Atlas C628 Problem

[absnut]

I have an Atlas C628 that, up until a few weeks ago, ran beautifully.  It is DC.  Then it started to slow down.  This happens on start-up, taking nearly 12v to get it rolling.  It slowly gathers speed and by the time it has circumnavigated the layout once, it is running fine.  I oiled trucks gears, worm, bearings but to no avail.  A friend suggested poor contact from grime getting into the cups the axle points ride in so, I removed the trucks and gave them an alcohol bath. I also buffed the brass contact strips. This seemed to improve things marginally but, I think it was just a wishful imagination because it's back to its slows again.    A trip around the layout and it's back to normal.  Has this happened to any of you fellas and what did you do to alleviate the problem?  Inquiring minds need to know. 

[MichaelWinicki]

Is this a DCC loco Dick?

If so have you tried to reprogram it?

[absnut]

No, it's DC.  Should have said that. 

[johnh35]

No, it's DC.  Should have said that. 

You did. What you describe is typical of an Atlas lokie with a Lenz decoder running on DC. However, the fact that it ran better to start with tells me that is not the case. I suspect the motor universals are slipping and that is why it is having trouble building speed. When you say it is back to normal, does that mean it operates fine from a stop after warming up? If it runs fine after warming, then I suspect that you may have over-lubricated your motor at some time in the past with an incompatible lube that is thick when cold.

[absnut]

I didn't do any lubing until after the problem started and, I kept it away from the motor. The only bearings I oiled were the ones near the worm gear. I'll get brave and check the commutators.

[E44A]

Have you tried to run it without the shell on?

As I have converted several C628 chassis to fit in E44 shells, I am quite familiar with it.
The slow-accelerating motor is one of the most common issue that I have.
After hours and observation and testing, I have found out that it is caused by the motor rotor rubbing the shell.


This can be fixed by centering the motor cradle (black plastic frame around the motor).
If it still rubs, super glue thin pieces of styrene on the two sides of the motor.

[Mr Z]

You said that your loco won't start rolling until you reach nearly 12 volts. When you are raising the voltage is the motor spinning but the dire train not turning?

I had a similar problem with mine that I believed I found the answer to on the old Atlas forum. Their is a universal cup on each end of the motor shaft that has a tendency to split and then spin on the motor shaft. I think I fixed mine by putting some CA on the part but I think you can also get replacement parts from Atlas. From wjat I recall this was not an uncommon problem.

Martin Z

[mecgp7]

Have you tried to run it without the shell on?

As I have converted several C628 chassis to fit in E44 shells, I am quite familiar with it.
The slow-accelerating motor is one of the most common issue that I have.
After hours and observation and testing, I have found out that it is caused by the motor rotor rubbing the shell.


This can be fixed by centering the motor cradle (black plastic frame around the motor).
If it still rubs, super glue thin pieces of styrene on the two sides of the motor.

Yep I, too, have experienced this. I shared it with Dick. The motor can get twisted in the chassis to the point where it hits the inside of the shell.
I have the same problem with my C628. I don't know why it runs better after a trip around the layout though. Seems to me if the motor is rubbing then it is rubbing.  Why would it get unstuck after running and then re-stuck when it cools down.
I have also noticed a lot of black grease in this particular loco. Don't know if it is factory or not.

[Cory Rothlisberger]

I had a similar problem with mine that I believed I found the answer to on the old Atlas forum. Their is a universal cup on each end of the motor shaft that has a tendency to split and then spin on the motor shaft. I think I fixed mine by putting some CA on the part but I think you can also get replacement parts from Atlas. From wjat I recall this was not an uncommon problem.

Martin Z

Winner! This was a very common problem on the C-628/630 as well as the H15/16-44. A drop of CA inside the flywheel usually does the trick. If you're not comfortable with doing that, send it back to us and we'll get it in under a warranty repair...

[mecgp7]

So what is happening that allows the loco to speed up after a while? I would think a slipping part will always slip. Why if you run it for a while does it operate normally under start stop conditions?  The motor runs slower with the drive shafts removed too so I think there is more to it than just the slipping universal cup.

[absnut]

Thank you, Cory.  Do I send it to you or another department?

[absnut]

OK, I popped the shell off again, gave it some juice and, sure enough, the motor was turning faster than the loco was moving.  So, I got brave and tore it down to its major component parts and discovered I could easily turn the drive shafts (both ends) in the flywheels.  So, with a toothpick, I applied some Loc-Tite to the shaft inside the flywheel.  After I was convinced the CA had "set", I re-assembled the chassis and gave it a run.  It still started slow but seemed to require less juice to move.  To be sure, I once again, disassembled the loco and discovered there was no slipping with the shafts on the flywheels.  After re-re-assembling the loco, I again put it on the layout, gave it some power, and found it would start to move at 6-7v.  A half hour of running at about 6v seemed to make it quite limber.  Giving it an idle period showed it again started slow but quickly ran "normal" after about a 20 ft. run.  I'll keep giving it shake-down time and see if all the ills go away.  Thanks for all your help and suggestions, fellas.