Recently while flipping through an NMRA Mag I came across an article about how real railraods place nuckles at certain locations where they are likely to break for emerency R&R.
My question is this :
When a nuckle breaks on a train running uphill what happens to the now loose end. Surley there is some safety feature that applies the breaks so that the freight does not now become a speeding missle down hill at some oncoming train ?
What causes these nuckles to break ? Jerking starts ? fractures from the factories ? Undue stress ?
TTYL
YGW
If a train parts, bot halvs go BIE (Brakes in Emergency)
Locomotives (and formerly cabooses) carried a variety of knuckles. The conductor drops off a new knuckle on the ground, the train pulls forward until the last remaining car is where the knuckle is. If that is the knuckle that is proken, it is fixed and the train put back together agian. If the distant coupler is broken then the knuckle is placed on the last car, and the train backs up to where the other end was left, the knuckle repaired and the journey continued.
It hepls to know what kind of car the other car is. Different kinds of cars use different knuckles. Your manifest will help you if you know where the break is, but if it is just back there somewhere, you may find that you have brought the wron knuckle with you, and you will have to reverse the process to obtain the correct knuckle, assuming that you have it on one of your locomotives.
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I assume knuckles break from metal fatigue because they take a pounding in service when slack is run in and out. Couplers in general take a pounding as you can hear if you visit a hump yard -- BANG when the cars meet. Of course ideally the knuckles are not closed during switching and yarding but sometimes they are.
Then consider the tensions and pressure from just normal train service where tons and tons of weight are being pulled, with each knuckle taking the brunt of it. Eventually the stresses of that magnitude would take a toll on any steel. It isn't undue stress it is normal stress, but years' worth of it, constantly. I suppose from time to time flawed steel plays a role too.
When the knuckle breaks uphill, the cars separate and the air brake hoses pull apart. This causes an immediate loss of air pressure in the line and the way the Westinghouse air brake system works, that is what causes the brakes to apply. I was once standing at a crossing when the hoses hit the crossing itself and broke open right there -- it was like an explosion it was so loud and the train went into emergency at once and stopped surprisingly quickly.
A more interesting question is what happens is the knuckle should fail while the train is headed downgrade and the cars and brake hoses do not pull apart, at least for a while. I guess the brake line remains intact then but at some point the cars will pull apart.
I have seen crewmen carry knuckles along side of a train. They are heavy items.
Dave Nelson
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Lion - really ? So are you saying the loose end of the train brakes ?
yougottawanta When a nuckle breaks on a train running uphill what happens to the now loose end. Surley there is some safety feature that applies the breaks so that the freight does not now become a speeding missle down hill at some oncoming train ? What causes these nuckles to break ? Jerking starts ? fractures from the factories ? Undue stress ?
First, google Westinghouse air brake system. It's a "fail safe" system, loss of pressure in the connecting lines caused the entire system to go into emergency brakes.
Why do they break? Good question. There could be one or more of many answers to that. Metal fatigue, internal flaws in the metal, not visible from the outside, localized crystalization of the steel causing a brittle part internal. Fatigue caused by normal usage, or from several hits that are a little hard. Then consider that the entire tractive effort of all of the locomotives has to be borne by the first coupler on the train. There are as many reasons for a knuckle to break as there are atoms in the coupler. Unfortunately, the cause won't be known until after it breaks.
Rich.
yougottawantaSo are you saying the loose end of the train brakes ?
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Thanks Jeff. I was wondering how that worked
When a train breaks apart on an upgrad there is still air in the reservior to hold the brakes on. What happens if that air is eventually depleted. This air must be released to allow cars to roll over a hump, but if the crew cannot get back there fast enough to set some hand brakes what happens then. Isn't that similar to what happened in Canada.
What happened in Canada was from not enough hand brakes being applied. In switching moves where the air hoses will be hanging loose the angle cocks on the ends of the car(s) are cut off. This keeps the air in the reservior tank from escaping so the brakes don't set up.
Yes, what happened in Canada was because none or not enough hand brakes were applied, but where did the reserve air in the brake reservior go. when a car is being rolled over a hump that reserve air is drained out with the BCO valve so the car will roll freely. When the airhoses part the angle cock valve is still open.
retsignalmtrYes, what happened in Canada was because none or not enough hand breaks were applied, but where did the reserve air in the brake reservior go.
That Canadian thing I suspect the crew "bottled" the air and it leaked off-several reasons come to mind including the air lined handle not being completly closed on the car where they made the cut which resulted in the lost of air..Laziness of the switchman in not sitting enough handbrakes to hold the cars.
As far as a break in two both ends will go into emergency and will come to a dead stop.The crew will need to fix the knuckle,connect the air and pump the air back up since it was dumped in a emergency application and then release the train brakes.
Larry
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Saw that video. the photog went and found both pieces. No rust in the knuckle where it broke