In theory, the knuckle thrower is going to keep my tootsies off the coupler itself, and therefore me out of the guage. Yes, it's mainly going to apply when opening a coupler which is not attached to another coupler.
If you're pulling two couplers apart, the unopened coupler will pull open the one you've pulled the pin on...
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...
THIS IS OBSOLETE EXPLANATION. REPLACED BY REVISED EXPLANATION PAGE 13, 9/1/09
Here is my analysis of the coupler function as clearly as I can express it:
On a single coupler with an open knuckle, the knuckle is loosely attached to the coupler body by the knuckle pin, and the knuckle’s force groove is swung out of alignment with the corresponding force ridge on the coupler body.
When the knuckle is closed, the locking pin drops into position, and the knuckle’s force groove comes into alignment with the corresponding force ridge on the coupler body. At this point the knuckle fits loosely with its pivot pin, with the locking pin, and in the relationship between its force groove and the corresponding ridge on the coupler body.
When a pulling load is applied, the knuckle is first inclined to rotate back open, but that movement is arrested by the locking pin, which blocks the swing of the coupler tang. Upon the tang being obstructed by the locking pin, a slight reaction force is created, which forces the knuckle to bear against the knuckle pivot pin in a direction crosswise to the coupler line of pull. However, both the primary force of the tang against the locking pin and the reaction force of the knuckle against its pivot pin are very small because they only result from holding the knuckle against rotation at the instant that the pulling force is applied.
At that point, while the knuckle is locked from rotation, it is free to slide forward in line with the direction of pull until the slack is pulled out of the sloppy relationship between its force groove and the corresponding ridge on the coupler body. Up until this point, the knuckle has been a rotating element. But when solid contact is made between the force groove and ridge features, the knuckle ceases to be a rotating element, and becomes a linear link, transmitting the pulling force in a straight line like a link of a chain. Once this function change happens, the pulling force no longer induces the knuckle to rotate.
The rotation of the knuckle and the action of the locking pin together only serve to install or un-install the knuckle as a linear, straight line, pulling link. The rotation of the knuckle and the action of the locking pin together are not involved with the pulling load.
Bucyrus Once this function change happens, the pulling force no longer induces the knuckle to rotate
Good point, thanks
What is that extra hole for on the tip of the knuckle?
Flag.
That's where we hang our "FRED", too.
Flag. FRED. Or other EOTD.
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Bucyrus [snip] But when solid contact is made between the force groove and ridge features, the knuckle ceases to be a rotating element, and becomes a linear link, transmitting the pulling force in a straight line like a link of a chain. Once this function change happens, the pulling force no longer induces the knuckle to rotate. The rotation of the knuckle and the action of the locking pin together only serve to install or un-install the knuckle as a linear, straight line, pulling link. The rotation of the knuckle and the action of the locking pin together are not involved with the pulling load.
What Bucyrus wrote above is true only if - pause a moment here to take a look at one of the knuckle top photos above - a straight line can be drawn from the point of application of the pulling force onto the knuckle tip - which would be about where the flag hole is - through the middle of the 'force groove and ridge feature', and into the draft gear, and said line would be parallel to the line of the train. That would be just about the same as a link in a typical oval-link chain - when pulled on, those links rotate as much as they need to until the points of application of the force on each end of them are in a straight line with the main line of the chain. No chain under serious tension is ever in a shape other than a straight line - unless there's an interference of some kind along its length.
But a potential interference here is the angle and curve of the 'force groove and ridge feature' at the back end of the coupler tang. Without knowing exactly how the coupler and the knuckle are fitting together when under load, we can't say for sure whether it's the angled part of the curved part of the grooves and ridges that are carrying the load. More importantly, the 'line of force' should be at just about a 90 degree angle to the straighter parts, or radial to the curve. If that isn't the case, then a partial sideways force or 'vector' will be induced by the skewed angle of those grooves and ridges with respect to the perpendicular to the main line of force. That sideways force will tend to rotate the knuckle - unless it is resisted and restrained by something else, such as either the locking pin, or the sliding friction between all those mating surface areas of the groove and ridge feature.
