Page 156 - Tribology in Machine Design

142 Tribology in machine design

Using this value of /? the equation for R becomes

For the retarding couple we have

and substituting for k in terms of R this reduces to

In all three cases, as the angle \l/ becomes small, the radius of the friction
circle approaches the value

and the torque

This corresponds to the flat block and the wheel rim. In the general case we
may write

where/' is the virtual coefficient of friction as already applied to friction in
journal bearings.
Thus