Revision 0.2 - Tim Barnard - 17th October 2002
Update to bring original up to date
Polystyrene sheets such as Slater’s Plastikard have revolutionised the lot of the railway modeller: it is possible to
make accurate models quite quickly with only a few tools, the most important of which are a small engineer’s
square, a steel rule and a craft knife. Polystyrene is cut as easily as paper or card, yet has many of the
characteristics of metal and can be easily drilled and filed. In 3mm scale, 10, 20, 30 and 40-thou thicknesses are the
most useful, together with .010” x .020” and .010” x .030” Microstrip.
Updating comments - Plastruct now produce a wide range of sections.
Many people have been out off Plastikard when they have found it difficult to cut. The correct way to cut plastic
sheet is to make a couple of passes with a very sharp craft knife, not attempting to cut right through, completing the
cut by breaking the sheet between the fingers; the result is a perfectly clean right-angled break. When making arc
shapes (such as a loco spectacle plate or a van end), the arcs can easily be cut by using a stiff pair of dividers to
make the initial score, completing with finger pressure. Small curves and apertures – such as cab windows – are
best cut with needle files after starting the hole with a drilled hole or two. It is possible to tack together using two
pieces of styrene temporarily, using the minimum of solvent, in order to cut out two identical components such as
cab or tender sides. The completed parts can then be eased apart with a razor blade.
Updating comments - Never assume that the styrene sheet you buy is cut square: always use an engineer’s square
to create a “base right angle” from which to start your work Always use a sharp knife blade, and change it when it
starts to become dull.
Another useful way of making arc shapes is to build up a collection of useful arc templates to cut round, such as old
coins, metal Mecanno wheels, etc. Be prepared to have to change the knife blade after doing this, as it invariably
dulls or removes the tip of the blade.
All cuts should be cleaned up as the work progresses, using wet-or-dry paper. Cuts and scribes raise burrs, which
must be removed if the completed model is not to look messy or amateurish.
The solvents available weld plastic: only a small amount – applied with a small brush – is necessary. Too much
solvent sloshed around softens the plastic and causes warping. Solvent takes a fair amount of time to harden
completely, but takes sufficiently for the model to be handled after a minute. Do not smoke when using solvent,
and make sure that the room you are working in is well ventilated. Make sure that you replace the cap on the
solvent bottle every time you use it: an upset solvent bottle can make an awful mess of a nearly completed panelled
coach side. To sum up: remember that solvent works by capillary action: a small dab will run along a joint and fix
it firmly, so resist the temptation to use too much. Only go over a joint if it is imperfect. If you make a mistake
(sticking a wagon side in one place upside down, say) it is possible to part styrene components up to half an hour
after welding if you are careful; this is not to be recommended, needless to say.
Updating comments - Comment on the makes and uses of different solvents?
Polystyrene sheet is a very springy material which has some useful properties and some less useful. When scribed,
styrene tends to bow, so it is worthwhile scribing the outside and the inside of a planked wagon side. (Make sure,
by the way, that you store sheets of plastic in the flat: bent sheets are impossible to flatten.) Gentle curves can be
formed by working the styrene round a small diameter rod, but the plastic has a tendency to spring back; it is better
to think in terms of a more permanent from of moulding when making such things as the tops of loco splashers or
any form of curved roof. Styrene can be moulded in hot water: tape the sheet to a former and plunge it into a
saucepan of boiling water for a few moments. Laminated roofs are quite easily made from 10-thou sheets in this
way. An even better method is to cook the plastic round a wood or metal former in a hot oven. Very classy
elliptical coach roofs can be made in this way and the 3mm Scale Model Railways wooden coach roof section makes
an excellent mould. Loco footplates with multiple curves (Gresley, D E Marsh) can be moulded on a
carefully-made plywood former. It is important to let the oven warm up sufficiently before putting in the styrene;
once the plastic has softened sufficiently, it can be removed from the oven and gently pressed on to the former with
light pressure from tea-towel-clad fingers. It is worth making a variety of differently radiused arc roof moulds and
moulding a batch of roofs if you intend to make a lot of vans; nothing is more infuriating than having to make a
one-off as it wastes so much time. 20-thou styrene is probably best for van roofs. The roughly moulded rectangles
are readily cut to size using a square and a very sharp knife; once cooked, the styrene retains its curve permanently.
Tubes for locomotive boilers (or tank wagons) are best made from 10-thou sheet – cut the length of the boiler and
smokebox – wrapped round a suitable metal tube. The styrene should be left for a day or two to harden, after which
time it will be found to be extremely tough. Again, the smallest amount of solvent should be used.
Updating Comments - Again, there are now Plastruct round sections which might suit.
For detail work, Slater’s Microstrip and plastic rod are essential; it is just not worth trying to cut thin strips yourself,
as 10-thou strips have an awful tendency to buckle as they are removed from the sheet – cutting them is possible, but
there are more interesting things to do with your modelling time.
It is worth investing in some 20-thou sheet in a variety of colours, as this makes positioning of components
extremely easy. The lighter shades are recommended as it is easier to mark them. (A rub over with the finest
wet-or-dry paper removes the gloss surface of styrene and makes pencil marking simpler.) Black styrene is
essential for loco footplates, which are likely to be rubbed free of paint. A stronger job can be made by using
20-thou sheet, which can be thinned or feathered at its edges to simulate thin platework.
Although styrene modelling is relatively quick, it should not be seen as simply a bodger’s medium. With care, a
loco body made from styrene can look as good as one made from metal, as some of the excellent models which have
taken the Tony Birch Memorial Award have shown. As with all modelling, the essentials are care in marking out
and patience in cleaning up the work as it progresses.