8. (a) Derive Petroff's equation from fundamentals.
(0) A radial hydrodynamic bearing has the following operational data:
i.Radial load = 3.5 kN ii Joumal diameter = 50 mm iiiBearing length
= 50 mm iv Journal speed = 1500 rpm v Radial clearance = 0.05
mm vi Viscosity, mass density and specific heat = 25 cp, 900 kg/m?
and 1700 J/kg °c.
Total oil flow is sufficient to carry the heat generated. Determine the following
parameters.
a. Coefficient of friction
b. Power lost in friction
c.Minimum oil film thickness d.Oil flow requirement and
e. Rise in bearing temperature.
9. A 305 work cycle consists of the following two parts:

Part | Part 11
Duration (s) 10 20
Radial load (KN) 45 15
Axial load (KN) 12.5 6.25
Speed (rpm) 720 1440

For this application the static and dynamic load capacities of a single row deep
groove ball bearing are 50 and 68KN respectively. Calculate the life of the bearing
in hours.

(2 x12 = 24 Marks)