T-226
3. Proper quantity of grease.
There must be sufficient grease to do the job. However, too much grease can be
harmful, particularly in an enclosed system. Excess grease will cause agitation, viscous
drag and result in power loss.
20.1.2 Splash Lubrication
Splash lubrication is used with an enclosed system. The rotating gears splash lubricant
onto the gear system and bearings. It needs at least 3 m/s tangential speed to be
effective. However, splash lubrication has several problems, two of them being oil level
and temperature limitation.
1. Oil level.
There will be excessive agitation loss if the oil level is too high. On the other hand,
there will not be effective lubrication or ability to cool the gears if the level is too low.
Table 20-2 shows guide lines for proper oil level. Also, the oil level during operation must
be monitored, as contrasted with the static level, in that the oil level will drop when the
gears are in motion. This problem may be countered by raising the static level of lubricant
or installing an oil pan.
2. Temperature limitation.
The temperature of a gear system may rise because of friction loss due to gears,
bearings and lubricant agitation. Rising temperature may cause one or more of the following
problems:
- Lower viscosity of lubricant.
- Accelerated degradation
of lubricant.
- Deformation of housing,
gears and shafts.
- Decreased backlash.
New high-performance lu-
bricants can withstand up to 80
to 90°C. This temperature can
be regarded as the limit. If the
lubricant's temperature is ex-
pected to exceed this limit, cool-
ing fins should be added to the
gear box, or a cooling fan in-
corporated into the system.
h = Full depth, b = Tooth width
d2 = Pitch diameter of worm gear, dw = Pitch diameter of worm
Table 20-2 Adequate Oil Level
Types of Gears
Horizontal Shaft
Vertical Shaft
Spur Gears and Helical Gears
Gear Orientation
Types of Gears
Horizontal Shaft
Worm Above
Worm Gears
Gear Orientation
Worm Below
Bevel Gears
Oil level
Oil level
3h
1h
1h
0
1
–– h
3
1
–– dw
2
0
1
–– dw
4
1
–– d2
3
1b
1
–– b
3
Level 0
Level 0