For the moment, I can see either possibility being valid - Larry and I seem to think it's the first, Bucyrus seems to think it's the second, as I understand it. Fot those of you who have followed along this far - stay tuned, as in future epsiodes we'll continue to explore the subtle and hidden intricacies of the modern knuckle coupler !
Bucyrus - you keep up with much more of those detailed explanations, and you'll be ready for a career in technical writing !
- Paul North.
Another way to look at it that occurs to me is to think of the main part of the coupler as a box, closed on four sides (top, bottom, left, rear, as you face the coupler). The front of the box is such that the closed knuckle can't be pulled out (rather like pulling on the pointy part of a nail that's been driven through a board - the head keeps it from coming through). That leaves the right side of the box open - and it is effectively closed by the locking pin.
As Bucyrus opines, the force ridges keep the knuckle from pulling out, while the other five "sides" of the box hold the knuckle in place.
In a purely straight-line pull, those five sides are of little import. Add any variables (slack, run-in, curves, irregular track) and they become most important.
Yes, I'm ignoring the rotary component of the knuckle movement.
I want to congratulate all you gentlemen for the excellent discourse on this topic. As I read, I cannot believe how hard it is to explain. I can still vividly recall when a mixed train conductor explained how it worked to my Dad and me when I was ten years old. Even then, I was surprised that my Dad had never really understood the intricacies of it, and at that point he had been working for the CPR for 17 years. It is an amazing aggregation of simple parts utilizing simple concepts doing an incredible amount of work.
It truly is something that needs to be seen in operation to be understood. I've been thinking that Larry or Carl needs to invite all of the non railroader forum members to their jobsites to show us how it works. Then Paul and Bucyrus can really give us a good explanation.
What sticks out in my mind even yet, is how the various ages and conditions of the couplers can still pull together. I've seen pre-WWI era MOW equipment hooked to ancient combine passenger cars, to WWI era cabooses, to the newest rolling stock available from the manufacturer.
In Paul's post above I am going to have to give the nod to both of Paul's conclusions, because as one part of the coupler wears out another component seems to step up and take its' place. Until age or load, or both, causes the inevitable failure.
Once again, job well done.
AgentKid
So shovel the coal, let this rattler roll.
"A Train is a Place Going Somewhere" CP Rail Public Timetable
"O. S. Irricana"
. . . __ . ______
Ok all you engineering guys...
Take a good look at the "pivot point" provided by the knuckle pin and note where it is in relationship to the lock pin and kuckle tang...it is to the left and forward of the center line, not quite in the middle of the knuckle so the needed leverage or rotation created when you pull on the knuckle is pretty large (you gotta give it a pretty gool pull to open it by hand because your pulling on the short leg of a lever)...so the force against the lock pin is small...as Bucyrus pointed out, once the slack is taken up, most of the force is applied to the lands and grooves of the knuckle and the coupler body...only a small amount of force is trying to rotate the knuckle because of the design of the knuckle inner faces when they are mated and closed and locked, the rest of the force is straight lined through the knuckle faces and the coupler bodys, to the drawbars and drawbar keepers and then the car center sill.
And the reason the knuckle thrower or hook works when you lift the cut lever is because the thrower is pushing on the back side of the LONG leg of the lever created by the knuckle riding on the knuckle pin.
The design of the lock pin pushes the thrower when you lift the pin (lock) with the cut lever, which is a long lever lifting a short pin, it creates a lot of leverage, and the thrower only pushes so far anyway...inerita finishes the task of opening the knuckle, once you get 50 +lbs of steel moving it tends to keep moving, and if the knuckle pin(pivot) or the knuckle is worn, you end up having to reach in and pull the knuckle open the rest of the way.
