 The British Army has introduced the Machine Care Plus® service in support of Challenger 2 and CRARRV* transmission units to detect problems at an early stage. By diagnosing problems from the materials found in the transmission oil, the assemblies can be proactively managed to increase availability and reduce support costs.
In this case study, the locktabs on a change speed clutch locknut failed, allowing the locknut to work loose and come into contact with a pump drive gear. Machine Care Plus® detected that the failure had occurred by a sharp rise in wear elements suspended in the transmission oil, created as the gear and locknut wore against each other. In addition to material originating from the gear and locknut, braze material that holds the lockwasher to the locknut was also identified.
Previous data and experience of this failure process, underpinned by a detailed Materials Atlas, clearly indicated that significant secondary damage was about to occur. If no action was taken, excessive wear on the locknut would allow it to come into contact with the pump idler gear. The support bearings would then fail, and the idler gear would damage the transmission casing. Finally, the loosening of the change speed clutch locknut would cause a "loss of drive", requiring vehicle recovery and repair.
Machine Care Plus® recommended action be taken after the locknut failure had been positively identified. This early warning enabled users to prevent expensive secondary damage to the transmission casing and also avoid "loss of drive" in the field, saving on resources required for vehicle recovery.
*Challenger Armoured Repair and Recovery Vehicle
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