12v motor repair

[Reker1000000]

Hello Eurobricks,

This is a post I've been excited to complete for a long time. I have scoured the Internet for information regarding opening/repairing a 12v motor, and found 2 excellent posts on Eurobricks a while back, but didn't have the supplies to do it myself. At this point, I have a pretty good collection of 12v train motors- 2 red and 3 black functional (and in sets), and another 1 red and 1 black broken/spare, both of which I had received in that condition. I had been holding on to the broken red one for a while, but only recently received the broken black one, which upped my count of broken motors to 2. Some of my other motors have some minor problems as well, such as worn contacts, hair wrapped around an axle, and one had a stripped axle that had little torque. This increased my motivation to open both nonfunctional ones up, see what was wrong, and hopefully repair one or both of them. A couple weeks ago I decided to take the plunge and even though I was still lacking information I purchased the supplies that would hopefully be adequate- these being:

1) Razor blades for opening the motor(s) (I purchased a case of 10 replacement blades for shaving razors at CVS which you will see in the video- any type of blade similar to this should work, as long as it's very sharp)

2) Lubricant- I used synthetic PTFE grease- for relubricating the worm gears and axles (link to what I bought: https://www.amazon.com/Super-Lube-21030-Synthetic-Grease/dp/B000XBH9HI/ref=sr_1_3? and no it's not affilate)

3) Super glue for reassembly of the motor(s) (link to what I bought: https://www.amazon.com/Loctite-Liquid-5-Gram-Longneck-230992/dp/B000BQMQJQ/ref=sr_1_2? and again no it's not affilate)

I also made a custom jig out of Legos to hold a motor while I opened it, which are covered in-depth during the video, and I had rubbing alcohol and a rag on hand to clean the internals of the motor(s).

After opening the broken red one up by breaking the seal of glue with the razor blade while the motor was in the jig and then disassembling everything, I concluded that there were several things wrong with it:

-The wiring disc's solder had broken and the disc itself had snapped in half, leaving it loose in the motor

-One axle had a cracked plastic gear, which was no longer holding to the axle allowing it to spin freely with little connection to the motor itself

-Worst of all: The commutator had melted. This is a vital piece that transfers electricity from the 2 metal blocks labeled "A" and "B" to the actual DC motor in the center. As a result of running under too much load for too long, the motor had over time run hot too much and the plastic piece which should hold the metal parts (and wiring disc) in place was warped, wavy, and overall badly deformed. From everything I've found on the Internet, this is almost certainly unrepairable. I suppose I could attempt to melt the plastic and try to reform the commutator, but I don't have the equipment for that and would probably mess it up even more. The only way that it might be fixable is to find a replacement DC motor from a train hobby shop or something, but I've had no luck yet. There was a thread here a while back about replacement 12v motors and someone mentioned the Motraxx 265 or Motraxx 260- I checked the website and they can't be shipped to the US. So for now, I don't think a broken commutator is a fixable issue for me. If anyone here has details of a DC motor that is the same size and takes the same power, I would really appreciate it if you let me know- I could definitely use those.

I proceeded to open the broken black motor and what do you know, it's the same issue. The commutator on this one was even more deformed- one of the metal plates had lost its connection to the plastic entirely. Plus the wiring disc had come unsoldered. So both broken motors are to my knowledge beyond repair without having to replace the DC motor itself. A valuable lesson to all owners of 12v motors: Do not run your motors under too much load. Maybe 3 long wagons in addition to a long engine (such as 7740 with 7815) for a single motor is probably the limit- any more and you will likely burn the motor out and cause irreversable damage which will render the motor unusable. If you run more wagons, you should use more motors.

Here is where the story starts to take a turn for the better, though. About a year ago I had purchased a red motor as the one I originally got in my 7730 was broken (I sent it back to the seller for a partial refund). The replacement motor, I learned quickly, was basically only functioning on one axle. The other axle was not connected to the drivetrain, and I thought for a while that the plastic gear on it was stripped. Running on one axle is quite bad- the motor is slower, has less torque, and overall the resistance that the motor encounters is uneven. It's also very inconvenient for trains (like 7730!) with those nice connecting rods- because you have a good axle doing the work of both axles AND trying to "push" the bad axle through the connecting rods, the locomotive often got stuck on curves and points and the connecting rods would become misaligned often. I had been running it with the stripped axle for a long time. However, the good axle ran smoothly, so I suspected the DC motor inside was good. Because I had opened both broken motors and determined they're not getting repaired anytime soon, I had many spare parts- including a spare axle which I intended to swap into the red motor with the bad axle. So, I opened the red motor running in 7730, and I was correct- the DC motor inside was still in good condition. However, the the gear on the front axle, instead of being stripped like I originally thought, was cracked and like the first red motor not holding to the axle. No problem- I disassembled everything, cleaned it with alcohol, reassembled it with the bad axle replaced by a good one, and tested it with the transformer to make sure it worked (it did!). I then put lubricant on:

