The Sump Valley Railway


The Layout Plan
Fictional history
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NOTE: The banner photograph shows Sump Valley railway stock and loco but on Richard Rundle's Pagham layout.

In 2006 I finally had the opportunity to do something about my long held dream of a 7mm scale O-16.5 Narrow Gauge layout. Over the preceding years I had made the three Peco based locos and much more recently, fell into the temptation of the some of the new Bachman On30 locos. (I have always had a soft spot for geared, articulated and other "non standard" locos.)

So, I set about producing a list of requirements most of which were essential although a few were merely desirable and could, if need be, be omitted.


All sorts of factors were  taken into account but the major ones were as follows.

1) Scale/gauge etc. The gauge would be 16.5mm and the scale 7mm:1 FT. This allowed a close to scale representation of around 2' 3" - 2' 4" which was good for several UK prototypes, in particular the Tal-y-llyn and Glyn Valley. Also, US prototypes in 1/4" scale could be run, their larger prototype size but somewhat smaller scale making them comparable. (more on this later)

2) The layout had to be lightweight, capable of ready dismantling and re-erecting. In short capable of easy transportation if I should accidentally build it well enough to exhibit it.

3) In line with the above, individual baseboards had to be narrow enough (22" max) to go through the loft hatch and short enough (55" max) to fit in my car!

4) The layout would utilise DCC. Since this was going to be a small layout with a relatively small number of locos and some of the Bachmann ones were already chipped this was an ideal opportunity to take advantage of what DCC had to offer, and, of course, to gain practical experience with it with a view to possibly converting the 00 layout in due course.

5) The layout had to be capable of both end to end and continuous run operation. The former to allow prototypical operation and the latter both to ensure there was always something moving and so that now and again I could just sit and watch trains go round!

6) Despite its portability, the layout size had to be such as to allow it to remain permanently erected - I know me and if I had to keep putting it up and taking it down I would soon end up in a mess and getting bored and frustrated!

7) The layout would have to have a number of operating features to add both fun and interest!

More detailed requirements

i) At least one turntable had to be incorporated. In part because I simply liked the idea, but also because I am sure that the US Shay locomotives with their side-mounted drive shafts, really need to run in both directions. This also might mean, in some designs that the turntable could also save space for locos to turn and run around their trains.

ii) The setting was always intended to be a fictional one but based firmly in West Sussex. I identified some very specific Sussex buildings I wanted to include. Chief amongst these were a small village church near Pulborough, a parade of shops in Broadwater and some flint cottages from Findon.

iii) A bridge was desirable but not essential. In any event, some water was essential even if limited.

iv) Operationally, everything had to be "hands-off" - even in the fiddle yard/hidden sidings.

v) A working level crossing was highly desirable.

vi) There must be at least a train length of plain track between the station and the exit to the hidden sidings. (a train length being designated as one large Tank loco or small tender loco and five 4-wheel coaches.)


I had space available in the second and smaller "half" of the loft which houses the 00 layout. This, however, had to be shared with other functions which was somewhat limiting. In the end there were two clear options. Either a) a layout measuring about 12' by 3' 3" which would have to be at least partly dismantled in between working/operating sessions, or b) a smaller layout measuring about  6'6" x 6' which could remain permanently erected.

Initially, I felt that option a) offered much better potential and a great many designs were prepared. Of these, two or three appeared to meet my design requirements. However, even while preparing these I was acutely conscious of the fact that they could not remain erected. In my case, this is not a good idea. I simply do not have the patience or perseverance to have to erect and dismantle the model every time I wanted to play. As a result, at the same time I constantly revisited the smaller, almost square space. At the very last moment, when almost committed to one of the type a) designs I was doodling almost aimlessly with the smaller space and all of a sudden, everything came together.

Thus the concept for the model of the Sump Valley Light Railway was born.

NEXT: The Layout plan