Popular Science Monthly 



959 



these machine screws are filed down, so that 

 they can be easily put in place and will rest 

 flush with the surface of the plates. 



From a strip of soSt brass 1/16 by 

 5/16 in., two i-in., and two 2-in. lengths are 

 cut. The ends of these, which should be 

 cut squarely, should now be bent over, the 

 short pieces once, and the long twice, to the 

 extent of ^-in., and M-in. holes drilled in 

 the center of each little square hill thus 

 formed. Now 3^-in. holes should be drilled 

 near the flat ends of the long strips, and 

 countersunk on the sides opposite the hills. 



A short brass strip should now be 

 slipped on the short end of each rotary 

 plate shaft, and a long strip on each long 

 end, hills facing up as in H and /. These 

 pieces can be slipped into the channels in 

 the pieces of fiber as shown, and then ad- 

 justed by moving them in and out, as well 

 as from side to side, till the rotary plates 

 line up well enough to be swung into 

 position between the fixed plates. The 

 flat headed binding-post bolts can now be 

 inserted in the holes in the ends of the long 

 bearing strips. 



The shafts for the rotary plates should be 

 sawed off so as to extend 3^-in. beyond the 

 top bearings, and the metal bushings on the 

 composition knobs drilled with the M-in. 

 drill to a depth of ^-in., unless they 

 already fit the shafts, as in the case of those 

 bought by the author. Those knobs should 

 now be placed on the shafts and adjusted to 

 such a position that the fixed and movable 

 plates will, when the knob bushings rest on 

 the top bearings, be equally separated from 

 each other, when in the full capacity 

 position. 



Now tighten the set screws in the knob 

 bushings and adjust the upper and lower 

 bearings little by little, until the centers of 

 the fixed and rotary plates lie as near as 

 possible in one straight line, without causing 

 any of the plates to touch. When the best 

 adjustment possible has been obtained, the 

 nuts on the small machine screws holding 

 the fiber blocks should be turned up tight, 

 and the ends of the lower sets of screws 

 sawed off flush with the nuts. In case a 

 few plates still touch slightly in one spot or 

 another, they can be bent a little by hand, 

 by pressing with th^ thumb-nail. All of 

 the plates should swing in one direction 

 without touching. The strip bearings 

 should not come in contact with the fiber- 

 support bolts. 



The two phonograph records should now 

 be marked with a compass on the smooth 



side for 3^-in. circles, which can be cut 

 from them by following the lines with a 

 pair of tin-cutters, or, if thick records are to 

 be cut, with a hack-saw. The edges of the 

 small disks formed should be made smooth 

 with sandpaper. 



The center holes in these disks can now 

 be enlarged to accommodate the knob 

 bushings, and three 3^-in. holes can be 

 drilled in each disk to correspond in posi- 

 tion with the small machine screws passing 

 through the fiber-bearing supports, and 

 also through the ends of the top bearings. 

 Similar holes should also be drilled ^ in. 

 from the edges of the composition tops in 

 line with the center and bearing-end holes. 



With the knobs removed, the condenser 



Two phonograph disk records are marked with 

 a compass and placed on top of the condenser 



tops are now temporarily fitted to the 

 condensers. Using the holes nearest the 

 edges as guides, drill 3^-in. holes in the lead 

 castings till the brass plates are struck. 

 The bottom screws from a set of binding 

 posts should now have their heads removed, 

 and be screwed into these holes in the lead, 

 making their own thread. They should 

 then be fitted with a pile of small brass 

 washers, equal in height to the top part of 

 the nuts on the bolts passing through the 

 fiber. 



To complete the condenser units the tops 

 should now be fastened on, smooth sides up, 

 and held in place by nuts on the two center 

 bolts on each unit and on the two binding 

 posts, as shown at /. The composition 

 knobs can now be properly placed on the 

 shafts and held in position by tightening 

 the set screws in the bushings. 



Suitable scales, pointers and stops can be 

 supplied to please the fancy of the individ- 

 ual. The instruments are then ready to be 

 mounted in the most convenient manner. 



