Greetings all -
I've got a bit of a mystery that I'm trying to solve.
I have a brass Precision Scale 0-8-0 switcher, which I've been breaking in on roller stands. I isolated the 12V Mashima can motor and temporarily installed a TCS motor-only decoder to test it on DCC.
The Mashima motor is sometimes becoming quite warm to the touch when operating the locomotivve at speed step 020 or greater. I have my Power Cab set up to monitor amperage. For the most part the motor is drawing roughly 0.25A. Occasionally, however, I've seen it spike to 0.9-1.0A.
The excessive warm temperature is not contingent on the spike in amperage. So, it can happen at 0.25A...or at 1.0A. The motor will slow down noticeably (or actually stop) when the motor gets too warm (hot).
I double-checked the motor leads and they are isolated from the frame. The linkage runs smoothly so I don't see any binding either.
Is this a sign of a bad motor? Or, is there something else I might have overlooked?
Thanks,
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
One additional test might be to ensure that the linkage and wheels continue to run smoothly at higher speed, or with weight on the drivers.
But this has the hallmarks of a motor fault. I take it you don't want to disassemble the motor to diagnose.
I think I'd remove the motor and test it using something like Mel's motor-as-generator dynamometer, loading it progressively and seeing if the temperature rise is dependent on actual load in some way. You might also drive the Mashima as a generator itself and see if that produces effects over time or if its output is unexpected in some way.
If a permanent-magnet voltage-controlled motor gets too hot, it can reach the Curie point of the part of the magnet close to the armature gap, which makes it stop acting as a magnet there. That increases the amount of current needing to pass through the windings to make torque... hence more resistance heating and bigger currents in the commutator/sparks at the brushes, which amplifies the magnet heating. Over time I have observed this causing permanent loss of magnetism in larger versions of this sort of motor which conventional 'rebuilding' won't address.
My is that you take the trouble to replace the motor now, whether in kind or 'better'. I am always nervous about transient problems with no clear cause...
tstage I have a brass Precision Scale 0-8-0 switcher, which I've been breaking in on roller stands. I isolated the 12V Mashima can motor and temporarily installed a TCS motor-only decoder to test it on DCC.
Implied, but not stated, is that the loco was earlier running nicely on DC on the test stand. And that the problem showed up once the decoder was "temporarily" installed.
Is that the case?
Ed
Ed,
Yes. I did break-in the locomotive in some using DC and it was running well. However, the shell was still on so I don't know if the motor was getting excessively warm or not.
I have also lubricated the motor shaft and the gear tower shaft bearings with Labelle #108.
You guys have to remember I’m older than dirt and many ideas and things I do are older than dirt too.I use a Canon EN22 motor as a reference motor to check out motors under test using a 2mm coupling. The EN22 being a generator.1) I use a digital voltmeter and ammeter to check the voltage from the EN22 generator and the output current.2) I shunt the EN22 motor windings with 12 volt bulbs as a load. I use #1815 bulbs that are rated at 14 volts at 200ma. I solder short leads to the bulbs with alligator clips. I have five bulbs allowing a 14 volt 1 amp load when in parallel. This is a Mel thing but gives me a good response curve to compare motors. You could run your motor under load to see if it gets warm.You could use a Mabuchi SF-266SA motor as the generator, it is very close to being an equivalent to the Canon EN22.Mel Modeling the early to mid 1950s SP in HO scale since 1951My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California Aging is not for wimps.
tstage Ed, Yes. I did break-in the locomotive in some using DC and it was running well. However, the shell was still on so I don't know if the motor was getting excessively warm or not. I have also lubricated the motor shaft and the gear tower shaft bearings with Labelle #108. Tom
Well, you've got TWO problems: the motor temperature and the erratic current draw. And you've hinted that they might be unrelated, since the timing doesn't match.
I suggest taking the decoder back out and running it again on DC. Check the motor temperature this time, and compare it to what you got with the decoder in.
