For most operating knuckle type model railroad couplers the force of pulling a train is transmitted through the knuckle pin. That is, the pin which acts as a hinge between the knuckle and the coupler body. If that pin is broken or missing the coupler is essentially broken and the train breaks in two (comes uncoupled).
Real train couplers do not work like that. The knuckle pin can be, and often is, missing entirely yet the train remains coupled and can be operated normally. I have ran many trains with missing knuckle pins, often more than one missing pin in the same train.
The Janney coupler design is totally ingenious in its entirety. The way the parts interact with each other to remain locked should be one of the greatest inventions of human existence. You are correct in that the pin is only used to keep the knuckle from falling on your foot when opening it in the yard.
You are correct - If the knuckle is closed, the locking pin is engaged and the actual pivot pin may not be needed. But if you lift the cut lever and the knuckle opens, the knuckle could very well fall out onto the ground(or your feet). Missing pins are an FRA defect and carmen should find/repair the defect before releasing the car for service.
To make a model coupler that locks up like a real coupler would require micro-machining of a high order, and the layout would have to be kept sealed up and as clean as a satellite assembly shop. A few grains of dust…
OTOH, real couplers can’t be coupled starting with both knuckles closed. For Kadees and clones, that’s not a problem.
Comparing the earlier posts above with Tony Koester’s April Trains of Thought column indicates that Tony is unaware of the actual working of a coupler. Or maybe the April MR has two April fool jokes…
I’ve long found it interesting that you could make a very good argument that the most realistic model railroad coupler ever made - except for being greatly oversized - was the old metal Lionel postwar coupler. It had an uncoupling lever that could either be pushed down to open the coupler by hand, or by a remote control track. The couplers would be in the open position, and when coupling would snap shut much like real knuckle couplers.
An equally valid claim could be made for the old Devore HO coupler, which was opened when the center pin was lifted and was locked when it wasn’t. And it didn’t take much more than a flake or two of dandruff to jam one…
one thing about the couplers on our models that i have always noticed. they are oversize and long enough that the spacing between the ends of the cars is excessive. not that i care enough to do anything about it but having spent much of my life on the 12"=1’ railroads, it just kind of gets my attention.
only Ichabod Crane would be able to move from one car to the next via the running boards.
The thread seems to be ignoring Sergent couplers. They are very close to the prototype in operation - knuckle has to be opened, and the coupler centered for coupling to take place. An internal steel ball is lifted by magnet to open the knuckle. And it’s true to scale size for HO.
Real train couplers do not work like that. The knuckle pin can be, and often is, missing entirely yet the train remains coupled and can be operated normally. I have ran many trains with missing knuckle pins, often more than one missing pin in the same train.
Wyhog
The coupler pin holds the knuckle closed remove the pin and the knuckle should open since it would be like lifting the pin with the uncoupling bar to uncouple the cars…
in my real life experiences i don’t remember ever seeing a broken knuckle pin but we sure broke a lot of knuckles. of course there were usually spares on the engine and caboose, usually an E and an F type.
replacing a knuckle was a two man job for sure. just carrying the darn thing was a day’s work. if you were lucky, you could pull or shove the train to where you had the spare waiting.
That’s because our model curves tend to be sharper than real train lines use, plus manufacturers have to cater to folks who use very sharp curves like 18"R curves in HO. If you have wider curves you can put in Kadee “short shank” couplers to bring the spacing closer together.
My luck the car was located 40-50 cars from the caboose! The head brakeman would help replace the knuckle.Some times the conductor would if the busted knuckle was closer to the caboose…
I think some people are confusing the knuckle pin with the coupling pin. I have seen brakemen remove the knuckle pins from coupled cars to put in knuckles they need to open on the next track. Since I have been out of the yard for 30+ years I have heard that they experimented with plastic knuckle pins. They didn’t seem like a good idea. I’m glad I changed professions when I did.
Pete,That could be…The 9 1/2 years I worked as a brakeman I never found the need to remove the knuckle pin in order to open couplers.Lucky I guess.
I’ve removed several in order to replace a broken knuckle.
BTW.One old line PRR conductor called the knuckle pin the “coupler hinge”. As a young brakeman I hAd no idea what he was talking about since other conductors and brakemen called 'em a knuckle pin.
When FRED stoled my job in '84 I was glad to get out of railroading.
I worked 3 1/2 years on the PRR and after the merger PC and 6 years on the C&O under the Chessie and CSX banner.
Knuckle pins are frequently lost when unit train coal cars are rotated to dump the coal at power plants or docks. There is supposed to be a cotter pin at its bottom to hold it in but those seldom get replaced when trainmen replace broken knuckles. Thus the pins just fall out when the car is turned over.
As for sometimes having to remove a knuckle pin to uncouple a car… this can happen if you go to uncouple a car and notice that its knuckle pin and the one on the car its coupled to are both missing. If you just uncouple a car with a missing pin the knuckle will fall out onto the ground. So you go to another car, remove the pin from it and insert it into the car you want to uncouple. That prevents the knuckle from falling out when you finally uncouple.
Knuckle pins are frequently lost when unit train coal cars are rotated to dump the coal at power plants or docks. There is supposed to be a cotter pin at its bottom to hold it in but those seldom get replaced when trainmen replace broken knuckles. Thus the pins just fall out when the car is turned over.
Ahhhh that explains how the knuckle pin would fall out…
I never seen that but,in my era three bay hoppers was still king.
My understanding is that the plastic pins are intended as a temporary fix and are plastic so that a trainman can easily carry a few around with him (or her) for emergency use. A bunch of steel ones would tend to bog one down a bit. One guy I know used small tree branches he found trackside for the same purpose.
Yeah Tony Koester got this one dead wrong. I know a lot of farmers and former farmers who also howled or shook their heads at his Trains of Thought insight of a few years ago that plowing would never be done right to the lot line of a farmer’s field. Under today’s farming conditions it is all plowed, even if parallel to the lot line, but it is plowed and grown. I seems to recall other MR staffers picked up that opinion-as-fact, too.
Kevin Keefe’s Feb. 1992 Trains magazine article on couplers is a useful resource on the general topic.
About 10 years or so ago, I had to change out a knuckle on a coal train made up of NS system cars. (It was a loaded train going to the NS from the Powder River coal fields.) The car that had the broken knuckle and the last car (where I stole the knuckle from) both had plastic knuckle pins. I think others did too. As I recall, those pins didn’t have cotter pins, but where held by tabs or friction. (I don’t remember if they were rotary capable.) I noticed that the pins did seem to work themselves up a bit, allowing me to notice some of the other car’s pins.