150 



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 



m 



^m 



•5' — 





DETAIL OF PRJN7 FRAME 



WOOD CUPS 



PLAN VIEW COVER REMOVED 

 PRIKT FRAMES 



TOP COVER COMPOSITION 60RR0 

 COMPOSITION BOARD 



-T— ■•> -^-f 



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 