The reason for the thrower is simple, there are times you don't want you hand in there, as when cars are close to each other, but static....and you are not sure if there is something like another car say, rolling in from either end and about to impact either of the static cars, so the last place you want a hand is inbetween knuckles...
If you stand directly in front of a car with the knuckle closed and the coupler centered, you will notice the leading edge or lip of the knuckle is dead center of the car, the body of the knuckle is to your left center...because you are going to pull on the short end of a lever, the rotational force is easy to control.
23 17 46 11
Paul_D_North_Jr Bucyrus [snip] But when solid contact is made between the force groove and ridge features, the knuckle ceases to be a rotating element, and becomes a linear link, transmitting the pulling force in a straight line like a link of a chain. Once this function change happens, the pulling force no longer induces the knuckle to rotate. The rotation of the knuckle and the action of the locking pin together only serve to install or un-install the knuckle as a linear, straight line, pulling link. The rotation of the knuckle and the action of the locking pin together are not involved with the pulling load. What Bucyrus wrote above is true only if - pause a moment here to take a look at one of the knuckle top photos above - a straight line can be drawn from the point of application of the pulling force onto the knuckle tip - which would be about where the flag hole is - through the middle of the 'force groove and ridge feature', and into the draft gear, and said line would be parallel to the line of the train. That would be just about the same as a link in a typical oval-link chain - when pulled on, those links rotate as much as they need to until the points of application of the force on each end of them are in a straight line with the main line of the chain. No chain under serious tension is ever in a shape other than a straight line - unless there's an interference of some kind along its length. But a potential interference here is the angle and curve of the 'force groove and ridge feature' at the back end of the coupler tang. Without knowing exactly how the coupler and the knuckle are fitting together when under load, we can't say for sure whether it's the angled part of the curved part of the grooves and ridges that are carrying the load. More importantly, the 'line of force' should be at just about a 90 degree angle to the straighter parts, or radial to the curve. If that isn't the case, then a partial sideways force or 'vector' will be induced by the skewed angle of those grooves and ridges with respect to the perpendicular to the main line of force. That sideways force will tend to rotate the knuckle - unless it is resisted and restrained by something else, such as either the locking pin, or the sliding friction between all those mating surface areas of the groove and ridge feature. For the moment, I can see either possibility being valid - Larry and I seem to think it's the first, Bucyrus seems to think it's the second, as I understand it. Fot those of you who have followed along this far - stay tuned, as in future epsiodes we'll continue to explore the subtle and hidden intricacies of the modern knuckle coupler ! Bucyrus - you keep up with much more of those detailed explanations, and you'll be ready for a career in technical writing ! - Paul North.
Paul,
I believe that the original Janney coupler did not have the force ridge engagement feature. Therefore, when under pulling load, that load was transferred to the locking pin and an equal reaction force was transferred to the knuckle pivot pin. So both the locking pin and the knuckle pivot pin would share the bearing of the full pulling force. With this coupler, it could not pull a load with the knuckle pivot pin missing. And also with this coupler, if the locking pin magically disappeared when the coupler was pulling under load the knuckle would open.
It would be nice to look at some detailed assembly views to see just how the engagement of the force groove and ridge fall into line with the basic pulling centerline. Looking at that actual parts or individual part drawings, it is very difficult to visualize because the parts are quite organic in their form. They almost resemble bone structure of anatomy. With regard to that centerline, you mentioned that it probably is on the hole in the tip of the knuckle. Actually when two couplers are coupled, the holes in the tips of their knuckle are not in a line. They are maybe a couple inches apart. The pulling centerline would pass midway between them.
I hear what you are saying about the force groove engagement needing to be on the pulling centerline. That is what I would like to see in a diagram. It looks like those interlocking groove features would be offset from the centerline, so I don’t know how that would shake out. I have to think about that some more. A chain can have bent hooks where part of the hook does not lie on the centerline of pull.
