Next take a piece of brass tubing five-eighths of an inch in diameter, and turn a screw at each end inside ([Fig. 16]). The screws turned on the outside of the cones must be the correct size to fit these; then drill a hole at A, and screw in a small tube for water-supply with tap; then drill another at B for the waste water to escape by. Finally, screw in the cone A ([Fig. 15]) and attach it to the boiler by a pipe, and the nearer the boiler the better, as if the steam condenses before reaching the injector it will stop working. The steam-pipe must of course have a tap to cut off steam when not required.
We must now screw in the lower cone B ([Fig. 15]) until there is an annular space between the two cones not exceeding a sixteenth of an inch. Then screw in the small pipe at C ([Fig. 15]), and attach the other end into the boiler below the water-line, where it must have a stop-valve to prevent the water returning.
To start the injector, turn on the water-tap until it runs out of the overflow freely. Then turn on the steam full power, and the overflow will cease, or nearly so. Should it still drip at the overflow, reduce the water supply by the tap accordingly.
It requires carefulness and patience to make an injector, but when done, and working properly, there are few boys with a mechanical turn of mind who would not think themselves well repaid in watching and controlling its mimic action. They would then have an engine fit to show to their most critical friends, and one they might well be proud of; and I shall be content if I have helped in any way to contribute to their happiness.
CHAPTER XI.—THE BOY’S OWN MODEL LOCOMOTIVE, AND HOW TO BUILD IT.
By H. F. Hobden.
CHAPTER XI.—THE BOY’S OWN MODEL LOCOMOTIVE, AND HOW TO BUILD IT.
By H. F. Hobden.
