I have started a new topic because this subject was developing under the Glenfinnan viaduct heading and relates to a different subject.
There is a photo of the partly completed model based on York Station under that topic and I have published photos before of my station on this site.
The station is a composite structure of ply, plaster cast wall sections and plastikard. This article deals only with the method of casting the plaster sections of the station walls which are huge thick structures with lots of repetition and lend themselves to this process.
Thanks are due to Alec Tiranti Ltd for supplying advice, instruction booklets and materials.
Alec Tiranti.
First of all, I selected plaster rather than resin because plaster is perfectly satisfactory and much cheaper.
1. These are the materials supplied by Alec Tiranti that cost about £24 in 2000. They have a short shelf life and these cans are empty.
There are alternatives and I have also used these:
2. I have produced a visual aid that gives a summary of the process and here is a photo of it:
Visual aid.
3. The first step is to take a photo of the wall section and decide where your repeat line is. Then make a scale drawing, or if you are very adept, enlage your photo to 1/76 scale and use that. The masters are made out of ply and plastikard, using the various products available from Ratio, Wills and Slaters etc.
At this stage, with a curving wall, you have to make compromises and size your brick panels so that the inner ones and the outer ones are perpendicular and your roof beams will be spaced out evenly.
4. I built mould boxes out of ply and Lego, initially making the side walls two full bricks high (not shown).
The master is stuck down in the bottom of the box with double sided tape. The box needs to be about 8 mm bigger than the master all round and the mould needs be at least 5 mm thick above the master. Make up your resin mix very carefully in accordance with the manufacturers instructions. This is expensive stuff, so it pays to calculate very accurately how much you are going to need.
Examples of moulds and masters.
First pour ina little latex mix and paint it into the detail on the master to remove air bubbles, then add the rest of the liquid up to the required depth.
Master in mould
5. Allow the mould 4 days or more to set and cure. Leave well alone. The material smells, put it in a clean dry shed/garage etc. under a cover. Keep it level.
6. Carefully peal the mould away from the mould tray, taking down the Lego side walls helps. Free the master and trim away the rubber shims. Invert the rubber mould in the empty mould tray.
7. You are now ready to start casting. I used Tirantis Basic Alpha plaster which has a high strength. You can add powder paints to colour the wall sections to avoid white plaster showing through. I have a selection of black, brown, yellow and red from the art shop. Mix your plaster, paint a little into the detail in the mould and add the rest, levelling off with the flat blade of a wallpaper/paint scraper sufficiently large to rest on each side of the mould at once. Vibrate out the air bubbles. Improvise something. I used the top casing of my pillar drill as a vibrating table. Leave to harden for 8 hours or so. I found that my moulds curled up very slightly and so I held them down flat in the mould tray with a wooden spacer top and bottom and a weight over them.
Carefully peal off the mould and make another cast.
8. Allow the casting to dry out thoroughly before use. You will need to rub down the back of your castings on a flat piece of sandpaper to get a constant thickness and you will also need to dress the edges to get a close joint.
9. I stuck them onto a ply base with contact adhesive. For the curving station walls, I fixed the ply base to my platforms, which were also fixed down to the baseboards. The walls were then built up in situ.
Partly constructed station.
10. The columns were made out of plaster and brass tubes. The bases ( B ) and capitals ( A ) were cast round dowel which was a tight fit in the brass tube.
Making a column.
11. The roof girders were cut on a Scroll saw. The wood all came from a marine and aircraft model shop.
12. The glazed front of the station is Slaters plastic strips stuck onto perspex with super glue . The perspex was pinned over a drawing of the station front produced by scanning a photograph and enlarging it to the right size. Having said that I have taken liberties. There are only three arches and they are all narrower than they should be. I had no choice but to make these compromises.
13. This system also works with engine shed walls. Here is an example of mine:
Engine shed wall.
I shall use it for terrace houses and for retaining walls in a cutting.
Best of luck
Colombo
