Page:Popular Science Monthly Volume 91.djvu/323

 �q Amateur - Electrician

��-And Wireless Operator

���A Quick Action Electric Switch for Photographers' Use

IN doing some work around my dark room I felt the need of an electric switch which would work more swift- ly and easily than those sold by sup- ply houses. The illustration shows a single pole switch that met my demands for something delicate and in- stantaneous in action and it was constructed quickly. The base A was made of well shellacked wood 4 in. long 2 in. wide and 1 in. thick. The hinges B fasten the block C to the base block A. The block C is about 23^2 in- long an d about 1% in. wide. A handle D is fastened with screws to the piece C. The two terminals E consist of brass screws and washers on pieces of bronze or copper. Across the face of the block C is a strip of bronze tacked in place with small brads. Closing the block C brings the strip of bronze in contact with the terminals E which com- pletes the circuit. — Virgil R. Tharp.

��A quick acting single pole single throw electric switch

��Making an Electric Searchlight for a Motor-Boat

A RELIABLE searchlight is a necessity for motor-boating at night, especially in crowded waters. The searchlight illus- trated is for use on small craft not equipped with a generator and is operated indepen- dently of the ignition batteries.

For the light unit, purchase one of the hand lanterns that operate on one dry cell. Many types are on the market, but for this use it is necessary to select one with a large reflector. Procure a tin can into which

��the reflector of this lamp will snugly fit. To this can rivet a swivel arrangement, as shown. It is made from 3^-in. nickeled pipe fittings and it consists of a flange, tee-joint, two ells with flanges and three short lengths of pipe. The flange is riveted to the side of the can and a hole is punched in the can so that the wires which come up through the piping may pass through.

The reflector and lamp are connected with the wires, a switch on the back of the can forms a handle to move the search- light, and the reflector is soldered into place. The flanges on the ells are screwed to the deck and a hole is bored under one to pass the wires through. The wires should be well taped to prevent abrasion and a short circuit.

The battery for this light consists of two or three dry cells connected in parallel. The cells should be placed in a wood or pasteboard box, connected, then com- pletely covered with melted pitch or paraf- fin. This effectively prevents short circuits and prolongs the life of the cells by her- metically sealing them. The wiring be-

��LOOSE THREADS ALLOW TURN- ING OF LAMP

���An electric searchlight for a motor-boat wherein only dry cells of battery are used

tween the batteries and light should be rubber-insulated.

The light thrown is very powerful. If three batteries are used they will usually last a whole season. This is due to their parallel connection, which splits the load and lengthens the life. The light on a whole is neat and serviceable. A good

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