NASA-TN-4109

Abstract

The low-speed (up to 4 miles per hour) yawed-rolling characteristics of two 40 x 12, 14-ply-rating, type VII aircraft tires under straight-yawed rolling were determined over a range of inflation pressures and yaw angles for two vertical loadings. One load was approximately equal to the rated vertical load and the other load was approximately equal to twice the rated vertical load for these tires. Static tests were also performed to determine the vertical, lateral, torsional, and fore-and-aft elastic characteristics of the tires. The quantities measured or determined included lateral or cornering force, drag force, twisting moment or self-alining torque, pneumatic caster, vertical tire deflection, lateral tire distortion, wheel twist or yaw angle, rolling radius, and relaxation length. Some supplementary tests which included measurements of tire footprint area and the variation of unloaded tire radius and width with inflation pressure were made. <br>During straight-yawed rolling the normal force generally increased with increasing yaw angle within the test range. The pneumatic caster tended to decrease with increasing yaw angle. The sliding-drag coefficient of friction tended to decrease with increasing bearing pressure. <br>Measured decrease with lateral and torsional spring constants appeared to decrease with increasing amplitude of tire lateral distortion or twist, respectively.