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Knuckle Coupler

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Posted by Paul_D_North_Jr on Thursday, February 4, 2010 9:39 PM

Bucyrus
  That's a great photo, but I don't see any comments that open with it. 

Hmmm - that's true enough, but odd - wonder why . . . oh, OK - now I see why - try the link below instead . . . learn something new every day.  BaltACD, you too may find the comments of interest.

- Paul North.

 http://www.railpictures.net/viewphoto.php?id=312176 

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by BaltACD on Friday, February 5, 2010 5:03 AM

Paul_D_North_Jr

Bucyrus
  That's a great photo, but I don't see any comments that open with it. 

Hmmm - that's true enough, but odd - wonder why . . . oh, OK - now I see why - try the link below instead . . . learn something new every day.  BaltACD, you too may find the comments of interest.

- Paul North.

 http://www.railpictures.net/viewphoto.php?id=312176 

One could say the crew performed a 'Coupler Test' on this car...Coupler failed!

Never too old to have a happy childhood!

              

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Posted by switch123 on Friday, February 5, 2010 7:12 AM

Looks like a brand new break instead of a old crack that finally failed.

Look how clean and shiny the break surface is, no rust or discoloration.

They had to really slam this one to break it like that.

Which is why we away open both knuckles whenever we can.

That's why I love my computer,,,,,,,, my friends live in it." - Colin Greg, Barnsley, South Yorkshire, England Pen Turner Extraordinary and Accidental Philosopher.
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Posted by Paul_D_North_Jr on Friday, February 5, 2010 8:30 AM

One of the comments - the 5th one - to the photo said much the same: 

Posted by Ky.CatFan on January 29, 2010

I can't see any rusting in the break that would indicate prior minor cracking, so there was a lot of force exerted here. As Joe said they had better have a look at their tapes.
 

However, here's what a response said:

Posted by Will Lohrbach on January 30, 2010

It was about -10 F. There is a prior crack that you can not see in this photo, and has rust spots in at least 3 places. It was caused by stopping after a kick, with a about ten loads behind 30 cushioned draw bars. They can download my tapes if they want.

Aside from the events indictaed by that response, are you thinking that was caused by a pushing or 'buff' force compression-type impact, as contrasted with a pulling or 'draft' force tension-type impact ?  The use of ''slam'' and especially the reference to opening both knuckles seem to indicate so - in a pulling situation, either the knuckles aren't wanted to be open, or they are - and if so, would only 1 knuckle being open lead to this kind of damage Confused

- Paul North.

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by Deggesty on Friday, February 5, 2010 1:51 PM

Two questions: How much of the draft gear had to be replaced? If this had broken out on the road, could two men have taken care of the repair?

Johnny

Johnny

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Posted by Anonymous on Friday, February 5, 2010 2:39 PM
 

Is that break in the photo consistent with being pulled apart by tension?  I see the locking pin sitting there.  If I am not mistaken, it is upside down, so perhaps it is loose and has merely been set there by someone.  In any case, there appears to be evidence of a compression impact on one corner of the locking pin.  I can’t see how that would occur with a pull-apart.

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Posted by switch123 on Friday, February 5, 2010 5:09 PM

The shiny spot on the lock pin is normal, that is where it rubs against the back of the knuckle when moves up and strikes the top inside of the coupler.

The lock pin has fallen forward, its top is facing the front of the photo..

Given the sparse info in the caption, my guess, and only a guess, was that the knuckles were closed and someone kicked a good size cut of cars in on top of it with the corresponding knuckle also closed.

But now, given the info provided by what appears to be the engineer/trainman involved, and the presence of other minor cracks, added to low temperature, it could simply be a straight out failure, which does happen.

See also the lift pin lever, the rusty spots and discoloration along with the obvious bending that has happened to it indicate a little abuse to this car, at least one bypass knuckle, the lever has been heated with a torch and bent back into working shape, although industry guys tend to move cars with a chain and tow motor by hooking up to any convenient protuberance like cut levers and hand brake wheels so that could be the result of their towing the car by the lever.

Keep in mind that along with the wheel set, knuckles and couplers are the most abused part of any railcar, they take a tremendous beating daily.

Without being able to examine the car in person and gather any more facts and make detailed observations, I feel you are looking at what I believe is a simple mechanical failure, not abuse by the crew.

That's why I love my computer,,,,,,,, my friends live in it." - Colin Greg, Barnsley, South Yorkshire, England Pen Turner Extraordinary and Accidental Philosopher.
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Posted by Anonymous on Friday, February 5, 2010 5:49 PM

switch123
The shiny spot on the lock pin is normal, that is where it rubs against the back of the knuckle when moves up and strikes the top inside of the coupler.

 

If that spot on the locking pin is normal, then it looks to me like a knuckle was pulled out of the coupler body by breaking the coupler body.  An alternative scenario of too much tensile force would be for the knuckle to break.  Another alternative would be to pull a coupler out of the draft gear.

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Posted by Rail Car Designer on Monday, April 6, 2015 12:48 AM
Is everyone satisfied that they understand the operation of the coupler and knuckle? I can supply design drawings and FEA loadings of couplers and knuckles that show how the loads are past through the components if anyone is interested.
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Posted by Rail Car Designer on Monday, April 6, 2015 12:50 AM
the mass of the coupler is too high to be replaced manually. lifting equipment is required plus tools to remove the yoke pin and the carriers
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Posted by Rail Car Designer on Monday, April 6, 2015 12:51 AM

The coupler is a double shelf coupler for a tank car and it is not unside down.

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