Also check the current draw. I suggest using a real power pack instead of your DCC throttle, and using an ampmeter (that's how I spell ammeter). I suggest this so as to take the DCC and the decoder out of the loop completely.
IF there's something wrong with the motor, it should be wrong on DC, too. It seems.
Something to also keep an eye out for is a loose wire connection: erratic operation? changing electrical load?..........
Good & logical suggestions, Ed.
I used a MRC 1370 power pack running it on DC before. The Power Cab only operates in DCC; no ability to run DC with it.
I did a decoder installation that had a warning in the instructions saying that the decoder might get very hot. I forget which decoder it was, but they were right. It was not hot enough to melt the shell, but that thought crossed my mind.
I think this was a sound decoder, and I have no TCS sound decoders. Still, are you sure the motor was getting hot and not the decoder?
It takes an iron man to play with a toy iron horse.
MB,
I've been touching the metal motor housing on each side with my fingers and that's what has been getting very warm.
The TCS MC2 decoder is secured to the top of the motor with Kapton tape. I'm wondering if the overheating motor is also causing the decoder to overheat and that's part of the problem.
I'll try suspending the TCS decoder to allow for more breathing room and verify that it's not the source of the overheating.
Tom, you can be well assured that the decoder, or critical parts of it, is getting pretty darned hot after maybe 15 minutes of use if the motor is running near constantly and drawing close to an amp.* I say this only on the basis of your observation that the motor is objectionably hot to you, and that the decoder sits atop it.
It may not be what you wanted to see in a reply, but.....................you know....
* You mostly see it drawing a smaller fraction of an amp, but over time that will warm things a smidge. Then, when you don't know it, or when you do, it draws about 3.5 times the amperage. THAT IS when it will heat up, and it won't take all that long. Not only that, but as the heat begins to transfer at the 4th power of the heat differential between it and the cooler decoder (Stefan-Boltzmann equation ], that rate continues unnoticed for a few more seconds or minutes. It can't take long for a whole lot o' heat to build up in there. Then, when the rate reduces, it's not a fan-cooled motor, or one with little radiating fins on it....it will stay hot for a few minutes, still heating up the decoder. Not good.
selectorNot only that, but as the heat begins to transfer at the 4th power of the heat differential between it and the cooler decoder (Stefan-Boltzmann equation...
Curious Tom, did you find your heat gremlin?
I'm currently awaiting a part for an older loco before converting her over to DCC, and while testing on DC, after a long while the motor did get very warm and reduce speed. But current draw never seemed to change.... Always .5 amps or less.
So I'm curious if you found anything to look for....
Ricky W.
HO scale Proto-freelancer.
My Railroad rules:
1: It's my railroad, my rules.
2: It's for having fun and enjoyment.
3: Any objections, consult above rules.
The thing I see is that it occassionally shuts off when it gets hot or slows down. Ever take a temp gun just to watch the temp range? That points me in the direction of two parts getting warm enough that metal expansion causes them to seperate breaking the circut. When you let it cool off and start it again after a shut off, does the amps go to .25 or higher? The temps remind me of of how a resistor gets hot from restricting current. If something is broke or not connecting properly, but still making contact to some degree; it will act as a resistor genrating heat . If the break is big enough it wll need more current to jump that gap or not increase current but slow the rotation down as if you turned the throttle back. Most likely that fault is in the collector assembly (commutator and brushes and such)
Either something is not soldered right like a winding lead, or just needs cleaning like the commutator. That has isolation gaps and they do fill with brush shavings. which do close that gap electrically to a small degree. Or something is just plain broke.
See if you can get a second motor of the same type (never hurts to have a spare anyway) install it the way you have the faulty unit, and see if it repeats.
Shane
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
Sorry for the long delay in getting back to this thread.
