Words and pictures: Peter Thompson
Article in Gazette volume 20 number 9 - Nov 2018

Part of the fun of O gauge modelling is making vehicles and locos that are not available elsewhere as a kit or ready to run. Therefore, if I see a photograph of a vehicle in a publication, particularly if it is an unusual type, I produce a basic drawing from the photo then use this drawing to aid construction of the vehicle in model form. Using this method will result in a model that will not satisfy those that require an exact model replica of the original as dimensions used for the drawing will be only approximate. However, I take the view that most modellers, and the public too, if the model goes out to exhibitions, would not recognise the discrepancies, as after all, most of us were not alive to see the real thing anyway.

It helps to have at hand a book such as the Pictorial Record of LNER Wagons by Peter Tatlow, or similar, that shows vehicles of your chosen railway company. Publications such as these contain many photographs and outline drawings of various types of vehicles that can help in deciding on dimensions and details to be incorporated into your own drawing.

You also need to be aware of the range of typical dimensions used when building the original vehicles and the 7mm equivalent for your drawing. The table below offers some guidance.

Note: In general, early vehicles up to 1910 or so were built narrower and less tall than those of later years.

Buffers are not always positioned at mid height of the buffer beam.

Van roofs have many forms from simple circular 7ft radius arcs to complex elliptical shapes.

Vehicles with wooden underframes have a different detail at the buffer beam compared to a steel underframed vehicle.

The following is an example of my method for producing a working drawing for a model brake van.

The NLR brake van in the left background is the prototype for the drawing and subsequent model.

This particular model was inspired by the photo on page 45 of the North London Railway, A Pictorial Record book, published by HMSO and photographs taken through the display cabinet glass of O gauge NLR models displayed at the York National Railway Museum. The vehicle is unusual in that the body is the same width as the solebars.

Although in the picture only part of the vehicle is visible, there is sufficient to scale up a drawing from which the model was constructed. The end view detail was cobbled up from a photo on page 27 of a similar vehicle in the far distance by using a magnifying glass and a sizable dollop of ‘near enough’! The working drawing was obtained by measuring the vehicle in the picture in mm of items or dimensions where the full size vehicle equivalent is known to a reasonable degree of accuracy, i.e. the wheelbase centres, wheel diameter, solebar height, vehicle width etc. Then I used a calculator and pro-rata calculations to convert to 7mm scale to produce a reasonably accurate drawing. Dimensions are checked as most photos of railway vehicles involve perspective.

For clarity of the method and calculations used, I have used the short wheelbase brake van in the foreground of the picture to demonstrate how dimensions are calculated to produce a working drawing. The same procedure was used to obtain dimensions to produce the working drawing for the model shown in this article.

Consider the vertical line at the left axle on the picture:

The axle centre height measures 14mm. The actual height is 18.5in (half of a 3ft 1in diameter wheel), so, the scale at this point is 18.5 divided by 14 = 1.32. From the picture therefore we can calculate:
• The floor of the van measures 40.5mm from top of rail, so 40.5 x 1.32 = 53.5in, i.e. approx 4ft 5.5in actual height, equivalent to 31.4mm in 7mm scale.
• The top of van cantrail measures 102mm from top of rail, so 102 x 1.32 = 134.6in or approximately 11ft 2.5in actual height, equivalent to 78.5mm in 7mm scale.
• The top of the veranda side measures 74mm from top of rail, thus 74 x 1.32 = 97.7in i.e. approx 8ft 1.5in actual height equiv to 57mm in 7mm scale.
To check these dimensions for perspective effect:
Consider the vertical line at the right axle on the picture:

Using the photo to calculate dimensions for the drawing. See text.

The axle centre height measures 12.5mm. The actual height is 18.5in again, therefore scale at this point is 18.5 divided by 12.5 = 1.48. So we can check our above calculations thus:
• The floor of the van measures 36.3mm from top of rail. So 36.3 x 1.48 = 53.7in. This checks with near axle dimension. Use 31mm for the drawing
• The top of van’s cantrail measures 90.3mm from top of rail. 90.3 x 1.48 = 133.6in. This checks with near axle dimension. Use 78mm for the drawing

The average of scales used at each axle is 1.4 Wheelbase on picture measures 57mm X 1.4 = 79.8in, i.e. approximately 6ft 8in on the prototype. Use 46.66mm in in our drawing

Note that the wheelbases of most four wheel vehicles are generally built in 6in increments. Therefore if required, adjust the calculated horizontal scale accordingly to give a wheelbase of 9ft, 8ft 6in etc then use the adjusted scale for all other horizontal measurement calculations.

Body length on picture measures 106mm x 1.4 = 148.4in, i.e. approximately 12ft 4.4in. Use 12ft 5in, equivalent to 87mm in our 7mm drawing From these outline dimensions and those shown in the table of typical dimensions, a working drawing such as that shown below for the NLR model used as this article’s example, can be prepared adding as much detail as required by repeating measurement and scaling calculations.

Below is the completed model built using the working drawing shown above it.

The model’s basic body was 60 thou. Plastikard on an 80 thou. Plastikard floor. A ‘scrawker’ was used to score ‘v’ shaped grooves to represent the external board joint lines. Evergreen Styrene sections of the section sizes stated on the drawing were fixed to the basic body with Slater’s Mekpak. Metalwork to secure the framing was cut from 10 thou Plastikard sheet; the most time consuming part of the model. Rivets were added by pressing a scriber tip into the Plastikard (placed on a sheet of soft card). Glazing was added, and holes were drilled through the floor to allow all trace of the solvent to disperse prior to fixing the roof. A set of suitable axle box castings and buffers were sourced from my ‘bits’ box. Most of these items I buy from bring and buy stalls at model shows usually at a fraction of the normal price. Slater’s wheels were used, running in their usual top hat bearings. I made up a subframe on one axle for this model to allow some rocking movement. Various bits of wire and brass section were used to complete detailing and for a representation of brakegear. It is important that the vehicle looks acceptable, be approximately the right size but, most importantly, run without fault.

The model was hand painted with Humbrol matt enamel paint and weathered with Carr’s powders and some dry brushing. I was not sure whether to paint the strapping and solebar in black, as the photo on page 45 of the NLR book did not offer any guidance, but in the end I took the easy option of leaving the model all over grey. The total cost for this vehicle was around £12, of which nearly £9 was for wheels.

The finished model with working drawing