Early Days
Basic Fabricated BodiesOver the years though we have noticed significant warping of the longer body parts, and have increased the thickness to 30 thou, and even 40 thou with little effect. It appears as though some brands (or maybe even batches) of styrene suffered worse than others with warping.
Our current technique for styrene bodies is to use a laminated approach, using a pair of 20 thou styrene parts laminated to produce an equivalent thickness of 40 thou. It is important to mark the styrene so as to ensure that these sections are joined "back to back". Whilst we do recognize that vehicle body sides and ends of this thickness are overscale, we have found that this approach reduces the incidence of warping to a minimum, possible even to nil, a benefit which clearly outweighs using thinner, more scale-size material.
The floor and ends are constructed of 40 thou styrene, although perhaps with flat wagons there may some justification in laminating, once again to avoid any likelihood of warping.
The basic body is glued using styrene cement, brushed onto the portions to be joined and later allowed to flow into the joint by capillary action. Bracing is then applied. This is typically styrene shapes, a mixture of L girder, T girder and maybe even channel.
The body is then spray painted - we mostly use Floquil SP Lark Dark Gray, with some wagons painted with a lighter gray colour for variety. The bodies are numbered by using letraset dry-transfers applied to blank decal paper, and then applied as for normal decals. The body is then glued to the underframe with styrene cement.
Cast BodiesFor the last few years, Peter has been using polyurethane castings to build fleets of vehicles. This technique has the advantage that quite a deal of time can be spent building a single "master" vehicle, which is then used to form a moulding and subsequent castings. We are using polyurethane castings for fleets of vehicles: the VA class covered van, the hoods on the HD class "gypsum" wagons, the ZB class end-platform brakevan for example. Some of these vehicles are direct replacements for older models; indeed the VA class and the ZB class have had models built using all three of the construction techniques.
We typically cast sides and ends, leaving the floor (and roof) to
basic styrene. The photo at left shows the appearance of the cast
components, ready for gluing. The polyurethane material must be handled
in a different manner to styrene as styrene cement has no effect. The
sides and ends are glued using supa-glue "gel", however the areas to be
joined must be roughed slightly with a file beforehand. The
polyurethane material appears to inhibit the setting time of the
supa-glue a little, giving adequate time to ensure that everything is
square.
 An OA class cast open wagon seen under construction on our Japanese friend Hiromi's work bench |
The supa-glue is also used to attach the floor and the roof to the
bodies. In this case however the setting time is more normal, and
everything needs to be pretty well in the right position when the
glue is applied. The cast bodies are sprayed with Floquil primer before the top coat of Floquil SP Lark Dark Gray is applied. We have also extended the use of casting to go beyond goods rolling stock. The loading bins at Kelvin had cast framing, and the "short tom" passenger cars have received cast Mansard Roofs. There is a fuller description of the techniques used for polyurethane casting on the DBT, which you may find interesting.
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I hope you have enjoyed this short description of the techniques used in constructing the bodies of the "standard" Dutton Bay Tramway goods vehicles.
Feel free to send any comments or questions to me by
email
Last Modified November 21,1998