Atlas U25B - I can't be the only one struggling with them.

[C855B]

I picked up three of the latest re-release of the U25B since they are square in the middle of my modeling era. I am having absolute fits getting them to run decently. They've been sitting on my bench for a few months for decoders, but the roundtuit beckoned and all three were upgraded this past week. What a headache.

Right out of the gate the wheel blackening is so dense that I have to spend 15-20 minutes each cleaning wheels just to get enough reliable conductivity to program the decoders. Once everything is back together (memo to self: do not put shell back on until it runs right!), inevitably one truck, or one half of one truck refuses to pick up power. Then once I have a bare chassis seemingly operable, reassemble... and... nope. Now it runs like crap. Clean track again? Better, but stalls on the unpowered frog. One-half of one truck isn't picking up.

Problem appears to be the pickup strips versus the fuel tank. In the taking apart for the decoder and subsequent reassembly, the strips become slightly distorted so they touch the top of the fuel tank and are lifted up from contact with the (too short!) riser on the truck. Then I've discovered contact issues where the strip presses into the chassis. I don't know exactly why as there is lots of metal-to-metal contact, but probing around discovered that issue on at least one.

At this moment I have one out of the three that runs to my satisfaction fully assembled. I've mucked around with the other two so much things are breaking such as handrails given the amount of resistance in removing and replacing the shells repeatedly. So I've already ordered replacement parts, including two pair of contact strips to hopefully return to factory shaping of the springy part so it doesn't touch the tank.

[...sigh...]

I do a lot of decoder installs, and these U25Bs just frost my butt. This can't just be me.

[peteski]

While probbaly not this specific models, some locos using this design lave the pickup pstrips loose in their retaining frame slots ionside the fuel tank. Instead of bending them for more positive contact my friend slid styrene strips into the slots along with the brass strip to provide a more positive contact.

As far as the sideframe metal nubs go, they shouldn't need to be very tall. If aligned properly the pickup strips will be perpendicular to them so they should be in solid contact. 

I like to sand and polish those nubs, and also polish the contact areas on the pickup strips.

According to Spookshow, these locos were last made in 2003.  20 years ago! http://spookshow.net/loco/atlasu25b.html
It is possible that the lubricant in the axle bearing cups has hardened and is affecting electrical pickup. I would take the entire model apart and give it a full cleaning.tuneup.



I believe that this design is also prone to poor connectivity of the motor strip contact to the light board.

I don't know what is your method of getting rid of wheel blackening, but what works well for me is the Minitrix brass brush wheel cleaner. 



Also, on 20 year old model (if you have the trucks apart for cleaning), I would just throw the wheelsets in a Naphtha bath (in ultrasonic cleaner) to get rid of any hardened factory applied oil on the wheels.  They often do that to prevent oxidation in storage

[C855B]

... According to Spookshow, these locos were last made in 2003. ...

Mark just hasn't updated his page. These are from a 2022 release.

I'll put that Minitrix wheel brush on my list for the next order. I tried the Woodland Scenics wheel rig a while ago... what a waste of money. I currently hold the loco with one truck on rails with the other end on a paper towel moistened with alcohol. Nice thing about that trick is it gives feedback on how much dirt/coating is coming off. These were pretty bad.

Now I better understand why the latest Atlas releases of their 6-axle chassis have wired trucks, although I never had troubles with any of those with the pickup strips (aside from breaking universal donuts ).

Good tip on the styrene shims. I'll give that a go, especially since I did ID it as a problem area during my own diagnosis. Thanks!

[spookshow]

FYI, I only update pages when something changes. AFAIK, the most recent U25B's are still the same as they were in '03.

-Mark

[peteski]

Mark just hasn't updated his page. These are from a 2022 release.

I'll put that Minitrix wheel brush on my list for the next order. I tried the Woodland Scenics wheel rig a while ago... what a waste of money. I currently hold the loco with one truck on rails with the other end on a paper towel moistened with alcohol. Nice thing about that trick is it gives feedback on how much dirt/coating is coming off. These were pretty bad.

While alcohol moistened towel will remove oily stuff and some surface blackening, the blackening substance is bonded to the metal. Best way is using abrasive method, and that is where the brass bristles in the Minitirix wheel cleaner come into play.

The most problematic blackening I had to deal with was on Kato GS-4 in American Freedom Train colors.  The drivers were blackened with a very dark and flat-finish coating. Different than on any other Kato wheels.  It was a perfect insulator - none of the drivers were picking up power!

On that one even the Minitrix cleaner was ineffective.  I took it one step further:  I removed the motor to have the drivers free spinning, then using a Dremel tool with a stainless steel wire brush disk placed against the thread, removed the blacking until the treads were shiny metal.

