Rotax 912 i Series Maintenance Manual page 153

Fig. 19
Magnification: approx. 1.5x
DESTRUCTIVE PITTING
See Fig. 20 and Fig. 21.
Features:
Extensive flank fractures, generally occurring as
zones of pitting. The bottom of the fracture gene-
rally has a mussel-shaped structure. The total
pitting area can be so great that the running
smoothness is noticeably affected and/or the
remaining flank area which still bears the load is
rapidly destroyed by wear etc.
Causes:
Pitting is attributable to the fatigue of the material
due to combined stresses from compression and
sliding. They are triggered when the material
strength is exceeded locally. Essential influen-
ces on pit strength are: oil viscosity and oil tem-
perature.
Conclusion:
Pitting of up to 5% of the flank area is permissi-
ble if the individual flank fractures do not exceed
a size (greatest longitudinal extent) of 0.5 mm.
Otherwise the gear set must be replaced
Effectivity: 912 i Series
Edition 1/Rev. 0
BRP-Powertrain
MAINTENANCE MANUAL
!
WARNUNG
The whole gear set must always be replaced.
Dog hubs or drive gears must not be replaced
individually.
Fig. 20
Pitted area in the dedendum flank region of a spur gear.
Magnification approx. 5x.
Fig. 21
Pit formation in the dedendum region of a spur gear tooth
system
Magnification approx.
1.5x.
NOTICE
72-10-00
Page 15
July 01/2012