Chris) A couple of things not mentioned so far, and not really relating to your specific problem (maybe), but important enough to know for future reference.
Check the traction tires if any. When not perfectly seated, or broken/worn, these tend to make that driver act bad enough to cause a bind. At the very least, it will make the loco look like its dancing. All the while your valve gear and quartering are fine!
Another thing to check is, is the valve gear hitting something during rotation? Normally one would think youd hear that, but not necessarily! This can cause a bind. Even when your valve gear and quartering are fine.
I bought an IHC Console not long ago listed as "...has bind in valve gear somewhere.... runs, but binds. etc etc.". Got a great deal on a somewhat new loco and all it needed was a slight readjustment of the yoke. One screw! I dont run my trains like race cars... so at low speeds, the eccentric banging the yoke couldnt be heard. But she sure did bind up.
Seperating the drive (motor, shaft, flywheel, gears, etc) from the running gear(valve gear and wheels etc)... i would only recommend as a 'last effort'. Especially for those who are new to the hobby. As many stated above, ever so gently laying her in a soft cradle upside down and using your fingers to find the bind - at the point it is in a bind - will be all you really need.
These "toys" we "play" with arent particularly accurate in the valve gear department, and rightfully so. By fingers touch, the drivers/rods not in a bind will be easily distinguishable from the one that is.
I dont own a Bachmann 2-10-2, so im not familiar with its axles, I am aware of the horrible axle designs Bachmann uses though. Definately give those some eyeball time. Prey that they are solid - one piece!!!
Lastly, how would the bind disappear under load (with cars) as opposed to binding while running light? The load is strong enough to overcome the bind. Lighten the load, the binding should reappear.
Good luck!
PMR
Hi. Apart from quartering issues, the friction may be associated with the piston rod or the brace that supports the crosshead wristpin. Friction may prevent these from sliding freely.
Simon
I've had problems with my 2-10-2 also. The problem (I think) is that instead of having one siderod connecting all the drivers, it's divided up into segments. That may be prototypical, but it seems like that makes it hard for all the model's wheels to be in synch and to bind up, especially at the slow 'drag freight' speeds the real engines were designed to run at.
Chris.
You can check quarter using two squares and a flat surface. But you did say you still feel a bind without the side rods off? Could the axle gear be rubbing on the sides of the gearbox? Perhaps the hole is not in the center of the gear? Is the gear on a blind ( no flange) driver? Without the side rods do all the wheels spin freely?
Pete.
Update:
Running the locomotive slowly upside down didn't reveal anything to my untrained eye.
I removed the motor and gear box and rolled the running gear on the track without feeling any binding or tightness.
I them slowly turned the geared axle at the gear with a small screw driver and I could feel the running gear get tight and loose every 180 degrees of rotation.
I removed the value gear and drive rod and the tightness remained.
When the running gear is in the tight portion of the rotation the connecting rods do not appear to be binding or tight on the crank pins.
Next I am going to check the bearing surface. The bottom plate looks fine. I am also going to order the quarter from NWSL.
Chris
I want to thank everyone for their advice, all good ideas. This weekend I plan to inspect again to see what I find. I will report back what I find.
In addition to the advice from Stix and Randy, here is what I have done to trouble shoot a steam locomotive that just doesn't run right. Admittedly these are things done with brass, Mantua and Bowser steam. I'm not familiar with the newer generation of steam models
Watching it run upside down as Randy suggests, looking for wheel wobble and trying to note exactly where things seem to "catch" if only for an instant. Side rod bind is one issue. The valve gear in general can be binding if bent or over tightened. By the way there are times when steamers have run better upside down than on the track which usually makes me wonder about the bottom plate that holds the axles in place. And it used to be standard advice with a new brass, Mantua, or Bower steam locomotive to run it for a while, in both directions, while upside down, to polish the axles and bearings and just let the kinks in the mechanism work their way out.
But the thing that usually is the most instructive is to remove the motor and gear and push the (temporarily) "dummy" steamer slowly down the track. That is where I find binding most readily. Easy to do for mantua, Bowser and brass. I have no idea about Bachmann.
