984 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1953 



1. Eliminate slack in gear train by introduction of loaded gear drive. 



2. Provide a constant force spring load on the worm drive so that the 

 distributor exactly follows the cam motion. 



3. Miniaturize wire guide assembly so that wire as placed on winding 

 core will more closely follow the distributor motion. 



4. Improve spindle bearings and distributor alignment. 



5. Provide improved shut-off counter so that machine will give exact 

 winding turns without overrun. 



Although it might appear from the above discussion that winding 

 coils on a controlled pitch basis will automatically result in the product 

 having a normal distribution around a specified nominal inductance, the 

 desired result can only be attained by continued vigilance, as many un- 

 predictable variations will creep into the process from time to time. 

 Gradual changes in control are readily observed from the charts, and in 



Fig. 8 — A shadowgraph of a coil winding showing uniformity of winding nec- 

 essary to meet distribution requirements for inductance. 



many cases, are enough indication to show need of replacement or repair 

 of worn winding-machine members which control the winding pitch of 

 the coil. 



The 320-type retardation coil used in the cosine equalizer of the L3 

 system, requires all of the control vigilance of the splitting coil and, in 

 addition, has introduced the necessity for even further winding precau- 

 tions. Although this coil has the same per cent tolerance as some of the 

 other coils manufactured under this specification, it is more difficult to 

 control, since it has only about one-tenth as many turns in the mnding 

 as most of the other coils. The major inductance variations in this coil, 

 therefore, are controlled by the variation in the end turn location and 

 the winder checks the inductance by a continuous sampling of the 

 product during the winding procedure. It is thus possible to promptly 

 make necessary modifications in the location of the final turn to main- 

 tain the inductance distribution within requirements. Experience has 

 shown that normal variations from operator to operator can run as high 

 as H per cent on coils having a tolerance of 1 per cent, until the operator 



