# Fixing Lionel magnetic couplers so they stay closed



## servoguy (Jul 10, 2010)

There has been a lot of discussion on this forum and others about the problem of Lionel magnetic couplers coming open all by themselves. Tonight, I was running a train of 22 cars behind a 2032 Alco single motor diesel. 14 of the cars are post war with metal trucks and 8 are postwar with plastic trucks. None have the low friction bearings and fast angle wheels. The car behind the loco was a long black gondola, NYC. Pulling just the cars, the front coupler came open. It did it twice after about 3 laps of the 072 oval. The 072 oval has 16 sections of 072 curved track and two 40" long straight sections. 

After the gondola coupler had opened up twice, I modified it using a Dremel tool with a 1/8" cutter. If you open the coupler and look on the knuckle where the pin touches it, you will see a witness mark where the pin has been rubbing up and down on the knuckle. This is where you want to make a groove in the knuckle that is parallel to the pin, or maybe I should say the groove should be parallel to the rivet that the knuckle pivots on. It takes less than 5 seconds to make the groove. Don't make the groove any deeper than absolutely necessary. If you examine the flat on the knuckle where the pin holds the knuckle closed, you will discover that the surface the pin contacts is not parallel to the pin. The pin therefore walks down due to vibration. The cattle of a 3656 operating cattle car work in a similar way. 

After I modified the gondola, I decided to increase the weight of the train. I put a 2032 Alco diesel dummy and a 2353 F-3 dummy behind the gondola. No problem, after several minutes, the knuckles remained closed on the gondola. Then I took the 3656 cattle car that was behind the diesel dummies, and put it ahead of them so it was immediately behind the modified gondola. As if by magic, the coupler on the cattle car opened up all by itself. 

I just modified the couplers on the cattle car, and now they stay closed. I think this is the solution to the couplers opening by themselves. Don't forget, you don't need to modify the plastic knuckles.


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## Patrick1544 (Apr 27, 2013)

Sounds like a good fix. Can you provide a few photos of what you did?


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## gunrunnerjohn (Nov 10, 2010)

Actually, I do a different fix, and it not only fixes the coupler for walking open, it also makes them close much easier. Note that this is for modern electrocouplers on command locomotives, either MTH or Lionel.

I remove the knuckle and smooth the mating surfaces. The reason the plunger walks is that it has friction and when it vibrates it just "walks" the coupler open. The added bonus is for switching duties the coupler is much smoother and lighter closing, so you don't have to bash the line of cars with the locomotive to couple up.

I'll have to look at Bruce's fix for the magnetic couplers, though there are several designs on newer rolling stock.


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## servoguy (Jul 10, 2010)

I said it takes about 5 seconds to make the notch, but it is closer to 1-2 seconds. It is very quick. I will try to get some pictures but I have to get my daughter to take them as she has a really good camera for taking close-up pictures.


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## BigAl56 (Dec 14, 2011)

Modern era plastic couplers are notorious for failing. 
When my kids were in braces I scored an extra package or two of orthodontic rubber bands. They were just perfect to wrap around a modern era coupler to hold the pins in.


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## gunrunnerjohn (Nov 10, 2010)

I've gotten pretty good as slapping new knuckles onto cars with plastic couplers. For stuff that I want to actually run, I use a cast knuckle and a real spring as the replacement.


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## servoguy (Jul 10, 2010)

I put a gondola with plastic couplers at the front of the train, just behind the modified gondola and modified cattle car. The couplers did not come open. The plastic couplers were not modified and have a rivet for the knuckle.

There are several types of plastic couplers. The ones without a rivet are very flimsy, and I would expect them to fail under high loads. Obviously, the die cast knuckles are stronger than the plastic knuckles, but I think some of the plastic knuckles (the ones with a rivet) may be strong enough.


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## gunrunnerjohn (Nov 10, 2010)

The biggest failure of the plastic couplers is the lame plastic spring tab, it loses it's "spring" and they no longer open on command.


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## servoguy (Jul 10, 2010)

I have some cars with plastic couplers and springs that work just fine. I have other ones where the springs is either missing or doesn't work. I have bought new plastic couplers with springs and they work just fine. Some significant number of the cars I have with metal couplers have broken hair springs, and when the spring on one end doesn't work, the one on the other end doesn't work either. I think Lionel had some problem forming the springs as putting a sharp bend into the spring wire would result in a stress riser and probably cause the spring to fail. Sharp bends of spring wire will increase the stress level by as much as a factor on 9.


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## BigAl56 (Dec 14, 2011)

Agreed. Those orthodontic rubber bands are a perfect fix.


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## servoguy (Jul 10, 2010)

Big Al, I don't agree that the rubber bands are a "perfect fix." With the rubber bands, the coupler doesn't unclouple at all. With my fix, the coupler still works. Isn't it important to have working couplers?


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## BigAl56 (Dec 14, 2011)

Well maybe not perfect. Cheap and easy definitely. I never tried uncoupling with the bands but honestly, I seldom if ever do any remote uncoupling. If I had to I would just couple the car to one with a working normal coupler.


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## T-Man (May 16, 2008)

BigAl56 said:


> Modern era plastic couplers are notorious for failing.
> When my kids were in braces I scored an extra package or two of orthodontic rubber bands. They were just perfect to wrap around a modern era coupler to hold the pins in.


WOW, I never knew that. 
It's the same band for HO tires too.


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## wsboyette (Jan 25, 2014)

I never planned on having to uncouple the cars remotely, so when I had a problem with a K-Line coupler coming open, I merely shot some CA glue all into it, and haven't had a problem since !


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## servoguy (Jul 10, 2010)

I have attached a picture of the modified coupler.


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## BFI66 (Feb 7, 2013)

BigAl56 said:


> Agreed. Those orthodontic rubber bands are a perfect fix.


I agree also with that quick fix......seems those rubber bands were a nice byproduct of my daughters very expensive trips to the orthodontist!

-Pete


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## Lee Willis (Jan 1, 2014)

The orthodontic bands work well. So does using a thin (1/4" wide) strip of electrical tape wraped twice around the coupling. I've done that a lot.


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## servoguy (Jul 10, 2010)

You can probably modify the couplers with a Dremel tool as quickly as you can put rubber bands on them. It takes about 2 seconds to modify each coupler with a Dremel tool, and then the couplers still work.


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