The next step -- and here I am thinking of Mantua and Bowser, and I do not want to suggest something disastrously stupid for Bachmann -- is to reduce the drive train to just the side rods, so basically taking away the modeled valve gear and main rod to the cylinders. (I do not do this for brass if I can help it) If all rolls free then, I reapply the valve gear and main rod and try again. How does it roll now. If a problem appears or reappears at any stage you at least can figure out the cause.
So what problems are we looking for? Rough bearings, or improperly seated bearings. Sometimes side rods are stamped and a sliver of metal survived the stamping process and it catching on the other rods, or is binding on the crankpin that holds it to the driver.
One old trick with Mantua and Bowser kits was to put thin paper between the parts of the valve gear when riveting them together (or as with some brass, screwing them together), just to create a bit of a space. A lighted match then disposed of the paper leaving a gap of just the right thickness. That is hard to replicate retroactively.
Finally I reapply the motor and gear. Oddly enough sometimes that alone fixes the issue, there was just some mismatch the way the worm gear was mating with the main gear. I don't even know if Bachmann uses worm gears
Dave Nelson
I agree with inverting the loco and running it slowly. But rather than just looking for issues also lay one finger lightly on each of the drivers. Feel for a thump. If you find something on one wheel look closely at the drive train near it for the issue.
I find this works well for finding quartering issues also.
Stop the locomotive when the bind is at it's maximum. Without moving it take a small poky thing like a bamboo skewer or dull screw driver and see if you can wiggle the side rods on each wheel. Also look carefully at the crossheads and piston rods for any burrs or casting flash.
One thing I've noticed with Bachmann is that fresh out of the box they often seem to have the siderods pushed in a little, so they often hit each other each revolution. I don't know if they're made that way in the factory, or if they bend while being bounced around on the trip from China.
If you can, try putting the engine upside down in a foam cradle and hooking up something like alligator clips for power and run the wheels as slowly as possible and see if they bind for a split second at the same place each time. If so, it most likely is the side rods. The rods are pretty flexible, you can gently bend them out a little with very little pressure.
Check the gears, could be crack that someone repaired, say that because of the thump, or it could be a gear with a bit of malformation, accually had this same thing happen with a gear on a turntable, ran smooth but thumped, turned out to be a malformed tooth, filed it a bit and ran much better but not perfect.
I am running DCC. The wheels and track are clean with no flickering of the lights. The hesitation is exactly every 180 degrees of wheel rotation. It makes a sort of thumping sound at these hesitation points.
When I pick up the locomotive and run it with the wheels off the track it runs smooth as glass with no clicking or thumping.
I checked the side rods when they are at the point of hesitation and they do not appear to be binding.
It seems odd that is gets smoother as the drawbar weight is increased.
I haven't disassembled it yet to check gear lube. I have put a small amount of light oil on the axles and side rods.
DC/DCC?
Have you opened it up to inspect the quality of the lubes...or even if there is any in the tower, say? Maybe it has a cracked gear somewhere, but it works better under load. I can't imagine how that could be, but...who knows....
Quartering doesn't have to be better than about 99% on most of our toys, but it gets rapidly worse below that. Would you consider looking around for a quartering tool to check? Maybe an active club nearby?
How about one of the driver axles that's just a smidge too wide at the flanges, just enough that on one or two curves it binds?
Does the headlight flicker? DC or DCC? Plugs from the tender inserted all the way? Wheels clean? Any bent side rods? Any clicking noise?
I have a Bachmann HO 2-10-2 I purchased used lately that runs very rough. With no cars it runs like the side rods are binding like it's out of quarter. With 20 hopper car train it runs much better.
The drivers appear to be quartered by eye. I checked the rods at each point in the wheels rotation and they do not seem like they are binding.
Does it sound like the wheels are out of quarter or some other problem? Could it be a cracked gear or maybe it needs to be broken in?
Back ground: The locomotive was purchased recently and was advertised as new in box and looks the part.
Thanks in advance for any words of wisdom anyone can provide.