So, in actual railroading:
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How often does a knuckle break?
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How often does a brake hose come apart by itself while a train is in motion?
From “Railroad Facts and Figures - Copyright AA Krug - How Much Force can a Coupler Withstand?” at - [link]http://www.alkrug.vcn.com/rrfacts/drawbar.htm[/link]
Actual Practices
“We routinely go up Parkman Hill with coal/grain trains and 3 SD70MACS. The ACs have Tractive Effort meters (TE) rather than the amp meters of DC units. I regularly see 120,000+ lbs on these units. Multiply that by 3 units and you get a figure of 360,000 lbs drawbar pull for the set. At that figure we do not break couplers unless one has been previously damaged. Break-in-twos are rare, perhaps 6-10 a year I’d guess and that is running perhaps 1500 coal trains up there per year”.
“When running trains in the 1980s with 5 SD40-2s I found out the hard way you can shear perfectly good drawbars (no slipping or jerking, just pulling) by going from #4 to #5 throttle while stopped and trying to start a train on a hill. #4 is OK. #5 is NOT. It will break almost everytime. (I am a slow learner, it took me 3 successive train break in twos to realize DON’T DO THAT).”
- Paul North.
Air hose parting is by far the more frequent occurrence. On a 1000 mile mainline territory, there will tend to be at least 2 occasions of train getting stopped account of air hose coming undone. They come undone for a variety of reasons…mechanical conditions of the cars they are mounted to…road crossing conditions…slack movement in the train coupled with mechanical conditions…debris place on the track and probably 101 other causes.
Knuckles will be broken in this same territory approximately 3 times a week with a mix of Intermodal, Merchandise and unit train mineral and grain trains. While most everyone believes that draft strain is the primary cause of knuckle failure…more frequently buff forces end up being the causative factor as conditions that create uncontrolled slack actions are the primary cause of broken knuckles.
The uncontrolled slack actions can be generated by a number of actions. Surprisingly, the engineer using improper train pulling (draft) techniques for a particular territory is not the biggest factor. The biggest cause of broken knuckles is air hose parting…the air hose part and the train, on both sides of the break begins applying the brakes in a emergency application, thus generating uncontrolled slack actions through the train - that may be on undulating terrain and thus various segments of the train are developing draft forces and other segments are developing buff forces and the force actions are not operating in concert with each other. The engineer, other than releasing the engine brakes to keep from flat spotting the engine wheels…is just along f
Depends on how good the engineer is!!! Kevin
The problem with knuckles is that they are normally subject to stresses over the yield limit of the steel. This means that they have a fatigue life. The problem is, nobody know the stress history of each knuckle or where it is in it’s fatigue life. An “unlucky” knuckle can just plain fail without any “outside” help simply because it reached it’s fatigue life.
Yes, and until they fail, they’re out there. Then, when they do fail, good engineer or not, the engineer gets to answer forty questions and the downloads are scrutinized for engineer performance. The engineer is usually thinking, just what did I do here.
1000-2000 per year nationwide is a good estimate. (on a fleet of 1,000,000 or so cars)
About 4 times as often as broken knuckles.
Once again, I find myself recommending one of Al Krug’s excellent essays - the same one that I linked above, but further down in it. There he explains why the knuckles usually break about 10 - 15 cars behind the locomotives. Besides his unusual candor as quoted above - ‘’(I am a slow learner, it took me 3 successive train break in twos to realize DON’T DO THAT)" - there’s a lot of practical experience and insight into this phenomenon there.
- Paul North.
I’ve only ever got one knuckle with my remote engine [:-^] (almost 100% break, I was quite proud of myself!)
But have had many more knuckle pins break, or arrive broken.
It’s a positive thing to be able to report that all the knuckles I’ve had a part in up until now had a good reason that they broke, usually a good percentage of old break or a undesired emergency application that couldn’t be avoided or overcome. May it always be thus for all engineers everywhere.
Now that I think about it, I hope I haven’t hexed myself by posting such a post!
sweet job zug… your even with me in the knuckle department then… havent got one with the RCO but have snapped one on a coal drag years ago… altho the coal drag was only a 25% clean break…