The Simplex rail tractor was first produced during the First World War from about 1916 and eventually numbered more than 500. The Bedford (UK) firm of Motor Rail & Tramcar Co. built them, ‘Simplex’ was a trade name and is associated with almost all of this type of locomotive produced by the company. These first locomotives were of a simple design, powered by a four-cylinder petrol engine and weighed in at 2 ˝ tons. The production of Simplex rail tractors continued after the war and was still in production in the late 1960’s. They were made in a number of gauges up to standard gauge. One two foot gauge loco has even been re-gauged to run on 15” gauge and is used on the Romney, Hythe and Dymchurch Railway in Kent, England.

My model depicts a later (1930’s?) plate frame ‘Simplex’ fitted with a Dorman two-cylinder diesel engine. A large number of these were produced for industry both in the UK and overseas. Unfortunately, the Playmobile chassis unit that I used is no longer available. The original unit is part number 02502 (I think) from the Playmobile range produced from 1980 onwards. It is a 4-wheel unit with both axles powered. The wheels are coarse, bright nickel-plated rims with bright red spoked centers. The unit could be used ‘as is’ but I chose to modify it a little by cutting the lower part of the chassis block back close to the wheels.

I replaced the wheels with Tenmille Products Gauge 1 4 hole coach wheels (part number AG163) and I added some phosphor bronze wiper pickups and took off the slider pickups from between the wheels. The chassis sits a little too high with these wheels and would probably benefit from using the smaller disc wagon wheels. The Playmobile axles are a little thicker than the Tenmille ones, so I had to carefully open out the holes in the wheel centers to a push fit on to the Playmobile axles. The chassis was finished off with some cast white metal brake blocks and hangers. The loco body is made almost entirely from styrene sheet.

I started by cutting out four rectangles from 1.5mm thick styrene. Two pieces 18mm x 173mm and two pieces 22.5mm x 85mm. These will become the plate sides and buffer beams. Measure and drill holes for the ‘rivets’ on the side frames. Also cut out the recesses above the axle box positions. Not all loco’s had these; there were several styles on those that did. The buffer beams are similarly treated. For rivets, I used Peco track pins, cutting the tails off flush on the inside. Bolt and nut details are 10BA hex head bolts with 10BA nuts. Some 12BA are also used.

Next cut out a rectangle, 88.5mm x 173mm from 1.5mm styrene for the floor. The prototype has a separate floor section each side of the engine compartment. I chose to make the floor the full size, but I did have to cut a rectangular hole out of the middle for the full length of the floor so that the body sat lower on the chassis block. This may not be necessary depending on what you use for the power unit.

Place the floor on your work board, stand one side up along one edge of the floor. Run solvent along the join, checking that all is square. The buffer beams can be fixed now. These fit between the sides and are deeper than the sides. Now fit the remaining side to form an open box.

Provision for fixing the chassis was now considered; this will vary depending on the power unit used. I made some clips out of styrene off cuts that clipped on to the ridges at each end of the chassis. The chassis can be clipped out for servicing.

Six long rectangles of 1.5mm styrene are now required to fabricate the channel cross bearers. The top and bottom pieces are 87mm x 5mm and the web is 87mm x 17mm. These are assembled to form a ‘[‘ section. The two completed cross bearers are mounted on the floor thus: ‘] [‘. Each being 25.5mm either side of the centerline.

The ballast weights that came from the chassis block were kept and mounted in a plastic box constructed in the engine compartment. Painting this black later will represent the engine.

Continued next issue:

Terry Bowden