Instantaneous Contact Area Research Articles

Supplementary Report

Abstract The leading ideas of Giese, Stein and Lauer's work may be expressed by the following statements. 1. In a rolling wheel-and-tire assembly, there are electric fields: (a) Between road and tire surface. (b) Between outside and inside tire surface. (c) Between inside tire surface and tube. (d) Between inside tire surface and rim. 2. Special attention is devoted to the so-called “inner field” between inside tire surface and tube; an attempt is made to measure and control it by suitable means. Regarding these fields it may be remarked that electrical boundary surfaces, and hence charge accumulations due to intimate contact, occur at the following points : 1. Instantaneous contact area between tire and road. 2. Points between casing and tube, especially in the flexure zone, where casing and tube may be displaced somewhat from each other. In the latter case—that of the field between casing and tube, henceforth to be called the “inner field”, the casing and tube section is to be regarded as a capacitance whose magnitude may be estimated as follows: area about 500 sq. cm., plate interval about 10−3 cm., due to elevations and depressions along casing at cords ; hence, capacitance of 5×104μμf. For very intimate contact, the plate interval may be reduced to about 10−6 cm., in which case the capacitance rises to 5×107μμf.