As some of you may know, I have an Atlas SDP35 with DCC that I’ve been having a shorting problem with. I dissasebled it, and judging from the minor sparking coming from inside the motor (there’s a few small holes in the side of the motor that I can see the sparking from) which I’m guessing is worn motor brushes.
My question is, how would I fix this problem? Is there a way to fix the brushes or do I have to buy new brushes? I’ve never seen new brushes for sale, does that mean I have to replace the entire motor?
However, there is not enough information to indicate if they will work with your engine. My advice is that the best thing to do would be to call Atlas and ask them what you need to do to replace the brushes, or if they are even replaceable.
i actually impressed myself once by replacing motor brushes on a Life Like engine with those from a different company. It actually worked and the thing ran again. Too bad the whole thing just crapped out after a short while. But I was impressed.
Mark: I have been having a shorting problem with this loco bad enough to make it unusable until it is repaired, and I have tested everything I can think of, such as lifting one truck at a time (it’s not in the pickups there) and disconnecting the motor (no problem with the decoder or wiring) so the only explination I can figure is the motor.
I suppose it could be a bit of metal in the motor picked up from off the tracks (although I don’t know how it would get in, it was hard for me to figure out how to open it up!) so I’ll open up the motor and check it out before I order any brushes.
WORN BUSHES come from heavy use. Your problems may lie elsewhere.
SHORTING can be caused by a multiplicity of things. Worse, if it is intermittent.
Diagnosis is problematical - starting with bypassing the DCC board & running the motor on DC to eliminate the board. Example: If you replace the motor, and still have the same problem, where are you?
Chicago’s MSI train exhibit runs continuously, and mentioned ‘brush replacement’ on Atlas engines was difficult. at best.
Hmmm… It is a duel mode decoder, but I don’t think I have the jumper plug to bypass the decoder anymore… Alligator clips?[:-,] The shorting is coming from INSIDE the motor, I’m still iffy on how that could be a decoder problem anyway…
I know that the motor sparking is the trouble because the shorting only comes when the motor is coming up to speed. When it’s running at a constant speed it is fine. The sparking is also like this, so I have reason to believe the two are linked.
As Mark said some sparking is normal for brushes and if it is running strongly out of the chassis, I don’t think the motor is your problem. If however it is arc welder bright, and sustained yes you do have a problem. Use a very fine pin point to clean out between the slots of the comoutator if the brushes have gone soft.
Is it possible the “shorting” is occurring when your loco changes direction through turnouts or starts of gradients or yaws on a bit of track that is not quite level etc?
I would be looking for a dicey contact between the insulated wheel side and the frame somewhere. The fact that it is intermittent would suggest to me a wire joint with one of the conductors bridging somewhere else.
I did have a hassle with an Athearn unit not that long ago with the split axle. The axle of one wheel was a tad too long and provided intermittent shorting with the other wheel side in the same axle. A half millimetre off the axle with a file and no further problems!
Mark, I think I know what this means but let me clarify…
You mean Open Circuit as in the motor shuts off for a second?
What I’m getting is a momentary problem where the motor may be making a problem like an open circut, but I can’t tell because of the flywheels, and my DCC system sort of flickers as if it’s starting to short but then it clears before the breaker trips all the way. After running it for around 10 seconds then it will shut down all the way.This leads me to believe it is a short circuit, as I don’t think an open circuit would get any response from the DCC command station.
I took the motor off the frame (disconnecting it from the trucks and moving it away from the decoder which was sitting on top) and ran it holding the motor. This is when I noticed the sparks/shorting in the motor. For some reason when the short in the motor (and on the DCC command station) only occors when the motor is accelerating.
I think it shorts when the motor is under strain, as once it’s up to speed the momentum of the flywheels are doing much of the work. This would also explain why when the motor is connected to the drive frame it shorts even when it’s not accelerating.
Would worn brushes cause this, or is it just a bit of metal in the motor? I’m going to fire up the compressor today and blow some air in the motor to try to clear it up. (Would that mess up the motor brushes?)
Based on your description, it really doesn’t sound like a short to me.
