The flywheel is a circular piece of brass 1 inch in diameter. Its center is drilled out and it is soldered to the crank as illustrated in [Fig. 54]. Two other holes 1/8 inch in diameter are drilled in the flywheel as illustrated, and two small brass pins are cut out from 1/8-inch brass rod and forced into these holes and then soldered. These provide a method of driving the propeller-shaft that is shown very clearly at [Fig. 57].
The steam feed-pipe that runs from the boiler to the engine can be of small copper tubing. It may be necessary to mount the engine on a small block, as shown in [Fig. 53]. After the steam in the boiler has reached a sufficient pressure the engine crank should be given a couple of twists in order to start it. Before operating the engine a little lubricating oil should be run into the cylinder through the inlet or exhaust ports. The cylinder should always be kept well lubricated. The contacting faces of the cylinder blocks should also be kept lubricated.
Caution. Always keep water in the boiler. Never permit it to run dry, as this would cause a boiler explosion. When the engine is started and cannot be made to run, take the burner from under the boiler so that steam will cease to be generated. With the safety-valve the model boat builder need have little fear of an explosion. Nevertheless the foregoing directions should be carefully adhered to.
CHAPTER V
AN ELECTRIC LAUNCH
THE little electric launch to be described is of very simple construction, and when finished it will provide the builder with a very shipshape little model from which he will be able to derive a good deal of pleasure. It has a speed of from 21/2 to 3 miles an hour when equipped with dry batteries or storage batteries. The hull is of the Sharpie type, and this offers very little trouble in cutting out and assembling.
The general appearance of the boat and hull will be gathered from the drawings. The pieces necessary to assemble the hull are shown in [Fig. 58]. Only five pieces are necessary: two side pieces, a stern piece, a bow piece, and a bottom piece. The length of the boat over all is 40 inches with a 7-inch beam. The widest part of the boat is 1 foot 10 inches from the bow.
After the pieces that form the hull are cut they are thoroughly sandpapered to produce a smooth surface. The heavy imperfections in the wood can be taken out with coarse paper, and the finishing can be done with a finer paper. It is understood that sandpapering should always be done with the grain, never across the grain. The sides of the boat are cut about 1/4 inch thick, but they are planed thinner in places where the bend is most pronounced. The side pieces are 23/4 inches deep at the stern and 21/4 inches at the stern. There is a gradual curve from the bow to the stern, which is more marked toward the head.