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  • Engine Tuneup

    You can make vast improvements in the performance of any ready-to-run imported brass locomotive with these minor adjustments.


    1001 Model Railroading Ideas - Fall 1971 - Page 57

    Your finely-detailed imported brass locomotives can run as well as they look. Most of us are satisfied to just have the little jewels run at all; but we don't have to be. Many model railroaders, who are at least as interested in seeing their engines run as they are thrilled to see the wealth of ready-built detail and realism, have found that the mechanism's of the Japanese imports can be adjusted and refined to the point where the locomotive will run as smoothly as a fine watch. The manufacturers and importers of these precision machines have refined their techniques of production to the point where nearly every visible detail of the full-size engine is captured in cast, coined, etched, and stamped brass -- there is little to fault in the appearance of these machines, but their performance is seldom up to their high standards of realism. Apparently the techniques of adjusting the working tolerances between the moving parts has no been refine to quite the point that the static detail has. It is far easier to make one of these engines perform that it is to try to capture all of that realism.

    One of the country's experts in locomotive performance is LeRoy Thompson from Phoenix, Arizona. LeRoy has been conducting locomotive performance "clinics" to relate his techniques to other modelers who attend the National Model Railroad Association's regional and national conventions. Hundreds of visitors to his home layout, during the 1971 Pacific Coast Regional N.M.R.A. convention this spring, saw two of his engines snake long trains of cars at life-like slow speeds for dozens of hours without a falter. Both locomotives were as smooth and silent as a sailboat; accelerating and stopping without any hesitation or growls of protest from the gears and drivetrain. I watched as he conducted is now-famous "clinic" on model locomotive performance in the hopes that his techniques could be passed on to the readers of 1001 Model Railroad Ideas. Most of the ideas that he and his contemporaries in his are of model railroading expertise have developed over the years are shown on these pages. Once you've seen what these men have done you can lose that fear that most of us harbor when contemplating the task of touching anything but a paint brush to our most-prized locomotives -- if you follow these steps carefully you'll find that the completed and "tuned" locomotive looks even more realistic as it glides down the track.

    1. Most of the HO and O scale imported brass ready-to-run locomotives use the same basic style of mechanism. The "tuning" tips are shown on the parts of Westside Model's HO scale version of the Virginia & Truckee's Baldwin-built 4-6-0 but the procedure will be nearly identical for virtually any other brand or type of locomotive.

    2. & 3. Examine the underside of the locomotive to determine which screws or nuts are used to hold the superstructure unit to the chassis. Usually there is a screw under the center of the cylinders or inside the smokestack. The same screw on this engine holds the four-wheeled pilot truck in place. Another pair of screws attaches the cab and the rear of the superstructure to the chassis.

    4. With all of the screws removed the superstructure should be free to be lifted away from the chassis. Work on a piece of soft foam truer to avoid damaging the delicate details. A set of plastic parts boxes or a divided jewelry drawer can be used to hold the parts you remove. Keep them segregated in order of disassembly so you'll remember just where each of them fits when you're ready to reassemble the engine.

    1001 Model Railroading Ideas - Fall 1971 - Page 58 1001 Model Railroading Ideas - Fall 1971 - Page 59


    5. & 6. Remove the screws that hold the motor and its lead wire to the tender drawbar. The motor shaft on this engine is coupled to the gearbox with a flexible plastic hose -- the shafts simply press into the ends of the hose. If your motor doesn't have this type of flexible coupling, make one from a piece of model airplane fuel line that is a press fit on the shaft. Cut the motor shaft apart between the motor and gearbox and file off 1/16-inch or so from the cut ends so they cannot touch when inside the tubing. IN some cases you may need to fabricate another motor mounting bracket or shaft bearing support.

    7., 8., & 9. Scrape away the insulation that may be glued over the screw slot on the motor brush holders and remove both holders, brush springs, brushers, and lead wire connectors. Keep careful note of where you put those motor brushes -- they're about the size of 1/16-inch piece of pencil lead -- your dealer may be able to supply replacement brushes if yours are worn (they should be at least as long as their diameter). You can clean the parts with lighter fluid.

    1001 Model Railroading Ideas - Fall 1971 - Page 60


    10., 11., & 12. A piece of soft iron (from a local scrap metal yard) must be used to hold the motor while you proceed with the rest of its disassembly. Place the motor on the iron scrap, press a piece of masking tape tightly against the layers of metal laminates (the motor's "pole pieces"), and then loosen and remove the screws that retain the two end plates. Only the end plate that holds the motor brushes will actually have to be removed; the other end plate can remain tape to the pole pieces. Remove that end plate and slide the armature out of the motor.
    1001 Model Railroading Ideas - Fall 1971 - Page 61