There are two centerlines to consider: One is the common centerline of the couplers. The other is the parallel centerline in the pocket of each knuckle where the lobe of the opposing knuckle seats. That centerline does pass through the hole in the tip of the knuckle, and that centerline may indeed line up with the force groove engagement. If the force diverted through those centerlines (one for each knuckle), it would amount to a staggered, symmetrical offset to the main centerline of force as it passes through the two coupler heads.
You mentioned that you and Larry see one scenario of operation and I see another. I am not completely clear about how you see it. Just remember that whatever scenario you propose, it has to allow the knuckle pin to be removed by hand while a loaded, stretched coupler is under way, and it will not affect the coupling.
Jumping in here...
If the knuckle pin is removed after the knuckle is closed, it will not affect the knuckle and the coupling will remain, be it under slack or tension...in fact the knuckle pin (pivot pin) rattle and jump up and down a lot during movements....if you have the nerves and were dumb enough, you could reach in there while the train was moving and lift it out with little effort.
If the lock pin could be made to dissapear while the knuckle was under load or tension, the coupling would remain, right up to the point tension was removed, then the knuckle with the "missing" lock pin would open.
Y'all are more than welcome on the Adirondack any time - just make sure I know so I can be there, too!
Ed - I think we've all been learning here. I may use couplers virtually every weekend during the season, but I rather take for granted that they'll do the job we ask of them.
Interesting study.
tree68 Ed - I think we've all been learning here. I may use couplers virtually every weekend during the season, but I rather take for granted that they'll do the job we ask of them. Interesting study.
I was going to tell Paul, "Leave it as it is, so long as it works." But, it is interesting to see how a wonderful invention that seems so simple has much more to it than meets the eye or the ear.
Johnny
edblysard Jumping in here... If the knuckle pin is removed after the knuckle is closed, it will not affect the knuckle and the coupling will remain, be it under slack or tension...in fact the knuckle pin (pivot pin) rattle and jump up and down a lot during movements....if you have the nerves and were dumb enough, you could reach in there while the train was moving and lift it out with little effort. If the lock pin could be made to dissapear while the knuckle was under load or tension, the coupling would remain, right up to the point tension was removed, then the knuckle with the "missing" lock pin would open.
That would be my take on it completely.
I'm like a poster back a ways......I doubt if I will ever understand it unless I'd see a real connection in action or a small working model of the assembly.
I sure have wondered for many years how that force is handled by the parts I see in the coupler.
Quentin
Ok...
A few photos I hope will clear up the knuckle function issue...(yeah, right)
Photo 1 shows a closed knuckle,
Note the lock pin is down, you can see the stop tang..this keeps the knuckle from rotating, it sits on a shelf or pocket in the knuckle tang.
Photo 2, open knuckle.
You can clearly see the knuckle tang and its shape, plus note the shiny surface on the end of the tang, this is where the lock pin and tang have rubbed against each other...this is the total surface contact that prevents the knuckle from rotating.
Photo 3 open knuckle.
This shows the contact area a little better.
Photo 4, Knuckle by itself.
You can see the lands and grooves, and the notch or shelf the lock pin drops into when the knuckle is closed, it is the shiny area at the tail of the tang.
Photo 5, Coupler with knuckle removed.
This clearly shows that the pocket the knuckle rides in curves away and towards the front of the coupler, so when under tension, the knuckle tang locks into the grooves...and it shows the knuckle thrower, the hook shaped device to the left...this is in the open position, with the thrower as it would end up after the cut lever was lifted, and you can see how the lock pin lifts up and over the tang on the knuckle...the little tang on the lock prevents the knuckle from rotating past a given point.
Observe all the shiny areas in these photos, these are the only constant contact points, and realize the knuckle pin is simply a axel for the knuckle to rotate on, you can see the small raised lips or ridges where the knuckle really rides on the coupler, not the pin.
