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I just removed the gear train cover plate on my DCC-equipped American Models K4 Pacific locomotive to check if the grease had hardened and needed to be replaced. The loco [and permanently attached tender] rotated and fell a few inches out of the its cradle, causing the gear train to partially slip out of its frame. After considerable difficulty and time, I finally managed to reinsert the assembly completely back into the frame and refasten the cover plate. However, the loco will no longer run; I just hear a clicking sound emanating from the tender as the command station throttle is advanced. Does anyone have any idea what went wrong and how I might remedy this rather “unfortunate” situation?

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It's REALLY crucial that the drivers be aligned properly.  The drive is basically a big 3 axle diesel truck with siderods.

Even with a driver gear being one tooth off, binding can occur.  Short of removing the rods, the easiest way to check is spinning the motor by hand at the flywheel and see if the mechanism is binding.

Also, straight DC can be applied directly to the motor leads.

It may be a pain, but you may have to disconnect your DCC.  It's easier to work on the loco drive without the tender attached.

Rusty

I completely agree with Rusty.  AM steamer gears are unforgiving.  They must be in perfect order relative to each other.  If all else fails, AM will do repairs.   I have never discussed this issue with them, but I assume they have some tool and/or process that allows them to quickly assemble these in exact alignment because doing it my way took forever.

@Chuck K posted:

I completely agree with Rusty.  AM steamer gears are unforgiving.  They must be in perfect order relative to each other.  If all else fails, AM will do repairs.   I have never discussed this issue with them, but I assume they have some tool and/or process that allows them to quickly assemble these in exact alignment because doing it my way took forever.

Don't feel bad, I had to do this on a Northern...

Rusty

Rusty, thank you for the potentially helpful tips you have provided. Attached are a couple of photos showing the exposed gear train after one of my many, many attempts to get the tops of all six silver-colored "blocks" to lay flush with the supporting frame. Here, only the front-most set of drivers [the one closest to the pilot end of the loco] appear to be fully seated. The other two sets are not. This condition notwithstanding, the drivers rotate freely in both directions [albeit somewhat wobbly] when the assembly is spun by hand. The height of the individual blocks rise and fall as I do this, suggesting that the gears are not meshed correctly. Screwing the cover plate back on completely prevents wheel rotation...obviously because of the presence of one or more raised blocks.

Why won't the gear assembly fully seat?

Alas, this is embarrassing to admit, but I can't identify the "motor leads" so I can apply DC current per your recommendation. Touching various parts of the frame and wheels with wires connected to my power pack just causes sparking to occur.

Another silly question- -one borne out of ignorance: Would disconnecting the tender require later reprogramming of the decoder?

Gears: overall view

Gears: close-up showing raised blocks at rear wheelset

Attachments

Images (2)
  • Gears: overall view
  • Gears: close-up showing raised blocks at rear wheelset
Last edited by Rich Melvin

It's really "go by feel" to get everything seated properly and it is a pain in the a**.  Frustrating, I know.

There are no power pick ups on the locomotive, it's all through the tender trucks.  Both sides of the outer truck wheels pick up power, the middle sets don't.

I usually peel back the heat shrink on the motor terminals and make my clip connections there.

The decoder shouldn't need reprogramming if it's disconnected.  I'm not sure if back DC voltage would hurt it if i remains connected.

Rusty

I spoke with Ron earlier today. He said that aligning all the drivers in the six -o'clock position would solve the problem, but it'd probably take "awhile." I'll try doing that; if this doesn't work, I'll send him the loco & tender and let AM fix it. [If I do that I'll also ask them to look into why I can't get this motive power's max S scale speed to exceed 56 mph.] According to Ron, the estimated repair price for the gear-related issue alone, less return shipping and handling, would probably be less than $50. It's looking more like Gunny and Chuck K's advice will be the proverbial ticket!

From the photo, it looks like the first and third wheelsets don't have the rod attachment in the same relative position (quartering).  I can't see the middle one.  That could be the problem.  As to the bearing blocks not seating, that's part of the mis-alignment.  They WILL come out of position without the bottom plate in place simply because the drivers are not aligned properly.  Even if they're properly aligned, they will raise slightly, without the bottom plate in position.   Follow Ron's advice and position them all in the 6 o'clock position and make sure that once the bearing blocks are seated, they're STILL in the 6 o'clock position (nothing magical about 6 o'clock, it's just easiest to determine by eye)

I know it takes time, but remove all the side rods and see if everything turns without binding.  That will tell you for sure that the wheels aren't positioned correctly.  On AM steamers, the side rods are for show only since the gearing does the powering of all axles.   If he rods are connected to the wheels, they fight the gears and binding will occur.  