-Motor axle (just a small amount with a paper towel, so it would spin smoothly on the rectangle plates that held it)

-Metal worm gears on the motor axle and plastic gears on the wheel axles

-Wheel axles ends inside the bearing sleeves

Everything was then reassembled inside the bottom part of the motor housing. I applied a small amount of super glue to the outside of the bottom part of the motor housing to prepare for re-gluing. This ensured that when I put the 2 parts of the housing together, all excess glue would be pushed outside the motor and not inside. If the glue is pushed inside and dries there, you will probably have a very hard time opening it up again if needed, as super glue "welds" ABS plastic together. Finally, I pushed the top of the motor housing down and held it to ensure the glue dried. After a few tests, the motor was performing on par with my other motors and was running smooth! I would call that a success- even though I didn't manage to repair either of the broken motors, I was able to use parts from them to repair a third motor which was (before its repair) functioning questionably, and I learned a lot about the internals of a 12v motor. I should also say this: It was not as easy as I make it sound, I was working on the motors over the course of several days and it took a while to go through the process of opening them, cleaning the parts, troubleshooting, and repairing. That's not even mentioning the many hours I spent researching plastic-safe lubricants and types of glue that wouldn't damage ABS, plus the time spent gathering information on the motors themselves. It was particularly tricky to find out what types of lubricant and glue to use, but I think I managed OK as the motor runs smooth and is firmly glued after the repair. This post (and the video) are the result of a lot of work, and I hope that those who need this information can save a lot of time by reading/watching the content I have created.

A picture is worth a thousand words- but a video is quite literally worth thousands of pictures. So, I have inserted a 20-minute YouTube video that I made below with most of this information plus more, and a thorough explanation of the internals of a motor. It also explains the custom jig that I made.

I hope you got a lot of information from this post- I am all too aware that there is almost no information on the internals of these rare motors, so I contribute this post in the hope that it will be very useful to those who need this information down the road (or, down the 12v track ). I am hoping that the video is adequate for visual content, but I took photos as well during the repair and am happy to post them, if requested (it's just a bit tedious to post images here).

For those of you that have been following my YT channel, tomorrow marks one year since I posted my first video, and I have some special content planned- if you haven't checked out my channel and are interested in 12v trains, be sure to drop by!

And of course, if you have questions about the motor repair, I'm more than happy to answer them here or if you comment on any of my videos I will respond there.

-Reker1000000-

[JopieK]

Thanks @Reker1000000, a lot of people will really like getting their precious old 12V motors up and running again using your tutorial!

[zephyr1934]

15 hours ago, Reker1000000 said:

-Worst of all: The commutator had melted. This is a vital piece that transfers electricity from the 2 metal blocks labeled "A" and "B" to the actual DC motor in the center. As a result of running under too much load for too long, the motor had over time run hot too much and the plastic piece which should hold the metal parts (and wiring disc) in place was warped, wavy, and overall badly deformed. From everything I've found on the Internet, this is almost certainly unrepairable. I suppose I could attempt to melt the plastic and try to reform the commutator, but I don't have the equipment for that and would probably mess it up even more.

I would say hold on to those melted motor frames and at some point use the black one for practice. I bet you could take a page from real steam engine repair- cut out the bad material and weld in a patch. Or in this case, cut out the bad plastic and make a 3D printed replacement jig to do the job if holding the motor with the bonus of potentially allowing you to use a slightly different sized motor too. Of course none of this is trivial and I wouldn't suggest attempting until much later, but it potentially offers a path to reviving the rarer red motors.

[XG BC]

you could attempt to 3d print the commutator plastic piece aswell.

[Reker1000000]

On 8/28/2022 at 8:40 AM, JopieK said:

Thanks @Reker1000000, a lot of people will really like getting their precious old 12V motors up and running again using your tutorial!

Yep! I figure, if they're already broken then you can't lose anything by opening them up, and you may even be able to repair them.

 

On 8/28/2022 at 12:46 PM, zephyr1934 said:

I would say hold on to those melted motor frames and at some point use the black one for practice. I bet you could take a page from real steam engine repair- cut out the bad material and weld in a patch. Or in this case, cut out the bad plastic and make a 3D printed replacement jig to do the job if holding the motor with the bonus of potentially allowing you to use a slightly different sized motor too. Of course none of this is trivial and I wouldn't suggest attempting until much later, but it potentially offers a path to reviving the rarer red motors.

Ah, it's not the motor housing that's broken, both are in good condition- it's a small plastic piece in the DC motor itself... as XG BC said, I could attempt to 3D print the commutator, but that might be difficult since in addition to having to print such a small part (and it must be strong!) I'd have to reinstall the metal pieces and find a way to get the worm gears and original commutator off of the motor axle. I'm done with motor repairs for now but maybe in the future I'll see what I can do about repairing those- or if I happen to come across a cheap lot of broken motors on eBay or something, I'll keep my eyes peeled...