Brake force of tracked vehicles

Abstract

It is commonly supposed that the slowing down and stopping of vehicle is caused by adhesion of its tracks to the dirt surface. However, force analysis shows that, although these forces play an important role during braking, the longitudinal components of the internal forces applied to the shafts of the vehicle’s braked drive wheels and the front support rollers of the tracked propulsion are directly responsible for its deceleration. The sum of these longitudinal forces directed against the motion of the tracked vehicle constitutes the braking force of the tracked vehicle. The value of this total braking force is ultimately determined by the ratio of the braking torque developed by the friction forces to the radius of the drive wheels with which the braking devices are coupled. Since when braking a tracked vehicle, the longitudinal reaction is balanced, it cannot be the direct cause of the deceleration of the vehicle, i.e. its braking force. In addition, the longitudinal reaction applied to the lower fixed part of the track does not perform mechanical work and cannot absorb the kinetic energy of a moving vehicle. This work is performed by the internal braking force Ртор, which develops negative (braking) power during braking. It turns out that during braking, the longitudinal reaction is needed not at all to cause a slowdown, but as an external force, to balance some of the internal forces of the tracked vehicle. As a result of its action, the unbalanced part of the internal forces forms the internal braking force, which directly causes the machine to slow down and stop. In this case, the longitudinal reaction of the supporting surface, without which the formation of an internal braking force is not possible, limits both the lower and upper values of the latter, and these forces themselves are numerically equal. The fact that the braking force of a tracked vehicle, like its traction force, is an internal force, does not contradict theorems on the movement of the center of mass or the change in the amount of motion of a mechanical system, which are valid only for isolated mechanical systems that do not have a source of active internal forces.