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Brown, Marshall & Co. Brake Van

The bodywork

To the best of my knowledge, there is no kit available for the brake van so it was going to be a case of scratch building. However the real thing was built by Brown Marshall and appears to have shared the same design of chassis with two of the coaches on the Talyllyn from the same builder, albeit eleven inches shorter but with the same wheelbase. Wrighlines do a kit for these coaches and the chassis can be purchased separately, so I sent off an order for two coach kits and one chassis kit.

The first step was to prepare a set of general arrangement drawings. I sometimes think that I spend almost as much time on research and drawing as I do building models. Even with the wealth of photographs and the drawings in J.I.C.Boyd's excellent book, many hours were spent cross checking all the available information until I was reasonably satified that my drawings gave a reasonable representation of the brake van as it appeared in the period being modelled.

The bodywork was to be built using plastic card, so the next step was to decide on the method of construction and to produce drawings of each of the layers (the rear layer showing the planking and the front layer the framing - see Fig.1). It is here that autocad really makes life a lot easier as drawings of each layer can be copied from the master and dimensioned. A dimensioned drawing can be printed as large as you wish because you won't need to scale from it. However, at 7mm scale, dimensions to .01mm are not necessarily that helpful if you can't mark out and cut that accurately! At this point I therefore rationalise the drawings so that all dimensions are multiples of 0.25mm. Again this so much easier on the computer.

Like many sheet materials, plastic card thicknesses are normally quoted in thousandths of an inch. The table below shows the equivalent thicknesses in millimetres as well as scale thicknesses for 7mm/ft and 4mm/ft. You don't often see 5 thou for sale so, if you come across any, snap it up!

PLASTIC CARD THICKNESSES
Thickness - inches 0.005 0.010 0.015 0.020 0.030 0.040 0.060
Thickness - mm 0.125 0.250 0.375 0.500 0.750 1.000 1.500
Scale thickness 7mm/ft 0.21 0.43 0.64 0.86 1.29 1.71 2.57
(in inches)
Scale thickness 4 mm/ft 0.38 0.75 1.13 1.50 2.25 3.00 4.50
(in inches)

The corner posts are 3" square so, as the ends are a butt fit between the sides, this defined the overall thickness of the sides as 1.75mm. Therefore cut the outer frame layer from 40 thou, which represents the prototype depth of visible framing pretty well, leaving 30 thou for the inner layer that will be scribed for the planking. Cutting out all those openings is pretty laborious but I think it gives a much crisper finish than building up the framing from strips. I mount the card on a small drawing board with parallel motion, make all the horizontal cuts then turn the card through ninety degrees and make the vertical cuts. Many strokes of the scalpel are required to cut through 1mm of plastic but don't be tempted to press too hard if you want a nice clean cut. Remove surface burrs with a scalpel and sand the surface flat prior to pushing out the unwanted bits of plastic. Don't force them, if they don't pop out easily check that the cuts go right into the corners and try again. The cut edges will probably need a bit of tidying up to make sure they are square to the face. Do this by using the scalpel as a scraper. The frames on this van are stop chamferred. At 7mm/ft you really can't avoid forming these, have a look at Figs. 2 and 3 and I think you will see what I mean. Mark the ends of the chamfers, ensuring that they all line up and make a small cut at 45 degrees on the arris of the frame before forming the chamfer between the cuts, again using the scalpel as a scraper. The second layer is much easier, I scribe the planks using an Olfa cutter before cutting them out. The two layers are now secured to one another with solvent and left to cure. The process is now repeated for the other side and the two ends. However, the framing on the end closest to the doors is much shallower so use 20 thou for the outer layer, 40 thou for the planking and 10 thou inside that to make up the overall thickness to 1.75mm as the ends also include the buffer beam. It's a good idea to drill out the buffer beams on the end panels for the buffers and coupling hooks at this stage.

sides

doorsPrior to assembling the sides the doors have to be made and fitted. Fortunately, in the period being modelled, there were only doors on one side! These are made just like the sides, in this case with 30 thou framed outer and 20 thou planked inner layer. An opening is left in the inner layer for the louvres. Supports for the louvres to set them at 45 degrees are secured to the rear of the doors (see Fig. 2)as are 40 thou strips to take a 20 thou blanking panel which is secured prior to fitting the louvres. These are built up in-situ from 15 thou plastic card, 3.25mm wide for the louvres and 2mm wide for the spacers. This makes the louvres deeper than the thicness of the door, hence the cut-out in the side panel. Butting them up against the blanking panel keeps everything square. Once the louvres have cured, the doors should be sanded so that the edges of the louvres sit flush with the face. The completed door assembly can then secured in place on the side panel.

The floor is going to hold everything square, so it needs to be robust and accurate. I decided on a sandwich construction, two layers of 40 thou with 40 thou spacers. The floor will be the same width as the ends (31.5mm) and the length of the sides less 2 x 1.75mm (91.5mm). While you are at it, cut out a third layer the same size, this will be the basis of your chassis. Mark out two holes on the centreline, 15mm from each end, align chassis and floor and drill out 2.3mm diam for 8BA mounting bolts. Secure two 8BA nuts on the inside of the floor. As the sole bars will butt up against the floor, locating the height in relation to the sides and ends is critical. The solebars that come with the chassis kit are a scale 10 inches deep whereas those on the brake van are only 8", so they will have to fit 1.25mm above the bottom of the sides. You also need to make allowance for the chassis structure (1mm) and floor (3mm), so fix 4mm x 1mm bearers 5.25mm above the bottom of the sides and 10mm above the bottom of the ends (allowing 4.75mm for the depth of the buffer beam), as the floor will be fitted from below. Secure one end to the floor, ensuring that they are at 90 degrees to each other and flush at the edges, and leave to cure. Once set hard secure one side, leave to cure then fix the other end, ensuring that everything is square at each stage. The second side can now be fixed and the completed assembly should sit perfectly on a flat surface. Plastic vans are very light, even with white metal sole bars, so I added some lead to the floor, glueing it in place and containing it within a box in case it broke loose.

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