Page 18 - B2B 1 to 7
P. 18

The diagram shows 4-inch deep sides. These match the “Freemo” module specification. For non-Freemo boards up to 4 ft long, shallower sides could be used. Two-inch deep softwood, 3/4” thick, or thicker, would be adequate. However, if you are planning to use large switch machines, such as Tortoises, deeper sides will offer better protection during transport.
Even with the interior frame omitted, the unit above is not particularly light. A pair of boxed boards 2 ft x 4 ft using this approach is about as heavy as anyone would want to move around. If you do the calculations, you will find most of the weight is in the 9 mm deck. The more lightweight designs below are attempts to minimise deck weight.
Thin Ply Board
This design was described briefly in Section 1. Although thin plywood doesn’t have a lot to recommend it for permanent layouts, it has distinct advantages for a portable one. The deck is made of thin plywood, typically 6 mm (1/4”). This needs to be well braced
and this is done by a honeycomb of thin ply supports as shown in 3. The diagonal members in each corner provide resistance to twisting.
The holes in the cross members are there to make wiring more convenient. They don’t save much weight.
A further consideration of having lots of supports is that some of them are guaranteed to be exactly where you want to fit switch machines (it’s the law!) and you will need to take this into consideration in your track plan.
One way to build a board like this is to use hot glue to tack the various pieces in place. A few small blobs are all that is needed. All the joints are then reinforced by building up a fillet of gap-filling adhesive on both sides, applied using a mastic gun (see 4). Suitable adhesives are the “No nails” and “Gripfill” types.
Styrofoam Boards
A very light unit can be made from Styrofoam sheet. This was described in Section 1. The foam used is the dense, rigid, coloured variety intended for insulation, not the white crumbly stuff used for packaging. One way to do this is shown in 5.
overhanging part of the sides are used to carry the board suitcase-fashion. It has been found that this puts a lot of stress on the glue joint. Although the glue won’t fail, it has been found that the side will come away with a wafer-thin layer of foam still glued to it. This hasn’t proved to be a problem with 9 mm ply.
Also, there can sometimes be considerable stress on the glued joint between the end board and the foam when several boards are clamped together. To strengthen this, it is a good idea to fit screws between the sides and end as shown.
It is possible to tack electrical wiring to the bottom of the foam using low-temperature hot glue (if that isn’t a contradiction!). This avoids wires being snagged and pulled off during transport.
If you want to use switch machines (point motors) for your turnouts you will need to recess them into the foam as the two-inch foam is too thick for the linkage to work well. Alternatively you could hide them on the upper surface or operate the turnouts manually
As mentioned in Section 1 of this guide, some people have found that the foam can bow over a few years. This has been to the extent of about 1/4” over a 4 ft length so, if you use foam it is something to keep an eye on.
Legs
First some good news! You don’t need four legs on every board. If one central board has four legs, all the other boards can have legs at their outer ends and “lean” on the four legged one as shown.
There is a huge number of leg designs for portable a layouts. This is probably because nobody has yet come up with the optimum mix of lightness, east of transport and speed of assembly.
Obvious methods of attaching the legs are to have bolt-on or hinged leg assemblies. Bolt-on ones can be slow to assemble. Hinged ones are quick to assemble but add to the weight of the unit.
Bolt-on Legs.
In this scheme a two-leg assembly is bolted to the sides of the board. The traditional way to do this was to use bolts
and wing nuts as shown. The problem with
this scheme is that wing nuts can be very
fiddly. A better way is to use bolts that pass though the side and the leg and into a T-nut on the other side. If a hex-headed bolt is used it can be tightened quickly using a ratchet wrench and socket. A socket in a cordless drill will make things even quicker but avoid using a high-torque setting on the drill. Modern drills have so much torque they can rip the T-nut’s prongs right out of the wood. Guess how I know that!
Hinged legs
An attractive leg system is to have the legs hinged at end of the board. It may blindingly obvious, but the board must be at least as long is the legs when they are folded. In addition, the length of the legs is determined by the rail height you want. For example, the HO NMRA (BR) module specification demands a rail height of 45 inches. After taking the 4 inch depth of the board into account, this means the legs must be at least 41 inches long. If they are to swing up inside the board, the thickness of the end boards must be taken into account to get the minimum overall length of the board. With an allowance of 3/4” at each end, this results in a minimum board length of 42.5”. If you plan on hinged legs, a calculation like this for your particular
       this is the only board with four legs
          Deck: 2 inch styrofoam
Ends 12m or thicker plywood
5
Sides 9mm plywood
Screws - see text
                                    The sides and ends can be glued to the foam using white glue or polyurethane wood glue. (Solvent-based glues can attack the foam.) To hold the side in place while the glue dries, long woodscrews can be used, passing through the plywood and into the foam, The dense foam provides enough “bite” to hold the screws while the glue dries. Afterwards the screws can be removed but you will then need to fill the holes. Alternatively just leave the screws in place. If you have, or can borrow, some long bar clamps, these can be used instead of screws to hold everything in place while the glue dries. There are a couple of things to be aware of. The protection for the side of the layout needs to be 9 mm or thicker plywood. Thinner ply can flex if the
3
  4
    6































































   16   17   18   19   20