Building "Kalrail" Pt 1
Rick Fletcher - NSW Australia
A Layout Based on XPS and EPS
Updated 22 June 2016

Whilst this is not a portable layout, I wanted to experiment with techniques I had previously used to construct test track modules. That was with lightweight timber and foam roadbed.   
For this layout I used 3 different types of foam board as shown below.

Expanded polystyrene foam EPS: this is a reinforced EPS product 120mm thick, light weight and used for forming concrete. The reinforcing layer is used at the bottom to give the material strength in tension on that side. For model rail use it looked like it had potential as it is self supporting over quite a long distance.
Problems: it is really too thick for our purposes and makes passing cables etc a little difficult. It is also incredibly messy stuff when cutting, drilling or routing. I wouldn't use it again although 2 giant sheets of it side by side made a good "train set" layout for the grand-kids.

Extruded polystyrene foam XPS: this stuff is the bees knees! It is beautifully formed into even thickness sheets
(2" 50mm in this case) and 600 x 1200mm (at least in Australia where it is sold at Bunnings stores for $20.85 as at June 2016) and is actually labelled in part for "Hobbies • Train / car set bases". Someone knows we exist!
It cuts and shapes easily without being messy. It is a near perfect thickness for mounting servos right in the foam - see below and I'll show you how later. Drilling is easy with the right technique (I'll show you how later) and the sheets are flat and square.

I have just discovered a cheaper Australian supplier - "Just-Rite"  price for 600 x 2200 is $20 (Pick up price)
Just-Rite are located at:
Sydney - 4 Kelham Place, Glendenning NSW, 2766    
Canberra - Hume Unit 2, 70 Sheppard Street ACT, 2620

Extruded polystyrene foam: in a thinner section (25mm 1"). As above but even lighter (duh). But it has special uses and can be made quite strong with a simple cheap technique (See THIS PAGE)

I planned the layout with the specific objective of fitting it into the available room - dah dah! The room wasn't all that big but it was fully lined and insulated and part of my large workshop building. All woodworking tools, machines and other stuff were outside the room to ease dust
With a size of 4090mm x 5000m (20 sq m) I didn't have a lot of space so I decided to build around the walls to get maximum track length and operate from the middle of the layout. The bench widths are close to 600mm which is a reasonable "reach" width.

The observant may note a servo peeking out of the foam. For foam users, the mounting of servos is a snack (I'll show you how later).

This was the rough plan of the room and the proposed benchwork

The section using the 120mm foam is in place with relatively few supporting battens. This material will easily span 550mm without support providing the reinforcing is at the bottom which is a stressed skin. The side plates are 180 x 17 DAR Hoop Pine.
The far side (West) is supported by the benches but it would have been better to use the ladder style frame shown to the right and have free standing benches.

With this reinforced foam supports can be 500mm apart.

Here we see the East side with the other end of the 120mm foam and preparations for the 50mm sections on the left.

The battens (25 x 17) across the frame are to support the less rigid 50mm extruded foam. They are placed long edge upright and spaced at approx 140 to 150mm centres and spot PVA glued in place. There are cleats along the side frames to support the battens and they can be any size.

Here is a short intermediate section. The side frames and ends make long rigid boxes (ladder type frame).
This is very rigid with 2" foam. I haven't tested it, but I suspect that the batten spacing could be increased (say 200mm) to make less obstructions for wiring and points servos under the benchwork. There is a way to achieve even more spacing - See the section on Reinforcing foam sheets. This reinforces the bottom surface giving it greater tensile strength & allowing longer free spans.

Here PVA glue is spotted onto the battens to hold the foam in place. I only spot glue it as I might have to slip a sharp blade under it to remove the foam some time later.

Heavy stuff to hold it down until the glue sets.
Incidentally - the box is a rolling stock/loco carrier under construction in an assembly jig.

The two photos below show most of the baseboards in place.

My workbench in an early state of development. Towards completion of the layout scenery, the workbench itself will roll away under the layout with the higher parts mounted on, possibly, gas struts to raise and lower them. The doors and windows shown, open to allow air to circulate in our hot summer but the doors can't be used to enter the room.

This is the entry door with a lifting deck to allow geriatric entry to the room. There will be separate notes on the construction of this deck which is strong but light and an explanation of why it has very minimal dimensional change.

View through the entry door..

Coming next: finishing the edges and corners of the benchwork then - track "planning".