I have an old red Gyralite that came off of a scrapped loco many years ago. I am just getting around to trying to make it work and have found that the armature has some broken wires where it connected from the commutator (where the brushes run) to the field windings. Of course the brushes are worn and the commutator is rough but otherwise this light is in good shape.

I would like to make this an operating light so have been exploring repair options for the motor. I took it to a local shop that does work on a lot of old electric motors and got a quote of about $300 dollars to rewind the armature. Since this is a restoration for fun and not profit I didn't know if anyone might know of a shop that might be cheaper. Or if there was a source of used but functional motors that might be more budget friendly. Or even a new substitute.

I believe the light is a model 17550 with a single red lens.

The motor appears to be model 241006 (not in the current RAE Corp catalog online). Manufacturing date of 11/79.

Runs on 74V and I do have a correct power supply.

Appreciate any leads/suggestions. Thanks All!

Did you check with the OEM?
http://raemotors.com/products/motors.php

I did search thru their website and didn't see it listed. I did try to call but no one was available at the time.

I have searched on Ebay but not finding this specific motor.

Looks like a brushed universal AC/DC motor with an integrated right angle gear box.

Probably a custom part for the Gyralite company. Motor manufacturers often do small batches (100's - 1000's) of "specials" with custom gearboxes, mounting brackets, wiring harnesses, etc.

Here is similar modern motor with a "parallel" (aka straight through) gearbox.

https://www.cshincorporated.com/2423-30 ... dc-90-rpm/

Could be difficult to find a direct replacement, and if you do find a new one it's probably going to cost at least $300. And a motor with different mounting holes/brackets would require fabrication of new mounting plates, more $$$.

And a used one may have other problems.

$300 for a rewind seems reasonable, it's at least a days labor plus parts. Have them remove the old windings, soak it in a de-greaser and bake the bare armature in an oven to drive out any oils etc before rewinding it.

Good luck.

It may not need a rewind. For a tedious afternoon project: Do a rough check of all the windings first with a multimeter. Disconnect the windings from the commutator and check for equal resistance of each winding. You may have to research how they're typically wired depending on how many poles there are. They should all be a maybe few ohms, not a dead short or open. If you're good there, see if the commutator can be cleaned and somewhat polished up removing any tarnish, carbon buildup or ridges around any pits. Pay close attention to cleaning out any oily muck and carbon buildup between and around the commutator plates - it's conductive. Wood toothpicks and contact cleaner would certainly be helpful. Brush off any gunk from the windings with a soft brush - that enamel coating should be considered delicate. Clean the brushes and put them back in their original locations and orientation. Having everything spiffy clean goes a long way towards potential success. Reconnect all the windings. Clean & lube the bearings and armature shaft, stick it back together and see if it works. It may have to run-in a bit to be a consistent runner.

Or, take it to a motor shop if you're not confident. That $300 is mostly labor.

I understand the principal difficulty is mechanical breakage between windings and comm segments.

Stone and level the comm as indicated, cleaning the slots carefully. Then be sure the brushes are in good condition and the holders and leads aren't crapped up (they could probably be fixed but it can be complicated).

You might be able to use a reflow gun (like a very precise hot-air gun) with appropriate flux, solder, and wire sections to repair the breaks without compromising more of the winding insulation. Check adjacent windings while energizing the one being worked on to test for shorts.

If that is a permanent-magnet motor, be advised that in my long experience with attempting to rebuild treadmill motors, I never had one that ran correctly after the process was done. Once the magnets approach the Curie point in operation they lose much of their magnetism, and will not recover it. Replacing them is a pain in multiple ways, even when you have proper replacements.

Yes that is the main problem. I have checked to the best of my ability and while the commutator does show some wear they still appear to be electrically isolated from each other. I did not find any indication of internal shorts. The brushes are worn but but still seem to make ok contact and the springs seem ok also.

I don't have access to a "reflow gun" but when I asked the motor shop they said it needed to be rewound and repair wasn't an option. They also mentioned about the Curie effect. They warned me it might not work well if the magnets are affected. They also say they had no way to test the magnets prior to putting the $$ into the rewinding.