You say after running 10 seconds it will totally shut down … is your system indicating a short ? If not, I would tend to believe you have an open circuit somewhere. DCC systems are rather sensitive to shorts - there’s no possible way your engine is going to stop “because of a short” and not trip out.
Blowing out the motor won’t hurt anything, but I don’t think this is your problem. However, seeing as how you have the motor out, you might as well check the condition of the brushes … just watch out for the springs when you remove the caps, they are under compression and will fly out if you’re not careful.
Do you have a volt-meter ? - this can be a very important tool to assist you here.
I’m no expert on DCC decoders, but I’m pretty sure that if the motor shorted out, the decoder would have fried. Do you ever have to spin the motor to get it started? If so, there could be a broken winding or two somewhere (that happened to me with an Athearn motor once). If that were the problem, the whole motor would have to be replaced, but that’s just a worst case scenario.
Both look the same by shutting down power, but from different causes.
‘LAWS of probability’ suggest it’s more likely the board than the motor. HAVE you run the motor without the board? An Atlas jumper is easier to replace than a motor (and cheaper).
If it runs for “10 seconds” before cutting off, suggests something is overheating - pulling excessive current. A circuit breaker then does it’s thing. DOES the motor get too hot to hold? (Clue).
If so, replace the motor.
WITHOUT an amperage indicator. we’re guessing, aren’t we? The motor is just part of the electrical chain.
I’m not sure what you mean about an open circuit, I though this meant there was a break in the circuit path, rather like a switch. I guess I was wrong…
The motor isn’t overheating or anything. It isn’t even warm.
I believe we have an amperage indicator, but I’m still iffy on what I should do with it… Could you give me specific instructions on what I should test?
I don’t really understand much about electrical problems such as this. Maybe I should bring it to someone who does?
Hopefully this will help you do your own electrical checks and I can provide further input if necessary
Have you a means of running the motor with DC? By the sounds of it you have. OK firstly rig your motor on the DC output (forget DCC for the moment) and run it. If you have a small digital multimeter, (one of those standard numbers that are right around the world or so it seems!) turn the dial to 20 DC volts or whatever scale yours happens to be.
Hold your multimeter leads to the DC power supply and turn your voltage up. If you have it connected the wrong way, the multimeter will simply read the voltage with a minus in front of it but this will not be a problem in itself. You can swap the direction of your leads to get a positive reading but it will not harm your meter. Check the following points
Does the motor start and run smoothly at about 2 volts or less?
Does it seem to be running a high speed freely at 12 volts?
At 12 volts or less, do the arcs from the brushes seem to be meeting? If this is happening, you may need to clean by undercutting the slots in the motor commutator using the pin head from before.
You made the point that the motor ran cool, is it still running cool after 10 minutes or so?
Winding the motor back does it seem smooth?
Now disconnect one lead from the motor to your power supply and couple your multimeter so that one lead goes to your power pack and the other goes to your meter. Your electrical path would be now in SERIES so that you have one power terminal, wire or
Based on the symptoms given, it sounds like the motor bearings may be worn and allowing the armature to move laterally and short against the field winding. How much free play is there in the motor if you push and pull on the drive shaft? There should be only very minimal movement in this direction. If you detect very much movement at all, the motor bearings are shot and the only cure is a new motor.
YOU seem convinced that the motor is the problem , and ‘brushes’ are the cure, (might be).
QUICK TEST: replace the motor. IF Problem persists It may not be the motor.
SIMPLIST: Have it looked at by someone else. NO ONE is versed in everything. (a) MOST repair fascilities get $25hr.to FIX things (b) Warrantee repair REPLACES within certain limited terms / conditions (c) You’re out shipping and time, either way.
WARRANTEE is only a 9 letter word. “LIMITED WARRANTEE” contains exclusions, incuding - non authorized work.
DIAGNOSIS is a process of elimination’ - no matter WHO does it.
This sounds like a real possibility. I haven’t seen an Atlas motor in a long time, but they used to have a bearing in the plastic end of the motor. If the motor got too warm, this bearing would re-locate slightly and the performance of the motor would degrade.
My experience is that motor brushes last longer than bearings.