Since I last posted I order and temporarily installed a LokPilot 5 in my brass 0-8-0. There was some noticeable improvement of smoothness at slow speed, which was surprising because I consider TCS & ESU to be pretty equivalent as far as motor-control goes. The one thing it didn't change was the occasional spike in current draw.
The motor didn't seem to get warm like it did with the TCS MC2 decoder. However, the spiking seemed to come more frequently. At speed step 030 the current draw would generally fluctuate between 0.1 & 0.35A. Occasionally it would spike and hold in the 0.7 to 0.9A range for a number of seconds. I could usually get it to drop again if I touched or slightly squeezed the motor housing. And, at one observation, I saw it briefly spike to 1.6A before dropping back down to 0.7 to 0.9A. So, I think the Mashima can motor has issues and needs replacing.
I've been poking around the internet to see what is available that would make for a viable replacement for this locomotive. The motor housing measures (in mms) 25(L) x 18.5(W) x 23.6(H) and "appears" to have a 2mm shaft. I say "appears" because there isn't a good way of measuring the shaft with a pair of calipers, which I'll explain momentarily.
To help with visualization, here are a few photos of the Mashima motor and how it couples to the gear box:
The end of the motor shaft and the gear shaft have a hexagonal nut wrapped in some sort of paper tape (Photo 2). These fit into each end of the shaft collar, which contains a short spring (Photo 3). I've never seen this sort of coupling setup with any of my other brass steamers. They have been simple shafts either going directly into the gear box, or mated using a short piece of flexible tubing.
Have any of you ever seen this before? I'm not opposed to using the shaft collar arrangement. However, I haven't seen any can motors with hexagonal nuts at the end.
I'm presuming that the end of the shaft is threaded and the nut can be removed. What is the best way to go about this because there isn't really a good way to secure the shaft in order to remove the nut? And, if I can't get the hexagonal nuts off, I presume I'll need to replace the gear box, too.
Any suggestions and ideas are appreciated. Thanks for the help...
It sounds like you have a bind. That is why your current draw goes up. I suggest you find the bind and fix it.
Tom, the hex-drive coupling is actually pretty easy to adapt to a new motor.
Just use calipers to measure the outside hex of the nut. It should be metric. One millimeter is pretty close to 0.040" for conversions.
When you get the new motor, find a brass metric machine screw with the needed size hex head. Cut the shank off the machine screw, and then drill a hole in the center of the head to match the diameter of the new motor's shaft.
I mount replacement motors with Kneadatite epoxy putty, so centering the drive nut to the hex coupling is no problem.
If it were mine, I would seek out a double shaft motor and put a flywheel on the end, but you will lose the backhead detail if you go that route.
It is easier than it sounds.
-Kevin
Living the dream.
7j43kIt sounds like you have a bind. That is why your current draw goes up. I suggest you find the bind and fix it. Ed
Wouldn't a bind occur at regular intervals of rotation? The higher current draw happens sporadically and for short periods of time before dropping again.
As a test to rule out any mechanical binding though, I disconnected the motor from the gear box and ran the motor alone with the decoder at speed step 030. (I believe that someone may have suggested that earlier.) The overall current draw was lower - i.e. in the 0.1 - 0.25A range. However, after a minute or so the motor whir changed noticeably (as if it were straining) and the current draw shot up to 1.0A and > before I shut the Power Cab down. I ran the same test again and got similar results.
So, I think that confims the motor is indeed bad and the binding is occuring inside the motor housing.
Tom,
if you are seeking a new motor, which seems unavoidable, then you could consider this motor: link. It is 12 V coreless motor, 17 mm in diameter, 24,5 mm long, 12000 RPM - so it fits in your locomotive (with some adaptation to motor seat). I bought several motors from this seller and never had an issue, but there are many other sources for this motor.
I have used this motor for my locomotive, its performance you can see on this video. It is virtually silent, has no cogging at all due to its design which is completely different from iron core motors.