I don't think you will have to go that far.  The other option (since Atlas wheels are thinly plated brass which is not the most reliable for electric pickup), replace the wheels with Kato wheelsets.  Other then having to modify the half-axle lengths, they are drop  in replacements.  And with narrower thread, lower flanges, and better-shaped wheel faces, then look great.  There is a lengthy thread about this retrofit.

[C855B]

Hi, Mark. Since you are "the authority" - which we are all grateful for - possibly think about noting subsequent releases even if nothing apparent has changed. I think there were QC or at least minor dimensional issues with this run, at least from what I experienced with all three.

One more on the "smooth running" roster. It's all about the contact strip:

• Shimming the strips in the center with styrene seems to address most of the issue. My eduguess is mcro-oxidation on both strip and frame in this location is the culprit.
• Be careful about lateral positioning of the strips above the truck contacts. It is too easy to push them in too far so they rub on the frame sides and stick there, out of contact with the truck nub.
• Contact cleaner on and around the truck/strip and trucks themselves seemed to be the last 'gotcha'.
• Be very careful placing the body back on the chassis so that the strips are not knocked out of position once "tuned" as above. Frankly, the way the walkway piece has to be jockeyed around makes this a nearly impossible task.

One more to go. Thanks again, Pete, for the shimming tip.

[peteski]

You welcome Mile  - I'll thank my friend, Ernie Poole as he came up with that one.

I don't remember - do these strips have 2 pointy "nipples" in the area that sits in the frames?  If yes, those nipples are supposed to provide positive electrical contact with the frame.  I know Kato locos have those nipples - I don't recall if Atlas has them too.  It is also possible that Atlas revised the shape of those pickup strips in the latest run, so the don't work as well.

If they were as bad as you experienced, I figured that since these models have been around since 2003, we would have seen more people having problems.

[spookshow]

Sorry, but I am not ambitious enough to try to keep track of every single release of every single model (yikes). Best to let Trovestar deal with all that noise

-Mark

[rrjim1]

I can't be that lucky, I purchased 2 EL U25Bs and installed decoders in them.  Not a single problem and they run great.

[mecgp7]

Brand new locos often come with a lot of lubricant in the metal cups that accept the points on the ends of the axles. Disassemble the trucks and clean the cups and the tips of the axles. Also, the same pick-ups in the trucks can be seated wrong such that they sit too low. The trucks roll properly, but don't allow for conductivity. A firm squeeze as if fitting the truck side frames onto the gear tower could help.

I have purchased a number of Atlas locos with this problem. Many were the GP38-2 era chassis.

Another tip is to not only bend the pick up strips from the chassis down, but also ensure they are perfectly perpendicular to the truck pick up bronze nubs. The strips will tend to angle toward the outside of the chassis which is enough to make the strip only touch the plastic part of the truck. If anything you could twist them slightly to angle towards the chassis.

[C855B]

Brand new locos often come with a lot of lubricant in the metal cups that accept the points on the ends of the axles. Disassemble the trucks and clean the cups and the tips of the axles. Also, the same pick-ups in the trucks can be seated wrong such that they sit too low. The trucks roll properly, but don't allow for conductivity. A firm squeeze as if fitting the truck side frames onto the gear tower could help.

I may have addressed this issue by spraying contact cleaner into the trucks when I had the chassis apart. Which reminds me that I need to order more.

I have purchased a number of Atlas locos with this problem. Many were the GP38-2 era chassis.

Could be why I haven't seen this before. I could be corrected on this, but I think most of my Atlas "Classic" 4-axle purchases were before the 38-2. They tend to be pretty spare offering locos in my preferred RR/era.

As mentioned above, it is practically impossible to reassemble the walkway/shell without bumping the strips to where they are out of position, particularly where they rub against the frame over the truck. I found (...duh...) that enough strip was accessible around the fuel tank to make it possible using the right tool - dental explorer in my case - to adjust strip positioning while fully assembled.

Another tip is to not only bend the pick up strips from the chassis down, but also ensure they are perfectly perpendicular to the truck pick up bronze nubs. The strips will tend to angle toward the outside of the chassis which is enough to make the strip only touch the plastic part of the truck. If anything you could twist them slightly to angle towards the chassis.

I did this to one and apparently my skills at doing so are wanting. It's sitting on the bench to be addressed when the replacement pickup strips arrive, possibly by this weekend. It was quite clear by the improvement in the other two that shimming the contact area against the frame solved the lion's share of the problem.

If these continue to behave themselves after this attention I'll leave them be, but if they act up again I may just run wires between the trucks and frame and call it a day. Not easy, but re-decodering the BLI RSD-15s broke me of any hesitance to consider that approach. They run smooth as silk once you toss their decoder into the dustbin.