MDC/Roundhouse 2-8-0 and 2-6-0

[ATSF_Ron]

Warning:  This post is text heavy and photo heavy!

I have several of these little gems, the MDC/Roundhouse/Athearn 2-6-0 and 2-8-0 locos.  Yes, they are a bit spartan in details, but man!  They are sweeeeet runners!  I have 4 of the 2-6-0s and 5 of the 2-8-0s.  ALL OF THEM, except for this one, run perfectly and are in great shape.  If memory serves, I paid around $50 for most of them on eBay.  Most are lettered for SP or CP.  This one here looks to be in mint condition, except it won’t run.  Earlier this year I took it apart to see what the deal was.  The gears were all bone dry and had what I assume was 20 year old lube gunk on them.  I cleaned it all up, oiled it, and reassembled.  It still wouldn’t run.  I could disconnect the tender and that would run just fine, solo.  (These are tender drive.)  Hooked it back up to the loco and it would just hum.  No light was working either.  I decided to let it sit a while as I was working on 3 temperamental locos at the time and wanted a break from the frustration.  Other than Spookshow Mark’s photos of one of these disassembled, I could find zero documentation of troubleshooting/disassembly/assembly.  So, I thought I’d share what I’ve done so far.  I welcome any feedback troubleshooting this loco.

I took another look at it recently and noticed that if I lifted the front of the loco off the track a wee bit then it would run.  As in the motor and light would work, but no drivers were turning.  Hmm.  As soon as I set the front end down on the track, everything stopped.  I assume there’s a loco short happening.  I disconnected the tender and it ran fine as before on its own.

I took everything apart again per the photos you see here.  The brass worm gear you see in one of the pics was extremely tight earlier this year when I made the first attempt at repairs.  I had put some synthetic plastic-safe oil in there and now it spins just fine.  The two issues facing me currently are:

Why won’t the loco operate with wheels down on the track?  and
Why will the tender drive & worm gear work but no loco drivers will move?

I can manually finger-spin the motor and it will make the drivers turn while I hold engine/tender in my hand.  On the track?  Nope.

In one of the pics you can see a loco drive gear in my hand.  All of them have “healthy teeth” and none of them are split.  The brass worm gear also looks fine to me and turns freely.

In another photo you can see the worm portion of the loco drive separately.  When I reassembled it earlier this year I marked one side of each black plastic part (bushings?) on either side of the worm with a white dot (not visible in pic) so I would know which way to put it back in.  It’s possible I had one too many adult beverages when reassembling and flipped it 90 degrees, haha.  That might explain #2 above, the tender drive runs but there is no movement of the drivers.  I will monkey with that and report back on my findings.  It still doesn’t explain the (assumed) shorting issue.
Everything looks “normal” when I have the loco disassembled.  I have zero clue as to what is causing the short.  I don’t have the original paperwork that shows an exploded view, but I know it’s out on the web somewhere.  I recall seeing it once.  Thank you in advance, Railwire folks!

Ron

[Chris333]

There is a clip on top of the chassis that holds the worm down.

[ATSF_Ron]

Thanks Chris, I forgot about the clip and should've mentioned it.  The problem was happening even before I removed the clip.

[peteski]

If the tender's wheels pickup power from the track, and there are wires in the drawbar connecting the loco to the tender.  Are those wires crossed, causing a short between the rails?  That could be likely since you mention that ig the tender sits on the track and loco is lifted up, the motor works and the headlight works.

As for mechanical issue, if spinning the worm with your fingers makes  the drivers turn, but when assembled the motor runs,  but the loco (and worm) do not move then it is likely that one of the universal couplings on either the motor or worm shafts is cracked do the shaft is slipping in it.  All very basic things to check.

Or maybe I'm not understanding your description correctly?

[Chris333]

Sorry I first read this on my phone...

It sounds like the draw bar is upside down or something isn't touching correctly through the drawbar. Maybe there is an insulating washer along with a screw to hold the drawbar on. I always hardwire mine.

