That’s a joke son… [;)]
Seriously - make sure you go back and read the parts of the thread where those in the know discuss what happens when you open a knuckle with no pin in place… (hint - step back!)
Here’s a coupler in action:
http://www.youtube.com/watch?v=bZk0OTCezqI&mode=related&search=
…Wouldn’t it be great if someone had a video camera mounted right above a coupler and could see just what the parts do as the two fasteners meet…Even then, to see it in slow motion.
Here is a link to a site with a video of a coupler from above
http://www.sdrm.org/faqs/couplers/
Click on “Joint #1” and “Joint #2”
…yo-ya37:
Congratulations…and thank you for such a great video{s}, showing the action to couple and uncouple…!
This subject has been kicked around here for some time and I, personally…have been trying to understand how these few parts of a coupler really do the job. I can certainly understand it a lot better now. Seeing the job the pin does in keeping the parts in position but not carrying the “load” is what I could not understand before…This certainly helped.
…And by the way, welcome to the forum. A very good start.
Ya Ya,
Excellent link…
Quentin, if you listen to the joint being made, both with the passenger car and the hopper, you can hear the pins drop, the double clink right after the coupler hit.
We listen for this, its one of the ways, besides stretching the joint, that we determine the joint "made.
Note the knuckle pins kinda jump a little in the freight part…and once the joint is made, you can see the knuckle pin now bears no real stress.
Oh, and just as Quentin already said, welcome to the forum, Ya ya…
…I’ll check out that sound a bit closer and watch for the pin action Ed. Sure was a great series of videos.
The problem with putting a camera there is most of the action in a coupler happenes behind the knuckle . When the cut lever is raised it forces the pin lifter up which disengages the coupler lock and forces the knuckle thrower out opening the knuckle .
…It certainly helped me more than any other view I’ve seen yet. I couldn’t understand how the parts functioned much at all before I witnessed this action. Now, {I believe}, I do have a much better idea what is happening.
[:)]
The videos were excellent. One comment, though, on the words that go with the second photo on the page. It says,
“The locking pin is visible in the center of this photo. When the cut lever and pin are raised the coupler is allowed to open, as shown here. The cut lever is on either side of the coupler. In the upper photo the pin is in the lowered position, which keeps the couplers locked together, allowing the locomotive to pull the train.”
This paragraph does not mention the “lock,” which is not visible in these photos. The pin we see here is attached to the lock for the purpose of pulling the lock up and letting it fall. The lock is the piece inside the coupler body that actually falls beside the tang on the knuckle to prevent the knuckle from opening after it closes.
If you go back in this thread you will find more photos and explanations of the lock and the pin we are talking about here, plus much more.
I still owe this thread pictures of a disassembled coupler. I haven’t forgotten.
[:)] [:)]
[:)]
I have updated the links to my photos with the URL of my new web page server. I apologize for not doing that sooner. I still haven’t disassembled our local caboose coupler to get a better look inside. I’ll try to get on that.
[:)] [:)]
Thanks for adding to this thread. I enjoyed the action of coupling and uncoupling, which brought back memories of thirty-five and more years ago when I often was in the yard in the small town where I then lived. I doubt that anyone now could do as I then did, working with the train and engine crew. I, of course, saw all the action from the side and never from above–but the sounds are the same.
Johnny
In thinking about this thread again, here is a synopsis of its development:
It starts with a question about the date and/or identity of a found coupler.
Quentin asked if anyone can explain how the forces are transferred through a coupler.
A general assumption was expressed that the knuckle pulls on the knuckle pin while the locking pin prevents the knuckle from rotating open. So the pulling force is transmitted from the knuckle, to the knuckle pin, and to the coupler body.
This assumption was disproved by the assertion that the knuckle pin plays no role in the force transfer because a coupler will function in pulling a load with the knuckle pin missing.
It was pointed out that there is a circular groove on the knuckle tang concentric with the knuckle pivot axis that engages a corresponding circular ridge on the coupler body when the knuckle is closed. These features, dubbed “force ridges,” transmit the pulling force from the knuckle to the coupler body in a straight line, parallel with, and centered on the coupler longitudinal centerline axis.
Good stuff here.
