MTH couplers uncouple randomly

Hi Doug,

Not an answer to your question,but I have one or .

two railking cars that occasionally do that also,that's why I opened your post,and you have no replies in a month.

But wait till there's a post on whats your favorite caboose

Why not just replace the mth couplers if it's a mechanical problem!

MTH Electric Trains (mthpartsandsales.com)

Alan

I was able to "calm" , several electro-couplers, by adding a 50 micro-farad capacitor across the coupler leads.  IMO. 

That is a no no for legacy and mth.  Only TMCC I thought.  G

@Doug F posted:

I searched this topic, I thought for sure it would have been covered multiple times before.  I have an MTH Premier 6 car hopper set that randomly uncouple, so far, 2 of the six cars.  I would like not to use the tried and true zip ties to keep the coupler closed.  Is there a way to adjust the locking pin into the knuckle, to keep the knuckle closed?  Can the locking pin or the metal piece from the coupler tab be bent slightly to achieve this?

Thanks,

Doug

First, as with any technical repair discussion, providing the product number of the car or engine in question helps us give you a more detailed and much more specific and accurate answer. This is because different cars and engines use different components and rather than talking in broad generalities we can refine our answer specific to the exact parts and components used on your rolling stock.

Is there a way to adjust the locking pin into the knuckle, to keep the knuckle closed? Most likely, the issue could be molding flash or other defect in the knuckle locking area. The problem is to get to that area with a file and cut a nice sharp edge that connects with the locking pin to form a secure lock. https://ogrforum.com/...08#24237557425414508

Can the locking pin or the metal piece from the coupler tab be bent slightly to achieve this? This becomes somewhat risky IMO. By that I mean trying to bend the pin only in relationship to the arm to form a slight angle such that the tip is more prone to locking into the knuckle you can break that bond to the metal arm and then you have ruined it. If alternately you mean bending the arm somehow such that the spring is more preloaded and the arm has more force into the knuckle, that is better served by a stronger spring.

Again, I think on most freight the coupler uses this basic style of armature.

As you can see, the large diameter pin is pretty sturdy and appears to be a welded connection to the armature. Attempting to bend or angle it directly compared to the armature to achieve a slight back angle could result in breakage. Additionally, bending in some way to achieve a stronger spring force, simply use a stronger spring or preload your existing spring by installing washers or shims.

But more likely than not, the fault could be minor molding defects in the actual knuckle and latching area. The problem with that is you then may need to remove the rivet to remove the knuckle to gain access to the latching area. MTH did not and does not sell just the knuckle piece as seen on Lionel replacements, nor the rivets.  I've seen pictures in the past of a knuckle up close and someone showing filing that sharp latch edge but searches I cannot find it. Again, the fundamental problem is to do that, you may need to remove the rivet and MTH does not sell that rivet nor the knuckle piece. I never tried to see if the Lionel parts work on an MTH.

This picture is of a Lionel plastic knuckle. That said, the MTH metal knuckle is similar and should have similar features. The important part is that back square edge that the pin is holding the coupler closed.

The goal, and I might be using incorrect terminology, is to have sharp edges on the mating surface of the locking pin and the sharp square edge on latch backside. I would liken this to a sear latch in a trigger. Again, the idea is, the angles of the parts bite into each other in that under force, it is not a ramp and does not push the latching pin back out.

If it is a newer set of cars ,the plate on the bottom of the truck needs to be adjusted, if its hanging down underneath. The whole truck needs to be disassembled and bend this piece of metal and it should be fine. Reassembly is not easy.