The Rubber Strand Motor.—The next thing to do is to fix one end of the rubber strands to the screw-eye in the warhead and the other end to the eye of the propeller-shaft. This gives you a cheap and simple motor that is at once light, powerful, and easy to manage.
Cut out a cover of wood to fit over the groove containing the motor, as shown in D, [Fig. 37], and screw it to the body of the torpedo. Melt some paraffin wax and run it around the cracks to make the motor chamber watertight.
Bore half a dozen or more holes ½ inch in diameter and about an inch deep along the exact middle of the bottom of the torpedo; fill each hole with shot and seal them in with sealing-wax. There must be enough shot in the bottom to weight the little torpedo so that it will just sink on an even keel when you put it in the water. Finally, paint the torpedo all over with black enamel (you can buy it in drug stores for 10 cents a can), and your model torpedo is ready for its deadly work.
Your Torpedo in Action.—To set your model torpedo scooting under the water and, perchance, aimed at an enemy ship, fix the steering rudder in a line with the long axis of the hull and tilt the diving rudder at a very slight angle, say about 2 degrees, down from the top of the torpedo.
Hold the hull with your left hand and wind up the rubber strand motor good and tight by turning the propeller clockwise—that is, in the direction the hands of a clock move—with your right hand. When you have done this, push the torpedo down under the water, let go of the propeller and she will shoot forward as though shot by compressed air from a torpedo tube.
After it has made a run of from 25 to 100 feet—the distance depends on the skill you have shown in building it—it will sink to the bottom.
Of course if you are playing a naval war game and you are shooting at some enemy ship, it will give her a good hard bump, and this counts ten points in your favor.
How a Real Torpedo Is Made.—A torpedo, as you can plainly see, is nothing more nor less than a miniature submarine boat that moves under its own power and that is self-controlled. And now that you have built and experimented with a little model it will be easy for you to understand how a real one is made and works.
The Warhead of a Torpedo.—A real torpedo such as is shot by a submarine to sink real ships is made of three chief parts, as far as the outside of it is concerned. These are: (1) the warhead, (2) the body, and (3) the tail.
The warhead is the blunt-nosed hollow part that forms the business end of the torpedo; it contains two things: (a) the charge of high powered explosive which plays such terrific havoc when it is touched off; and (b) the detonating mechanism which fires it.