Building an Extensible Layout

This article first appeared in the November/December 1999 issue of AMRA's 'Journal'.
By Stephen J Chapman.

I have read on several occasions that a typical station is about three to five times the length of the longest train that the station is set up to handle in normal circumstances. "How can this be right when the platforms are scarcely longer than these trains?" you ask. Isn't the length of the platform the same thing as the length of the station? The answer to this is almost always NO.

A station is more than just a platform (or pair of platforms on your double track main line). Unless the station is just a passing halt where trains stop briefly on their way through but are never shunted, the station will also includes those sections of track necessary to allow trains to be shunted, reversed, pushed out of the way onto a siding, or any of the many other things which makes a station an operational feature of your model railway. In practice whether you are looking at the real thing this distance works out to be about three to five times the length of the longest normal train.

The actual length of the station can be easily determined for the typical steam era absolute block working railway that is popular with many modellers. In this instance the length of the station can be measured from the outer home signal (which stops trains running into the station until it is clear) through to the advanced starting signal (which stops trains leaving the station until the next section of line is clear). Of course these signals need not be aligned between the up and down lines of a double track main line in which case the station limits will not be same on each line. In this case the overall length of the station will be measured from advanced starter to advanced starter or outer home to outer home - whichever are further apart. More modern (or earlier) stations may not have all of the same signalling to make the station length so obvious but similar distances will be required for the operation of the station.

So a typical station takes up a significant amount of space when scale length is considered. In HO scale a typical steam train with say 57' carriages (each about 20cm long) will require about 30cm (1') of platform length per carriage to allow for the gap between carriages and space for an appropriate locomotive. This means that the platforms alone for an eight carriage train will be about 2.4m (8') long and the overall station length should be somewhere between 7.2m (24') and 12m (40'). Few of us have this amount of space available to devote to a station so we need to consider ways of reducing this to more manageable proportions.

Some ways of doing this include:

  1. reducing the train length - a station that handles four carriage trains only requires half the length of one for eight carriage trains.
  2. Use a smaller scale - an 'N' scale station requires only about half the length of the equivalent station in 'HO'.
  3. Model only part of the station - if the line disappears under an overbridge at one end of the platforms then only 2/3 of the station actually needs to be modelled with the rest of the station being "offstage".
  4. Don't include a station at all or put the platforms offstage and just model the bit that is beyond the overbridge mentioned in (c).

Unfortunately, none of these options seems to solve the problem if you don't want to change to a smaller scale and you really want to model a full length, relatively complex, station in all its glory. So what can we do when the station that you want to model requires a lot more space than you currently have available?

The answer is to build an extensible layout where part of the layout is built to fill the available space and the rest of the layout is stored. "What use is this?" you may ask. Well an extensible layout has several advantages.

  1. The layout is built in sections and the first two or three sections can be built and be operational before construction even starts on the further sections,
  2. If designed appropriately, the sections can be interchangeable allowing different sections once built to be substituted for one another effectively giving you different layouts in the same space dependent on your mood,
  3. One day you may have more space allowing more sections to be operational with fewer (or no) sections stored,
  4. The layout will be portable allowing it to be exhibited and its modular form will allow it to be exhibited in many different forms over the years.

So what is the difference between building an extensible layout and one that is not? The first thing is that the layout must be designed to be extensible. To be extensible, a layout need not be modular however all modular layouts are extensible and have the additional benefit of allowing boards to be assembled in different orders giving different layouts from the same boards.

To build a layout that is extensible but not modular, you start building from one end. A temporary board to connect up the tracks at the other end completes the layout. Different temporary boards may be required depending on how many boards that you have the space to assemble (see figures 1 and 2).

Figure one initial layout
initial layout extended Figure two

With a modular layout, on the other hand, you can start by building the two end boards to give you a working layout (see figure 3) and then add additional boards in between to fill the available space. As the end of each module will need to have track and scenery aligned to match the end boards, these intervening boards will be interchangeable given sufficient space (see figures 4 and 5). Also temporary boards to connect up the layout will not be required.

Figure three modular layout
modular layout extended Figure four
Figure five modular layout further extended

So how does this work out in practice? The last 'N' scale layout that I was building (which was disassembled to commence construction of my current layout) was an extensible (but not really modular) layout. The double track main line appeared from a tunnel at one end and passed the goods yard on its approach to the platforms. An overbridge was modelled over the platforms to sit on the temporary board to complete the scenic section of the layout (see figure 6). The layout was about 2.35m long made up of two boards each about 1.4m long and a temporary board about 450mm long to complete the circuit. In my case the rear 300mm of the boards which held the fiddle yard was removable from the scenicked 600mm section but this was not required to make the layout extensible, I was hoping to be able to reuse the fiddle yard on later layouts.

original layout Figure six

Prior to disassembling the layout I had commenced construction of another 1.4m section that contained the rest of the station platforms with an overbridge at the end (see figure 7). This section was never finished but as the tracks ran straight through it was possible to reuse the same temporary board (without its removable scenery) to again complete the layout in a form now 4.75m long.

as extended Figure seven

At this point, I moved house to my current address and the available space for the layout while long enough to fit the layout in its shorter form was not really wide enough to allow access to the fiddle yard. I decided to take the opportunity to rebuild the layout in a more modular form and to take the opportunity to replace the pineboard trackbeds with plywood.

The reduced weight has allowed me to construct boards 1.7m long instead of the 1.4m of the previous layout. This means that the two end boards fill the 3.4m length that 1 currently have available. To allow easier access to the fiddleyard from the front of the layout and to allow the door to be able to be fully opened I have reduced the width of the layout slightly at the ends (to 750mm) and the central section of the layout even further (to 600mm). This has meant that there is no longer the available width to retain the fiddleyard boards previously constructed and the fiddle yard has been integrated into the new boards (see figure 8).

Figure eight current layout

From the start the layout has been designed with one additional board that will fit between the end boards to include the station platforms. Construction of this board commenced at the same time as the end boards and proceeded at the same time as the end boards through the track laying stage. This allowed me to incorporate a rather clever idea that I had to increase the capacity of the fiddle yard automatically whenever this additional board is inserted into the layout (see figure 9). Further boards can be added between this centre board and each of the end boards (or instead of the centre board) at a later date to add a goods yard, carriage sidings, and locomotive storage.

current layout extended Figure nine

The overall result of building an extensible layout like this is that it will progressively turn a relatively simple layout consisting of not much more than a double track main line with a siding and a loop into a complex mainline station. I may never have enough space at home to assemble more than just a couple of boards but I will still have a working layout at home and, at some future date, I will also have a much larger layout containing what will eventually be a full length station that I can take to exhibitions.

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Copyright Stephen Chapman