A Model Railway

A Model Railway – Talk by P.M. Harvey and R.A. Parsons, members, at the Durrington Community Centre, 9th March,1994.
Most men were introduced to model railways when they were very young, by the toy train set on the floor, usually a circle or oval of track and an engine with a short train endlessly chasing its tail. I certainly can remember this, including a Bowman steam engine which went so fast it derailed on the curves and fell on its side, setting the carpet on fire! My interest in full-size railways was stimulated by spending many holidays at Teignmouth in Devon, where I was able to watch the old Great Western trains along the sea wall, a marvellous vantage point. Most men grow out of the hobby but a few carry on, as I have done, throughout their lives and build larger and more satisfying model railways. In the 1950’s I became interested in modelling American because of the high quality of American models then available on the market. There are seven popular scales for modelling, but by far the most popular are “00” in this country and “H0” in the rest of the world. These scales are 4 mm and 3.5 mm to 1 foot respectively, but both use the same track gauge of 16.5 mm; this width is of course only correct for “H0” scale. I won’t go into the reasons for this, but it has caused a lot of heart searching in this country.
As an Engineer, I consider model railways to be a part of engineering, i.e. in miniature and the railway is part of a transportation system which consists, not only of track, locomotives and rolling stock, but includes land, buildings, civil structures, signalling, power and control devices, and has a purpose to move freight and people from one place to another. A model railway should reflect these aspects. Because I model American, I use “H0” scale. In designing a model railway then, its imagined purpose and the scenery should be considered first, not after designing the trackwork.
I belong to an American club, known as the National Model Railroad Association (NMRA), which has around 26,000 members worldwide and 600 members in the British region. The NMRA produces a large amount of technical and engineering data, formulated by engineers and other specialists, who are members, to enable others to construct models which are true copies in miniature of the full size prototype. These data sheets cover design of track, points or turnouts, wheels, bridges, etc., and are invaluable for the model railway builder. Clubs usually have a club layout, which may be permanently installed where a room or hall can be continuously occupied. In other cases, nowadays, more and more clubs use modular layouts. These modules, made by individual members, must all be made to the same standard, i.e. length, width, height, positions of tracks, etc., so that they may be joined together to form a larger layout. The modules must be of such a size that they are easily moved in the boot of a car and, when in a member’s home, can be used as a small layout. Thesizeofamoduleisusually3ftor4ftby2ftdeepandstanding3ftor3ft 6in. abovethefloor.
The layout is usually constructed of wood framing with, in the case of a permanent layout, the main horizontal supports being assembled from two strips of timber to form L-shaped girders, themselves supported by square legs. Joists are fixed across the girders and the track beds are then supported by a system of risers andsecondaryjoists. Sceneryisformedbymeansofseverallayersofpapertowels,soakedinplasterandthen draped over the formwork, consisting of a mesh of card strips, roughly forming the shape of the terrain required. The plaster can be shaped or carved before or after setting. Rocks and rock faces can be made by casting plaster in latex moulds, the moulds having been formed over a natural rock surface. Colouring is done by the use of dyes, oil and acrylic paints. Texturing is done by the use of differently coloured dyed sawdust, use of lichen, etc.
The speaker had been showing slides illustrating the points made so far, as well as layouts under construction and the use of modules. He went on to mention control panels, nowadays using sophisticated electronics. Model motors have progressed from the crude open permanent magnet and 3 pole armature, to the latest “can” type highly-efficient motors, with 5 or 7 pole skew wound armatures.
The speaker concluded by showing a number of slides of models he owns, including one locomotive made from sheet brass, and then a series showing pictures of the layout of the late John Allen of California, a professional photographer, who had produced a model railway with scenery stretching from floor to ceiling and producing some most realistic effects. Altogether a model railway can be a very satisfying hobby for anyone interested in railways, and particularly the engineer.
Peter Harvey
After the tea break, Ray Parsons spoke on a series of slides taken of his own “00” gauge 4 mm model railway, built for timetable operation.
Schematic diagrams showed the track layout and how points, isolating switches and controller inputs were arranged. All the electrical equipment used was of 1940/50 vintage, obtained from government surplus stores, most of which is easily recognisable to older electrical engineers.
The main running lines, comprising a double track continuous loop, are formed into a “clove hitch”, to double the length in the available space. Each track is split into eight electrical sections, fed through current relays, so that a train “in section” gives 12 v to the first behind, 0 v to the second behind, and 10 v to the third behind; and as it progresses round the loop, a train takes these four sections with it. So, if a second train is put on the loop exactly opposite (electrically) the first, they can be operated by one controller. Provided that they run at equal speed, each will take its own four sections round with it quite steadily. Should train A gain on train B, it will come onto train B’s 10 v section, thus slowing until train B moves onto the next section, when train A picks up to normal speed, etc. Should train A be much faster than train B, it will pass through the 10 v section on to 0 v and stop until train B moves ahead and re-energises train A’s section at 10 v. The only snags with this system are: 1) jerky starts/stops and 2) “fail to danger” as, should train A fail to restart, train B sees “line clear” and the operator has to stop train B pronto.
The layout is operated to timetable to ensure that running sessions remain interesting for the operators.
The next batch of slides showed the thirty engines built between 1950 and 1976. All have hand-built chassis, about half have scratch-built bodies and the rest castings or kit bodies. A few examples illustrated the basic methods of construction of all these engines, which changed very little over the years.
Finally, a series of slides showed the various stages in the construction of the layout, taken at intervals during the eight years, from initial support steelwork to final completion of the scenery.
Ray Parsons