788 



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 



Bench 



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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Fi^ 3 



A bumt-out fuse can be made as good as 

 new at very small cost 



