Abstract :
Using as a basis the previous papers by Simon on the subject of progressive and ordinary universal coils, their theory is extended to improve the accuracy by taking additional factors into account. The present paper offers a more thorough treatment of the subject by deriving accurate results, and by employing theoretical expressions to replace previously required empirical rules. In addition, due to a certain convenient change of definition, equations are derived for practical use which are considerably simpler and, at the same time, more accurate than those given by Simon. It is shown that the proper number of throws of wire per coil revolution is a function of the coefficient of friction between the surface of the coil form and the insulation of the wire. To avoid confusion, the symbols used by Simon are also used here, and for the sake of completeness and a minimum of cross reference, the entire analysis is presented, including the derivation of formulas for the rate of progression and the gear ratio. A brief description of the geometry of the winding is included, and, finally, a section is devoted to an outline and discussion of practical design procedure.
