Page 18 - November December 2001

CONSTRUCTOR’S CORNER...
MORE NOTES
ON PAINTING
BRASS
Paul Doggett
Most modellers know that getting paint to stay on brass can be a pain. Unless the lacquer is good, an etched brass primer is a must.
Railmatch - Howes of Oxford do etched brass primers in black, white, grey and oxide red (boxcar red to US modellers). I’ve only used black but found it an excellent satin finish. It is not glossy enough for decals, so a coat of gloss varnish such as Johnson’s yacht varnish is used (it needs only about 10% thinning with white spirit) - an excellent hard finish is obtained.
The black etched brass primer needs the Railmatch thinners for this product. Amongst warnings on the tin (e.g. don’t drink it - it tastes rotten) it says not to over- thin the paint. I first thinned it 80% to 20% and got lovely black cobwebs everywhere. I tried different tips and pressures, then more and more thinners getting a better and better finish till I ended up with 40% paint + 60% thinners.
I ‘phoned Howes and they said if that ratio worked carry on using it, but if I wanted to check further I should ring the makers, H Marcel Guest.
They confirmed that if a good finish had resulted from 40/60 then that was fine. They will mix paint for you, fin a tin or in an aerosol, and also match specimen colours sent to them. They are in Collyhurst Rd., Manchester, about 3/4 mile from Victoria Station.
Sometimes you have to remove existing paint or lacquer from a brass model; Nitromors is very good at this but needs extreme care in use. Ideally rubber gloves, old clothes and eye protection should be worn, leaving no exposed flesh! (See COSHH regulations regarding Nitromors.)
Read labels before use, not after a visit to your local A&E department!
An old toothbrush is good at getting the old paint off but don’t allow it to flick the Nitromors everywhere.
Afterwards, clean up the brass with “Shiny Sinks” then dry the model well - avoid too much further handling, and you are ready to paint.
An old hair dryer is useful for quick drying the coats of paint, and reduces the chance of dust settling onto the model; it also enables the next coat to be more quickly applied.
Another aid is to allow the model to dry under a cover such as an old biscuit tin or the anti splash dome from the wife’s microwave. Just don’t get caught - silent, cold meals can be very boring!
NEW BRIDGE
FOR OAKLAND
DIVISION
Tony Martin MMR
Crossing one of the aisles between Bond and Deer Park on my B & O Oakland Division is a lift up bridge (so that oldies such as I do not have to duck under when following trains into or out of Keyser). The bridge comprises a length of mature seasoned wood 45” long, 3.5” wide and 3/4” thick. On top of this lies the track bed and single track main line. Until recently I had installed Peco truss girder bridge sides along its length. However, these were only about 2” tall and, frankly, did not look the part. What I wanted was a good, large and strong looking structure that seemed fit for the job of carrying trains across the river. Somewhere in my railroad library papers I had a Plastruct catalogue and in it was a scale drawing of a truss bridge. I unearthed it and was somewhat surprised to see that it was dated 12-1-68. Here was a full scale (HO) drawing of a truss almost 17” long, 5” high and 2.75” wide. Just what I was looking for! Further examination showed me that if I added an extra panel to the side I could make it 22.5” long. Two bridges, end to end, would therefore give me the 45” I wanted. Fortunately I have a flat bed scanner attached to my PC and I used this to make a copy of one end of the bridge. I then cut this out and stuck it over the end of the plan to give me 22.5”. It worked out exactly. Looking at the catalogue, I saw that the Plastruct H-columns, Tees, I-beams and channels came in various lengths - 10”, 15” and 24”. The next thing was to work out exactly how much of each shape I needed so as to minimise wastage. Eventually, having checked and double checked the measurements, I placed my order with a hobby shop near Leicester and took delivery about two weeks later and some £28.00 lighter in my wallet. It was time to get scratch-building! I laid greaseproof paper over the plans I had taped flat to a large old wooden drawing board.
Before I made a single cut, I checked my measurements again especially to confirm
where I would make the joins which would be concealed under gusset plates. The main H-beams running the length of the top and bottom chords were supplied only in 15” lengths and I wanted 16.75” and 22.5” respectively. The uprights were 4.125” and so I combined cutting the chords with cutting the uprights to give the lengths needed with minimum wastage. I used M.E.K. (Methyl Ethyl Ketone) as the bonding agent for the ABS plastic shapes. (ABS stands for acrylonitrile-butadiene- styrene.) I had plenty of .020 sheet styrene to use for making the steel rivet gusset plates used for connecting the uprights and diagonal braces to the chords. I eventually ended up with four identical sides which became two truss bridges when the cross members were fixed to the top chords. I made no bottom cross pieces as I wanted to slip the bridge sides over the existing road bed so as to rest on the wooden base. This worked out a treat. I had to spring the sides very slightly to go over the track bed but that made for a good tight fit. There are masses of steel gusset plates on structures like these, on the sides, the ends and the tops!
Using my scanner and a program called UMAX VistaScan, I scanned the various rivet plates into the computer and produced sheets of each type. I cut each one out individually with a single edged razor blade. That took quite a time - there were 196 of them! Using a single pointed punch tool given me by an artistically talented daughter-in-law, and working over a piece of soft wood, I laboriously punched out the 9440 rivet heads! (I counted them!) Then, turning them over so that the ‘bumps’ showed on the outside, I glued these paper overlays over the pre-cut gusset plates. These bridges would be heavily weathered not only from rain but also from the soot from countless steam and diesel locomotives. I first sprayed the bridges with matt grey followed by matt rust red. When dry, I painted on several thinned coats of Crayola black (a water based paint from Partners) and then, in places, a mixture of the black with Crayola red. Using a water based paint on plastic is not easy but, with patience, it can be done with great effect. Now I have a bridge worthy of the name!
18 ROUNDHOUSE