Real couplers

I have not seen that magazine, but if they actually said that, someone fundamentally does not understand how couplers work.

I've "borrowed" a pin or two here and there over the years. 

Good explanation, Wyhog, as usual.

Can someone supply links to diagrams of this?

Thanks

Another misconception... 

Infact, a lot of the rotary bathtub gons in our trains actually have plastic knuckle pins. First time I was one, I was a bit surprised, but they are in fact plastic.

There is a lock mechanism inside the coupler head. The lock is released by a lift link (top operated couplers) or by other means (in rotary and bottom operated couplers) by the uncoupling levers or rods on the car ends.

While the lock can be moved by uncoupling, it's designed not to move when engaged to the knuckle and being subjected to shocks from buff and draft stresses.

Once the knuckle is unlocked from the head it will turn open by rotating on its pin. The lock is also designed limit how far the coupler knuckle will open.

When a coupler knuckle is pushed shut the lock is moved into place, securing the coupler closed. It can only be opened manually, by means of the uncoupling mechanism on a car's end sill to release it.

It is (or was) possible for a train crew to remove a knuckle from a coupler and replace it if necessary. Very simple to do. Take out the pin and release the knuckle lock by uncoupling. The knuckle will then fall out. 

Spare knuckles were at one time carried in cabooses and sometimes in locomotives along with spare air hoses, etc. A knuckle can fail from fatigue and stress cracks. They usually develop at the locking point, which bears all the draft and buff forces of a train. 

Our engines don't carry spare pins, just a chisel, hammer, and a  %^&%!@# wrench.

It can be handy to keep a pair of pliers in your grip to bend back the cotter pin that is there half the time to keep the pin in. Usually it's bent, or rusted. If you can find a spike laying around, or a rail clip, you can sometimes use that to beat it into place. 

Changing a knuckle isn't exactly hard, unless the guts fall out. Then it can be a little more challenging. 

An interesting problem I encountered about a year ago was a certain series of TILX tank cars would not "lock" when making a joint. For the life of me, I could not get the pin to fall when coupling up. It would just cut away everytime I would stretch the slack. The mechanical dept came up, and examined the car, and using a crowbar, was able to jimmy the pin inside the coupler to drop. At that point, I would just make the joint with the TILX car knuckle closed, and the opposing knuckle open.

As it turns out, the internal pin that falls inside the coupler on these particular TILX tanks have a bit of flash on the casting. That would prevent the pin from falling, as it would get caught on the inner lip inside the mechanism. When this happened to me again a few days later with the same series of TILX cars, I found a chunk of steel laying next to the track. I used it to jockey the pin around, and got it to fall & lock the coupler closed. Kind of an "on the fly" fix instead of having mechanical come out and mess with it.

BTW, the steel knuckle pins are great for loading somebody's grip up with!

One conductor told me that he went back to replace a broken knuckle that had a plastic pin. He said the knuckle broke in a way that messed up the plastic pin so bad that he couldn't get it out. Had to call the shop forces to come out to repair the car.

 You don't even have to have a pin in the knuckle to keep it in. The way they lock inside the knuckle head they stay put when in the closed position.

 You have to really watch for this on coal cars since plants sometimes break the knuckle pin when switching and or turning cars in a rotary dump setup .I encountered a few when working as a brakeman/conductor.

  A few plastic pins have found their way on NS unit toolboxes.Their suppose to be strong...ah a still think metal is best.They've worked for how many years now.

Wyhog , thats correct about the metal pin damaging a coal crusher . in fact a RR sipke will damage it

If a plastic pin is subjected to a shear force, it will offset between the knuckle and coupler head bores, thereby locking it into place.

To get it out in such a state, it probably heeds to be heated with a torch to soften it some, in order to drive it out of the bores.  

quote:To get it out in such a state, it probably heeds to be heated with a torch to soften it some, in order to drive it out of the bores.  

Now that might be a good idea...if the conductor has a lighter or a fusee and the plastic is willing to burn. Just set it fire and let it drip out.

I saw a knuckle pin (steel) laying in a window sill of a yard office one time.  The yardmaster told me he used it for a clerk starter . . .

EdKing

 I appreciate this post. I'm trying to understand this better. It makes great sense that the pin would not see the load, with the huge stresses aplied to these things. I'm staring at toy couplers (Lionel, MTH and KD). They obviously do have stress applied to the joints and pin area. I've seen them snap if too many cars are yanked too fast.

 In a Jan OST article are some pictures of real couplers. The one on the engine looks quite larger than the one on the car it's connected to. The picture is from the side only and shows how the coupler appears to be trapped into the mating one once coupled. I can't see evidence of how the stress is applied.

 Would the missing pin not matter then because of how the knuckle is trapped??

Anybody got a picture of a set of real couplers connected?

 Thanks for the patience, Joe 

 Thanks for the photos. Great shots! It really doesn't help me with understanding the applied forces to the coupler. It does show clearly how the real ones are built.

 Now I have even more questions.

 Looking at the bottom photo post, the gentleman refers to a variation in the # of steps on the two engines ( is this you?).

 I thought that maybe it was about different years of production? or maybe a loco that was repaired after a crash and updated with the 6 step pilot? If a loco is repaired does it get updated to conform with newer regulations? Maybe just gets the new parts that are available?

If you look at a photo or diagram of the movable part itself, you will find that it is cast with a similar horizontal lip, which engages the main casting of the knuckle. So the main casting knuckle holds the movable part which engages the movable part of the next cars coupler which engages the knuckle casting. The pin only serves to pivot the movable parts as they engage.This can be seen in manufacturers diagrams or on display equipment.