This motor is DC with 2 permanent magnets. While the outside of the motor shows some corrosion it doesn't appear to me that the windings overheated or are in bad shape internally. If the wires weren't broken I would do the cleaning process that was mentioned above first. (Thanks for that helpful info also!)

Cumbres

Obviously, I can't see what you're looking at. If the winding is broken off the commutator, you may be able to bridge that with a soldered extension. If broken or shorted within the winding, the you're out of luck.

I'm not too concerned about the Curie point effect in just getting it to run occasionally on display. If the armature isn't obviously fried to a crisp, or the broken connection/loss of continuity is the reason it died, you're probably OK with the magnets. I'd guess that these are ceramic or alnico magnets, most likely ceramic. I doubt the armature or the entire motor would survive approaching those temperatures. If your screw driver sticks to them well, I'd give the motor a shot at repair. You have nothing to lose if you fail.

If you do try to repair it, when you test it, start on a lower voltage and work your way up. You'll be able to tell if it's going to turn easy enough on a lower voltage by giving it a spin. You may be able to feel the "cogging" as the poles pass the magnets. Just don't let it sit long in a stall. Be aware of current draw and generated heat. Those are motor killers. If you smell burning enamel, you're done.

Those are not the field windings. You mentioned this motor has a permanent magnet field. The winding is the armature winding. Are you able to remove the armature from the motor and take a photo of it?

If the problem is that a few coils have become disconnected from the commutator, but the armature winding is otherwise OK, the continuity can be restored by bridging the affected commutator segments. It sounds like the winding is not encapsulated and that you have access to the commutator riser necks, in which case it is a fairly simple repair.

You would need to know how many poles are on the motor (count the field magnets) and whether it is lap or wave wound. Probably lap wound considering the voltage and application but you never know. For a "toy" use such as this, most likely you can make it run again.

Still, $300 is not an unreasonable price to rewind it. Even on a little toy motor, the motor shop is going to have at least a few hours of labor into it.

Before you try to remove the armature from the field be sure you push it out with a piece of steel. Some permanent magnets loose much or all of their strength if this is not done. Rewinding armatures may be tedious but not complicated. Map the number of turns. Note if the windings that come out of the slots in the laminations of the armature come directly to the slots in the commutator or are offset between the commutator and where the windings leave the armature. Clean the slots between the commutator bars and check for shorts between the bars, there should be none. Insulate the slots and the ends of the armature to prevent shorts from the windings to the steel parts of the armature. Depending on the size and speed of the motor you may want to wrap and tie the wires between the armature and the commutator, use the original construction as a guide. Depending on the condition of the commutator you may need to take a very light finish cut on a lathe. With a very narrow blade cut down the insulation between the commutator bars and polish any little burs that you may have created. Reassemble the motor and test. If the operation is satisfactory take the armature to a motor shop and see if they will varnish the assembly. The varnish or what ever they use will help protect the windings, keep the windings fused together, this will keep the windings from rubbing and breaking down the very thin lacquer the insulates the wire. I have rewound several fractional HP D.C. motors

A good point, but applicable mostly to AlNiCo permanent magnets. It was recommended to use a "keeper" to keep the magnetic circuit intact. So in this case, it would have to be a steel tube or pipe not much smaller than the OD of the armature. Alternatively, if you can squeeze it in there, some strips of steel shim stock touching adjacent poles.

With a manufacture date of 1979, probably those are some kind of ceramic material, which does not have such a drastic 2nd quadrant demagnetization curve. This is a motor that doesn't need to do much, so any field weakening is probably survivable. Even open turns on the armature, as long as they are jumped out to prevent sparking and flashing at the affected bars.

The original poster never responded with photos. A motor of that size and working on low voltage (74) is probably random-wound with just enamel wire. At that voltage, it would be sufficient to just spray it with common electrical insulating varnish right out of the spray can, available even at auto parts stores.