Laying Track to Foam

I chose to use foam as the baseboard of my layout. I started experimenting with this in 2008 (Photo). This actual track on the test rig was only pinned in place as it was never permanent.

  • Foam base is great to lay my Peco code 75 HO flextrack. I can easily pin it in place using ordinary dressmaking pins. But you can’t nail it down.
  • Instead, I use an adhesive, LATEX CEMENT and I buy it from carpet suppliers or carpet layers. I take a 1 or 2 litre plastic container and get it filled for say $10 or so.
  • It needs to be thinned with water to a consistency of milk. I originally thought it would need to be thicker, but the thinner it is the better it penetrated under sleepers etc.
  • What happens if you change your mind and want to move something? It is actually reasonably easy just by dissolving the dried latex – see the last photo.
For the track base I use a product from DCCconcepts (in Western Australia) called Trackbed OO/HO Scale 3mm
The company describes the product as:
“A box of 100 feet (31metres) of high quality, OO/HO Scale trackbed (3mm thick / scale 9~10” approx high).
Made from very long life EVA, closed cell foam trackbed with precut ballast shoulders and a pre-scored track centreline underneath to allow it to be easily split for laying along track centre-lines if wanted.
Based on tests and feedback each piece is 605mm / 2 feet long for easy handling. Cuts perfectly with a snap off knife.”
STEP 1 – track pieces were pinned into position according to the layout sketches. The layout plan was derived in a slightly odd way. Firstly I laid out old code 100 track, some points, paper copies of points until things were as I wanted them to be. I then took a whole series of overlapping “aerial photos” as shown above and below.
And subsequently “stitched” all the photos together on a PC so that I had a somewhat bizarre mosaic diagram of the layout:

STEP 2 – the Code 75 Peco flextrack was adjusted into position with dressmakers pins (easy in foam)
Curves were laid out with Masonite (hardboard) templates. In this case 1m radius.
Note the use of plywood alignment pieces to keep the track joins in line.
STEP 3 – once I was convinced I had the track in the right place, guidelines  were needed to allow the underlay to be glued in the correct position.
To do this I made a little mobile jig from an old loco pony truck with a ply guide screwed up from the bottom so it just cleared the rails.
  • This foam roadbed is lightly cut down the centre to make it easier to lay curves.
  • The other advantage of gluing the track to foam is that it provides an improved noise barrier.
  • That is lessened of course when the track is ballasted but I am experimenting with very dilute latex as a ballast adhesive.
STEP 4 – I ran this mobile jig along the pinned track to get a guideline for the edges of the underlay.
STEP 5 – I took no photos of this process, but the diluted latex cement was brushed along between the guidelines onto the foam (none was brushed onto the bottom of the underlay). The underlay was butted up to the end of the previous piece with a little cement brushed onto the end. No weights or clamps were necessary although some pins were used around curves.
The photo above shows the container of diluted latex glued to a block of wood to help prevent spills. The photo actually shows a point being glued to the underlay and weights ARE needed for this process.
STEP 6 – The track is held in position by long dressmaking “T” Pins.
This aligns the track but allows it to be lifted to coat the underlay lightly with latex cement.
STEP 7 – for long runs, I held the track up with paddle pop sticks which allowed me to brush on the cement.
I used a chisel shaped brush about 10mm wide and applied it sparingly down both sides.
As above but a little more latex cement was needed under the PCB sleepers which were later cut across the join. A better solution would have been to use a more powerful adhesive under the PCB sleepers eg. Liquid Nails, as this track needs to be cut and remain strongly fixed.
STEP 8 – Once the glue is in place, remove the paddle pop sticks and place weights on the track until the glue sets.
The long brown strip is paxolin – about 3mm thick and cut to fit precisely between the rails. It serves to align long straight section and can be left in place until the glue sets. It can be made from any similar rigid maerial.
I have many of these 2mm (0.080″) plywood pieces cut to be a neat fit inside the tracks.
They guarantee alignment of track especially with crossovers.
Small pieces are great for keeping curves aligned where flex track joins. In this photo Carr’s Flux has been used to get a good soldered join between rail and sleeper (tie).
Using a long straight edge on the edge of the rail and the paxolin stip between the rails to align trackwork past the future station site.

WHEN THERE IS A DISASTER:

If everything goes pear shaped, then Latex bonded track or points can be lifted. Realising an extra crossover was needed, I had to lift a section of track. Brush some water onto that section and leave it for an hour or so and a thin spatula can be worked under the sleepers to free the track/point. The old latex can be removed with a wet sponge.

Yes, yes … I know if I am flooded out, the trackwork may be in trouble. But the bloke in the house across the road will really be in strife. The peak of his roof is lower than my floor!

Drilling Holes in Foam

Since my layout uses foam sheets as a trackbed, there is a need to drill holes, often many of them, through the foam.
The drill used is made from a piece of metal tube. I use brass tube which does the job and is available in in a variety of appropriate diameters (eg. K&S). I use two main sizes:

  • 6mm for track feeders and points (turnout) wiring.
  • 12mm for mounting Servos in foam
  • + 10mm for other odds and ends

You could use aluminium tube but it doesn’t hold its edge well. Steel tube would work well if you could get the size.

