Page 217 - Tribology in Machine Design

202 Tribology in machine design

where Wis the load on the bearing, V is the linear speed and D is the shaft
diameter. Alternatively

where co is the angular velocity of the shaft and p = W/LD is the nominal
contact pressure on the projected area of the bearing. This will be
satisfactory, subject to the bearing material being capable of withstanding
the applied load and to the temperature of the system being kept within
acceptable limits.
In the case of a white-metal bearing lining, a permissible load on the
6 2
projected area can be assumed to be 8 x 10 N/m . Then

A reasonable temperature limitations for white metal is 120 °C, so that

where T m is the maximum temperature and T i is the inlet temperature of the
oil.
Maximum temperature, T m, having been obtained, an oil of a viscosity
equal to or above n for this temperature should be selected by reference to
Fig. 5.22, which shows a normal viscosity-temperature plot. If however the
selected oil has a viscosity greater than /* at the temperature T m further
adjustment will be necessary. Moreover, it is unlikely that a bearing will be
required to operate at a constant single speed under an unvarying load
throughout the whole of its life. In practice a machine must run up to speed
from zero, the load may vary over a wide range, and, because bearing

Figure 5.22