[snip] '' . . . plus note the shiny surface on the end of the tang, this is where the lock pin and tang have rubbed against each other...this is the total surface contact that prevents the knuckle from rotating.'' [snip]
Professor Ed -
Thanks much for the time and effort to disassemble that coupler - a shelf-Type F, right ? - take the photos, and write-up the explanation above. This goes a long ways towards answering all of the questions [and serves as a dandy substitute for the ones I took of the old L&HR [?] caboose in Warwick, NY, that's now a Visitor's Center or a Chamber of Commerce office, or similar, about 2 years ago, but can't seem to find now . . . ]. A lot to study and think about here.
So now that most schools are back in session, there's the weekend homework. Class will resume Monday morning.
Thanks again, Ed. Have a good weekend.
Yes, a F type shelf coupler on a tank car...but only the 1 shot with the knuckle open...it was the first car I came up on, and showed the lock pocket well...the rest of the shots are of an E type coupler.
Just look at the photos for a while and it will all click...simple gravity and levers and "puzzle work parts" , no tools needed beyond a ball peen hammer to persuade stuck parts and a pair of plies to remove cotter keys if used...
Pull knuckle pin out, toss in the track, lift cut lever, knuckle falls out in between track...reach in, pull lock pin out coupler throat, slide off cut lever end, (smack with hammer if stuck)...lift out thrower...use pliers to remove cotter key on the outside of the cut lever, throw leaver in between track...use hammer to knock out coupler shank key lock, and coupler shank sill key...(see photo 2, just behind the anglecock) get fork lift (locomotive or high rail)and draw bar strap, pull coupler out your done.
Thanks for the photos Ed. That does help evaluate the “force grooves” or “lands and grooves” that we have been talking about. I am revising my theory so that if the locking pin magically disappears from a stretched coupler, the knuckle will open.
I think what I concluded about the knuckle shifting function between a rotating element when open or closed, but not stretched; and a straight-line link when closed and stretched is true, but how it becomes a straight-line link is different from what I had assumed.
I thought it became a straight-line link by pulling directly into the lands and grooves engagement more or less perpendicular to it. This would relieve both the locking pin and the knuckle pin from any loading.
However, I see that the lands and grooves are nowhere near perpendicular to the line of pull. In fact they appear to be about 45 degrees to it. So in effect, the lands and grooves surfaces and the locking pin surface become opposing sides of a “V” groove or cavity. And the corresponding features of the knuckle tang wedge into that tapered cavity. So the lands and grooves pulling surfaces and the knuckle pin surface share the pulling load that wants to wedge them apart.
This still leaves the knuckle pin un-involved with the loading, but not the locking pin. I think that Cordon may have proposed this functionality when he said that he thought the knuckle loaded against the locking pin and placed its reaction force against the force ridges. I could not quite see that because I was thinking that the reaction force would need to be rotational. But it is not a rotational reaction force. It is a reaction force from one side of a wedge to the other.
The lands and grooves do not really look robust enough to be taking the full pulling force. But together, top and bottom, they look about equal to the strength of the locking pin in its backing pocket, which would make sense if they were opposite sides of a wedge cavity.
I would say that if the lands in the lands and grooves feature ever broke off from overloading, the coupler would revert back to the elementary Janney design as the reaction load from the locking pin shifted to the knuckle pin. I would also speculate that the lands and groove feature was added somewhere along the evolution of the automatic coupler to help the survival of the knuckle pin.
So just as the knuckle pivot pin could be missing while the coupler still functions, so too could the lands and grooves. But one or the other needs to be there.
edblysard Ok... A few photos I hope will clear up the knuckle function issue...(yeah, right)
Ed: You have provided the most comprehensive photos I've ever seen of the coupler parts...
And your description as well...
One remaining question I have is: I'm having difficulty seeing why there isn't excess force on the rotating knuckle pin......Surely, the rotating pin is not able to take all the tension applied thru the coupler.....Surely, it just can't. Something must be {by design, over center to take the force, and not the pin}.