This motor has 1,5 mm shaft, so if you want to use the original hexagon connector, you need a tubing (ID 1,5 mm to OD 2,00 mm). I think such tubing (brass, stainless steel) is available from NWSL, or it can be found on Amazon or even at nearby hardware store (like Home Depot). Or you can buy universal joint set from NWSL if you want to remove hexagon coupler completely, but this requires much more work.
This motor is more than strong enough for this small locomotive. It performs beautifully with ESU decoders. I do not recommend using TCS decoder with it because I noticed that with 2 out of three different coreless motors, TCS WOW sound decoder had issues in lower speed range. But as you have both at hand, you can test both.
Regards,
Hrvoje
SeeYou190When you get the new motor, find a brass metric machine screw with the needed size hex head. Cut the shank off the machine screw, and then drill a hole in the center of the head to match the diameter of the new motor's shaft.
Be careful that the hole is at right angles to the hex as well as centered inside it -- again something that is facilitated by using the shank as a guide.
Hi there. Before doing anything on the drivetrain, I would eliminate all other possibilities. Now that the motor has been removed, you can check for binds by rolling the engine by hand. There should be no friction. You can also benchtest the motor separately.
Simon
snjroy Hi there. Before doing anything on the drivetrain, I would eliminate all other possibilities. Now that the motor has been removed, you can check for binds by rolling the engine by hand. There should be no friction. You can also benchtest the motor separately. Simon
I agree - if worm is removed, and locomotive positioned on a track, or even glass sheet, when pushed, locomotive should roll without any hesitation or binding.
But note that he HAS tested the motor outside the chassis, and HAS verified the issue to occur in the isolated motor precisely as it appeared when installed. And he said he roll-tested the chassis for binding when the motor was out.
I don't think it's 'worth' trying to fix the motor, other than to do some forensics on what's causing the observed issues. Replacement -- ideally improved replacement now that that famous mother, necessity, allows for invention -- is the sensible track to follow going forward.
tstage 7j43k It sounds like you have a bind. That is why your current draw goes up. I suggest you find the bind and fix it. Ed Ed, Wouldn't a bind occur at regular intervals of rotation? The higher current draw happens sporadically and for short periods of time before dropping again. As a test to rule out any mechanical binding though, I disconnected the motor from the gear box and ran the motor alone with the decoder at speed step 030. (I believe that someone may have suggested that earlier.) The overall current draw was lower - i.e. in the 0.1 - 0.25A range. However, after a minute or so the motor whir changed noticeably (as if it were straining) and the current draw shot up to 1.0A and > before I shut the Power Cab down. I ran the same test again and got similar results. So, I think that confims the motor is indeed bad and the binding is occuring inside the motor housing. Tom
7j43k It sounds like you have a bind. That is why your current draw goes up. I suggest you find the bind and fix it. Ed
Well, since you put it that way......
Yup. Good sleuthing.
Dumb question: does the shaft 'shift visible length' at the moment the straining starts? If the armature moves against, say, inadequate thrust bearing capacity or excessive clearance, the internal resistance might go up substantially, perhaps including brushes hanging up on the edge of the commutator's structure.
Perhaps this could be kludged by restraining the shaft motion externally: the end of the shaft in the direction of shift could be pointed, and a plate of hard material on a bracket of some sort provided...
But replacement would still be the preferable choice...
OvermodBut note that he HAS tested the motor outside the chassis, and HAS verified the issue to occur in the isolated motor precisely as it appeared when installed. And he said he roll-tested the chassis for binding when the motor was out.
Just to be clear: I removed the shaft coupler (that connects the motor to the gear box) only and operated the motor mounted on the bracket and connected to the chassis, as shown in the photo below:
This way the motor shaft was more easily observable, as I monitored the current draw with my Power Cab at the same time.
I didn't recollect the shaft moving axially when the current spikes occured so I ran the test a 3rd time. While I didn't observe any axial movement of the motor shaft as the current spiked, the motor shaft did bind and completely stopped rotating.
