ENCLOSED LINK VALVE GEARS FOR LOCOMOTIVES

AN OVERVIEW

ADVANTAGES – DISADVANTAGES

AND THREE SPECIFIC APPLICATIONS

October 2018 ASTT CONFERENCE

ADVANTAGES

• ELIMINATES THE TASK OF OILING-UP BEFORE DUTY

• CONSTANT OIL FEED WITHIN THE ENCLOSURE ENSURES LONGER BEARING LIFE

• INGRESS OF DUST AND GRIT IS ELIMINATED BY THE ENCLOSURE

• QUICK REPLACEMENT DURING OVERHAUL WITH A PREVIOUSLY REPAIRED UNIT

• PURELY FUNCTIONAL DESIGN OF COMPONENTS WITHIN THE ENCLOSURE ALLOWS FOR

OVERSIZE BEARINGS AND MINIATURISATION CAN REDUCE INERTIA EFFECTS

DISADVANTAGES

• HIGHER FIRST COST – ALTHOUGH THIS IS MITIGATED BY REDUCED MAINTENANCE AND

HIGHER RELIABILITY

• ABSENCE OF AESTHETICALLY PLEASING FLASHING RODS!

PROBLEMS ENCOUNTERED

WHEN FIRST BUILT

Unbalanced slide valve forces too great

Remedy: convert to balanced slide valves with 70% area balanced

Conversion to slide valves not an option due to expense

ONGOING

• Condensate leaking into the enclosure

Traced to pump action of the valve spindle as it passes through support

bearing

Small amount with no apparent ill effects

Oil change was originally annually but recently extended to every other

year

• Internal oil pump occasionally ceases to work

No apparent reason other than lift ball sticks

RESULTS OF 1ST MAJOR O/HAUL - 8-10,000 miles (45 < 50,000 scale miles)

•Both sliding surfaces (die block and reverser slide) no perceptible wear

•All valve rod bearings no perceptible wear

•Spiral bevels no backlash

•Suspension arm bearings seized due to blocked oilways

•Splines on universal shaft some wear – due to bent return crank mounting spindle causing gearcase nodding

REMEDIAL ACTION TAKEN

•Wherever possible oil distribution pipe moved to exterior of enclosure for to enable

visual checking of oil supply. Remaining internal pipes and oilways increased in size

•New mounting spindles made for driver gearcases