# Driving Rod / Wheel Issue.



## Groovytrains (Sep 27, 2021)

If this isn't the correct place to post this, please let me know. I have a Bachmann 4-8-4 from either the 80s or early 90s. Whenever it goes around a 9" radius curve, one of the driving wheels pop out. I've been able to push it back in, but now the driving rod is misaligned. There's a lot less resistance on that entire side compared to the one that isn't broken, and all the wheels move freely. Is this something that can be fixed? This machine has significant sentimental value to me. Thanks!


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## traction fan (Oct 5, 2014)

Groovytrains said:


> If this isn't the correct place to post this, please let me know. I have a Bachmann 4-8-4 from either the 80s or early 90s. Whenever it goes around a 9" radius curve, one of the driving wheels pop out. I've been able to push it back in, but now the driving rod is misaligned. There's a lot less resistance on that entire side compared to the one that isn't broken, and all the wheels move freely. Is this something that can be fixed? This machine has significant sentimental value to me. Thanks!
> View attachment 568999
> View attachment 569000


Groovytrains;

Your locomotive is N-scale, so you're posting in the right place. If you hadn't mentioned the "significant sentimental value," my advice would be to hold the locomotive over the nearest trash can, and let go. This is not a good locomotive. The next best option would be to replace the locomotive. Bachmann still makes their 4-8-4 Northern, and from what I've heard on the forum, the new locomotive will likely be a lot better than this old one. To try getting this one running right is going to take a lot of fussy, difficult, work, with no guarantee of success at the other end. Do you want to run it or would you be OK with using it as a static display next to an engine house?

I had one years ago, and if you still want to save this one, here goes.

The drivers on steam locomotives need to be in certain positions relative to the other drive wheels, both on the same side, and the opposite side, of the locomotive.
Starting with the locomotive's right side, as shown in your second photo, the wheels are not in the right positions. The pins in the side rods should all be in the same relative position. Easiest to explain would be all at top center. To do that, you'll need to pull the drivers off their axles, one-at-a-time, and re-mount each one with its crank pin at top center. When you pull the wheel, you may see splines in the axle, that are supposed to align with grooves in the wheel. You have to get each wheel's grooves in the same slots as the other wheels. One slot off won't work, the rods will bind. (NOTE: To test alignment you should remove the motor from the locomotive, so that you can hand-push it along the track. This will let you feel if things are aligned correctly or not.) Once you get the four drivers in the right positions on this right-hand side, look at the drivers on the left side. The crank pins on this left side should all four be in the same position as each other, but NOT in the same position as the pins on the right side. Instead they should each be one quarter revolution ahead of (or behind) the pins on the right side. If they are not, then the wheels are said to be "out of quarter." On a real steam locomotive having one side a quarter off the other is necessary to get it started, and keep it moving. On a model, the rods & pins are just for show, but still need to be "in quarter" or the mechanism can bind. Once you have gone through all that, very slowly roll test the locomotive and feel for any binds of hiccups. There shouldn't be any, the mechanism should roll very smoothly. Next, use an NMRA gauge to check the gauge of all the wheels on the locomotive. Spread them, or narrow them, until the wheel flanges fit into the "wheels" slots on the NMRA gauge. (see photo) Doing this keeps derailments, especially on turnouts, to a minimum.
Finally, having put in all this effort, you'll want to keep things as you have set them. Put a drop of super glue on each axle end where it meets the wheel hub.

Good Luck, I think you'll need it.

Traction Fan


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## Jscullans (Jul 8, 2019)

I agree with traction fan. If this model absolutely MUST run you’ve got your work cut out for you. I’ve got an ho scale brass locomotive I paid out the nose for that has one of the six driver wheels out of quarter and I’m still not willing to take on that project after being in the hobby again for around 4 years and having a small “shop” room in my basement with just about any tool I could ever need. I would suggest possibly looking into the nwsl “quarterer” tool to help you get them dead on accurate before you glue them


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