Page:Popular Science Monthly Volume 92.djvu/166

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��Popular Science Monthly

��Making an Electrically Heated Blue-Print Dryer

AT times atmospheric conditions make i, drying of blue prints very slow, and when it is necessary to hurry up such work some means of drying by heat must be employed. The illustration shows an electrically heated chamber for the purpose. The dryer inclosure consists of composition board applied to a light frame of wood 2 in. square, of the dimen- sions given.

The top piece of the box is perforated to cause a circulation of air. A wire A is stretched from corner to corner on both upper ends of the sides to provide a sup- port for the dryer frames. These frames are constructed as shown at B. The frames are built of furring strips and cheesecloth, drawn tightly and tacked to one side to make a surface having con- siderable absorption. As many of these frames may be used as may be required for the inclosed space.

At the base of the inclosure two racks are made to hold two 250-watt heating lamps. Metal or asbestos should be used

��in the notches to avoid the possibility of the heat from the lamps burning the wood. Over-drying should also be guarded against. — J. E. Cahill, Jr.

��How to Insulate the Ends of Chair Posts

A CHAIR that is provided with insula- tion against electrical surges is in- valuable for safety and efficiency in electrical operations, such as wiring, telegraphy, or high frequency work. Most chairs may be very easily adapted to such a use.

Four large common green glass insu- lators, such as are used on the crosstrees of telegraph poles, should be obtained. The four feet of the chair should be made to fit tightly into the holes of the insulators.

Since the hole in the bottom of the insulator is threaded, the insulator should be twisted on with a rotary motion. Be- sides insulating the chair, these insulators will serve in the place of domes for the legs of the chair. — Joseph Braff.

��WIRt A, PRINT FRAMES L I

��{holes for CIRCUUTION

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�� ��DETAIL OF PRJN7 FRAME

��WOOD CUPS

��PLAN VIEW COVER REMOVED PRIKT FRAMES

��TOP COVER COMPOSITION 60RR0 COMPOSITION BOARD

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��EYE HOOK TO FIT OVER WIRE

��fl-2 FURRING STRIP

����CHEESE CLOTH COVERING

��1- 250 V^ATT iM'WOD HEAT LAMPS

��DETAIL Of RACK FOR LAMP

��A drying box made of composition board with frames covered with cheesecloth on which blue prints may be hung over electric heating lamps and dried quickly

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