| Highland Steam - John
Foulds Photos:Eric Harlin |
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This article was prompted
by Ron Haywood’s The Last of the Highland in the May 2002 issue.
Like him, I can remember my first images of model railways. This was during World
War II when I was a youngster. My father came home one day with an
oval of Bassett-Lowke O gauge track and a live steam loco (make unknown).
After preparation, the track was laid on the lounge floor and steam
was raised. The loco was placed on the track and it set off. Speed
increased rapidly and the loco shot off at a bend, straight across
the carpet and under the settee where it turned over and set fire
to the upholstery. The loco was never seen again! After a few days
the track reappeared with a centre third-rail and Bassett-Lowke Midland
Compound which I still have today. However, the desire for real steam never left me, and in 1976 my son and I built a very crude 16mm/ft narrow-gauge loco from a Mamod No 1 steam engine and boiler; pot boiler, meths-fired, singleacting oscillator, and Mamod band drive. This was duly christened Suzuki by the 16mm brigade. After building many 16mm engines, in about 1994 I tried my hand at 7mm/ft and one of the engines I built last year was a Highland 4-4-0T, like Ron Haywood’s model. As I could not find a drawing, the model was based a mix of old chassis drawings and photographs. The model is built in coarse scale which allows me to run it on my NG garden track, but it will also run on Peco finescale track and points. The model uses Walsall coarse scale drivers and die-cast Bassett-Lowke bogie wheels machined down to coarse scale. The boiler is a copper tube, silver soldered, proof-tested to 100lb/in2 and is pure pot. The burner has 4 x 3/16 in diameter tubes with a wick. The safety valve uses a very small silicon O ring and blows off at 35lb/sq.in. The engine is a double-acting oscillator mounted vertically in the smokebox. This is 5/16 in bore by 8mm stroke and drives the leading axle via a train of 64DP gears giving a reduction of 4:1. This allows the loco to run at a sensible speed and pull a decent load. The pot boiler supplies wet steam and, as there are no combustion gases going up the chimney, the exhaust is a plume of steam. This and the plume of steam from the safety valve, which exhausts as on the prototype out of the dome, is quite realistic, especially on a cold day outside. The dome and chimney are machined from free-cutting aluminium which is easily machined and shaped. The buffers are made from drawing pins fitted into machined brass bosses. To machine the turned parts I have a Unimat 4 lathe/drill mill. Chassis and bodywork are very similar to etched brass kit parts but you have to design them for bolted construction. Mark the metal out, cut it out and then drill and tap it. Main bolt and screw sizes are 8, 10 and 12BA: steam fittings 3/16 in x 1/4 in x 40TPI. Steam supply is via a 3/32 in dia copper pipe which starts at the top of the boiler near the centre and goes via a regulator fitted onto the rear of the boiler. The regulator is brass and has a 3/32 in diameter spindle threaded 8BA with a coned end. The entry from the boiler is 1mm diameter. The throttle lever is in the coal bunker. The steam pipe then goes down alongside the boiler, near the flame but not in it. The lubricator, which holds four or five drops of 460SAE oil, is just behind the smokebox and fitted into the steam pipe. The steam pipe then enters the mainframe of the engine and goes via a reversing block to the cylinder. Both the valve block and frame are made from free-cutting brass and the cylinder is brass with a free-cutting aluminium piston and nickel silver piston rod. The piston drives a pin in the brass flywheel. Exhaust is from the valve block into the chimney. One of the problems with small engines is that they get very hot. This causes problems with the meths supply. To overcome this the meths comes from a goods van fitted with a chick-feed supply to the engine through a silicon rubber tube. Number and nameplates are from Guilplates. Nameplates are used because this part of the engine gets very hot. The loco is mainly painted with woodburning stove spray paint. For steaming up the boiler is filled with 30cc of hot water and the fuel tank with 12cc of meths. About 3 minutes after lighting the safety valve lifts; open the throttle slightly to warm the front end, then after a few seconds open it to about 45deg, give a gentle push, and off she goes. The usual train I run is two or three goods vans plus an ACE coach which will run for 10 or 15 minutes at a scale speed of 40 to 50 mph. It will run on track with a radius down to 2ft 6in. The loco will run outside as long as it is not too windy. The ACE coaches are fitted with very coarse wheels which are very easily altered from 27.5mm back to back by machining the inside of each wheel down by 0.25mm and reducing the flange height to 1.5mm. They will then run on Peco finescale track and points. However, the wheels are not insulated. I have now built 16 steam locos in 7mm scale using direct drive down to 7.5:1. They have been fitted with both pot and C Type boilers. I would, however, recommend that for small locos without radio control that they are geared down to between 3:1 and 5:1. The reason: as shown by the ‘lounge incident’, direct drive locos can move! I built a model of a Cambrian 2-4-0T with direct drive, piston valve and C Type boiler which would not pull anything but was timed at a scale speed of over 240mile/h. This has now been rebuilt with an oscillating engine, 4:1 gears and a pot boiler, and now runs and pulls satisfactorily. I hope this short article will get the grey matter stirred and a few more of you will leave your beautifully decorated electric motors and get your fingers burnt. My current project is GER J65, No 17. |
The
author with the Highland 0-4-4 in steam on the test track by High
Lane GOG; the steam runnning track is SM32
Author’s
Caledonian Railway 0-4-0T Dock Shunter. Double acting oscillator,
4:1 gear ratio, pot boiler, fuel in van.