Bucyrus wrote:No need to worry about pocket screws because there are no screws. I have only seen a couper being disassebled once, but as I recall, there are no fasteners. They come apart like a puzzle, and it is not completly obvious how to do it. You remove the knuckle pin, then the knuckle, and after that, it gets a little tricky. You will probably be able to figure it out. I admire the elegance of a design that requires no fasteners.
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!)
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Here's a coupler in action:
http://www.youtube.com/watch?v=bZk0OTCezqI&mode=related&search=
Dan
....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.
Quentin
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...
23 17 46 11
....I'll check out that sound a bit closer and watch for the pin action Ed. Sure was a great series of videos.
.....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.
This revelation raised the question of how a pulling force can induce a knuckle to open when the locking pin is lifted. In other words, why wouldn’t the pulling force simply transfer straight through the knuckle to the force ridges with the knuckle acting like a link in a stretched chain? The knuckle is not free to rotate when a pull loads it against the force ridges, so why doesn’t it bind and refuse to rotate when you pull the locking pin and try to pull away in an uncoupling move? This basic question develops and is explored on pages 6 and 7 of this thread.
There are further mysteries to be resolved as soon as cordon gets that coupler disassembled and photographs the pieces.
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 !
- Paul North.
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 ! - Paul North.
Paul,
This is precisely were the deeper mysteries lie. I have to think more about it to put my thoughts into words. But I make an assumption that if the locking pin suddenly, magically disappeared in a loaded, stretched coupler, the knuckle would not open.
Bucyrus This is precisely were the deeper mysteries lie. I have to think more about it to put my thoughts into words. But I make an assumption that if the locking pin suddenly, magically disappeared in a loaded, stretched coupler, the knuckle would not open.
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.
tree68 Bucyrus This is precisely were the deeper mysteries lie. I have to think more about it to put my thoughts into words. But I make an assumption that if the locking pin suddenly, magically disappeared in a loaded, stretched coupler, the knuckle would not open. 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.
Certainly there must be some load on the locking pin when the coupler is stretched. Otherwise you could pull the pin when the coupler is stretched. But my point is that the pulling force does not place a dynamic load on the locking pin. It only loads the locking pin with a relatively small force as the pulling force is initiated. But then the force ridges take up the load and lock the knuckle against rotation by their friction. At that point, the small force on the locking pin becomes a static force that persists as long as the slack is stretched. When the slack runs in and then runs back out, the whole process starts again.
So the locking pin is needed only to initiate the lock against knuckle rotation only until the slack stretches. From that point, the locking pin is irrelevant as long as the slack is stretched. If it disappeared, the knuckle would not open.
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 ?
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 ? - Paul North.
What I am saying about the lock not being needed once the coupler is stretched and loaded is a further development of my thinking in my post on page 7 from 5/14/2007. I could be wrong, but this point needs to be made: My theory on this cannot be proven or disproved by studying an actual coupler, whether you operate it, or take it apart, or section it to reveal the operation of the assembly. My theory can only be proven or disproved by the design engineering on which the actual coupler is based, or by modifying an actual coupler so that the locking pin does actually disappear while the slack is stretched.
Such a modification would replace the normal locking pin with a pin that was made to be collapsible in the direction of its loading from the knuckle tang. This collapsibility could be created with a controlled hydraulic cylinder. When the coupler makes a joint with another, the hydraulic cylinder pushes the locking pin into its locked position. Then you put a stretch on the couplers of say 25,000 pounds. Then release the hydraulic cylinder so that the locking pin feature is free to fall back away in line with the force of the knuckle tang. I don’t think the knuckle would open.
edblysard
Using Ed's illustration from earlier in the thread, I might buy somewhat into your premise, Bucyrus, but keeping the knuckle closed will require constant tension. Without the locking pin in place, even momentary slack will cause the coupler to open when pressure is applied to the bearing face. Your premise also assumes that there is enough friction between the grooves and slots within the coupler to prevent it from rotating under load.
Note that the bearing face of the knuckle is not in line with the pivot point. The offset is enough that the locking pin does not have to bear the full load, but the offset also guarantees that if any force is applied to the bearing face (sans locking pin), the knuckle will pivot.
I will tell you that it doesn't take a lot of stretch to keep the pin from lifting, thus it doesn't take much slack to cut it loose.
tree68Using Ed's illustration from earlier in the thread, I might buy somewhat into your premise, Bucyrus, but keeping the knuckle closed will require constant tension. Without the locking pin in place, even momentary slack will cause the coupler to open when pressure is applied to the bearing face.
I agree that the instant the slack begins to run in, the knuckle bind-up will be lost, and the kuckle will open upon re-stretch if there is no locking pin in place.
As I mentioned, I do not know whether my conclusion about the locking pin not being needed when the couplers are stretched is true or not. However, there is something about what this thread has revealed so far that drives me to that conclusion. That is the fact that the knuckle pin serves no load transmitting function, but rather is only there to keep the knuckle from falling out. It would be logical to conclude that the pulling load tries to open the knuckle, the locking pin prevents that opening, and so the locking pin is bearing a dynamic force that rises as the pulling load rises.
However: If you pull on the knuckle and that pull induces it to rotate, and the locking pin counteracts that rotation force, then there must be a reaction force back to the knuckle pivot pin. And yet the knuckle pin carries no load. The knuckle pins can be missing and the mated couplers will continue without them. That is why I have to conclude that there is no active force on the locking pin. If there were, it would cause a reaction force, and that force would need to borne by some other feature.
