Page:Popular Science Monthly Volume 88.djvu/816

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��Popular Science Monthly

��How to Make an Electric Horn

ANYBODY having a little mechani- . cal ability can make a very satis- factory electric horn from a couple of coils and a few odds and ends.

In the accompanying diagram, the electromagnets and horn are fastened to a continuous piece of band iron, which in turn is screwed to a wooden base. On the end of the band iron over the electromagnets is fastened a piece of heavy clock-spring. This serves as a vibrator or armature. At the free end ' of the spring a hole is drilled, through which is screwed a heavy stove bolt, which acts as a striker. A small strip of strap iron is screwed into the base, bent over the vibrator, and drilled to hold a 'set-screw, which is merely a small bolt with a nut on both sides of the iron. This is the interrupter. It also controls the pitch of the horn.

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��A practical electric horn which was made from odds and ends

The mouth of the horn is cut from a piece of tin and soldered to the bottom part of an old machine-oil can, the flexible base acting as a diaphragm when set in vibration by the striker.

The electricity runs through this horn in exactly the same circuit as in a door-bell. When connected up and the button is pressed, the vibrator is drawn to the coils and the circuit broken by the interrupter, causing the striker to move back and forth. The less room given for movement by the interrupter, the higher the pitch of the horn.

The vibrator, being made from a spring, lends still more force to the vibrations.

��This horn may be worked on the house-lighting circuit by connecting in series with an incandescent light, or it may be run by batteries.

It can be used for many purposes, being especially good for a burglar alarm. — Ed, Gettins.

Making Coils of Resistance Wire for a Small Electric Stove

RESISTANCE wire may be easily wound in coils for a small electric stove by means of a hand drill. Place

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��Support for Spool

of Resistance

Wire

��Resistance coils can be wound evenly by

means of a hand drill fastened securely in

a vise during winding

the drill in a horizontal position between the jaws of a small vise. Insert a rod of about 3^-in. diameter in the chuck oi the drill; an old curtain rod will do. Make a support for the spool, as shown in the illustration. Then, by turning the handle of the drill with the left hand and guiding the wire with the right hand, the wire will come off very easily without becoming tangled.

With about i8 ft. of No. 30 nichrome wire, a small electric stove will con- sume practically 100 watts of electrical energy. — Frank Hiemer, Jr.

Repairing a Burnt-Out Fuse

A BURNT-OUT fuse may be easily repaired with the aid of a little solder. Substitute for the old fuse wire a new one of the same capacity. Solder a length of copper wire to each end of the fuse wire (Fig. 3), and after cleaning

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��A bumt-out fuse can be made as good as new at very small cost

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