Fixing Lionel magnetic couplers so they stay closed

servoguy posted:

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.

I have a similar problem with a new "Lionel TTX Trailer Train Husky Stack - 6-27524".  One of the coupler does not hold any traction and opens immediately. 

Do you have pictures of the modification you have done ? 

It is not clear to me why you wrote "you don't need to modify the plastic knuckles" while you also wrote "This is where you want to make a groove in the knuckle".

All help will be appreciated.