If you look at the lock pin, you can see it is keyed, shaped in such a manner that when in the down position, it prevent the knuckle from rotating, lifted, it allows the knuckle tang to slide on the grooves, and the knuckle opens....but also note, although it is not shown, that the lock pin is almost totally encased inside the solid coupler body...the small amount of "play" in the knuckle never allows enough of an impact to shear this lock...it is about 2 inches thick both ways...even though thousands of tons of force are applied to it, just like a bolt or rivet in a structure, because there is little if any "play" in it the force is transmitted to the knuckle and coupler...trust me, remove the lock pin and the knuckle will open..you can replace a knuckle and the lock pin with zero tools...that said, with the way the rear of the tang is designed, if the knuckle was always under constant tension, (slack out) and some how the lock pin was removed, it is possible the lands and grooves in the tang would hold the knuckle in place...but the first little bit of slack and it would open.
To clairify some,...the knuckle pin is the pin the knuckle rotates on, it bears little if any load witht he knuckle closed...the lock pin is the device located behind the knuckle tang that locks the knuckle into the coupler body...it is load bearing, the rotational force of the knuckle under tension is applied to it and the straight line directional force to the tang lands and grooves.
No promises, but I will try and get some photos tomorrow to explain....
I didn't mean to re-start all the analysis, but now that we are here again......
I think that the angle of the large ridges (2/2A and 3/3A in my photos on page 4 of this thread above) is enough so that stretching forces (along the tracks) create considerable force at the forward end of the tang on the knuckle towards the right (as you face forward) against the lock, even though there may be some sticking between the ridges. I don't think any sticking between the ridges would be anywhere near enough to inhibit the knuckle from opening. Therefore a stretching force will open the knuckle when the lock is raised out of the way.
I think that the reaction force (reaction to the force towards the right against the lock) is a force towards the left from ridges 2 and 3 against ridges 2A and 3A. And those same ridges carry most of the stretching force.
In addition, with the knuckle closed, ridges 1/1A and 4/4A carry any load in the location of the knuckle pin. OTOH, with the knuckle in the open position, ridge 1 is not in contact with ridge 1A and ridge 2 is not in contact with ridge 2A; and the knuckle pin is the only thing holding the knuckle to the coupler.
cordon I didn't mean to re-start all the analysis, but now that we are here again...... I think that the angle of the large ridges (2/2A and 3/3A in my photos on page 4 of this thread above) is enough so that stretching forces (along the tracks) create considerable force at the forward end of the tang on the knuckle towards the right (as you face forward) against the lock, even though there may be some sticking between the ridges. I don't think any sticking between the ridges would be anywhere near enough to inhibit the knuckle from opening. Therefore a stretching force will open the knuckle when the lock is raised out of the way. I think that the reaction force (reaction to the force towards the right against the lock) is a force towards the left from ridges 2 and 3 against ridges 2A and 3A. And those same ridges carry most of the stretching force. In addition, with the knuckle closed, ridges 1/1A and 4/4A carry any load in the location of the knuckle pin. OTOH, with the knuckle in the open position, ridge 1 is not in contact with ridge 1A and ridge 2 is not in contact with ridge 2A; and the knuckle pin is the only thing holding the knuckle to the coupler.
I think we are picking up exactly where we left off. I always had kind of a lingering feeling that there were a couple issues left unresolved. I want to think more about your above quote, but in the meantime, consider this:
In lieu of a graphic diagram, consider a clock face and compass directions for reference to the knuckle movement:
Say you are looking down on the end of a coupler with the knuckle pin on the left. That pin is the center of a clock face. The pulling load is applied at 3 o’clock and pulls south. The knuckle tang is at 12 o’clock and loads east against the locking pin. How can that force not create a reaction force that loads west against the knuckle pin at the clock center?
I agree that there will be some load in the location of the pin. What I'm saying is that ridges 1/1A and 4/4A take that load, not the pin.
Maybe this shot will help.
All the movable internal parts are out of the coupler at this point, or at least not in their normal place.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
I still have a hard time "seeing" the action and shape of the lock. This link confuses me.
http://www.mcconway.com/rail_prod/rail_prod.htm Look at "coupler parts"
There must be different kinds and shapes of locking pins.
NP Red I still have a hard time "seeing" the action and shape of the lock.
I still have a hard time "seeing" the action and shape of the lock.
As to the action, here's a really simplistic drawing. I am no artiste.
The left image represents an open knuckle (kinda). As I understand it, the lock pin will be riding on top of the knuckle body (I was a little off...). When the knuckle pivots on the pin, the lock pin drops in at the notch, as noted by the red dot representing the lock pin.
Obviously there will be variations, but this covers the basics.
You'll notice that there will have to be a certain amount of force exerted on the locking pin, but that the lever distances make that force relatively insignificant compared to the total force being held by the coupler.
Here's that "open" coupler, with some parts labelled. If I mis-named anything, fire away!
I see only 4 different locking pins - 2 for Type E couplers, and 2 for Type F couplers. And among those, 1 of each is for the top, and the other is for the bottom. I presume that designation means for where the cut lever/ rod is located - on top or underneath the coupler itself, per the previous posts, such as in rotary couplers on unit trains, etc.
But now, after seeing those diagrams - and in partial response to the latest debate about whether the coupler knuckle would open when under load if the locking pin were removed, etc. - let me ask this:
What is the function of the 'knuckle thrower' ? I presume that when the locking pin is lifted, it moves the knuckle thrower to push and rotate the knuckle to the open position. So if the locking pin was removed, there'd be nothing to motivate the knuckle thrower. But since the knuckle thrower is most likely for the purpose of and designed to open the knuckle when there is nothing attached to the coupler, in that circumstance the knuckle thrower may be superfluous and unncessary - the pull on the coupler from the next car may be enough to open the knuckle, even without a knuckle thrower. So I suppose the debate can continue on . . .
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