I started the new year with some locomotive maintenance. Both of my primary locomotives - C424 #801 and GP35 #902 - are having some issues. I decided to start with the 801, which needs attention for the following 2 reasons:
- It growls when running forward, though it's silent when running in reverse.
- It stutters in a few places on the layout, especially at the curved turnout.
The growl has bothered me for a while but I've just lived with it, mostly due to fear of damaging the shell while trying to remove it. However, the stuttering is completely unacceptable so it was time to face my fears and take the 801 into the shop for an overhaul.
Removing Atlas shells is a touchy process for me because I'm terrified of breaking off one or more of the latching tabs near the four corners of the shell. Once broken off there's really no way to fix them. To remove the shell, I inverted the locomotive on the workbench and one at a time gently pried each tab away from the frame with a small screwdriver and inserted a strip of index card between the tab and the frame. Once I had done this for all four tabs, I set the locomotive right side up and carefully lifted off the shell.
One thing I noticed right away after removing the shell was that the motor was loose. I fixed this by tightening the two motor mount screws. You have to first remove the plastic fuel tank to access these screws.
The stuttering is almost certainly a power pickup issue. The locomotive nearly stalls when the rear truck is sitting on the frog of the curved turnout, so it would seem that the front truck must not be picking up power. I confirmed this by test-running the locomotive with only the front truck wires connected to the circuit board; it basically didn't run at all in this configuration.
I removed and disassembled the front truck. Here are all the parts:
The brass contact strips that rub the axle ends were oxidized and the axle bearings were flush with dirty grease.
I gave all of the truck parts a bath in warm, soapy water, scrubbing them with an old toothbrush. After letting the parts air-dry overnight, I started reassembly. I polished the contact points on the brass strips with a wire brush in my Dremel. To polish the insides of the axle bearings, I used a strip of 600-grit sandpaper wrapped around a piece of styrene rod and attached with double-sided tape. I also soldered the wires directly to the tabs on the brass strips and omitted the plastic clips. The wheels weren't too dirty, but I polished the treads with the Dremel wire brush anyway.
Next I reassembled the gearboxes. Two of the three spur gears are identical and the third is slightly larger. The exploded parts diagram was not helpful for reminding me which gear went where; I found out through trial-and-error that the larger one goes in the position farthest from the worm gear. I lubricated the axle bearings with Labelle 108 oil prior to reinstalling the sideframes. I also lubricated the worm bearings with Labelle 108 and used Labelle 102 on the gears.
After completing the reassembly and reinstallation of the front truck, I test-ran the locomotive again with only the front truck wires connected to the circuit board. It ran much better than before, but this exercise illustrated just how important all-wheel electrical pickup is for good performance. While I had everything opened up, I removed the rear truck and gave it a similar bath and overhaul.
The fully reassembled locomotive runs smoothly and quietly through the curved turnout.
I suspect that the growling noise was related to the loose motor. As expected, cleaning all of the electrical contacts fixed the stuttering. Hopefully it will be a while before it needs the full overhaul again.