This is why I needed to drill lots of holes in foam: Track feeders; Points wiring; Servo Mounting plus other odds and ends.
Prepare the cutting edge by bevelling the end of the tube on the INSIDE.
I carry out that operation on a lathe using a scraping tool but it could be done in a drill for short tube drills.
It may even be possible to use a tapered reamer to form the bevel. There may be a need to touch-up the edge from time to time.
Use a battery drill on a fast speed. This 12mm hole is through 50mm foam to fit a micro servo
(eg Tower Pro SG90 or my preference Micro 9g Metal Gear Servo). The marks on the “drill” indicate just how deep I need to go for the servos.
The result is a very clean hole
For 12mm brass tube it is necessary to reinforce the end held in the drill to prevent crushing.
I machined a small piece of aluminium in the lathe (about 20mm long) and epoxied it into the top end. But anthing will do eg. a piece of dowel or plastic can be hand filed while spinning in a power drill and have a (say) 6mm 1/4″ hole drilled through.  Or fill the end with epoxy and drill a hole.
A hole is necessary through the middle so you can use something to push the waste foam out.
Pushing the waste out… and below:

Here 4 holes have been quickly drilled to accept a servo with minor trimming.
MORE DETAILS ON MOUNTING SERVOS IN 50mm XPS FOAM – COMING SOON
In this photo a hole was drilled under a point to carry the wiring from the micro switch under the layout.
Note the use of a length of paper drinking straw to line the hole so that the chemicals in the foam don’t attack the wire insulation.
The straw is held in place with a dab of PVA woodworking glue or similar.

This is the underside of the layout showing five 6mm holes, lined with a drinking straw, to carry track feed droppers.
The centre 6mm hole carries 3 wires from the microswitch fitted to the point.
The 4 x 12mm overlapping holes have accommodated the micro servo and its connecting wire.
Working Expanded Styrofoam (EPS) can produce a SNOW STORM!!
I use a suitcase type vacuum cleaner with the nozzle directed at the work area whenever shaping EPS
The drilling process is fairly mess free but care needs to be taken when pushing the waste out of the drill.
The attachment shown above holds itself on by suction and has a hole to accept a drill to capture waste before it escapes!
Brilliant for working up under a layout. My suitcase type vacuum came from a local chain store (BigW in Australia).

Reinforcing Foam Sheet

This section explains the important step of reinforcing (or stressed skinning) the 1″ (25mm) foam sheet to give it tensile strength on the bottom surface. The top is not such a problem as the extruded foam seems to have reasonable compressive strength.
This technique borrows from bridge building and surf board building techniques – remembering that our loading is occurring primarily from the top. You can also use it on 2″ foam to allow increased distance between the supporting battens.

I am assuming that you are not going to be walking around on the top of the layout! Having said that, I have stood on the layout by placing strategic wide pieces of plywood on distributed spacers between the tracks and close to the edges.

The technique is extremely simple – coat the bottom side with a layer of cloth glued to the the surface with PVA. You could use exotics like fibreglass or carbon fibre cloth – but we are not building a spacecraft! Just some cheap muslin cloth is what I use from a fabric shop. A tea towel may do the job. Cut it a bit oversize; coat it with a generous layer of PVA glue and squeegee it into the surface … as below.
foam-reinforcement
Reinforcing using muslin cloth and PVA glue.
Squeegee / roll/ brush the PVA so that it fully impregnates the cloth.

No hi-tech tools here! You may need to thin the PVA with water just a little to help spread it. Re-coat if doubtful.

When it is completely dry, cut around the edges with a sharp knife. The reinforced surface will be the bottom!

Then glue the sheet in place with PVA. (No, this is not an advert for Valvoline!)

The underside showing additional cross bracing, both to support the 1″ (25mm) foam and to restrict any shrinkage or expansion at right angles to the track so that the latter remains aligned where it crosses the joins. There has been no problem with track alignment or binding of the lifting panel since July 2014 even through flooding rain periods and temperatures in the room between less than 10°C and over 32°C.

The reinforced side is down (up in the photo) and and the assembly rests on a flat surface to keep the top true. I then glued the battens and all the support timbers to the bottom of the foam and to the supporting structure so no screws were needed.

Shown below is a  test run I did in 2008 when I lived at Bensville (I tend to live in places with strange names). It was a test track for both DC and DCC which fitted on the bar in our lounge room. It vaguely reflects the track layout (considerably condensed) used at Oberon in the Central West of NSW when I lived nearby at Hazelgrove. The latter was a station on the now closed/ suspended railway from Tarana to Oberon. A model of the mighty Hazelgrove station will feature on Kalrail layout (later to be re-named “Brolgan Road”).

I couldn’t resist adding this photo of Hazelgrove Station posed on a temporary diorama. Yet to be finished and weathered.

The underside of the test track shows that 1″ foam has been coated with muslin and fitted with a light weight frame. The ugly blocks on the right were added to help it fit on the bar which was a bit narrow. It is 2m long, 58cm wide and weighs 4kg. Could be made much lighter with thinner timber and no ugly blocks.

Could be a neat way to take a 2m x 1/2m layout to a display. Carry it in one hand.