"Well done, our side!" shouted Tom, arriving a moment later. "That's what I call blindman's-buff on a new principle, and no mistake!"
A STEAM-ENGINE OUT OF A TIN CAN.
BY THE PROFESSOR.
Few boys seem to be aware of the entertainment they may obtain with a soldering iron, a pair of shears, and a file. With them it is easy to manufacture working models of machinery, and philosophical apparatus almost without limit. Skill in the use of the iron is readily acquired with a little practice. The quickest way to learn is to observe for a few minutes a tinman at his work. A good-natured one, politely approached, will quickly explain all the mysteries in the process, and take pleasure in filling the office of teacher. For heating the iron, a charcoal fire is generally preferred; a gas stove is also good; and even a common coal fire can be made to answer. The first point is to make a little of the melted solder stick to the point of the iron. For this purpose the iron is filed bright about the point, to remove the oxide and expose the clear metal; then the iron must be quickly applied to the solder. If the heat is sufficient, the iron will get coated, and be ready for use. The oxide has to be removed also from the surface of the material that is to be united; it is the chief obstacle to successful soldering, as the solder refuses to unite with anything but pure metal. Sal ammoniac dissolved in water is good to cleanse off the oxide; better still is muriatic acid, with a little zinc and sal ammoniac added. This is known as the soldering mixture.
One of the most convenient materials for use is common tin, which can be obtained almost everywhere. A tin box can be melted apart, and cut into any desired shape. Pipes to convey liquids, steam, or gas can be made by cutting strips of the tin, and rolling them upon an iron rod. To make a pipe, say, a quarter of an inch in diameter, get an iron rod of that size, cut a strip of the tin about one inch wide, roll it upon the rod, allowing the edges to lap a little. If the tin be not bright, make it so by applying sal ammoniac with a small brush along the seam. Put on a little powdered resin, and then solder neatly by drawing the heated iron, with the solder clinging to it, over the joint. In this way a pipe strong and tight is obtained; and such pipes can be joined to one another indefinitely, in a straight line or at any angle. To unite them in a straight line, pass the end of one into the end of the other before soldering, or else wind an additional piece of tin over the two ends. To make a turn, or elbow, file the ends on a bevel, or slant, bring them together, and apply considerable solder for strength. If the solder be rightly put on, it will hold surprisingly.
A pretty device to illustrate the force of steam is shown in the accompanying picture. The boiler is a simple tin can, which need not be more than six inches high and four in diameter. To make the wheel, cut a circle of tin two inches in diameter, and pieces for the buckets, shaped as in the diagram. Bend each piece at right angles along the dotted line, and solder them one after another on the circumference of the wheel, which will then appear as in the picture. Bore a hole through the centre, insert a piece of wire for a shaft, and solder it fast at right angles to the wheel. File shoulders on the ends of the shaft, and mount it in uprights fastened to the top of the boiler. Make a small opening through the top of the boiler, and place over it a little spout in such a position as to send a current of steam directly into the buckets of the wheel. Make also a larger opening in or near the top of the boiler, and surround it with a neck to receive a cork. Through this the water is introduced. For this purpose a small funnel will be found convenient.
When all is complete, the boiler may be filled about half full, and set on a hot stove. When the water boils, the steam will emerge through the spout, and propel the wheel. As the steam constantly escapes, no explosion need be apprehended. To remove all possibility of creating too much pressure, place the cork in the neck very lightly, so that it will pop out if more steam is generated than can escape through the spout. Then the miniature steam-engine and boiler may be regarded as harmless as a tea-kettle. As the quantity of steam that can be produced is very limited, care must be taken that there be no leaks, that the mouth of the spout be quite small, and that the current of steam be discharged accurately into the buckets. The bearings of the shaft should be oiled, and everything arranged so that there will be the least possible friction. Then the wheel may be expected to spin very rapidly.