Trackwork for Ashburton





Photo by R C Riley. Trackwork mostly Peco. Rolling stock by Dapol


Introduction

From the outset it has been my aim to build a model of Ashburton Station as accurately as possible. It was immediately evident that the trackwork would be a challenge. My starting point was the GWR 1:480 scale site plan. However, this plan is dated July 1921 and the layout was drastically altered to extend the loop around 1931. The date I have chosen for my model is 1955. So, my first task was to try and get my head inside the mind of the GWR Permanent Way Engineer who designed the new layout.

Firstly, I digitised the 1921 site plan into CAD. Next was the difficult task of redesigning the layout using photographs for guidance, to produce the 1930’s layout as accurately as possible.

Immediately several issues became apparent. Essentially 32mm gauge track is not the same as 7mm to the foot. For Fine Scale O Gauge I had to design the trackwork to a scale of 32mm representing 1435mm (full size track gauge) or 1:44.844, while at the same time maintaining linear measurement and track centres to 7mm scale. Compromises had to be made with accuracy with such details as timbering arrangements to make things fit while at the same time keeping to the railway design rules.



Ashburton 1931 layout


Details of GWR turnouts were obtained from publications by the Permanent Way Institution. The GWR was unique among the Big 4 in using switch blades with curved planing. However, after 1948 British Railways standards were applied to trackwork renewals. The BR Standard was closely allied to the straight planed switch blades used by the other three companies. As might be expected track renewals were undertaken at Ashburton in the BR era resulting in a mix of GWR and BR types. R C Riley’s photograph of 14xx No.1427 and a crimson BR auto coach clearly shows a recently re-laid release crossover in the platform with freshly creosoted timbers and uncontaminated ballast. The use of GWR style 2-bolt chairs is not necessarily an indication of a GWR turnout as these chairs continued to be used by Western Region for some years after Nationalisation.



Recently renewed crossover with freshly creosoted timbers and uncontaminated ballast.
Photo by R C Riley - www.alextrack.co.uk


Other photographs suggest the A7 turnout in the siding by the goods shed also had BR straight planed switches even though physically curved to suit the alignment. The fact that the GWR did not use ‘flexible’ ‘A’ type switches lends support to this conclusion. The GWR used ‘loose heel’ switches for shorter turnouts.

The type of switches in use for the facing turnout into the siding is uncertain. There is a photograph, plate 105 in the book ‘Branch Line to Ashburton’ by Vic Mitchell and Keith Smith but the switches are difficult to see in the long grass of 1965. They do appear to be BR type switches and I will model them in this form.

The turnout and trap by the engine shed appear clearly in photographs taken after closure to be GWR curved planed types.

The turnout into the engine shed also appears to be GWR type but photographs are not clear.

From all this research and design, it became obvious that to model the track layout as accurately as possible would require every turnout at Ashburton to be individually hand built. There is no chance of taking short cuts buying ready to run products.

The Model

At an early stage I made the decision to build the trackwork for Ashburton ‘off layout’ rather than in situ. A couple of issues prompted this decision. Firstly, before the baseboards can be constructed my previous P4 layout has to be dismantled to provide the required space. Secondly, the baseboards will be 4 feet deep and I would rather not strain my back reaching across them to construct track in situ. So, the decision was made to construct the trackwork in modules which could be easily managed in a workshop.

The layout at Ashburton can be divided into four main modules, the release crossover in the platform, the two turnouts making up a crossover into the goods shed, the loop points and trap adjacent to the engine shed and the turnout off the loop into the engine shed. Each of these modules will be built separately in my workshop. To date the first two modules have been completed.

Method of Construction

All trackwork on the layout is being built using code 124 bullhead rail and chairs from Peco with some minor components from other suppliers. Timbers for the turnouts are from 3mm thick balsawood, which is ideal for this purpose being quite easy to work with and giving a realistic finish after colouring with walnut wood stain. Dark oak is also a suitable colour. A 3mm thickness provides a match of the rail height with Peco flexible plastic based track.

Extra care must be taken as balsawood is easily damaged during construction. I have needed to replace several timbers during construction due to mis-haps with pin pushers and a dropped steel straight edge.

