I’ve always been intrigued with hump operations and classification of freight cars. Just out of sheer curiosity, I was wondering how long a train can be before it is considered “unsafe” to push over the hump. In other words, would it be safe to push a 100-car manifest over the hump all at once or is it performed by cuts of cars. This may sound fundamental but I’ve never really studied the process to know. If it is performed all at once, the compression stresses on those first few couplers of the train have to be incredible!
If a hundred cars were to go to one track or two cuts of 50 to two tracks it would not need to go over the hump, humping is only done when trains need to be broken up into different blocks going to different places.
The compression stresses on the couplers wouldn’t be too much different than the compression of a long train moving downgrade with dynamics bunching the slack.
There are many considerations to be taken in determining the length of a hump shove. Yes, we’ve humped cuts that contained well over 100 cars, with no safety problems. Operational problems, possibly–if something went awry and no engine were available to take care of it, it could be difficult to classify the rest of the cut without drastic action or “creative classification”.
The practical answer is that the length of the hump shove would be governed by the length of the track in the receiving yard–so if your yard can handle a train of 150 cars, you could probably shove a train of that size up to the hump, without any safety problems.
A new factor has come into play, though–remote control operations. The distance between the operator (box) and operated (locomotive) is somewhat limited, though this can be adjusted by the judicious use of repeaters. Since RCO has taken over, I haven’t seen hump shoves of more than 90 cars.
I’m only speaking from my own experience, which comes from only one such classification yard. There my be different characteristics to other yards that preclude longer shoves, or permit shoves even longer than anything I’ve seen.
Carl, I think what the OP was asking was if you’ve ever just run a 100-car block over the hump and down into a single track without breaking them up. Don’t you always break them up into groups of four cars or less, even if they’re all going into the same destination track?
Assuming no hazardous material issues, the pin puller at the hump crest will probably allow only one (and in some cases two) loads to uncouple at a time.
On the other hand, multiple empties coupled together and destined for the same classification track would be allowed to remain coupled together as they roll down the hill and through the retarders. As for the number of “multiple empties coupled together,” that depends on how the hump was designed and what the retarder technology is capable of handling. Usually the maximum number is somewhere between three and five cars.
So, for example, if a 100 grain empties were all to be routed to the same classification track, the pin puller would let them roll down the hill in cuts of four or five. As a practical matter though, the crew would probably shove the entire cut, intact, over the hump and past each retarder blocked in the fully released position.
In your grain train example. Would’t they just run he entire 100 car grain train through the hump bypass track and onto a classification track? Thus avoiding any need to tie up the hump with cars that are all staying together and do not need to be classifiied to different destinations.
In that case, we wouldn’t have a classification track capable of holding that many cars. A train like that would be very unlikely to come over the hump anyway, but there have been times when an exceptionally long block has come up. We usually work with the other end so they’re ready to pull it right out the other end for a departure track. Saves them the work of doubling it up.
We aren’t supposed to cut off more than two loads at a time, or ten empties. It seldom works out in such absolute terms, though. As for hazmats, we’ll put the entire cut over (regardless of length) and hold them in a retarder for handling. There are any number of reasons why one of the CROs would prefer that you give him the entire block of loads, and a smart hump conductor will respect his wishes. I don’t get involved in such requests myself (that’s done more by the lower towers, which have to be concerned about the location of cars in the tracks, proper coupling speed, long drawbars, etc.). If the conductor does something stupid, like splitting up cuts of hi-cube box cars (by far the leading car type in crossed-drawbar derailments), I will definitely say something.
Because of the emphasized words above, I took the question to mean, ‘‘How long / how many cars can the cut be when being pushed on the approach to the hump ?’’, not how many cars can then roll down the other side.
Carl’s reply above about the length of the receiving or hump lead tracks being the governing constraint is of course correct. Such tracks are usually flat or nearly so; if they’re on any kind of a grade, that and the resulting tractive effort needed to push the cut along them will govern instead. The usually short and steep grade up to the hump itself won’t govern - there’s not enough cars or weight on it at one time to seriously impede the hump pusher engine. For example, here’s a zoomed-in photo* of our local NS Allentown hump approach - you can see that there’s only about 10 to 12 cars on the slope at a time:
Sounds exciting! I’ve always wondered how a real hump yard worked! [;)], of course!
Of course, such an undertaking would probably never be condoned by the railroad, and you’d need too many synchronized cameras for most companies to even consider such a thing.
And “my” yard is unique (as far as I know) in the country with its method of operation. We may be the only practitioners of the art of Car Retarder Operating left. A few people who read this Forum have been lucky enough to see where I work; even fewer have actually been able to watch us perform. At times it seems like nothing is going on, but the actual volume of activity would make one’s head spin.
One might be better served by going to a place like the Golden Spike Tower in North Platte, armed with a scanner. The docents up on the observation level are often retired employees who could give one a good idea of what’s happening, when, and where (but they might be annoyed with the scanner!).
Paul, for the record our hump leads are on a long, sloping ascent to the top–most of the shove is on this gentle grade at any given time.
That public road appears to have given me yet another destination for our grandiose post-retirement trip out east! (No idea yet how long post-retirement!)
I have a picture I would LOVE to post in this thread, but I won’t unless the subject grants his permission, which probably won’t happen until said subject retires.
A few - it looks like 1 in Allentown, 1 in Bethlehem, and maybe a few more within 10 - 20 miles or so, such as Kutztown, PA and Clinton, NJ. The real ‘world-class’ concentration of those is about 1 - 1-1/2 hours southwest in the ‘Pennsylvania Dutch’ - Amish - Mennonite Lancaster area.
Here’s the link to a Spring 2008 newsletter about quilting from the Allentown place, which is a regular stop for my wife Marie and ‘on the beaten path’ for my travels, too:
Our hill in Oregon is about 30 ft high, the longest train i’ve seen shoved in one pull was 12000 tons and something like 9300 ft. It was really the limit of what the 2 SD40’s could stop; maybe only a thousand feet of pull back track left as well. We are also only allowed 1 load and 2 MTYs at a once.
Your statement made me recall the same or similar story from TRAINS. The way I remember it, the person involved was Cotton Belt’s crusty old yardmaster at Pine Bluff, AR. He finally got a bellyfull of complaints from higher on the food chain about cars sitting too long or taking too long to get over the hump, so he rounded up enough locomotives to shove all the cars waiting to be humped, coupled them all together, and dragged them far enough out on the main line that he could push the last car up on the hump, and proceeded to hump everything. As he got enough cars for a common destination to make
