A linear mathematical model is developed for studying the directional response and yaw stability of many-axled, multi-articulated tanker trucks. Analytical results provide an understanding of the factors leading to unstable lateral responses of double tankers when only the rear compartment of the rear (pup) trailer is loaded, and the likelihood of rollover of the pup trailer in obstacle-avoidance manoeuvres on the highway. It is indicated that the double tanker configuration corresponding to the "Michigan double-bottom tanker" (shown in a Highway Safety Research Institute study to have a peculiarly low level of rollover immunity) has a lightly damped mode of pup trailer oscillation resulting in instability at highway speeds when the rear of the pup trailer is loaded and its other compartments are empty. Also, the lateral acceleration of the pup trailer of the Michigan double tanker exceeds that of the tractor in obstacle-avoidance maneuvers at highway speeds. Modification of the vehicle by making rigid the connection at the pintle hook greatly reduces the tendency for such pup trailer lateral accelerations. Careful evaluation of the steering response of multi-articulated highway trains must be made in order to develop vehicle configurations with satisfactory directional response. It is claimed that the present analysis provides valuable assistance in deciding among various approaches for developing vehicles of appropriate size and weight in order to deliver flammable liquids safely and economically.
Samenvatting