Geared Gears

[Frisco]

I have heard that the geared steam locomotives ( Shay, Climax) have a problem with the gears breaking. Could some-one please expand on this. Thanks

[railtwister]

The problem really doesn't involve the fact that the loco is a "Geared" type (shay, climax, heisler, etc.), because this problem can happen on any loco, steam or diesel. The problems  appears when a gear develops a crack, usually in the 'valley' between the teeth. This allows the gear to open up slightly, and this increases the spacing between the two teeth adjacent to the crack. If the spacing increase is slight, it will usually result in a clicking noise accompanied by a slight jump as the crack rotates through the worm or next gear in the transmission. The bigger the gap in the crack, the more noticeable the noise and 'jump' becomes. the worse case scenario will have the gear jam up when meshing with other gears, or the cracked gear will open enough to lose it's grip on the axle, and just spin freely without transmitting any power to the wheels. the causes of this problem can be axle hole in the gear not being large enough, and stress building up when the gear is mounted on the axle, or the gear material not being stable, and suffering from shrinkage as it ages, impurities in the gear material itself,  or just the stress of the gear doing it's job causing it to crack at the weakest spot. On rare occasions it may even happen with a brass gear, though it is more common with plastic gears. The only good fix is to replace the gear with a new one. Without replacement parts, the loco becomes a write-off.

This has been a major problem with many locos, even the expensive brass ones, and has been a chronic problem with certain manufacturers. It also seems more common in gear sets that use small gears with very little 'meat' between the teeth 'valleys' and the axle hole.

Hope this helps,
Bill Nielsen
Oakland Park, FL USA

[Frisco]

Thank you.