Model Train Maintenance
Model trains today typically run well right out of the box and for years afterwards, but sometimes they don’t. And if you run them long enough, eventually even a good runner will need some maintenance. This section provides some guidance on what can be done to improve performance of a typical model.
Mostly maintenance consists of checking for smooth-rolling wheels, good electrical pickup (and on a related note, clean and properly-powered track) and doing basic cleaning and lubrication. There is some additional maintenance that can be useful for locomotives, but it’s less common.
The small DC motors used in model trains are often sealed units not intended to be maintained. But this isn’t true of all of them, and there are some things that can be done even if the motor itself is not maintainable. In the end, you may need to replace the motor, and the replacement may even be better than the original was when new, particularly if it’s an older model. But it’s worth trying some basic maintenance first. If not, see the Repowering section on my DC Model Train Motors page.
Eliminate the Obvious
First, check the easy things. By one estimate 80% of “locomotive problems” are actually electrical pick-up problems. I’m not sure of the statistic, but it wouldn’t surprise me if it is indeed that high.
Electrical Pick Up - Track
Clean the track. This should be obvious, but track gets dirty easily. I prefer alcohol on lint-free pads or micro-fiber cloth (not a lot; you don’t want to strip paint off the ties or nearby scenery), or rubber block erasers. I don’t use abrasive cleaners like the popular “bright boy”, because these leave microscopic scratches and pits that will collect dirt in the future. And I don’t use fancy chemical cleaners, because most of these leave a sticky residue that attracts dirt (causing you to buy more of the expensive cleaners; call me cynical, but I see who is profiting there).
Test the track. Run several trains to be sure you’ve eliminated any track-based problems. If not, use a voltmeter for DC or an RRampMeter for DCC with a running train in the block, and make sure that at full throttle you’re getting an expected track voltage if you see a problem. Solder joints can be bad, and if you feed power through a rail-joiner, these can collect dirt over time. You need to have a train, because some feeder problems only show up under load.
Testing the Train
Before servicing a model, make sure the model has a problem. Run it on a clean track with a good power supply. If it has problems, clean the track again.
Be aware that a cold motor doesn’t work as well as a warm one. That’s due to both the behavior of the armature’s magnetic field and the behavior of lubricants. Before drawing any conclusions about lost performance, run the motor with a load at moderate speeds for five or ten minutes to get it warmed up. That’s particularly important if you are working in a cold basement or shed.
Electrical Pick Up - Wheels Etc.
Dirty wheels or the brass pickups that touch the wheels or axles to convey power to the motor will reduce the power getting through, making the motor harder to start and producing less power for a given voltage.
Clean the wheels similarly to how you clean track: rubbing alcohol on a cotton swab will do, but make sure not to get cotton fibers into the wheel mechanism; a lint-free cloth you can wash when it gets dirty could also be useful. You can also buy or make special devices to clean wheels, but beware the ones that use metal brushes rubbing against the wheels, as these can destroy rubber friction tires on the wheels that aren’t used to pick up electricity (harsh solvents could also have that effect). An ultrasonic jewelry cleaner is supposedly good for this, although I haven’t used one.
Abrasive cleaners are also bad for wheels (as for track) because they create small pits where dirt can adhere in the future, making regular cleaning more necessary.
The Rest of the Train
A good locomotive can still have problems if it’s pulling problematic cars. Address your freight or passenger stock as well as powered equipment. Passenger stock may also suffer from electrical pick-up problems similar to locomotives.
Wheels should be free-rolling, and ideally made of metal to avoid leaving plastic residue on the track as they wear, which creates a need for more cleaning. If you lubricate wheel bearings, make sure that they aren’t used as electrical pick-ups (or use conductive lubricant).
Check the weight. While cars that are too light will derail more easily, cars that are too heavy put an unnecessary load on the locomotive. The NMRA’s recommended weight guidelines (RP-20.1) can be hard to obey at times, but they’re still a good guide to striking an appropriate balance on weight. In N scale, this is 1/2 ounce (14 grams) + 0.15 oz/inch of car (1.7 g/cm). So a 4-inch (10 cm) car would need to weigh 1.1 oz (31 g).