Perhaps the answer is that the longitudinal force is transmitted through not only the ‘force ridges’, but also to some degree through the coupler’s locking pin. So, when the locking pin is lifted and out of the way, the force ridges are all that’s left to transmit / resist the pulling force. If the center of those force ridges is not pretty much right on the coupler’s axis - and they probably are not, because that’s where the locking pin is - then the off-center/ ‘eccentric’ location of the force ridges will cause or allow the coupler to rotate. In view of the magnitude of the pulling forces, it wouldn’t take much of an offset to generate a considerable rotating force or torque. For example, if the off-center distance is only 1 inch = 0.083 foot, for a 390,000 lb. tension pull or ‘draft’ (max. required coupler strength) the resulting torque or ‘moment’ would be on the order of 32,000 ft.-lbs. Or, if the rotating force on the coupler is even a mere 1 % of the draft force, that would still be 3,900 lbs. or so.
Looking forward to other and more accurate information from other souces and those with better knowledge of this !
[quote user=“Paul_D_North_Jr”]
Good stuff here.
Perhaps the answer is that the longitudinal force is transmitted through not only the ‘force ridges’, but also to some degree through the coupler’s locking pin. So, when the locking pin is lifted and out of the way, the force ridges are all that’s left to transmit / resist the pulling force. If the center of those force ridges is not pretty much right on the coupler’s axis - and they probably are not, because that’s where the locking pin is - then the off-center/ ‘eccentric’ location of the force ridges will cause or allow the coupler to rotate. In view of the magnitude of the pulling forces, it wouldn’t take much of an offset to generate a considerable rotating force or torque. For example, if the off-center distance is only 1 inch = 0.083 foot, for a 390,000 lb. tension pull or ‘draft’ (max. required coupler strength) the resulting torque or ‘moment’ would be on the order of 32,000 ft.-lbs. Or, if the rotating force on the coupler is even a mere 1 % of the draft force, that would still be 3,900 lbs. or so.
Looking forward to other and more accurate information from other souces and those with better knowledge of this !
Each time I break the locomotive away from the cars for our usual runaround, I (not so mysteriously) make the locking pin “disappear” by lifting it. The coupler opens. That’s how they work. If the joint is stretched, I may have trouble lifting the pin due to friction on the pin, in which case the coupler doesn’t open. But if we take your hypothetical magical disappearance, where friction isn’t a factor, my bet is on the coupler opening.
But in my hypothetical example, friction is a factor.
Sure when you lift the locking pin, the knuckle will open, but you can’t lift the pin when the coupler is stretched, and my example of the pin magically disappearing is predicated on the coupler being stretched. There is to practical way to demonstrate it, so that is why I use the term, magic.
Bucyrus, I think I understand what you’re saying - I’m sure that in an ‘alternate universe’, that could be the accepted design. But here, I’m inclined to agree with Larry / tree68.
What we really need is an actual 1:1 coupler to play with and jiggle and see for ourselves. Perhaps coincidentally, during a bike ride one morning last week I found that one of my distant neighbors - 1.5 miles across some farm fields - is a pretty senior general foreman in the mechanical department of a Class I. After the usual preliminaries, the first question I asked was about knuckle couplers. [8D] My subversive intention is to get to be able to photograph one close up, perhaps even one that’s been cut in half - ‘sectioned’ - with a cutting torch. Give me a few weeks or a couple of months to work on that . . . . [;)]
Either that, or get a video that’s been shot by someone else who’s experienced in close-up videography of similar moving parts from many different angles - say, an ‘adult’ movie photographer ? [:-,]
[quote user=“Paul_D_North_Jr”]
Bucyrus, I think I understand what you’re saying - I’m sure that in an ‘alternate universe’, that could be the accepted design. But here, I’m inclined to agree with Larry / tree68.
What we really need is an actual 1:1 coupler to play with and jiggle and see for ourselves. Perhaps coincidentally, during a bike ride one morning last week I found that one of my distant neighbors - 1.5 miles across some farm fields - is a pretty senior general foreman in the mechanical department of a Class I. After the usual preliminaries, the first question I asked was about knuckle couplers. 
My subversive intention is to get to be able to photograph one close up, perhaps even one that’s been cut in half - ‘sectioned’ - with a cutting torch. Give me a few weeks or a couple of months to work on that . . . . 
Either that, or get a video that’s been shot by someone else who’s experienced in close-up videography of similar moving parts from many different angles - say, an ‘adult’ movie photographer ? 