Design, Fabrication and Calibration of a Vehicle Tow Bar for Platoon Drag Measurements: A Working Report

A longitudinal stability model for a 2 vehicle platoon yields a pair of linearly coupled equations that model the dynamics of the tow bar and the vehicles. Using reasonable approximations, the vehicle separation distance obeys a second order non-linear differential equation with constant coeficients. Spring force and damping are provided by a special shock absorber link. The towbar linkage can be made to serve as a low pass mechanical system. The design spring constant of 60 1bfAn and a damping rate of 200 lbf/ft/sec yield a low-pass system with sufficient damping and a cut of frequency of 0.78 Hz. Steady state spring extensions are of the order of several inches for vehicle spacing from 0.2 to 1.0 vehicle lengths (200.24 inches).