Motor for Fox Valley Hiawatha

[kschmidt626]

Happy New Year

I have a friend who was running his Fox Valley N Scale Hiawatha at a show.  While it was running he left it running with another member while he took care of some business.  Upon his return he was told that something happened and the steam engine was no longer steaming.  Something happened and there was a short and the motor burned out.  It's a DC unit so no decoder.  He is looking for a replacement motor for the locomotive.  Anyone have any thoughts.  Nothing available at the FVM website. 

Thanks in Advance
Keith

[peteski]

Keith,
Is your friend sure the motor is really bad?  It is really, really difficult to kill that type of N scale motor.  Maybe it just needs a good cleaning (commutator/brushes)?  If that area gets covered with oily carbon powder from brush wear, it can cause problems and even smoke.

The motor might also need new brushes.  Unless your friend knows for sure, I would not declare the motor dead.


This is the motor. It is pretty much a standard size N scale motor used in many models.  The differences usually are  in the the flywheel and electrical connection.

If the motor is dead, I would try contacting FVM directly (through email) to ask if they have any spares.  Matt is usually very helpful when it comes to takign care of defective parts (assuming he has any spare motors).  If not, there might be other motors which will fit (the flywheel would have to moved to the now motor).  But for now let's hope the original motor can be revived.

[mmagliaro]

I agree.  "Something happened", "There was a short", "the motor burned out" are all guesses"based on the engine
stopping, maybe a breaker tripping, and maybe some white smoke or a hot finger when touching the area of the motor.  You won't really know unless you take the motor out and make sure the commutator slots are clear, and you check the windings with an ohmmeter for a short.  That's the first thing your friend should do.

[davefoxx]

I agree.  "Something happened", "There was a short", "the motor burned out" are all guesses"based on the engine
stopping, maybe a breaker tripping, and maybe some white smoke or a hot finger when touching the area of the motor.  You won't really know unless you take the motor out and make sure the commutator slots are clear, and you check the windings with an ohmmeter for a short.  That's the first thing your friend should do.

Dumb question of the day: Where do you place the probes to “check the windings with an ohmmeter”?  I replaced an Athearn Genesis motor last week, and I’d love to test the failed motor.

Thanks,
DFF

[mmagliaro]

Dumb question of the day: Where do you place the probes to “check the windings with an ohmmeter”?  I replaced an Athearn Genesis motor last week, and I’d love to test the failed motor.

Thanks,
DFF

Here's quick, simple way that I do it.

First remove the brushes.  (you have to, or they might conduct across commutator segments)

Second: Make sure you clean out the commutator slots with a toothpick and some alcohol, and then use a soft brush and alcohol to clean away the black debris and allow to dry.  (same reason: you don't want shorts from any black slot "goo" to affect your test)

Next:
Measure across two successive pads of the commutator and note the resistance.  Then measure across the next two and so on.  You should generally get the same value across every pair.  Note, you are not measuring the actual resistance of a single coil - that would depend on how the armature is wound and whether it has 3 or 5 poles.  And even if you knew all that, the coils are not isolated from each other, so you will get parallel resistances.   But the point is, if you don't get the same value between each successive pair of pads, a coil is either shorted or open.   They won't be identical, but they should certainly be within a couple of ohms of each other (they are usually within 0.1 ohm).   If you get a resistance much lower than all the others, you have a short.  If you get a higher resistance, you have an open (broken wire).  Believe me, if you have a bad one, you'll get a completely wild value.

ANOTHER IMPORTANT TEST that people often overlook:

Measure between the armature shaft and each pad of the commutator to make sure that none of the coils are shorted to
the shaft.  It is quite possible for all the coils to be okay, but have one of them shorted, or partially shorted, to the shaft.
That can happen if there is a melt or break in a coil wire anywhere it passes close to the bushings, washers, or the shaft itself.
The motor may even run perfectly until you put it in a loco, wherein the motor will now be shorted out to the frame.

I bring this up because it has burned me a couple of times with a motor that seemed to run perfectly on its own, but would short out the moment it was inserted into a metal chassis.

[SkipGear]

It's a standard Atlas / Kato motor. I have a black brush hood "hi-speed" older Atlas motor to transplant into one of mine because "something I never thought I would say" the loco runs too slow. This loco could do 120mph in real life, the  model tops out at around 70 running through a buddies speedometer. Running on Ntrak, it's in the way unless I am wide open and I hate that.

[davefoxx]

Here's quick, simple way that I do it.

First remove the brushes.  (you have to, or they might conduct across commutator segments)

Second: Make sure you clean out the commutator slots with a toothpick and some alcohol, and then use a soft brush and alcohol to clean away the black debris and allow to dry.  (same reason: you don't want shorts from any black slot "goo" to affect your test)

Next:
Measure across two successive pads of the commutator and note the resistance.  Then measure across the next two and so on.  You should generally get the same value across every pair.  Note, you are not measuring the actual resistance of a single coil - that would depend on how the armature is wound and whether it has 3 or 5 poles.  And even if you knew all that, the coils are not isolated from each other, so you will get parallel resistances.   But the point is, if you don't get the same value between each successive pair of pads, a coil is either shorted or open.   They won't be identical, but they should certainly be within a couple of ohms of each other (they are usually within 0.1 ohm).   If you get a resistance much lower than all the others, you have a short.  If you get a higher resistance, you have an open (broken wire).  Believe me, if you have a bad one, you'll get a completely wild value.

ANOTHER IMPORTANT TEST that people often overlook:

Measure between the armature shaft and each pad of the commutator to make sure that none of the coils are shorted to
the shaft.  It is quite possible for all the coils to be okay, but have one of them shorted, or partially shorted, to the shaft.
That can happen if there is a melt or break in a coil wire anywhere it passes close to the bushings, washers, or the shaft itself.
The motor may even run perfectly until you put it in a loco, wherein the motor will now be shorted out to the frame.

I bring this up because it has burned me a couple of times with a motor that seemed to run perfectly on its own, but would short out the moment it was inserted into a metal chassis.

Thanks, Max!

DFF

[peteski]

Please be careful and gentle when placing meter probes on the commutator. The segments are made of soft copper and they can easily be scratched or scored. Personally I don't touch the segments or clean the gaps with anything but a wooden toothpick.  Scored commutator will wear the brushes down quickly.
If possible, touch the meter's probes to the tabs at the inner side of the commutator to which the winding wire is soldered.   Most meter probes might be too thick to do that.  You might have to improvise some thinner probes.

[mmagliaro]

Please be careful and gentle when placing meter probes on the commutator. The segments are made of soft copper and they can easily be scratched or scored. Personally I don't touch the segments or clean the gaps with anything but a wooden toothpick.  Scored commutator will wear the brushes down quickly.
If possible, touch the meter's probes to the tabs at the inner side of the commutator to which the winding wire is soldered.   Most meter probes might be too thick to do that.  You might have to improvise some thinner probes.

Yes yes yes, don't use anything metal to clean out the slots.  One slip of a blade or screwdriver will put a score mark on the commutator, and that will wear out the brushes and collect dirt.  As for the probes, I do see the point of not wanting to score the commutator.  But the probes I have are pretty smooth with roundy tips.  I don't think they could make any marks.
Touching the little solder tabs is sometimes very difficult, and if you slip there, you can break off a soldered coil wire, so I prefer to touch the commutator pads instead.

[kschmidt626]

Thanks to all of you for the responses on this request.  This has been great.  My friend is hoping to get the locomotive running again.  Maybe in time for a show in February in Madison WI. Will have to see how things work out. 
Keep the ideas coming. 

Thanks again

Keith