AF Wide Gauge motor problem

Check to see that the wheels are not rubbing on the motor frame, also that there’s nothing between the field and armature like a washer or trash/dirt. Hope you figure it out.

John

@John A in N.C. posted:

Check to see that the wheels are not rubbing on the motor frame, also that there’s nothing between the field and armature like a washer or trash/dirt. Hope you figure it out.

John

I have the wheels and idler gear off, and it still makes the noise. The armature spins easily when rotated by hand and is not rubbing against anything. Something that may be important to know is that the field winding gets warm and the commutator segments get extremely hot when power is applied.

Something is wired wrong! Can you post a picture?

It's difficult to get a clear picture, but the center rail pickup is wired to the bottom wire coming out of the field. The wire coming out of the top of the field goes to the center clip on the reverse unit, and the two outer clips are wired to the brushes.

I'm not a Standard Gauge guy, but I have some experience with O gauge AC motors.  It's possible that the commutator timing may be "off", especially if the armature was rewound or taken from a different motor.

By "timing", I'm referring to the angle of the slot between the commutator segments, relative to the protruding poles.   If it's off, the motor will run slow and/or hot, and it may be reluctant to start turning.  The only way to know the correct timing is to reference a known good motor/armature combo.

I compared the position to another motor and the slots on both were in the same place relative to the poles. I also measured the resistance between segments and found it was 2.2 on all of them. Is there anything else I should check?

You should check the resistance from the commutator segments to the shaft. See if any of the armature coils are grounded. On a large motor the way to find the proper timing of the commutator is to rotate the brush rigging to find the optimum operation. This may be difficult depending on the brush plate design. The field is hard to check without a growler, but the defect might be turn to turn shorts. Reducing the field strength should cause the armature to turn faster, but with less torque.  The run out on the commutator can reduce performance, but this problem usually comes with excessive sparking. Allowable runout, bar to bar, is 0.0002”  Try increasing and decreasing brush tension and see how that impacts the speed of the armature.   Take a look at brush resistance, maybe swap the brushes with a motor that runs well.  Excessive bearing clearance can cause a motor to run slow. These little motors need very tight clearance on the armature bearings, maybe 0.001” or less.   Good luck.

@David Johnston posted:

You should check the resistance from the commutator segments to the shaft. See if any of the armature coils are grounded. On a large motor the way to find the proper timing of the commutator is to rotate the brush rigging to find the optimum operation. This may be difficult depending on the brush plate design. The field is hard to check without a growler, but the defect might be turn to turn shorts. Reducing the field strength should cause the armature to turn faster, but with less torque.  The run out on the commutator can reduce performance, but this problem usually comes with excessive sparking. Allowable runout, bar to bar, is 0.0002”  Try increasing and decreasing brush tension and see how that impacts the speed of the armature.   Take a look at brush resistance, maybe swap the brushes with a motor that runs well.  Excessive bearing clearance can cause a motor to run slow. These little motors need very tight clearance on the armature bearings, maybe 0.001” or less.   Good luck.

What should the resistance be between the shaft and segments?

It should be very high. Maybe 10,000 ohms or more. The shaft and the segments should be insulated from each other.

I tested it and it showed about 11 ohms, which was the same as another motor that is working perfectly. I tested putting the armature from this motor into the working motor and it had the same problem. Does this mean that the armature is the source of the problem?

Yes. With 11 ohms of resistance between the commutator and the shaft there will be about 1.6 amps, at 18 volts,  of current flowing that the only thing it does is generate heat. You could try cleaning the commutator and if there are suspect spots that look burnt, try repairing them a little epoxy.   I believe that Hennings has made and sold replacement commutators for these early motors. You might want to give them a call and see what they say. The Lionel motor expert is Robert A Hannon, hannon@trainrefs.com.  You could also talk to him.  He could probably repair the armature for you.

David gave you some amazing advice.  But... you said that the armature taken from the working motor also measures 11 ohms between segments and shaft.  What happens when you install THAT armature in the troublesome motor field?  Does it restore the balky motor to normal operation?  Thanks for sharing!

@Ted S posted:

David gave you some amazing advice.  But... you said that the armature taken from the working motor also measures 11 ohms between segments and shaft.  What happens when you install THAT armature in the troublesome motor field?  Does it restore the balky motor to normal operation?  Thanks for sharing!

I tried that, but that armature is slightly larger in diameter and rubs against the field.

Is the armature bearing\spacer missing from the end?