Just wanted to ask the experienced model vets here what symptoms a motor going bad will present? I am DC only. I have a Rivarossi Pacific with what I believe to be a can motor in the cab (if the cans are cylindrical, this one being about an inch long and maybe a little less in diameter, haven’t measured). Recently this loco has begun to “surge”, particularly when going upgrade. The surges are quick in nature, meaning as it climbs, it seems (and sounds) to slow, then speed up again, all in about a one second time frame, doing this randomly but repeatedly, while under load on the grade. It is pulling 6 Athearn HW’s, all with weights removed, so the consist load is light. All wheels, including tender, are squeaky clean, as is track; I keep checking both hoping to find something I have overlooked.
I have had the shell off three times now looking for problems. The last time I unscrewed the motor, unscrewed the worm gear housing, spun the driven gear by hand thereby turning the wheels and rods, and could not feel or see any binding. The drivers all look straight; rods are all clearing each other. When I assembled it this last time, it seemed to run like a champ for a while (several hours spread out over two or three days) but is now surging again. Take the consist off and I cannot detect any surge.
So, I am left with wondering if the motor is going gunnysack on me? I am mechanically, and to a fair degree, electrically proficient as far as skills, and because of the forums here have gained the confidence to dive into my locos lately (it’s really not too scary once you do it-thanks all). That being said, what specifically do you all recommend as far as tests?
It’s been my experience that a motor going bad wouldn’t be surging in the nature you describe. The armature is turning quite a bit faster than the wheels so if there was something like a weak pole it could stutter quite a few times in one wheel turn. I’ve seen the problem you describe several times and in most cases it was caused by the worm being able to move back and forth on the drive gear. This normally doesn’t cause a problem on level track but going up or down grade it can cause the loco to have a surging motion that can appear random if the conditions are right. Teh way to prevent this or at least lessen it is to install thrust washers on the worms shaft so it can’t move back and forth so much.
LION would inspect the rest of the drive train. Look for loose or broken gears, gears with missing teeth, any binding parts, especially those that bind intermittently such as on curves or on grade transitions. Check for free movement of the trucks and wheels, and look for imperfections in the tracks.
Motors are sturdy little beasts and should not give problems, but check bearings, bushings, thrust washers and other mechanical parts. If the motor is old enough to have replaceable brushes, maybe it is time to examine them.
Let the motor be the last suspect on your list, but yes motors can go bad, usually a burned out winding or a loose connection to a winding. What symptoms they may display depends on what is wrong with it of course, but since LION has never had to look closely at motors him can help no further.
I agree with checking the worm gear and other gears first. There are many ways to tell if a motor is going bad or just too weak.
Check the amp draw, if it’s abnormally high, it’s probably got brush or related problems. This points out the advantage of motors which have replaceable brush and brush springs.
Check for smell and over heated motor.
Generally weak, not just going up a hill, but also slow on level ground.
Hard to get moving from standing still.
There are others, but these are just top of mind as I write.
The best way to diagnose this is to observe the headlight. If no headlight, attach a small 12v bulb to the motor connections at the motor and string it out one of the cab windows or back of cab.
If the light stays on, suspect a motor / worm issue. Before you open the motor or replace, check the connections at the motor.
If the light goes out/ blinks during this surging event, suspect a loss of voltage to the motor.
Since you have cleaned wheels and track, continue to check the electrical path to the motor.
How are the tender pickups?
Does it use a wire to the tender or is the draw bar used to send power to the motor?
How is the motor to locomotive frame wire?
Wiggle and tug on the wiring, it could be a wire held on by only a few strands.
Does the motor RPM also drop or does the locomotive just slow down when it surges? Hopefully the motor makes enough noise that you can tell. With these modern can motors sometimes it’s hard to tell.
It sounds more likely that something is slipping, drivers on rail, pressed on gear or coupling on shaft, something like that. When motors die they usually either stop or just generally get weak.
Assuming this is straight DC, I would run it with the shell off at about 10 volts and load down the drivers with my fingers to try and make the surging happen. At that point it should be pretty obvious. If there’s lots of torque at the drivers and the motor loads up, it’s probably slipping on the rail. If not much torque and the motor doesn’t load up, there is internal slipping.