If it binds without the rods, you have a different problem.  Are all the gear teeth solid?  Are there teeth missing?  It's extremely rare, but it does happen, especially on some diesels.

As to any damage to the DCC if you back feed it, I'd not take the chance.  Disconnect one wire from the motor, and power it directly if you chose to.

If my advice works, I just saved you $50 (plus shipping).   I hope it does!

Last edited by poniaj

I have a AM Northern and luckily never had to do much to it. The previous poster has given a lot of good tips to resolve the problem. All I would say is that if you remove the side rods and take out all three axles with the intermediate spur shaft/gears and set them up so that they all align correctly on a flat surface and then drop the chassis on top, then you ensure that the quartering is in alignment for all three axles.

I can’t see why this is difficult, I assume AM have a tool that sets the axles in place for assembly, a five minute job at best.

Trouble is the intermediate gears that transfer motion from one set of drivers to the other would then fall out.

Rusty

I understand what you are saying, it needs a tool that has a slight hump between the drive axles to accommodate the gap for the intermediate spur gear/axles. I have it in my mind as to what it would look like, I would just need to make one but as I don’t have a AM pacific I am not able to play around doing it.

According to Ron of American Models, the universal joint was broken and had to be replaced. The loco runs fine now but is still just as slow as it was originally [see my Jan. 18, 2021 Layout Building/Electrical Forum post titled "Measuring the current draw for a locomotive and a string of cars in motion"].

Total turnaround time for the repair was only eight [8] days. Great service!

@Bob G (WNY) posted:

According to Ron of American Models, the universal joint was broken and had to be replaced. The loco runs fine now but is still just as slow as it was originally [see my Jan. 18, 2021 Layout Building/Electrical Forum post titled "Measuring the current draw for a locomotive and a string of cars in motion"].

Total turnaround time for the repair was only eight [8] days. Great service!

Have you had it from new? Has it always run slowly since you had it? I can’t imagine Ron would send an engine back if it still had a problem.

A common problem on AM drive. The universal socket that is pressed on the motor shaft develops a longitudinal crack that is difficult to see. Symptoms are a clicking noise when running on track or the engine spins and there is no drive wheel movement when the engine is under load and on the track. I have replaced several, even on older engines that were never run. Probably is something with the type of plastic used in construction. It is a relatively easy fix.

@Ukaflyer posted:

Have you had it from new? Has it always run slowly since you had it? I can’t imagine Ron would send an engine back if it still had a problem.

Yes, it was an online purchase brand new from [apparently now-defunct] Chick's Hobby Shop. Chick upgraded the unit for DCC operation. No problem there- -all functions installed work perfectly.

Ron told me [via phone] that American Models is unable to evaluate the performance of any DCC-equipped locomotive [their shop lacks even a rudimentary DCC system for this purpose]. Presumably he ran the loco on DC after completing the repair. Evidently it didn't run "too slow" for him; otherwise he would not have shipped it back to me without indicating [on the invoice or by phone] that it had such a problem.

@Rayin"S" posted:

These locomotives run much slower than an American Flyer. There is nothing wrong with it, it's set to run at a more realistic speed. I have seen these at the S Fest train race events, they are geared to run at a lower speed.

RayDigitraz Zepher

Your observation is very enlightening, Ray. In view of my response to Ukaflyer [see the post immediately above this one], there is indeed nothing wrong with my locomotive. That said, apparently my basic Digitrax Zephyr DCC system is quite adequate for handling this loco and a six-Budd passenger car consist. The upgrade recommended by Digitrax Tech Support- -an added DB210 booster and PS615 power supply- -will not be needed. I just have to get used to watching my train travel at a "more realistic" top speed. As a former longtime Lionel train operator, I was accustomed to rotating a handle on my ZW transformer and making my trains zip along at reckless, admittedly unrealistic, speeds. Alas, those were the days...

@Rayin"S" posted:

These locomotives run much slower than an American Flyer. There is nothing wrong with it, it's set to run at a more realistic speed. I have seen these at the S Fest train race events, they are geared to run at a lower speed.

Ray

My childhood train was a K5 Pacific. I think it was 312AC; not fast at all. Top speed was prototypical 80 mph at best. It was 1/2 the speed of my friends Lionel.

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