The manufacturing tolerances of the drive pinion and crown wheel are designed to guarantee proper operation when the installed dimension and gear backlash are precisely adjusted.
The contact pattern of the ring gear and pinion should, however, also always be checked as an additional inspection.
P33.30-0361-01
Checking contact pattern
1 Coat two teeth of ring gear, offset by 180°, with blue ink.
2 Turn drive pinion forward and backward while simultaneously braking ring gear with holding device.
3 Compare contact pattern with contact pattern examples shown below and take specified remedial action if necessary.
W33.30-0020-01
Ideal contact pattern
Test performed under load conditions (ring gear braked).
An ideal contact pattern is rarely obtained in practice. It is, however, important to ensure that the contact pattern on the tooth face does not extend to the outside edge of the tooth at any point.
W33.30-0021-01
Unacceptable contact patterns
Contact at base of tooth flank
Cause:
Installed dimension of drive pinion too small.
Remedy:
Increase installed dimension between drive pinion and crown wheel slightly. Install thicker shim for the drive pinion and repeat the test for gear backlash and re-adjust the gear backlash if necessary.
W33.30-0022-01
Contact at top of tooth flank
Cause:
Installation dimension of drive pinion is too large.
Remedy:
Reduce installed dimension between drive pinion and crown wheel slightly. Install a thinner shim for the drive pinion.
W33.30-0023-01
Contact at heel of tooth
Cause:
Gear backlash badly adjusted, gear backlash too large.
Remedy:
Set crown wheel closer to drive pinion by turning the threaded rings and repeat the backlash check again.
W33.30-0024-01
Contact at toe of tooth
Cause:
Gear backlash badly adjusted, gear backlash too small.
Remedy:
Set crown wheel further away from drive pinion by turning the threaded rings and repeat the backlash check again.
