loco runs better in reverse

Discussion in 'FAQs' started by leon, Sep 28, 2008.

  1. leon

    leon Member

    I have a older loco which must be around 25 to 30 years old and it runs a lot better in reverse than forward. I remember an article which addressed this problem but my memory escapes me as to what they said was the cause and also what to do to remedy this. Would appreciate some feedback.

  2. Squidbait

    Squidbait Recovering ALCO-holic

    If it's a steam loco, that seems to be par for the course. ;) All my old clunker steamers seemed to run better in reverse for some reason.

    Aside from that, there could be several things that are causing this. What type of loco is it? Make and model? Does it have flywheel? Power trucks? Not knowing makes it very hard to offer useful suggestions.

    If it's a mid-mounted motor with flywheels, universal shafts, worm gears and towers, it may be that there's enough play in the mechanism that the flywheels or worm gears shift position and rub on the frame or don't mesh well with the gear towers. That can be fixed with some strategically placed washers in the driveline.
  3. leon

    leon Member

    Hi Squidbait;

    The steam loco in question is a 4-6-0 old timer. It was my first HO set bought and I think it was called the 'Old Timer' The drive gears are what I would call average with the worm gear attached to the motor which is meshed to the main drive gear. No other gears involved except the worm and the gear on the driver axle.

    Thanks; Leon
  4. Squidbait

    Squidbait Recovering ALCO-holic


    OK, steamers, because of the valve gear and siderods, have an added layer of complexity. Run the loco slowly forward and backwards in front of you, and look very closely at the rods and stuff on each side. See any binding? Anything rubbing?

    If you can get the boiler off and can run it, look and see if there's any play in the motor shaft to the worm gear. If the worm is pushed or pulled too far off centre, it can affect how it runs.

    When you say it runs "better" in reverse, how do you mean? Smoother? Quieter?
  5. yellowlynn

    yellowlynn Member


    Leon, I had one of those a long time ago. If the motor is at a slant, with a worm gear to the drive axle, that's the one. If you look REAL close at the motor shaft (and worm gear) when going slowly forward, stop and watch it going slowly backwards, you will see some play. Mine had a screw that mounted the motor. If that screw is too tight, it won't turn easily in one direction. It is trial and error in the EXACT and PRECISE adjustment. It should run much better, but I never could get it close to perfect.

  6. Squidbait

    Squidbait Recovering ALCO-holic

    Leon, is this your loco?

    ... or this?

  7. nachoman

    nachoman Guest

    sometimes there is end play in the motor armature. That means, as the motor rotates, the armature of the motor moves fore and aft depending on the direction of travel. Sometimes, there is enough play that it forces the armature into either the front or back of the motor housing causing friction. The solution is either to take the motor apart and add the appropriate thickness of shim washers to the motor shaft to remove the end play, or to replace the motor. I'm not sure if this is your problem, but if it has an open-frame motor and you can run it with the boiler off, you should see the motor armature moving back and forth as you switch from forward to reverse.

  8. diburning

    diburning Member

    I've noticed the same with with an older proto2000 gp18
  9. leon

    leon Member

    Hi Squidbait; Yellowlynn and Nachoman;l

    Thought I would answer all of you at once. First off--it is the top photo Squid. Lynn--I know what you mean about the motor mounting but the performance varies way too much and Nachoman I think what you suggested is what I read awhile ago. All of you have been very helpful and I will try your suggestions. Will get back to all of you later.

  10. doctorwayne

    doctorwayne Active Member

    I think that you've probably got the solution to your problem with the excess play in the armature - some thrust washers at either or both ends should help with that problem. The brushes should be centred, lengthwise, on the commutator. The screw holding the motor in place should be tight, to prevent the motor from moving. Then, if necessary, use paper or cardstock, placed under the motor, either under its entire length or at one end or the other, to achieve the optimum gear mesh. The gear teeth should not bottom-out in the other gear - tight gear mesh places an extra load on the motor and is noisier, while an excessively loose mesh will also cause vibration (which translates to noise). However, a gear mesh slightly too loose is preferrable to one too tight. Don't forget, too, to lubricate those gears with a suitable plastic-compatible oil such as LaBelle #102.

  11. Squidbait

    Squidbait Recovering ALCO-holic


    You've got a Tyco/Mantua Dixie Belle. The valve gear is very simple, so I doubt the bind is there. My guess is you've got some slop in the open-frame motor driving the worm gear. Either it's loose on its' mount or the shaft is loose in the frame. It could be difficult to get washers on the shaft, since you'd have to completely disassemble the motor to do it. Look for excess play at A and B in the photo. If the armature moves back too far, then it's pretty easy to slip a washer over the back end of the shaft (B). If it moves forward too far, and you can't get the motor moved back in the mount, then you'll have to pull the worm gear off, slide the shaft out of the frame and add a washer at A.

    Attached Files:

  12. leon

    leon Member

    I had already installed a new washer in the motor at point 'B' of Squidbaits demo and this already fixed the problem pretty good. So I figure problem solved; but I do have another question pertaining to the worm gear. I have no gear puller and was wondering just how to best go about this should I have to pull off the worm in the future doing little or no damage to the gear?

    I thank all of you for your support.

  13. 60103

    60103 Pooh Bah

    Leon: how is the gear mounted n the shaft? If it's soldered on you probbly have to dismantle a lot of the motor before you heat it up (don't trust me -- I've never done it). If it's just a force-fit (especially plastic) you can pull it off with a NWSL gear puller. (You can also use this for regauging wheels). One of our club has a geal/wheel puller made from an old C-clamp ith a slot cut where the anvil was.
  14. leon

    leon Member

    David: I know about the C lamp modification but wasn't sure if it work judging how longthe length of the worm gear is. I guess one would just have to grind the clamping part of the 'C-clamp" the accomadate the gear. Thanks for refreshing my memory.


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