good visual difference.

Matt

And it depends on the era. For the late 19th century N cork in HO would be appropriate for many of the smaller lines.

And a little further back there were quite a few small lines with ties laid right on the ground, sometimes with rock ballast between them, sometimes with just plain old dirt, and occasionally with no ballast at all.

Now that's interesting. Doesn't that defeat the whole purpose of using foam in the first place? I'd have to hunt for 1/4" homasote. Most suppliers around here carry 1/2". Well none the less, i'm going with straight 2" foam as my other friends did with great success as a matter of fact.

Hmm... never thought of that... Thanks...

Big Rich Soprano wrote in news: snipped-for-privacy@4ax.com:

Not if he uses the homosote for only the road bed. I considered doing it like that myself. (I'd lay the homosote directly on plywood and not on foam, myself. Your layout construction may vary.)

Puckdropper

Yes i did many years ago in a pinch but it worked so well i continued it. I used flex track so size didn't matter (remember when that was your catch phrase hehehe...) so i didn't split the pieces to get the beveled edges. I just put it down as a rectangle and put the HO track over it as is. It worked fine with the minor difference of using slightly more ballast. No big deal!

Another method i tried after reading MRC was double sided foam tape. This didn't last long and the track came loose after a year or so. I might have not installed it right - who knows.