Hello folks. After much tinkering on my own, I thought I would give the forum (where I have procured much useful knowledge) a chance to help me out. I have quite a few N scale Life-Like SW8/9 switchers. All run beautifully and I have no real complaints. I also want to preface my problem by stating that I do not yet run DCC. So out of them all, I have one that requires me to provide more power to the tracks before the light comes on and it begins to move. For example, on a number scale the others light up and begin to move (creep actually which is why I love them) at around 10 to 12. However my finicky one requires the power to be at about 20 or maybe a little less before it lights and moves. And when it does move it just jumps to life and moves at the same high speed the others would be moving at if they were running at a level 20. Now once it’s running I can reduce the power to around 10 or 12 and it will run with the others just fine. I have taken it apart and lubed and oiled an checked the gears for hang ups, etc. and can’t seem to find the problem. If anyone out there has had a similar problem I would appreciate hearing of any possible fixes. I really love my little fleet of switchers (I am in the process of repainting them to model the local short line that I plan to model one day soon) and will have to fix this problem or replace it with another loco. Thanks to everyone in advance for any help.
You say that you don’t yet have DCC on your layout. This leads me to beleive that you are planning on using DCC, does the loco in question have a decoder in it? Because that is typical of running a DCC equipped loco on traditional DC power.
Since there is no decoder in the engine, the problem may be the light board. You mention that the lights do not even come on until you get to a higher throttle setting. Swap out the light board from one of the other great running engines ans see if the problem stays with the engine(motor/gear train) or if the light board causes the good running engine to have the problem. You might want to check the little wiper contacts to see if they are dirty as well.
Although you have checked for hangups in the gears, I believe that’s exactly where the problem is. You have something mechanical which has considerably more friction in the stopped position than it does once it starts to turn. The described situation would cause the jack rabbit starts and the smooth running at slow speed once started. Poor electrical contact would continue to have problems at slow speed once started.
The most likely cause of changing mechanical friction from stopped to running is worm shaft axial play, that is the ability of the worm shaft(s) to move slightly forward and backward in relationship to the worm gear(s). This is not an uncommon problem in HO and smaller model locomotives. The fellow with the thread on gear lash likely has the same problem. What is happening is that when you first apply voltage the worm turns very slightly, “screwing” itself slightly backward in its gearbox and bearings. With the worm shifted backward, gear mesh is no longer optimum, and more voltage/current is neeed to get the locomotive moving. Once the worm gear (on the wheel axle) starts turning, the worm reaches an equilibrium position, gear mesh is improved, and drive friction is reduced. A pretty reliable symptom of this excess axial play on the worm shaft is “bucking” or “pogoing” while going downgrade, especially with a load behind.
The cure is to stop the axial movement of the worm shaft. Often this is done by adding washers on the shaft to take out some of the play. If the gearbox ends are actually flexing, the gearbox may need reinforcement as well. If possible, observe the gears with the body shell and gearbox cover removed. It may give some clues as to what is actually happening. Another possbility I just learned about is the rough end of the worm may be catching on the bearing or gearbox. The washers help, but polishing the end of the worm is the real cure. This is done by turning the worm end against a flat piece
Make sure your wheels are clean, and if pickup is via wipers on the wheels, make sure the wipers are clean, the area they are pressing against is clean, and make sure they press flat and level against the wheel. I had this same problem with a Life-Like Teakettle, because the wipers were bent and making poor point contact. Tweaking them slightly, to lie flat when compressed against the wheel back, cured it.