A SIMPLE TIP FOR BUILDING PLASTIC COACH KITS
I’m building a number of ‘OO’ plastic coach kits and the mouldings need cleaning up before assembly. I’m struggling to get the edges of the sides straight and true with a file. Any suggestions?
Wilf Watkins, by e-mail
George says: As mentioned elsewhere in this issue, it’s important to get plastic components to meet as closely as possible in order to form strong bonds, especially when working with liquid poly cement. Fettling parts carefully and test-fitting before assembly is, therefore, a vital step.
Broad, flat files are usually sufficient for dressing square edges flat and true, but working on longer components, especially carriage sides, can prove difficult. Mounting the sides in a padded vice and running a longer file along the edges offers more control. Checking with a steel straightedge at regular intervals helps to identify any high or low points.
The process can be eased further by creating a simple aid, using an old mirror, a sheet of coarse (120grit) wet/ dry paper and strong double-sided tape. By rubbing the edges of the components on the abrasive sheet, any waste material is removed and the surfaces levelled. The flatness of the glass also doubles as an ideal reference surface, revealing how flat the edges are.
Once the parts have been prepared, test-fit everything before any glue is applied, making any further alterations where necessary. A way of ensuring that the parts are correctly aligned before the liquid poly is applied, is to clamp them together with masking tape. This also removes the need for the elusive ‘third hand’ that we modellers often wish we had.
For even more control over alignment, mini lightweight bar clamps are also useful, especially when installing carriage roofs. As seen here, a combination of tape and clamps allows the roof’s position to be fine-tuned and restrained before the glue is applied with a fine brush, directly into the joint.
Just enough pressure should be exerted by the clamps to hold everything in place, without distorting the soft material. Furthermore, clamps should only be employed once the rest of the bodyshell assembly is fully cured.