The document discusses gear tooth failures and lubrication. It addresses the key performance parameters for gears, the two main forms of gear failure, and the common reasons for gear failures. These include stresses, poor design, material defects, heat treatment issues, and excessive operating temperatures. The document also outlines the importance of lubrication for gears to reduce friction, remove heat, and protect against damage. It describes various lubrication methods including hand lubrication, drip feed, splash/bath lubrication, and pressure lubrication.

1. Gear tooth
failures
& lubrication

2.  Basically, the performance of a pair of
gears can be assessed by the measure of
success achieved in providing a positive
drive, while operating at the requisite
speeds, transmitting the maximum
designated power

3. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

4. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

5. Performance parameters
 strength - life and durability
 noise level - smoothness in operation
 efficiency - operating temperature
 size and weight of transmission
 cost of manufacture - materials,
machining, heat treatment and assembly
running costs

6. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

7. The failure gear one of two forms:
The failure gear one of two forms:
A. complete fracture of the gear tooth; this
usually occurs at the root of the tooth
B. damage or destruction of the working
surfaces of the gear tooth
Either of these forms of failure may be the
result of one or a combination of any of the
following factors:

8. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

9. Failure reasons
 failure may be the result of one or a
combination of any of the following
factors:
1. Initial stresses.
2. Poor tooth design.
3. Use of an incorrect material.
4. A material defect.

10. Failure reasons
5. Incorrect heat treatment for the selected
material.
6. Poor mounting and casing design.
7. Surface damage in final machining or
grinding operation.
8. Excessive operating temperatures.

11. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

12. Lubrication of gears
 Up to a few years ago the engineering
world in general paid little or no attention
to the gearbox lubrication system during
the initial design stages.
 Thus when the internal running gear was
finalized, lubrication became a major
problem when the design of the gearbox
casing commenced.

13. Lubricants used for:
 Lubricants used for:
 Reduce friction coefficient between
gears
 Remove the dissipation heat
 Protectbearings &gears against external
pollutants

14. Main points
 Performance parameters
 The failure forms of gear
 Failure reasons
 Lubrication of gears
 Lubrication methods

15. Lubrication methods
1) Hand lubrication -where the lubricant is
applied from an oil can or similar type of
container.
2 ) Drip-feed lubrication - where the
lubricant is applied from an oil container
by means of a wick or a restricted oil feed
pipe.

16. Lubrication methods
 3) Bath-type lubrication or, as it is more
commonly known, ‘splash lubrication’ where
the gear teeth are used as paddles to
circulate the lubricant.
 4) Pressure lubrication - where the lubricant is
circulated by one of the various types of oil
pump through oil galleries or oil pipes to oil
jets which are directed at the gear.