Has anybody seen how some people ba***he hell out of the cars when switching the yard? It looks like they are trying to go for the Roman galley charging at another ship thing. I can’t imagine the couplers do well after repeated bashing like that.
Well, uhhh,lets see if I can explain.
Oh, never mind…
Let me see if I can explain.
A properly designed product (including couplers) will have the severity and frequency of loading (force applied) considered when designing it. The people who design couples know well what type of loading the couplers will be subjected to and that they will experience fatigue due to cyclic loading. Therefore, they use a suitable material and design the knuckles and rest of the coupler so that they will last for a certain amount of couplings at a certain loading before failure. Due to the nature of coupling and uncoupling cars, varying train lengths, varying grades, skill of the engineer, and impurities in the material, the amount of couplings before failure is only a good guess. Does that sound right Mr. Blysard?
I would think you’d see derailments before you saw compression shock failures of the couplers or draft gear.
Having said that, throwing cars against each other at high speed isn’t going to have shippers happy with you in the long run…
Ed…I thought the only time you guys beat up cars was when they had …umm …let’s say uninvited guests onboard…[}:)]
Is metal fatigue common?-- only I witnessed a coupling failure the other day out on the CN mainline near Mission BC - the train an eastbound mainly empties - suffered a coupling failure after the slack ran in quite heavily as the train was slowing for a bridge.
Somewhere here around the house I have a DVD produced by the railroads on switching in the yard. I have not watched it lately but if memory serves me correctly (might or might not) it seems like it said that if the humped car couples with another car at 3 miles per hour that is ok. However, at 4 mph, or greater, loads can shift and the goods inside are subject to damage.
In eight years of kicking em’, I havent broken a knuckle.
Have seen one shatter, though…both the knuckle on the loaded car kicked and the loaded one it was kicked againt were closed…the incoming cars knuckle and the drawbar head snapped, and exploded into several pieces…
Yup, 4 mph is the max our rule book allows, although, as anyone who has ever flat switched knows, its rarely followed.
A guess would be most are let go between 4 and 8 mph, I have sent one down the lead at 12 once or twice, but only to knock a car or two back into a track, and in the clear, or close up some gaps in a track.
Like ericsp pointed out, these things are designed to be beat up.
More common in flat and hump switching is having the knuckles by-pass each other, and damage the end sill or cut leaver…and if you do this when the cars are in a curve, you can get them on the ground pretty easy…
Ed
I here those couplers can be pretty dangerous to replace at times.
Ed – probably right; engineers probably do kick cars at more than 4 mph… to those of us on the ground, though, I’d remind us all that a car always looks like it’s going a lot faster than it is when you’re close to it – and certainly sounds worse when it couples!
I haven’t done a comprehensive study of metal fatigue in couplers, but from the few I have looked at, fatigue wasn’t the problem – pre-existing flaws are common enough (in such a large piece, they are almost inevitable); low temperatures raise havoc with strength; and just plain old shock loads – which are very hard to predict – probably are the villains in most failures.
I have witnessed many hard coupleings over the years and never saw any car damage.
I did see a load of telephone poles shift end ways about 5 ft when it and 3 cars where kicked in to a string of standing cars. Even the best crew can goof once in a while.
The classic hard coupling that I heard was over the scanner and went like this
“Ok when you get them CRASH!!! stopped 3002” Joe sorta misjudged that one.[:)]
Gave a few railfans somthing to laugh about.
I have heard similar before, and it was like "3 cars Charlie…2 cars Charlie…BOOM!!
Nobody knows what happened to “1 car”[(-D][(-D][(-D]
Take care,
Russell
Since coupling speed (or lack of it) is suggested by my job title (car retarder operator), I thought I’d better jump in.
So far in my career, I’ve seen literally hundreds of derailments that have involved attempted couplings, either excessive speed or bypassed drawbars (as Ed says, on curves that can happen very easily–often with turned rail complicating the process). To me, the scariest cars to hump are 86-foot hi-cube box cars and 73-foot center-beam flat cars. Not only do they have long drawbars that move freely, but they also seem to have high centers of gravity that make them more susceptible to tipping. Surprisingly few derailments at our yard involve auto racks, which share those traits with the other cars.
We were always told the the effect of an impact on a car increases proportionally to the square of the speed: e.g., a 2-mph impact is four times as damaging as a 1-mph impact, a 3-mph impact would be nine times as damaging, etc. Four miles per hour is the commonly accepted maximum safe coupling speed.
Having said all that, I can say that I’ve seen some pretty spectacular overspeed incidents, usually caused by the retarders not being able to handle the cars involved (quite often, loads of tallow or similar commodities have the stuff on the wheel surfaces, which makes the cars slide right through the retarders–and a number of the cars right after them, too. Finely ground powders, such as flour, starch, or corn sugar can have the same effect). Those cars have gone into tracks at speeds of over 20 mph, and hit the cars standing in the track. When that happens, our rules state that the cars have to be inspected before the track can be used again. More often than not, everything is OK (at least as far as the equipment remaining on the rail and not sustaining damage). If couplers are bypassed, there are likely to be problems–a derailment, sometimes with telescoping of cars, can occur. The cars sometiimes lift a little, allowing the truck to roll out
Ahem…it’s more socially acceptable now to refer to them as “cars with special needs” or “exceptional cars”
But more importantly…does that mean you take the “short” crew van?[;)]
Four mph is supposed to be a safe coupling speed. If you have ever been on an engine that couples into cars at 4 mph you will want to do it at much lower speeds after the experience. Even higher impact speeds, whether intentional or accidental, are bound to cause some damage to the car, the lading, or both. The damage may not be apparent at the time but will lead to failures later. Using cars as battering rams to drive other cars into a track or couple it up shows disrespect for the equipment and the shippers goods.
KE=(1/2)mv^2
KE = Kenetic Energy
m = mass
v = velocity