Data were obtained in the study of an 18-wheel western-type log truck outfitted with central tire inflation (cti) and carrying a highway load. Operating on grades of 20 and 25%, drive shaft torque wasmonitored to quantify stress levels on the drive train while varying tire deflection. Information is provided on the limits of additional traction to be gained through the use of tire deflection when operating on steep terrain--without excessive tire slip or vehicle maintenance. Torque levels for each grade and deflection combination arepresented. A combination of steep topography and escalating road construction costs have led to the use of shorter, steeper roads. In order to reach landings of harvesting operations with a minimum road length, spur roads are often constructed in the 20 to 25% slope range. Haul roads exist with grades of 15 to 20%. An assist vehicle is often appraised when grades exceed 16%. Using the proper tire deflection for the application (based on speed and load) appears feasible through the use of cti systems. Benefits have been seen in reduced vehicular damage to forest roads and increased tire life. An additional benefit realized with the use of cti is improved traction on some road surface types because of the increased tire tread length. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2.
Abstract