[ATSF_Ron]

Peteski & Chris, thanks for those suggestions.  I still have everything apart, so I snapped a few more pics to go with this response.  The drive shaft/worm gear shaft is shown in the first pic.  The last tiny black piece you see extending out snaps into a female connector on the worm side and another female connector on the tender side.  It snaps in & out easily at each end.  There is flexibility in its design so it can move a bit with variations in track elevation and curvature.  I read somewhere that these can break easily.  In fact, there's a guy named James, I believe, who makes or made these little parts (3D printed I think) since the locos and parts are no longer produced or carried by Athearn.  I used the highest magnification I have to closely look all of these pieces over, and to the best of my ability I see no cracking and felt no slipping.  I think these are all good to go.  I'll be looking over the drawbar and taking it apart this weekend when I have more time.  It's entirely possible that it was flipped over when I reassembled things.  I have no idea.  Luckily, I have a couple others that run fine where I can look at the assembly of them to clarify if I did it correctly or not.  The last pic is the tender shaft connection.  The two middle pics are different views of the assembled drawbar.  As I understand it, the 2-6-0 tender is supposed to be a better design than the 2-8-0 tender.  There's supposedly less wiring in the drawbar as well.  Thanks again, guys!

[Chris333]

The bigger end of the drawbar with the spring wire sticking out is the side that goes on the tender. That spring touches a tab that sticks down hidden by the axle in your photo.

The single finger you see in the hole touches the metal tender frame.

The smaller end goes to the loco and each of the fingers you see in the hole touch each frame half.

So if you have the drawbar flipped over the wrong way you are causing a short.

[Chris333]

I have a tender floor, but no drawbar to show you. But this is 2 different ways you can attach the drawbar:



One of these is wrong. Sorry I don't know which is which, but one of the two ways is incorrect.

[peteski]

Ron, looks like Chris has the electrical issue covered.

As for the mechanical coupling of the motor shaft to the worm shaft,  simple test:  When the model is assembled, if you spin the flywheel, can you see the worm turning?  And as I mentioned earlier, when the worm is turning, are the drivers also rotating (slowly)?

Like I mentioned, I have no personal experience with this model, but I have successfully repaired many models which I handled for a first time. These are all rather simple devices.  I'm just going by what I see in your photos.

[EdKap2]

The drawbar has two metal strips that conduct both polarities to the tender.  One has to contact the drawbar screwpost and the other contacts the metal post.  The larger loose strap has to contact the metal post.
I had the shorting problem when i got one of the moguls.  It works fine now.

[peteski]

.
I had the shorting problem when i got one of the moguls.  It works fine now.

And how did you fix it so it is now working?

[Chris333]

The drawbar has two metal strips that conduct both polarities to the tender.  One has to contact the drawbar screwpost and the other contacts the metal post.  The larger loose strap has to contact the metal post.
I had the shorting problem when i got one of the moguls.  It works fine now.

In my photos, both show the larger strap touching the post. But one way is to the left side of the locomotive frame and the other way is the right side of the locomotive frame.

[ATSF_Ron]

Chris, the pics were helpful.  I looked at another mogul I have and the 2nd pic looks to be the correct placement.  Peteski, sorry I missed your question earlier.  I believe the worm was turning but can't say for sure as the clip which covers it was still on.  I just took apart the two halves of the loco frame, a step I had not done before, and found more gunk on the gears.  You can see the crud in the photo.  It was really bad and was making the gear turning difficult.  That might explain why there seemed to be hesitation, even with the loco wheels lifted a bit. I put the gearing & loco frame halves all back together but no drawbar or drivers yet.  Then I connected the tender for power.  I wanted to be sure everything turned properly before the tough job of putting drivers and valve gear back in.  It's a tedious step.  At this point everything seems to ok.  I'll hopefully get the rest reassembled tonight and report back.

I also put in a couple pics of the worm.  Does it seem like everything is normal?  I've never pulled a worm gear before.  As I said, everything seems to be working normally.  With no drivers in, I can see all gears turning as they should.

EdKap2, I'd also like to know what you did to fix it.  Was it simply a flipped drawbar?

[Chris333]

Also thought I'd add that these locomotives are almost impossible to find anymore. Been looking for Athearn 2-6-0's black drivers (not MDC 2-6-0's silver drivers) for kitbashing and keep coming up zero.

[ATSF_Ron]

Chris, for sure they go fast when you find 'em!  This particular one in Central Pacific hardly ever shows up anymore.  Same w the 2-8-0s in CP.  Well, at a sane price, anyway.  There's one listed now for over $200.  Seriously??!