Strange Atlas Motor Action

[BCR751]

I put a right-out-of-the-box Atlas C-630 on the track to try it out.  It's about two years old, is DC and has the standard Atlas DC light board.  When I advanced the throttle, it took what I would call, an excessive amount of voltage to get it moving.  Figuring it might be something haywire in the mechanism, I took it all apart.  There was a huge amount of very sticky grease in the mechanism, which I cleaned out.  I also hooked the motor directly to a variable power supply and it ran fine.

I re-assembled everything and put it back on the track.  This time, as the throttle was advanced, the motor started to "growl" but no movement of the loco.  Further advancement saw the motor continue to growl and then, with the throttle at about 30%, the motor stopped completely.  More advancement and the motor literally took off at about 70% on the throttle but at full throttle there was not much speed to it.

I connected an analog volt meter to the rails and watched it as I advanced the throttle. It tracked very linearly (if that's a word) with no hesitation at the point where the motor stopped.  The motor started its first growl at about 2.5 volts, died completely at 4.5 volts and jack rabitted at about 7 volts.

Anyone else ever had this problem with an Atlas mechanism/motor?  Could it be the light board?  I have no idea what could be causing this.

Doug

[peteski]

The dried up and extremely sticky lubricant is a known problem - I've seen it many times on many different locos (even non-Atlas brands). The entire mechanism should the thoroughly degreased (I use Naphtha) and re-lubricated.

The growling is probably caused by the split ball-joint for the universals. Another somewhat common issue. They split on the motor shaft allowing the motor to run without powering the loco, with slippage where one truck is running while the other truck is stalled..

[Albert in N]

The motor contact strips also can be a problem.  I recently replaced the slipping ball universal joint that was inside the motor flywheel in my Atlas FM H15-44.  The chassis ran until I put the body shell back on. After working with it, I put it away in my junker box.  If I ever get a wild hair, I may try hard wiring the motor contacts to the wheel pick up strips like I did with HO USA-made Athearn diesels back 30 years ago.  In the meantime, the dependable Katos keep the trains on schedule.  Yes, I still use DC MRC Tech 4 powerpacks.  BTW, this same Atlas was returned to the factory for slipping universal joints and repaired while still under the 90-day warranty about 10 years ago.  It probably has less than a total of five hours running time on it since I bought it brand new at a local hobby shop.

[BCR751]

I'm reading the other thread started by atsf_arizona discussing the causes for the growling sounds.  That is really great information and lists some things I can try on my Atlas C-630's.

However, it does not address the reason(s) for the motor speed changes as the throttle is increased.  I have two other brand new Atlas C-630's and when I ran them through the same test, those motors acted the same, slowing down and speeding up as the throttle is increased.  Could this issue be related to the noise issue?  That is, could there be some binding issues in the mechanism that is causing excessive load on the motor at certain RPM's that shows up as motor slow-down?  Just guessing here......

Doug

[peteski]

However, it does not address the reason(s) for the motor speed changes as the throttle is increased.  I have two other brand new Atlas C-630's and when I ran them through the same test, those motors acted the same, slowing down and speeding up as the throttle is increased.  Could this issue be related to the noise issue?  That is, could there be some binding issues in the mechanism that is causing excessive load on the motor at certain RPM's that shows up as motor slow-down?  Just guessing here......

Doug

I would say that it is a very good possibility.  Maybe only one shaft coupling failed and it sometimes starts slipping?  Then the motor could rev up while loco slows down as one of trucks starts dragging on the track while the other truck is propelling the loc slowly while the wheels are slipping.

If some of the sticky lubricant is still in the mechainsm that can bind it further. If some of the sticky lubricant is in the cracked coupling it can sometimes make the coupling adhere to the motor shaft making it run better.  Just speculatign here.

Other common source for growling sound is lack of lubrication on the motor or worm shafts.  But sticky lubricant might also have the same effect.

If you haven't thoroughly take apart the entire mechanism, degreased and re-lubricated it -  I highly recommend doing so. While it is apart and cleaned, you can easily check the U-joints on the motor shafts and see if they are split.