Type of Project: Niigata Transmission assembly repair for a locomotive
Customer Name: Railway Heritage Preservation Charity
Location: Queenborough

Summary

• Transmission received with reported issue of ‘sticking in gear’.
• Full strip down carried out to inspect all parts.
• General wear found throughout; roller bearings recommended for replacement.
• Clutches and associated parts found in good condition.
• Freewheel mechanism worn, causing potential sticking in direct drive.
• Air driven selector valve heavily corroded; pistons not traveling smoothly.
• Output shaft splines heavily worn and pitted; recommended for replacement.
• Input and output seal diameters require polishing/dressing.
• Unit to be reassembled and tested with necessary replacement parts.

Initial Enquiry

The industrial equipment operator contacted our team with a reported issue of the Niigata transmission assembly ‘sticking in gear’. Upon receiving the transmission at our workshop, we noted that this unit does not have gears in the traditional sense. Instead, power is transmitted through the converter or the direct drive clutch to provide 100% power transmission via clutches within the converter itself. Suspecting an internal issue related to the clutch plates and associated parts, we proceeded with a full strip down to inspect all components thoroughly.

Project Description

Transmission Strip Down and Inspection

Upon disassembling the transmission, we found general wear throughout the unit. All roller bearings showed signs of wear due to time in service and were recommended for replacement. As a standard procedure, all sealing mediums will be replaced to ensure optimal performance.

Interestingly, the clutches, including clutch plates and associated parts, were found to be in good condition despite the initial diagnosis suggesting otherwise. This indicated that the issue might lie elsewhere within the transmission assembly.

Freewheel Mechanism and Valve Block Inspection

Further inspection revealed that the freewheel mechanism was heavily worn, particularly the cage that retains the rollers in their correct position. This wear could cause the converter to stick in direct drive, contributing to the reported issue.

The valve block was stripped down, uncovering significant corrosion within the air-driven selector valve. The pistons did not travel smoothly through the cylinder, and pitting on both the piston and cylinder allowed air to pass the O-ring. This was identified as another likely reason for the transmission being stuck in direct drive.

Output Shaft and Seal Diameters

Additionally, the output shaft splines were found to be heavily worn and pitted, necessitating replacement. Both the input and output seal diameters will require polishing and dressing to ensure a good seal and prevent future issues.

Reassembly and Testing

With the necessary replacement parts identified, the transmission assembly will be reassembled. Once reassembled, the unit will undergo rigorous testing to ensure that all issues have been resolved and the transmission operates smoothly without sticking in gear.

Conclusion

The project to repair the transmission assembly for the industrial equipment operator was comprehensive, involving a full strip-down and detailed inspection of all components. The initial diagnosis of clutch plate issues was ruled out, with the primary causes identified as wear in the freewheel mechanism and corrosion in the air-driven selector valve. The output shaft splines and seal diameters also required attention. With the necessary replacements and reassembly, the transmission will be tested to confirm its proper functioning. This project highlights our team’s expertise in diagnosing and resolving complex transmission issues, ensuring the equipment’s reliability and performance.