One more: It appears when two knuckles are locked together {when coupled together with another}, they take all the force thru those pieces of metal....and I have difficulty understanding how a piece that size doesn't just break off when the load is in the high limits.
Thank you for your effort Ed, to provide the photos and make it clear....
ModelcarOne remaining question I have is: I'm having difficulty seeing why there isn't excess force on the rotating knuckle pin......Surely, the rotating pin is not able to take all the tension applied thru the coupler.....Surely, it just can't. Something must be {by design, over center to take the force, and not the pin}.
Quentin,
See my previous post. The knuckle pin does nothing except keep the knuckle from falling out when the coupler is uncoupled and the knuckle is open. Those pins can be pulled out of every coupler in a train and thrown away, and the train can continue without them. That knuckle pivot pin is not involved in the train pulling force.
Bucyrus See my previous post. The knuckle pin does nothing except keep the knuckle from falling out when the coupler is uncoupled and the knuckle is open. Those pins can be pulled out of every coupler in a train and thrown away, and the train can continue without them. That knuckle pivot pin is not involved in the train pulling force.
Thanks for additional info Bucyrus.
Seeing it in action might help explain the lock pin...
That's all there is to it.
Hope the link works.
It does, but its slow...
If the vid wont play for you, go to
http://s87.photobucket.com/albums/k143/edblysard/
And look at it there...
you can check out my hobby there to.
....Yes, the link worked Ed....Once again, thanks for your extra effort to show us fans. Thanks. I fully see the pin falling in place to prevent the knuckle from rotating....Think I'm using the right description.
To go a bit farther with one question: Is there a part in the coupler assy. that has a weakness, or does it more or less work until it's a worn out assy...?
Did you notice how easy it was to push the knuckle closed with one hand?
Thats because the knuckle rides on the two bosses or ridges where the pivot or knuckle pin is...all the pin does is keep it from skewing up or down, once locked the pivot serves no purpose except to provide a axel for the knuckle to ride on when opening.
I may down load a few other vids to the phot bucket page.
Yes.....I did notice the "hand" moving the knuckle rather easy....
I'm as close now to understanding just how the forces are directed as I've ever been.
I realize with two couplers connected, one couldn't see much of the workings but it just might tie it all together. Maybe clinch {for me}, really how connected assy's really lock the coupler assy's together.
Thank you Ed for the video demonstration. It is amazing how you can use a tiny camera in one hand and push with the other hand to demonstrate a century old technology. I like the way you can hear the loco in the background.
You can hear the pin sliding solidly into place, yet it is so small a piece compared with the size and weight of all the other pieces involved.
The last time I was that close to a moving coupler was the summer of 1964 watching a coupler work on a caboose built in 1917. The conductor, my Dad and me opened and closed it and looked it over for 5 minutes, and the coup de grace was watching it couple to a passenger combine as old or older than the caboose. And yes, as described on the other coupler thread, in the last few seconds before the time it really counted the conductor had to pull the knuckle open by hand to make the connection.
And you filmed the same technology yesterday. Thanks.
Modelcar To go a bit farther with one question: Is there a part in the coupler assy. that has a weakness, or does it more or less work until it's a worn out assy...?
The pin goes when you fail to open the knuckle on a car you kick, and the car it comes against has a closed knuckle also...there is just enough play in the pin and the hole it rides in to allow the knuckle to shear the pin...the thrower is not a robust part compared to the rest of the coupler, it gets bound up and breaks...but because it is not absolutely necessary to the function of the coupler, it goes un reported for a long time and only gets repaired when the car is shopped.
Draw bars, really the coupler shank, bears the greatest of all the force, the keepr and its keeper key get sheared, and the shank can develope stress cracks and then fail...
Over all, I would say the knuckle pin fails the most...a lot of times it is broken about 4 inches down from the cap, and the pin still does its job...
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