One other rare possibility to look into is the internal wiring. If there is a wire somewhere just hanging on by a thread, the additional amperage going up a hill may slow things down because the wire can’t pass enough current.
Thanks to all for the tips so far. I DO know it is not drivers slipping on rails… I have been looking at this closely, and also trying to determin if this is happening each driver revolution or not. So far no, easily shown by watching the counterweights. I’ve done the shell off thing with manually weighting and have not been to successful. Headlight is lighting steady, as DC goes, dependent on speed (voltage).
This last run prior to post I have been running (at scale speed), and the loco actually cut out a time or two. Very quickly, instantly, then go again, the momentum of things carrying it through. I have the shell off now looking closely at wiring and internal connections.
Question: How hot should that mnotor really be? Hot enough to burn you? I’m rechecking all these basics mentioned so far… have not found anything in the drive train broken or damaged. The worm seems to be tight in the box. Not tight in the sense hard to turn, just tight as in it does not seem to be flopping around in there. The driveshaft, motor and worm are all in alignment and turninig evenly.
Question 2: How exactly do I check amp draw? Test leads on the motor? On the track? Do I check “starting” voltage (on motor, on track)? This is where I need specifics; I have a good Fluke digitial meter. I just need to know where I’m actuall connecting the leads and on what settings.
Thanks again for your experiences and please keep the info coming!
PS- I should add that it is difficult on my layout to test anything on level track. I have very little. With the 6 cars on it to give some load, by the time the tail is coming onto level so as to not be pushing the loco, the loco quickly begins to climb again… I suppose I could lose the consist and weight the tender to simulate.
Sorry about the triple post here; I’m trying to be as detailed as I can. This thing got hot enough to disfigure the mounting “bracket” it goes on. Since I had it apart this morning, motor, gear drive and all off, I re-assembled it. After running prior to these posts, upon disassembly I discovered the motor screws slightly loose. When tightening things did not look right, and lo and behold, the plastic bracket is disfigured now allowing the ears the screw go through to widen out. So that’s how hot the motor got.
Motor heat is a big indicator. Warm is OK. Hot is not. If it’s getting so hot it can burn you that can point to a problem inside the motor or it’s pulling too heavy a load. Being that the cars the loco is pulling are very light we can dismiss the consist load as the problem. The shaft and drive are turning freely with little or no resistance? If yes then this points back to the motor as the problem. It could be the brushes are worn down, the commutator could be dirty, there could be a bad spot in the windings. With the way modern motors are made it can be easier to replace the motor than to replace parts inside it. I’ve replaced quite a few motors in my time. The hardest part is finding a suitable replacement. I usually use whatever motor I can find laying around provided it meets the requirements. I’ve used motors from other locos, printers, disk drives, etc.
Sounds like shorted pole windings. Heat melts the insulated coating from the windings, resistance goes down, current goes up, motor gets even hotter. It may be an intermittent condition which occurs when the motor gets hot.
Be careful, if you blow the fuse inside that Fluke, you will not be happy. Some of the Fluke meters have a 9-12 dollar fuse. Its an 11 amp special duty safety fuse designed to give it a high CAT rating. DO NOT REPLACE WITH A CHEAP ONE [swg]
The fuse is only used during current testing. You could use a 10 amp fuse inline using a jumper wire so that fuse will blow instead of the internal one.
To test current draw:
Turn off the power pack.
Insert the Fluke leads into the proper banana terminals on the front of the meter.
Select the 10 amp scale.
Disconnect one lead at the power pack which supplies power to the track at the terminal screw.
Attach one lead of the fluke to the pack terminal screw.
Attach and the other lead to the now disconnected power pack wire.
The meter is now part of the circuit.
Run the train and observe the reading.
Return the leads to the proper banana jacks on the front of the meter before you use it for voltage.
