Page 164 - Tribology in Machine Design

150 Tribology in machine design

rotate the front axle about a vertical axis will be instantaneously produced,
resulting in unsteady steering action. This explains the importance of equal
distribution of braking torque between the two wheels of a pair.

Brakes applied to rear wheels only
When L 2 =0, eqns (4.157)^(4.159) become

from which

These results correspond with eqns (4.145) and (4.146) for driving
conditions.

The maximum retardation
In this case limiting friction is reached on the rear wheels only, so that
Fi =/Ri and, applying eqn (4.168),

where

Again, writing W=Mg, eqn (4.164) may be written as

and, eliminating F^ and F 2 from eqn (4.173)

maximum retardation =

4.13. Tractive In the foregoing treatment of driving and braking, the effects of friction in
resistance the bearings were neglected. However, friction in the wheel bearings and in
the transmission gearing directly connected to the driving wheels is always
present and acts as a braking torque. Therefore, for a vehicle running freely
on a level road with the power cut off, the retardation is given by eqn
(4.160), where Lj and L 2 may be regarded as the friction torques at the rear