    13., 14., & 15., Model airplane supply stores can furnish a clever little gadget made by Austin Craft called a "Teeter Prop" that is designed to help balance propellors. Two razz blades are bolted to the sides of this tool with their edges precisely parallel and level. You could use a small plastic parts box and glue the razor blades to its sides. Place the motor's armature on the edges of the razor blades and roll it a bit; marking where it stops rolling each time -- the marks will usually appear on one of the armature's "poles"; this is the heavy side of the armature. File away a bit of the metal and try the rolling and marking steps again and again, filling a bit more on the heavier pole if needed, until the armature stops at random poles. It is then statically balanced. Some model car racing shops can perform this service for you for a dollar or so.
    1001 Model Railroading Ideas - Fall 1971 - Page 62


    16. & 17. Chuck the end of the armature in an electric drill or motor tool and spin it while you hold a piece of fine sandpaper (#400 grit or finer) against the commutator (the copper end where the brushes contact) until it is polished. Do not use emery paper or emery cloth. If the commutator has extremely deep cuts you may need to face it off with a flat jewelers file using very light pressure and a brace to steady the file so it only hits the high spots. When the commutator is perfectly smooth, round, and shiny, clean out any grit from between its segments with a knife blade tip and then touch the sandpaper to it again to smooth off any accidental knicks from the knife.
    1001 Model Railroading Ideas - Fall 1971 - Page 63


    18. & 19., Temporarily reassemble the armature and the end plate to the motor and check to see if there is any end play in the armature. Usually you'll need to add at least one thin washer to keep the armature from "floating" from end to end while the motor operates. Use enough washers so the amount of end play is about equal to the thickness of a piece of paper. Most model railroad shops can supply steel spacer washers and thicker brass spacer washers for just this purpose. When you're satisfied with the end play, assemble the armature and end plates.

    20. Screw the motor brush holders about a single turn into the end place with the spring inside the holder. The motor brush itself can then be inserted into the holder between the commutator and the hollow holder and the holder tightened down. Be sure the brush is fitting inside the holder so you don't crush it when you tighten the holder.

    21. Many of the larger imported brass ready-to-run locomotives use a motor like this one from Tenshodo with solid steel pole pieces and the magnet on the end of the armature. These motors can be disassembled just like the one in the previous pictures. The space washers that control the armature end play should, however, be inserted between the brush end plate and the commutator to try to hold the opposite end of the armature shaft against the steel magnet.

    1001 Model Railroading Ideas - Fall 1971 - Page 64

    22. & 23., Some types of motors have hex nut-shaped ends on the motor brush holders. Use an automotive ignition wrench or needlenose pliers to remove the holders and brushes. The motor should, once again, be resting on a soft iron block to retain its magnetic charge while the armature is out from between the pole pieces. The armature can then be balanced and the commutator polished and trued as before.

    24. & 25. This next step is strictly optional, but well worthwhile in quieting and smoothing the performance of your locomotives. The complete motor mounting bracket is removed from the chassis first. A piece of foam rubber (model airplane supply stores sell an adhesive-backed foam type under the DuBro label) will then be sandwiched between the motor mount and the chase to isolate the motor's vibrations from the rest of the locomotive.

    1001 Model Railroading Ideas - Fall 1971 - Page 65

    26., 27. & 28. Slice DuBro foam rubber in half (or use the type of thin foam rubber shoe stores sell for insoles) so it is about 1/32-inch thick. Glue the foam to the chassis with Goodyear Pliobond cement or Walther's Goo cement and allow it to dry. Finally glue the bottom of the motor mounting bracket to the top of the piece of foam with the Pliobond or Goo. Be sure that the motor's armature shaft is in exact alignment with the shaft from the gearbox; trim the foam until the shafts do line up. Do not replace the screws that hold the motor-mounting bracket to the frame; the glue and foam will hold it firmly enough and yet still isolate its vibrations from the chassis. You'll have to solder an insulated flexible wire from the second motor brush to the frame to "ground" the motor to the frame.
    1001 Model Railroading Ideas - Fall 1971 - Page 66 1001 Model Railroading Ideas - Fall 1971 - Page 67



    29., 30., & 31. Check the gearbox for excessive end play on the ends of the worm gear shaft. This one hand nearly 1/64-inch of "slop." Remove the screws that hold the gearbox end in place (or, with some brands, the entire gearbox and driver wheel) and insert as many steel or brass spacer washers as are needed to get the end play down to less than the thickness of a piece of paper. Check the mesh of the worm gear with the spur gears on the drivers or idler shaft. Again, there should be about a paper's thickness clearance. Shims under the end plates of this gearbox can be removed and replaced with thinner ones cut from .005- or .010-inch thick brass shim stock. Replace the gears and lube with LaBelle-brand model grease.
    1001 Model Railroading Ideas - Fall 1971 - Page 68

    Article Details

    • Original Author 1001 Model Railroading Ideas
    • Source 1001 Model Railroading Ideas
    • Publication Date Fall 1971

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