Servicing the steam locomotive mechanism
The model steam locomotive mechanism is more complex than that of other models mainly because of its various rods, valve gearing, screws, rivets, etc. All of these little components must be in proper order and alignment for the loco to run correctly. Although this type of mechanism can vary greatly depending on the brand and type of locomotive, I have listed the basic steps for servicing below.
1) If the locomotive has a tender, carefully remove it, as well as the tender wire. Next, remove the locomotive boiler from the mechanism (on many locos, this will be a screw going down through the smokestack and one or two on the back coming up through the frame into the boiler). Remove any wires going to a light or smoke generator on the boiler so you can free up the motor/mechanism unit.
2) Next, remove the motor from the frame. Turn the frame upside down on a soft surface and remove the cover plate which holds the driver axles in place. I like to remove each driver from its place enough to run a Q-tip along the surface of the bearing to clean it. After doing this, apply a small amount of alcohol to a new Q-tip and clean again. Also, wipe the axles clean to make sure there is no grime or buildup on them that would hinder free movement. When the axles and bearing slots are clean, reassemble them and place a drop of quality oil in each axle slot. (note: The Mantua locos normally have replaceable axle bearing inserts that can easily be replaced during this step. Simply lift up each driver enough to pull out the brass axle bearing and replace with a new one). Reassemble the cover plate.
3) Inspect the mechanism carefully by gently spinning the wheels to see how the rods and linkage "mesh". The rods should have absolutely NO resistance at any point in the revolution. Check the rod bolts for tightness by gently applying pressure using a hex wrench ( Yardbird Trains part # M5511 for most rod bolt/screws).
4) Carefully go over each component of the rods, crossheads, crosshead guides, valve gear linkage, etc, paying close attention to the connecting joints. Loose rivets may be tightened by applying slight pressure with a small pair of pliers (be careful not to over-tighten these). Also check for clearance as the linkage revolves. Many times the eccentric cranks (where the valve gearing is attached to the main rod) will interfere with the side connecting links as they go around. Make any adjustments with a small pair of pliers, checking the alignment often.
5) When you are satisfied with the operation of the linkage and wheel rotation, replace the motor and bench test the locomotive mechanism for smoothness (when the motor is off is also a good time to service it - see the section on servicing the 12 volt motor). If it does not check out satisfactory, redo the above steps to find the problem. Otherwise, reassemble the boiler to the mechanism.
6) Turn the engine upside down on a soft surface and hook up the leads to power it up. Apply a small amount of quality grease on the driver gear (I use a white lithium grease safe for nylon, etc.), applying a little and then spinning to another area to apply more. The idea is to get an even coating on all of the teeth of the gear. Run the loco and let the gear gently wipe over a cloth to clean up excess grease.
7) The final step, with the locomotive still on its back and running, is to clean each driver wheel with a soft, metal-bristled brush to clean (brass bristles are the best for this). In extreme cases of oxidation or build up, a very fine sandpaper can be used for this. When the wheel tires are clean, reattach the tender connection. Wipe all of the parts clean and test the locomotive on the track. This concludes the servicing of the mechanism.
Normally, this operation will be done in conjunction with cleaning and servicing of the motor and tender. If all processes have been done and the locomotive does not run to satisfaction, or if you have any questions or comments, please feel free to contact us.
Yardbird Classic Trains