The balsawood timbers are glued to a 7mm thick plywood sub-base with PVA adhesive. These sub-bases will eventually be screwed to the baseboards at their edges but to reduce noise and vibration transmission 6mm thick cork floor tiles are being inserted into the ‘sandwich’. The plywood and cork are glued together using Evostic contact adhesive or an Australian equivalent from Selleys in my case.



The first two trackwork modules under construction. Left, the release crossover looking towards the buffer stops. Right the facing crossover into the goods shed, facing Buckfastleigh


One of the challenges has been deciding where to place the baseboard joints without making them too big, and at the same time avoiding buildings and other infrastructure. Unfortunately, this means that there will be joins through both crossovers. Each crossover module will therefore be in two parts, one either side of the join. To hold both parts in alignment during trackwork construction in the workshop temporary timber battens have been attached.

The chairs are attached to the timbers by Peco track pins. The pins will push into the balsawood with ease but to achieve a firm fix they need to be driven into the plywood sub-base. This is a risky operation! Pins can bend, pushers can slip, and balsawood timbers can be damaged. To avoid problems of this nature pilot holes are drilled for each pin. A 0.6mm drill provides a hole which is suitably tight for Peco track pins.

A significant problem with Peco plastic chairs is that there are only two types available, a standard BR S1 chair and a switch slide chair. All other types need to be fabricated by applying a craft knife to these two types. Whilst this is a practicable way of producing a variety of chairs, unfortunately the rails are not held firmly. The solution is to insert screws into the plywood between the timbers to which the rails are soldered. I am using half inch 1G brass countersunk screws and a 1.5mm drill for the pilot holes. The screws should be driven in with great care. One slip of the screwdriver can and has resulted in significant damage to balsa wood timbers necessitating their replacement. It’s not a big problem but it wastes time. The height of the screws is set by using an off cut of rail sitting in a couple of chairs. Allow sufficient clearance for the tinning of the screws with solder. The locations which need the support of screws are: the crossing vee (3 screws), wing rails (2 each), check rails (2 each), the running rails adjacent to the check rails (2 at each), the flexing point (heel) of switch rails (2 at each) and the unsupported section of stock rails (2 at each). So, in normal situations each turnout will need a total of 23 supporting screws.



Three screws have been driven into the baseboard to support the vee of the common crossing


To give the turnouts as much strength as possible rail joints are avoided wherever possible and the maximum possible length of rail is used. One of the ironies of the traditional rail joiner is that on the one hand it looks completely unrealistic, but on the other hand it is very effective in holding the rail ends in both horizontal and vertical alignment. When I was building P4 track the ‘H’ type fishplate was hopeless at holding the rails in vertical alignment. I was expecting the same problem working in O Gauge. I purchased some ‘cosmetic’ fishplates from C & L Finescale and found them rather slim for attaching to the web of Peco code 124 rail. What was interesting was that if rails were joined with Peco rail joiners, there was still room to attach a cosmetic fishplate over them. Insulated joints cannot be avoided and I have used Peco insulated joiners. These joiners, being made of nylon are somewhat fatter than the ordinary metal ones but even then, it is still possible to file down a plastic, cosmetic fishplate just a little to make if fit over. Note: the Peco rail joiners are filed shorter to fit between chairs while the insulated joiners are simply shortened using a craft knife.

At the beginning of this article, I said “From the outset it has been my aim to build a model of Ashburton Station as accurately as possible”. Well, avoiding rail joints wherever possible is contrary to this aim. After I have completed the construction of the pointwork, at locations where a real rail joint would occur, I have used a Dremel to cut through the head of the rail but no further than the top of the web. I have then glued cosmetic fishplates to the web of the rail.

Photographs of Ashburton suggest there were many short rails in the track layout. One would expect to find nothing longer than a 45 ft rail, some even shorter. To maintain the strength of the track I have adopted the same practice as for the pointwork described above.

To date I have soldered wire to the switch blades as an attachment location for the tie-bars. I am planning to use Tortoise slow action point motors with mounting plates from Exactoscale. The components will be recovered from my P4 layout when it is dismantled. Possibly I might run into problems and my plans will have to change. In which case I might have to consider the use of servos.

Current Progress



Composite 'A' chair supplied by C & L Finescale




Completed release crossover




Completed crossover to goods shed. The wagons are standing on Tucker's Malthouse Siding



Paul Plowman
23 February 2021


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