136 



THE WORLD'S ADVANCE 



Fig. 5 



Different Members of the Hot Wire Ammeter Movement, as Well as a Side View of the Movement 



When Assembled. 



the styles shown at D and one similar 

 to that shown at E are required. The 

 two D pieces are made from ^x 1/16- 

 inch brass strip drilled and tapped as 

 shown, while the piece E is made from 

 a ^4 -inch piece of 24 -inch diameter 

 round brass rod. The details of the 

 fibre knob for the adjusting screw are 



Details of the Binding Posts and Insulated Bushings. 



shown at F, while the adjusting screw is 

 illustrated at G. 



In Fig. 3 the reader will find the de- 

 tails of the movement. The part B, 

 which holds the pointer, is made from a 

 piece of J4-inch rod which is turned to 

 the shape indicated in the drawing. The 

 pointer is fitted into a radial hole on one 

 side while a small counter weight W is 

 fitted in the opposite side. The spiral 



hair spring which carries the pointer 

 across the scale is made from a piece of 

 thin phosphor bronze sheet, or, if the 

 builder happens to have one handy, he 

 may employ the steel hair spring from 

 an old alarm clock. The spring should 

 be very light and it should be put on 

 counter clock-wise. The steel center or 

 pivot D is made from a piece of 1/16- 

 inch drill rod or a phonograph needle 

 pointed on each end and hardened. 



The main support shown at E is made 

 from a piece of 3/g-inch round brass 

 turned-down and threaded as shown. 

 The small hole is to take a screw which 

 fastens the end of a spring used to ro- 

 tate the entire movement clock-wise. The 

 piece which holds the movement F is 

 made from a piece of brass bar, drilled 

 and bent as shown in the illustration. 

 On the lower arm of this piece there 

 should be fastened a small piece of brass 

 upon which the adjusting screw may 

 bear. The addition of a small projec- 

 tion M to which the end of the spiral 

 spring is attached completes the holder 

 for the movement. The assembly of the 

 movement is shown in Fig. 3 in the com- 

 pleted view. After the movement has 

 been assembled, the balancing weight W 

 should be adjusted until the pointer will 

 rest at a given point regardless of the po- 

 sition of the meter case. 



The hot wire for an instrument to be} 

 used in connection with a I K. W. outfit 