Thank you Jim and Jeff (and all others so far). When I had it apart, I put the carriage with no drive gears in it on the track. Drivers and all running gear (rods and such) all turned freely as I pushed it by hand. The brass gears on the axle and in the gear box are good with all teeth intact. The worm is intact, and had maybe .014 play back and forth (front to rear)… geussing here by eye from memory of .016 point gap in the old distributors[:|] (dates myself a bit). I made a shim out of some thin sheet metal and took the gap to 0 with free ability to spin. Reshaped the mounting ears. Ran the motor for a while with no load, just the motor mounted with no drive train attached. Seemed fine. All the internal connections seemed fine and moving things around did not affect the motor operation. Put it back together with the shimmed worm gear to try that and no difference; she’s still surging, even with no load.
One thing I noticed is while turning the motor by hand, it had a “dry” sound from inside. I have lubed the bushings on both ends prior to all this with 3-in-1 and a toothpick, so I don’t think the bushings would be dry… the sound very much, to me anyway, seemed internal. I don’t know if this is indicative of anything?
I will have to wait until tomorrow to try an amp draw test but I very much appreciate the “how to”, even if it seemed “Barney style”. During this test, I assume by “run the train” you mean assembled, on the track and moving under it’s own power as opposed to suspended or upside down off the track? Otherwise, simple enough!
That motor is definitely bad! How many hours has it run? You should get a hold of Hornby/Rivarossi and explain the problem. They’ll probably suggest a new motor.
I don’t know how long it’s been ran or if it is original. It IS a Rivarossi motor, says so right on it- I saw that today. I bought the loco used a while back from an elderly woman selling her deceased hubbies stuff. It was in pretty good shape, no detectable wear on the drivers… wheels including tender as well as the pickup’s were all spotless. The motor was loose in the frame when I bought it but all looked clean as a whistle. I’m not sure if the original owner may have been having problems and began to tear into it, who knows. I even wondered if the motor had been replaced and the screws not tightened enough, until I saw the logo on it today. It’s ran wonderfully up until now- no indications or issues prior to this.
Tomorrow I’m going to do the amp draw test and see where I’m at. I just saw a RR motor on Ebay the other night…[*-)]
So, I’m getting readings, but no running doing this. No loco’s put on the track will run while doing this, but their are readings registering? Am I doing something wrong?
I had gotten an Atlas/Kato RS2 once that would run irratically.
Words to describe it can be mistaken & can be thought to mean something else between person to person.
Although I called my model Surging, it was more like somone dipping a clutch in a car, or one with a slipping automatic transmission.
What I did was to isolate the motor power & then test it.
I removed the drive shafts to eliminate any drag effects.
Then I direct connected the poles of the motor to my power source & began testing.
I spun it up & it would falter.
I did a cleaning & a lube, & tried agian.
Same thing…
Looking at the commucatior sparking noise, it looked inconsistent, I had cleaned it & polished it with an abrasive (eraser type) tool, & it looked good.
Checking further I found the brushes seemed real weak with the contact face, a sharpened toot pic would almost lodge them AWAY from the comm…
So, I disassembled the Brush guides one at a time & put a slight stretch on the springs, one was almost completely collapsed!!!
After I did that, this unit has become one of the smoothest runners I have!!!
Probably due to the extra attention to ALL running/working points on the model, but also because I have paid attention to everything that can make it ‘Right’ as it can be.
So make a check list, add to it, & think of way to test things that can lead you to results, it’s a Process.
Mine was a simple fix, yeah it took a few days, but now I learned new things, & saved a lot of work.
Thank you. I’ve looked, felt, desassembled, pushed with no driveshaft hooked up, everything I can think of. I feel no drag or binds anywhere. I’m attempting to get this amp draw test done, however, when I put the meter in circuit as written above, I get meter readings, both amps and voltage, but not one loco I have will move while the meter is hooked up between power pack and wire to track. If I understood the directions from above, the loco (any loco) should operate, while this test is being conducted, correct?
I’m now trying to confirm that I am doing this right or if there is something I am missing. I’ve disconnected one wire from power pack to track, hook meter leads, one each to pack and wire, leads in the amp ports, set to 10 amps, run the train and read meter? Except no train is running when I do this. I’ve tried each wire, and have tried switching leads. No “running train”, just sitting there, while the meter gives me numbers increasing and decreasing in correspondence to power pack setting.
Am I missing something when trying to do an amp draw test?