II.—A Simple Toy Engine.
The most simple form of toy engine is that [illustrated] herewith. It consists of a tin boiler, a single-action oscillating cylinder, and a fly-wheel. These parts are sold ready for putting together at a very low price, and a complete engine may be bought for a couple of shillings, though one of ‘superior make’ at twice that sum is by far a preferable investment.
Fig. 1.
Fig. 2.
The [drawing] represents the most simple way of constructing a steam-engine, and, if the workmanship is fairly good, a working model will be produced. First is the boiler; a tin box 13⁄4 in. deep and 2 in. in diameter, will serve for this. The joint at the side should be made by folding the edges of metal over each other, and then soldering. The top and bottom are both soldered on their respective places, steam-tight, of course. The top of the boiler must be provided with small bosses of metal, soldered on the inner side, into which the pillar ([Fig. 3]) and the safety-valve ([Fig. 5]) are screwed.
The tin plate is not sufficiently thick to afford a hold for the thread on the pillar and valve. A disc of brass, say the size of a sixpence, and 1⁄8 in. thick, is soldered on the under side of the lid, and the holes, which are tapped to receive the pillar and valve, are bored and threaded before the lid is fixed. By this means a strong hold is secured for the fittings. The screw plug A ([Fig. 1]) is similarly provided for. When each piece is screwed into its place a little hemp or cotton, placed between the shoulder of the ‘fitting’ and the surface of the tin plate, will assist to ensure a steam-tight joint.
The standard or pillar is brass, about 2 in. long from end to end. Any form may be given to it, according to fancy, the one shown in [Fig. 2] being perhaps as good as any. The lower part is circular, 1⁄2 in. in diameter, and it has a flat face on one side, against which the valve face of the cylinder works. [Fig. 3] shows this. The centre of the pillar is bored up in the middle of the screwed part to meet one of the holes a b, it is immaterial which. The other hole is bored right through the pillar to the opposite side, and forms the exhaust port, the one communicating with the central hole in the pillar being the steam port. For the sake of distinction we will suppose that a is bored into the central hole, and b is bored through the pillar; then, when the pillar is screwed on to the boiler, and steam is generated, it issues from the port hole a.