One is that it is usually too big and heavy for a child to carry to the track and lift on to the rails; secondly, it would need more skill - and probably patience ! - than the average child possesses to fire and drive the engine and operate it in the proper manner.
Now a few sympathetic "dads" who remember the time when they were children themselves have suggested at various times that I should give a brief description of a small locomotive which any child could operate, and which would be simple and cheap to build. Jack and Jill could then enjoy themselves to their hearts‘ content; and if there should be a pitch-in, children being what they are, repairs or even replacements would be easy and inexpensive. With our editor‘s permission I am glad to oblige.
Casting memory back over the years, I recollect a small single wheeler that I built when I was still at school. Her frames and superstructure were made from stout tin and the wheels were light brass castings. The cylinders were made from brass tube. The boiler was a long tin canister fired by four spirit burners mounted on a tube and supplied with spirit from a reservoir under the cab.
She had a six-wheeled tender which was merely an ornament and carried neither fuel nor water ; actually she did not need it, as she would run about 40 min. with the water in the boiler and the spirit in the tank. She could go all right, and could pull several coaches. As the wheels were given to me, and the cylinders were homemade, she cost me nothing, but she gave me much pleasure. Incidentally, this was the engine on which I tried my successful remote-control experiments.
The locomotive shown in the accompanying drawings is a modernised version of the same kind of engine. The frames are 16-gauge steel or brass, and the buffer and drag beams are brass angle. The wheels are light castings and the axles run in bushed holes in the frame. The cylinders arc built up from brass tube as before, but better fitted. They are of the single-acting oscillating type, and are reversed by a simple valve operated from the cab.
As the children will need to operate the engine outdoors, a "pot" boiler with open spirit flames underneath would be useless, as the slightest puff of wind would deflect them from under the boiler and steam would fail at once. I have, therefore, substituted a simple water-tube boiler of the usual type. The boiler itself is a piece of thin copper tube mounted on a 16-gauge copper backhead, the front end being closed by a flanged disc of 16-gauge copper; two water-tubes are fitted. The casing can be made up from thin sheet iron or steel, but if a tin can of required length is available it will do just as well if lined with 1/16 in. asbestos millboard.
Fittings consist simply of a safety valve, screw down valves for regulator and blower, and a valve or cock for testing water-level when filling. Any shape of cab, chimney, etc., can be substituted for those shown, to suit builder‘s or children‘s wishes.
I have kept the whole bag of tricks as small and light as possible to make her easy for the children to carry and handle, and also to keep cost and labour to the minimum. As shown, she is arranged for a 2½-in. gauge line, but can be adapted for 3½ in. gauge by making all the parts half as large again.