Interesting note: After shutting down the Power Cab (to preserve the decoder) and restarting it again, the bind in the motor shaft was still present when I set the speed step to "30" and the current draw remained at 0.01A - as if I had not applied any current to the motor at all.
I did roll the drivers last night on my cutting mat and I did not observe or feel any binding with the linkage so I think we can rule that one out of the equation.
So it looks like a replacement motor is the direction I'll be going. Thanks all for the suggestions and ideas.
Spalato68 Tom, if you are seeking a new motor, which seems unavoidable, then you could consider this motor: link. It is 12 V coreless motor, 17 mm in diameter, 24,5 mm long, 12000 RPM - so it fits in your locomotive (with some adaptation to motor seat). I bought several motors from this seller and never had an issue, but there are many other sources for this motor... Regards, Hrvoje
if you are seeking a new motor, which seems unavoidable, then you could consider this motor: link. It is 12 V coreless motor, 17 mm in diameter, 24,5 mm long, 12000 RPM - so it fits in your locomotive (with some adaptation to motor seat). I bought several motors from this seller and never had an issue, but there are many other sources for this motor...
Thanks, Hrvoje! Using your link I was able to find a similar 12V coreless motor for the same price and it looks like it has identical (or nearly identical) mounting holes to the Mashima I'm looking to replace:
It also comes with a 2mm OD shaft, which matches - as best as I can measure it - the shaft on the gear box.
[Update: Ordered 1 and one extra. Should be here by mid-August. Looking forward to trying these out - Thanks, Hrvoje!]
LastspikemikeI'm betting it's pressed on. Should be feasible to try pulling on it a bit to see if it budges.
You were correct, Mike. The hex nut was press fit onto the motor shaft:
I used one of my beefier Wiha flathead screwdrivers to slowly pry it off the shaft. I'll try doing the same with the gear box but will need to be a little more careful since it's still connected to the chassis.
Unsure whether I'll stick with the original hex-drive coupling with the new motor...go silicone tubing...or use a NWSL universal u-joint.
If the mounting holes on the new motor don't precisely match just drill new ones in the bracket at 90 degrees, which preserves the ability to 'restore' original if ever desired.
I look forward to see how this runs, and I'm tempted to see how the various alternative types of drive might perform with this motor...
Tom, I am glad that you found this motor, I completely forgot that recently I also saw this version, with 2 mm motor shaft. This version came out after I already bought several pieces of version with 1,5 mm shaft, so it had priority in my mind. 2 mm shaft is even better, especially now when you managed to remove hex coupler from old motor.
If hex drive coupling does not work from any reason, I would rather use NWSL universal u-joint over silicone tubing.
Btw, mounting holes on motor I linked above are 10 mm apart, and accept M2 screw (there is a drawing in technical specificaation part). If your motor has the same design (except for motor shaft), then mounting holes should be 10 mm apart. I think your motor has mounting holes that are 12 mm apart (I conclude this from drawing that can be found here). Ok, this is all guessing, because you will know exactly only when you receive the motor. I am sure you will find the way to install new motor in correct position.
In any case, I am looking forward to read and see about new motor when you install it. If this is the same motor as I used in my locomotive (it seems so), then you should be very happy about it.
Spalato68Btw, mounting holes on motor I linked above are 10 mm apart, and accept M2 screw (there is a drawing in technical specificaation part). If your motor has the same design (except for motor shaft), then mounting holes should be 10 mm apart. I think your motor has mounting holes that are 12 mm apart (I conclude this from drawing that can be found here). Ok, this is all guessing, because you will know exactly only when you receive the motor. I am sure you will find the way to install new motor in correct position.
You are absolutely correct, Hrvoje. The holes on the Mashima motor I have are indeed 12mm apart.
I decided to contact the eBay seller to ask them if they can tell me that information. That way I can have the bracket holes drilled out and ready for the new motor when it arrives.