Spectrum 2-8-0 consolidation strange running

[EffUnit]

I got a nice used Bachmann spectrum N scale 2-8-0 consolidation, (first production run), non DCC that runs fine in reverse, but in forwards, the wheels nearly stop rotating at about each quarter turn.

At higher speeds its not so noticable, but still a bit lumpy running.  Clean and lube, or something else?  
I hope its not a return to Bachmann job, because they dont seem too interested in dealing with North American items in Europe.  

[gatrhumpy]

Most likely the wheels are not in quarter. You will have to figure out which one(s) and put them into quarter by adjusting them slightly.

[bbmiroku]

I've had a similar problem with used steam engines in larger scales (HO) and among some brands.  They run perfectly in reverse at all speeds, but tend to be sluggish, emit a grinding noise, or otherwise work wonkily in forward.  The problem may be a loose motor, or a loosely installed rotor.

In reverse, the motor itself may twist slightly, enough to put it in true with the gearing for the wheels.  But in forward, it may twist out of true, causing wonky (or strange) running.  In this case, remove the shell and whatever else is in the way of getting to the motor, then run it in reverse and pick it up off the track without shutting off power (so the motor is in true alignment).  Then shut off the power.  Tighten any screws you see.  If that fixes it, alright.  If not, go to step 2 and don't put the cover on yet.

If your problem is a loosely installed rotor, you should be able to push the axle coming from the motor in and out of it slightly more than on a properly working model.  This is the problem where you'll hear a grinding noise and have sluggish operation.  The rotor and attached axle (with worm gear) will tend to move forward or back before the gears on the wheels pick up any motion.  Through the years, this gets worse and worse (as the worm gear and first gear wear down) until someone decides to sell the model.  In the larger scales, this is a noticeable movement of the worm gear backwards and forwards.  In reverse, the gears on the wheels tend to make the rotor axle push into the motor, making it work slightly better, so you don't notice any ill effects.  But in forward, the gearing pulls the rotor out of the motor slight enough that there is a noticeable reduction in performance.  Unfortunately, I know of no remedy for this except a new rotor assembly.  But good news!  You can find these things a dime a dozen at train shows usually (maybe a little more).

But before you try any of these things, take it apart as much as you feel is in your capability to put back together (at least take the wheels and gears out).  Wipe and clean off everything.  Re-sellers tend to over-grease these things.  Put on a tiny dab of plastic-safe grease on the wheels and a drop of plastic-safe oil on the gearworks.  If this solves your problems, then you're good to go for another couple of months or years (depending on how often you run the engine).  And you know how to fix it in the future.  I do this for every single engine I buy second-hand, even if it looks unopened in the box.  There's a reason someone is selling it, after all.

[spookshow]

Do you see any sort of eccentric rotation or up-and-down movement from the drivers when running forward at slow speeds? One common problem with Bachmann steamers is that the cut-outs in the frame wherein the driver bearing blocks seat are occasionally miscut, allowing for excessive movement of the bearing blocks (and ultimately the drivers).

The solution there is to remove the plastic driver bottomplate, pull out the offending driverset and bearings, and then put some sort of shim in the frame cut-out to eliminate the excess freeplay of the bearing blocks. I usually just use a small piece of electrical tape.

-Mark