122 



THE WORLD'S ADVANCE 



Details of Switch Points and Connecting Lugs. 



also important that the curvature be ab 

 solutely regular, for the successful opera- 

 tion of the completed outfit depends 

 largely on the fact that the secondary 

 cores be exactly alike. In turning the 

 cores, the builder should make a tem- 

 plate of desired radius which can be 

 applied to the surface to determine if 

 the curvature is regular. 



Holes should be bored as indicated 

 with a 1/16" drill, as well as a hole along 

 a diameter with a 3/1 6" drill. Exactly 

 31 turns of No. 30 s.s.c. wire should be 

 wound on each side, making the cross- 

 over as indicated. The crossover should 

 be 90 on the circumference one-quar- 

 ter of the circumference from the 3/16" 

 hole. It is necessary that these cores 

 hold the same amount of wire, distributed 

 over the same number of turns. The 

 wires should begin and end at small bind- 

 ing posts to facilitate connecting. 



LOADING COIL : Obtain a mailing tube 

 4}4" diameter and 7" long, or make one 

 of cardboard or fiber as previously de- 

 scribed. It will probably be cheaper to 

 make the tube. Wind on 192 turns of 

 No. 22 s.c.c wire, taking taps at 6, 12, 

 1 8 turns, then every eighth turn until 

 130 turns have been put on. Next tap 

 at 142, 156, 172 turns. Wire is started 

 and taps made in a manner similar to 

 the method used for the coupler, leav- 

 ing about 8" of wire projecting beyond 

 tube. 



CONTACTS: The materials necessary 

 for making the contact points are: 



2 ft. y%" brass rod. 



50 8-32 brass screws S/&" long. 



50 washers or burrs for above screws. 



Fifty contact heads should be cut from 

 the y%" rod, 11/32" thick. This allows 

 1/32" for filing. If a bench hack saw, 

 equipped with a vise for cutting bars at 

 right angles is used, these contact heads 

 can be quickly made. Moreover, the cut 

 is smoother than when done by hand and 

 it is at right angles to the sides, thus 

 eliminating a good deal of filing. The 

 pieces should be placed flat on a rather 

 fine file, the contacts being moved and 

 not the file. They are then drilled and 

 tapped for an 8-32 machine screw, with 

 further filing to remove all burrs. The 

 contacts are then assembled on a smooth, 

 level-surfaced piece of wood. A wide 

 fine file is then used to level off the con- 

 tacts, which are then finished by using 

 the finest sand or emery paper obtain- 

 able, the special oo grade, if possible, 

 placing the sandpaper on a block of wood 

 and taking care not to round contact 

 edges, as well as to use sufficient oil. 

 After all traces of oil are removed, the 



B/odej for 4&0 

 ~/fo/es M for 4, N forB 



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Jtvifc/rfiandfe Section 



Jrcford 



Details of Switch Arms, Handles and Contact 

 Pieces. 