The Harder Stuff
Once everything else works, if you still have a problem then more serious maintenance is called for. This involves taking the locomotive apart, inspecting and testing it, and then doing appropriate cleaning and lubrication.
Electrical Pick-up
If the locomotive has been stored in a humid environment, you may need to disassemble it and polish the brass pickups any place where one piece rubs on another, using a very-fine grade of sandpaper (emery cloth). However, more typically, for very mild dirt or corrosion a pencil eraser may work equally well (just clean the eraser bits off later with an alcohol swab), and avoids the “pitting” problem you’d get from emery cloth.
Gear Train
Poorly lubricated gears between the motor and the wheels can have a lot of friction, wasting power from the motor (as heat, which isn’t good for the gears either). Gear assemblies may also be poorly assembled, with one or more gears not quite where they should be, resulting in friction or even jamming. Disassembly of the gear train, cleaning, and lubrication with a proper hobby lubricant may do wonders. Note that gears, motor bearings and motor brushes all need lubrication, and three different types of lubricant are often used. And too much is nearly as bad as too little. This is a topic to read up on before doing anything. See the Lubricants section below for a starting point.
A quick test is to take off the locomotive body and disconnect the motor from the drive shafts (be careful, it’s easy to break tiny parts doing this). Then turn the motor with a finger, and see if it’s binding anywhere. Similarly, turn the drive shaft leading to each gearbox and watch the wheels turn a full rotation, was it smooth and easy or stiff? Did it bind anywhere? We’ll get to the motor in a bit, but binding in the gears means that they should be cleaned (an ultrasonic cleaner may be good for this) and re-lubricated.
Plastic gears can wear with time, particularly if they weren’t properly lubricated. Replacing these probably means buying a whole new gearbox (from the manufacturer, or a replacement one) rather than replacing individual gears.
Motor Service Life and Maintenance
A small DC motor has a service life of several thousand operating hours under “average” conditions. This can be extended considerably under ideal conditions, and shortened drastically (to less than 100 hours) if abused. But what constitutes abuse as opposed to average operating conditions?
Load, which affects current and thus heating of the motor windings and armature is a big part of this. If you have an ammeter on your power supply and can subtract other uses of the electricity (e.g., current drawn by headlights and lit cars doesn’t affect the motor) you can compare that to the motor’s stall current. Keeping the motor current below 1/3 to 1/2 the stall current will likely extend the life of the motor, where pushing it close to the stall current for an extended time is probably going to shorten the service life. Unfortunately there’s no easy way to define a specific “safe” limit for an individual motor based on what we know as consumers. The motor designer could provide one, and these used to be given on data sheets supplied with motors, but nobody appears to publish those today.
Note that much of the “wear” from higher speed operation affects the brushes, as speed creates both friction and increased “arcing” at the commutator, which causes brushes to wear faster. Operating at lower speeds will extend brush life. However, brushes normally last for decades, and probably will outlive the modeler, particularly if treated well, even with high-speed use.
Maintenance of a DC motor consists of two things: brush replacement (uncommon today) and cleaning/lubrication of its bearings and possibly the brushes. The usual symptom is that the motor starts drawing more current than it used to for the same load. Obviously you could only detect this with careful monitoring, such as periodic bench testing of a locomotive with a known load and voltage. But if you notice that a model doesn’t seem to be running as well even after cleaning the wheels and track, that’s probably a sign of a problem. Cleaning and re-lubricating the gears is the first thing to do. Only if that does not improve things should you move on to lubricating the motor, brush replacement, or whole motor replacement.
Replacement brushes may not be available for many motors. That depends on the manufacturer of the model to offer suitable ones, and most motors today are “sealed” can motors not designed to be services (Kato’s open-frame motors are an exception). If you can’t get replacement brushes, then eventually worn brushes will require motor replacement. So extending brush life as described above can save you significant money over a fleet of locomotives.
If you replace carbon brushes, be sure to clean out any carbon dust from inside the motor (which came from wearing down the old brushes).
