Lightweight Support
The thickness and width of the supporting structure need not be excessive.
For example, a 20mm x 8mm rib/extrusion can reduce the deflection of a 4mm thick plywood baseboard, by a factor of 70. Additionally, place ribs only under the track bed; putting material where it contributes and not where it doesn’t. This arrangement is 2.5 times better than the same track bed laid on 12mm chipboard, and also it is much better at holding its shape against time and damp. The positions of the ribs need to be chosen to suit the track plan and to avoid point motors and uncouplers.
Holes weigh nothing!
Holes can be used to pass wires through, for access to point and uncoupler operating switches, for hanging control panels on, and for seeing what is going on in tunnels. Holes obviously add lightness, but often do not reduce strength.
Cutting out holes in the main Baseboard Support, can significantly reduce weight without affecting rigidity. The best way to produce holes of over 4cm in diameter, is with a Hole Saw. The cost of these range from about £10 to £20; the one we use is from the cheap end of the range, and has cut over 150 holes so far. When cutting holes, first pilot-drill in the correct place to suit the pilot of the Hole Saw. Cut the hole about half way through, and then finish off from the other side. This minimises splitting which can be a problem with plywood.
Double-Skin support
Cutting lots of holes may significantly reduce weight, but it’s not that easy, unless the support is 12mm thickness or more. One solution is to use a double-skin approach. This is particularly beneficial when thin plywood baseboard tops are used, 4 to 6mm. so that the side supports can be cut from the same piece of plywood.
Obtain two pieces of plywood, pre-cut to width, and cut them to the required length. Between these two lengths of plywood, position vertically, pieces of strip-wood, which are about 35 to 40mm (1.5inch) width, 12 to 18mm (½ to ¾ inch) thick, and length equal to the width of the plywood. These pieces of strip-wood should be positioned at each end of the plywood support, and spaced about 15 to 20cms (6 to 10 inches)apart, such that they are evenly spaced or positioned where boards need to be joined.
Part B - Supporting Structure
Cookie Cutter’ Method
A 'cookie cutter' approach to the track bed can be an effective method to reduce weight of the baseboard. The base is only present around the line of the track and polystyrene foam provides the support for scenery elsewhere.
To attach the foam to the frame, make a ledge for the foam to rest on, either by extending the track base or by attaching a piece of timber (say 6mm square) to the framework. It is found that the latex adhesive, sold for flooring and cork tiles, works well as glue for attaching the foam to the frame, but a word of warning! – it is difficult to remove from fingers.
In order to prevent the framework from lozenging (i.e. going diamond shape), it is important to ensure that the outside framework is rigid, and that there is cross-bracing, either side to side, or diagonally. It is unlikely that the ‘cookie cutter’ track base method will have enough top surface to provide any base-board rigidity, but with placing of ribs under the track-bed will definitely help (see “lightweight support” above)
General Advice
The end cross-pieces, and front panel should be profiled to suit the scenery. The rear sheet of 6mm plywood should be extended upwards to form the sky.
If using timber, select this for straightness and freedom from knots, particularly important for small sections.
Glue and screw (using 3/4in. No. 6) all joints; pin and glue smaller joints.
Try to ensure that all exposed surfaces are coated with some form of sealer (paint, varnish etc.) to minimise moisture ingress.
