Atlas B30-7

[carmelmodelrr]

On my DC layout, the train begins with a 10 ft. straightaway and then enters a 2.5 degree hill on a curve.  Given enough locomotive power (usually 3 locos) I've not encountered any running problems until I put the 3 (old) Atlas B30-7's to pull the consist.  When the train begins, it pulls the consist up the curving hill with no problem.  However, the longer the train runs, the more difficult it is for the locos to make the hill.  If I run it for 45 minutes or so, the locos almost come to a stop on the hill.  If I supply more power via the power pack, the locos will sort of make it up the grade but the wheels are spinning.  Once the locos reach the straightaway, they run just fine.

I've taken the locos apart and cleaned the wheels and the "cups" at the end of the axles, so I know dirt is not an issue.  I'm at a loss as to why I get this gradual reduction of power.  One thing I thought of but have not tried is to add some weight to the locos.  Would that help?

Any other ideas are welcome.

Thanks for your help.

carmelmodelrr
Richard Wroblewski

[tehachapifan]

Are you certain the wheels are spinning on all three locos when this problem occurs?

[carmelmodelrr]

Not sure if all 3 locos are spinning.  I'll have to run the locos for awhile and check this out.  That's a great point.

carmelmodelrr

[u18b]

Sounds like possibly a speed matching issue.

Does each B30-7 run at exactly the same speed as the others?  Cold?  Warm?

The B30-7 is a relatively light loco.  What are the other locos you do not have problems with (as a comparison)?

[carmelmodelrr]

I ran the consist for about a half hour, then tried to determine if only one or two of the locos was slipping.  Difficult to determine but it appeared that all were slipping.  I also took off the 3 locos and placed them on level track, but separated from each other,  and they all ran at pretty much the same speed.  I also checked the voltage of the track in the "offending" area and it was consistent with all of the other tracks.  Maybe I'm just expecting too much from this relatively light group of locos--and I should shorten the consist.  (I'm running a 21 car consist).  What's surprising to me, though, is that it works fine when the locos are "cold" but performance deteriorates as the locos warm up.

carmelmodelrr

[tehachapifan]

Sounds like possibly a speed matching issue.

Does each B30-7 run at exactly the same speed as the others?  Cold?  Warm?

The B30-7 is a relatively light loco.  What are the other locos you do not have problems with (as a comparison)?

Ron makes excellent points. In addition to these points, I would also be curious as to if the motor contacts to the lightboard in at least one of the locos are making spotty contact (a known issue with many Atlas DCC and DCC-ready mechanisms). This would not be the problem if the wheels on the loco in question are spinning upon stalling.

Something else that comes to mind is if these locos have the cracking flywheel doughnut problem. I haven't had mine apart in some time and don't remember if these locos have that doughnut (only a handful of Atlas locos have these). A sign this may be the issue is if the wheels in only one truck are spinning, unless both doughnuts are cracked. In which case it would be hard to distinguish between that and the aforementioned motor contact issue without taking the loco apart (well, you would hear the motor running with the cracked doughnut problem and not with the motor contact problem).

[peteski]

Something else that comes to mind is if these locos have the cracking flywheel doughnut problem.

Yes, that s a common and annoying problem, but when the cracked donut coupling is slipping on the motor or worm shaft, that results in the wheels dragging, not turning while slipping.

[tehachapifan]

Yes, that s a common and annoying problem, but when the cracked donut coupling is slipping on the motor or worm shaft, that results in the wheels dragging, not turning while slipping.

That's what I said (or at least it's what I intended to say).

[peteski]

That's what I said (or at least it's what I intended to say).

Yes, you did mention one truck dragging while the other one is spinning its wheels, but in my silly brain that wasn't clear. Sorry.   The OP did not mention about only one truck in the loco slipping.

[tehachapifan]

He said it was still difficult to determine. Which it is unless the wheels have some debris or a mark on them that you can easily see. Might be a moot point anyway, as I don't think these locos have the doughnut but can't recall for certain.

[peteski]

He said it was still difficult to determine. Which it is unless the wheels have some debris or a mark on them that you can easily see.

I suspect that when the problem starts occurring (the loco is warmed up during a long run), if one placed the misbehaving loco (by itself) on a track close to the layout's edge, using a flashlight and maybe even magnifying glass, would be able to determine if one truck is dragging while the other one is slipping.  Marking a wheel in each truck (like meter-maids* put a chalk mark on parked car's tire) would make identification even easier.

* Hopefully that is still a proper word to use in today's post "Blazing Saddles" days.

[NtheBasement]

The nature of slippage is that once one wheel slips, the rest, which were close to slipping anyway, suddenly have to pick up the extra load and so the whole thing goes south in a cascade.

Theory: one of your locos is getting hot and losing speed, eventually causing the whole thing to slip.  Test: send them up cold and uncoupled a few inches apart, see how close they are in speed.  Then do your long run and when things slip, uncouple them again and see if one has really slowed down relative to the others.

[Steveruger45]

How old are these locos?
I ask because I’m wondering if maybe one or more of the motors are suffering from weakened magnets.
You can check by removing the motor and rotating it by hand and feel for notching as each poles pass. The stronger the magnets the stronger the notching.
Unsure if this would be your problem but worth a check and it’s easy to do.
I think I would try to narrow down the issue to each loco to see if one or more is worse than the others.  Try running each loco individually with a train of cars and rinse and repeat with the same train on each loco and then go deeper from there.

[peteski]

How old are these locos?
I ask because I’m wondering if maybe one or more of the motors are suffering from weakened magnets.
You can check by removing the motor and rotating it by hand and feel for notching as each poles pass. The stronger the magnets the stronger the notching.
Unsure if this would be your problem but worth a check and it’s easy to do.
I think I would try to narrow down the issue to each loco to see if one or more is worse than the others.  Try running each loco individually with a train of cars and rinse and repeat with the same train on each loco and then go deeper from there.

That used to be a common problem with many older H0 locos which used metallic blocks as magnets. But very few N scale locos used that type of a magnet. Old Mehano (then early Model-Power) was one such brand of locos.  The locos in this thread use a typical Kato-clone motor with ceramic magnets.  Personally I have never seen that type of magnets lose strength.

They also have a skew-wound 5-pole armature. Because of that design, these motors show almost no cogging (notching), so it would be difficult to check the strength of those magnets by rotating the armature by hand.

[jagged ben]

I don't think it's super reasonable to expect much better.  These are small, light locos.  7 cars per loco is right around what I'd expect them to pull up a 2.5 percent grade, which is steep for any train.  I suspect others are right that as the locos get a little warmer you lose some motor speed and power.  But the fundamental problem may just be that it's a very boderline situation to begin with.  That train needs more locomotives,.or heavier ones. Not exactly sure why you don't see it with other locomotives but perhaps it's a few otherwise marginal differences in the type of motor, the weight of the frames, and the design of the trucks are just enough to tip the balance with the B30s.