Lubricants
Just about everyone agrees that proper lubrication of model trains is important. But what “proper” means is somewhat less clear, as everyone has an opinion, and few of those seems to be based on much of anything other than someone else’s opinion. I’m afraid I’m stuck in the same camp, as I don’t know much of anything about the chemistry involved, so I have to look to others for facts, and those are thin on the ground. Further, I can’t claim any real experience here. Most of my trains are still running with factory-original lubrication, since the modern stuff lasts a long time and I don’t run individual trains all that often (I have too many for the size of my layout). Some could probably benefit from a cleaning and re-lubrication, so I have spent some time reading up on this, and the following are my notes from that, but don’t mistake them for anything authoritative.
Another thing to watch for is that most lubricants are non-conductive. In some models, electrical pick-up is via the wheel bearings rather than from the axles, and on these lubricating the wheel bearing is going to interfere with proper operation unless a conductive lubricant is used.
Model trains are made of plastic. Some lubricants will happily eat plastic. Even if the gears/bearings are metal, they’re probably held in place by plastic or used with plastic drive shafts. So first, make sure what you use is “plastic safe”.
Second: just about everything benefits from lubrication. Even teflon gears, which are very smooth and slippery, will get hot from friction without lubrication.
In the past some people used WD-40. The current conventional wisdom is that this is too thin to serve as a good lubricant, isn’t “plastic-safe”, and contains non-synthetic elements (fish oil?) that make it unsuitable.
There’s a division of opinion on the value of specialty lubricants. Some recommend one lubricant for bearings and gears. Most suggest that gears need grease (a heavy lubricant) while bearings need a light oil. There are also specialty conductive dry lubricants suitable for brushes in motors.
Sewing-machine oil is frequently cited as suitable, and some recommend 3-in-1 oil, while others do not consider it appropriate, but I haven’t seen any statement of why it would be unsuitable.
Some people swear by Dextron II brand automobile automatic transmission fluid. It’s synthetic, plastic-safe, and a reasonable “weight” for the purpose. I haven’t tried it myself, so I can’t comment. Be aware that not all “synthetic” transmission fluids are the same, and some aren’t entirely synthetic (and thus aren’t a good choice).
Older non-synthetic lubricants contained volatile components that would evaporate over time, leaving a sticky residue (or “gunk”). This made re-lubrication necessary more often. Some modern lubricants are still non-synthetic, so read the label carefully.
Synthetics include silicone-based oils and grease containing PTF (Teflon).
Different oils are often recommended for motor bearings (thin), brushes (thin and conductive, if used at all) and gearing (thick). Brushes on most motors in use today are self-lubricating graphite and do not need to be lubricated, although older motor designs used metal-on-metal brushes that needed lubrication. If you live in exceptionally dry conditions, very carefully lubricating the brushes (with an appropriate conductive lubricant) may be helpful, but for most of us brushes aren’t something we should have to lubricate.
Before applying new lubricant, disassemble the drive train and clean out ALL of the old lubricant (this doesn’t apply to motor bearings or brushes, where disassembly is probably hard to impossible). An ultrasonic cleaner is a good way to clean things like gearboxes without fully disassembling them, just make sure the fluid you use is plastic-safe.
With any lubricant, use only the minimum necessary for smooth operation. Over-lubricating is not only messy, it will tend to gather dirt and probably need cleaning again much sooner than necessary. And if it gets on the track or electrical pick ups, it can prevent conduction and make things much worse.
Labelle (sold by Walthers and thus available most places) is probably the most common line of model train lubricants used in North America. An alternative is Aero-Car (ACT) lubricants. A third option is Lucas Oil tacky red #2.
Lionel also sells a lubricant kit (6-62927) containing gear oil and grease, and several unrelated things (“track cleaner” and eraser) that raise the price.
Bachman sells a plastic-safe conductive oil for use on contracts (e.g., conductive wheel bearings on brass pick-up strips. (part 99981).
Across the pond, Hornby, Fleischmann, and Rocco all sell suitable oils, and Trix and Rocco grease, but I have no details about any of them.
Labelle #106 plastic compatible grease is often recommended for gear boxes.
Dry graphite can be useful for things like coupler pockets that are binding.
References
Caboose Hobbies, Train Tips: Care and Maintenance of Your Trains
Lionel Trains, Lubrication for Your Locomotives
The Motor Doctor, Motor Tune Ups
