Gradeability of log trucks

Abstract

Gradeability of log trucks is limited by either vehicle rimpull or ground-tire adhesion. The analysis presented shows that log trucks in current use in the Pacific Northwest are limited by tire-slip gradeability rather than by rimpull. Analytic techniques were used to determine that gradeability is greatest for piggyback and least for empty truck configurations. Effects of horizontal curvature and superelevation rates on truck "seen" grade were analyzed as well as road design gradient limitations. Road design criteria graphs are presented in the appendices by log truck configuration for varying curve radii, superelevation rates, and centerline gradients.