Page 264 - The Tribology Handbook

Oil flinger rings and drain grooves B21

Oil issuing from a bearing as end leakage will travel along Where shafts must operate at any speed within a speed
a shaft for a finite distance before centrifugal dispersal of range, flingers should be designed by the foregoing me-
the film takes place. Many clearance seals will permit oil thods using the minimum range speed.
leakage fkom the bearing housing if they are situated Where shafts are further wetted by oil splash and where
within the shaft oil-film regime. Flinger rings and drain oil can drain down the inside walls of the bearing housing
grooves can prevent the oil reaching the seal. on to the thrower itself, larger thrower diameters than
given by equation (1) are frequently employed. Figure
2 1.2 gives a guide to ‘safe’ thrower proportions to meet this
GENERAL PROPORTIONS condition.
The natural dikpersal length ofthe oil film along the shaft
varies with the diameter and the speed as shown in Figure
21.1. 1.4 0 100 200 300 400

1.3

1.2
210
1.1
4 1.0 ‘ , I
I
1
150
0 50 100 I I 200 250
rev/s
(751 rnm
3
Figure 21.2
.-
-
c
_I
2 TYPICAL THROWERS
Scale details of some well-proven throwers are given in
Figures 21.3, 21.4 and 21.5. Relevant values of Do/D for
the originals are given in each case. The application of
each type may be assessed from Figure 21.2.

0
Figure 21.1

Notation:
L, = natural dispersal length of oil film-in (mm)
L, = distance of oil thrower from end of bearing-in
(mm)
D = shaft diameter-in (mm) Figure 21.3 Throwers for slow/medium speeds
Do = outside diameter of oil thrower-in (mm)
N = shaft speed--rev/min (rev/s) These are simple throwers of the slip-on type. Mild steel is
the usual thrower material while a self-lubricating ma-
Using the value of L, corresponding to the design value
of ND3 in Figure 2 1.1, the oil thrower diameter should be terial such as leaded bronze is preferred for the split
housing.
derived from:
Note:
Do =
1. The drain groove from the annulus in (a) and the drain
hole in (b).
where C has the value 2. The chamfer at the outer periphery of the (b) split
housing to drain away oil washing down the walls of the
30 X IO6 for inch rev/min units. bearing housing.
and 136 X IO6 for millimetre, rev/s units. 3. The chamfer at the back of the main thrower of (b) and
the mating chamfer on the housing.
In general, high-speed shafts require small throwers and
low-speed shafts require large ones, particularly if the The above features are also common to the other types
thrower is close to the bearing. shown in Figures 2 1.4 and 2 1.5.
B21.1