Bachmann NScale J Class 4-8-4 question

Discussion in 'FAQs' started by Herc Driver, Nov 15, 2008.

  1. Herc Driver

    Herc Driver Active Member

    We had a major repair for the back shops here on the Ballantyne Division...the J-Class stopped working. Now, I'm no expert on engine repair, but a magnifying glass soon confirmed that two small parts had become seperated and another part had bent as a result. Straighting out the bent thin metal was the easy part, but reconnecting the two other parts proved challanging. Finally, I got it back together and gave it a test run. At first, it would only run in the forward direction. In reverse, the wheels would almost make a complete revolution, then stop as if jammed. If slight pressure was placed on the engine, you could feel/hear a faint click and it would start moving backwards. Obviously, there's still something outta whack and not as it should be. After running it (at forward, full speed) it seemed to run without a hitch. And following the full speed test run, it would even run in reverse...only jamming up every once in while, and for a while, not at all. I'm sorry I can't name the parts in question. I have the exploded view of the Bachmann J-Class but don't know what the actual parts are called (in real life) to explain it better to you. Basically, the piston drive parts came apart and bent one of two thin metal guiding arms (but I'm sure that's not the right terms). What I noticed was this...there is a slight difference in how the main drive wheels are aligned and attached to the driving rods...are they supposed to match up? What I'm asking is, if one rod attaches at say the 7:00 position, should the matching wheel on the opposite side also be connected at the 7:00 position? Right now, if the left side drive rod attaches at the wheel at 7:00, the right side's are positioned at about 8:00...just a bit different. I was thinking when I reconnected the two small parts, I should have made sure the wheels were at the same point, or maybe that the pistion should have been at the same point.

    This is probably way to hard to follow, and I'm sorry I can't explain it better...I have very little steam engine knowledge, and none of my books here at home help. If anyone could direct me to a good steam website, maybe I can figure this out and fix the engine properly. But I'm open to everyone's ideas and expertise on how to fix this guy right!
  2. chooch.42

    chooch.42 Member

    Hi, Herc. I'm not a tech/mech expert either, but the connection where the rods attatch to the driver are the "crank pins" and there SHOULD be a difference in location from one side to the other. Drivers' crank pin locations are 90 degrees offset - if the left side is at 7 o'clock, the right side will be at 4 o'clock (or 10 - I'm not sure which way). You should be able to see by looking at the other driver pairs. If the others aren't "Quartered" either, it may be that the engine was disassembled and not rebuilt right. Wish I could be of more help - sure somebody else here will have a more complete answer. Bob C.
  3. Herc Driver

    Herc Driver Active Member

    Thank you! That's more than I knew before. It ran well before, and seems to run ok now, except in reverse when it jams up again. But outwardly, I can't see anything causing the sudden lock up of the wheels.
  4. Russ Bellinis

    Russ Bellinis Active Member

    Herc, Bachmann has a lifetime guarantee on all of their locomotives. If you didn't do any damage to it, they will replace it or repair it for the cost of shipping it to them and return postage. I model ho, so am not familiar with n-scale Bachmann steam, but I had a problem with the old style 2-8-0 (not Spectrum). They had designed the locomotives with some side to side slop in the drivers to allow for it to operate on tight radius curves. The drivers would move far enough sideways that the crank pins on the front drivers would hit the valve gear and lock it up occasionally. Thin styrene shims carefully glued to the plastic frame behind the front driver set restricted the side to side movement enough to eliminate the problem.
  5. Herc Driver

    Herc Driver Active Member

    Ahhhh...interesting. I'll need to figure out if that may be the cause of this whole problem. I normally run the layout clockwise, and I'll look to see which side was affected...either the inside (of the track turn radius) wheels or the outside set and see if there's a fix. The tiny Nscale parts were a challange to align, even with a magnifying glass and sugical tweezers...but I'd like to make sure it's fixed for good.

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