Boys' Book of Model Boats

by Raymond F. Yates

A little safety-valve and filler-plug suitable for use on the boiler are shown clearly in [Fig. 78]. A piece of sheet tin is cut out to the size and shape illustrated in [Fig. 79] at A. The piece is bent up at the dotted lines and the seams are soldered. Two angle-plates, B, are then cut and fitted and soldered in place. Next a piece of brass tube with a ¹/₈-inch bore and 1 inch long is cut and soldered in place for the bearing of the crankshaft. A lead flywheel 1¹/₄ inches in diameter and ¹/₂ inch thick is then mounted firmly on a piece of straight steel wire 1³/₄ inches long, which acts as a shaft.

The shaft is made to run freely in the crankshaft bearing that was previously soldered in place. The cylinder is shown in section in [Fig. 80]. If the reader will refer back to the construction of the engine described in Chapter 4 he will readily understand the operation and construction of this particular engine.

A little crank must be cut from ¹/₁₆-inch brass, and soldered to the crankshaft after fitting a wire crank-pin to the outer edge. This crank-pin should be of such a size that the joint on the end of the piston-rod shown at A, [Fig. 80], turns on it easily. The throw should be only half the stroke of the engine, which is ³/₈ of an inch.

The boiler is now fixed in place by bending the lugs B, [Fig. 79], so that they just support the boiler nicely. They are then soldered in place. Next fit the short steam-pipe K between the boiler and the steam block on the cylinder. The builder should take care to keep the steam-pipe well up to the top of the boiler.

The lamp should be built at this time. The container for the denatured alcohol is made from a well soldered tin box of suitable size. It can also be made by cutting a sheet of tin to the size and shape shown in [Fig. 81]. The corner joints are soldered and then a tin lid is soldered in place. The builder should not forget to make the filler-tube E and air-tube D, as shown in [Fig. 77], before soldering the top piece in place. The burners should be made as high as the container, and these should be made from little pieces of tin bent to shape and soldered on to a bottom pipe, as shown in [Fig. 77]. The builder should also remember to cut the holes through this pipe so that the alcohol can get into the burner-tubes, and also to solder the open end of the bottom or feed tube. Before the wicks are put into the lamps, the container should be tested by filling it with alcohol to see that it is perfectly tight at all joints. If it is not the container should be gone over again with solder to assure its being leak-proof.

Before operating the engine with steam, it can be tested with a small bicycle pump through the opening for the safety-valve. The engine should turn over briskly at every stroke of the pump, providing it does not come to rest at "dead center." If it does come to rest at "dead center," where no air can enter the piston, the crankshaft should be given a little twist and the engine will then start. Before steam is applied it will be well to experiment until the engine runs with the air-pump.

Having made the engine run smoothly with air, steam can be generated in the boiler. The wicks should not be placed too tightly in the burners. After they are in place the container may be filled with denatured alcohol, and the burners lighted and placed under the boiler. In a very few minutes steam will be up. At the first indication of pressure in the boiler the engine should be given a twist with the fingers until it starts and goes of its own accord. The constructor should remember to keep his engine well lubricated.

The propeller-shaft is merely a piece of steel wire, perfectly straight and fitted with a crank A, [Fig. 82]. This crank is similar to the one fitted to the engine, but with a small slot cut out for the crank-pin to fit into. This is done so that, as the crank-pin on the engine turns around, it also turns a slotted crank on the propeller-shaft.