The cars are not uncoupled. At least one couple on each car is a rotary coupler. The car rotates but the coupler stays right side up. Not sure just how the rotating part of the couple is made but it works. You have to make sure when the train is built that two nonrotating couples are not put together. That would make things messy. Some cars, though not very many, have rotating couplers on both ends. It costs more you don’t have to worry about how the train is built.
Derrick
No judo flips…the whole point is that the cars do not need to be uncoupled, saving a lot of work in making separations, reconnecting air hoses, and so on. The coupler at one end of the car (sometimes both) is designed to swivel. Denoting the end with the swiveling coupler is the reason you see the coal gons (and hoppers) with a contrasting color at one end…be it a band, panel, or solid paint job. The couplers are of the tight-locking variety, preventing accidental uncoupling during this operation.
I might add that a rotary dumper capable of unloading two cars at once would not be bothered by the orientation of the cars…in other words, you could dump cars no matter which way the rotary coupler is facing (if two non-rotary couplers were together, this would be the middle joint on the cars in the dumper…you might have to move the train forward only one car-length instead of two, but it would still stay intact.)
There are two types of rotary dumpers. One type handles uncoupled cars only and the other coupled. You have asked about the coupled type. In its simplest terms, you take an open topped car, rotate it 180 degrees, shake it a little, perhaps, and then rotate it back the way it came 180 degrees. As mentioned in the earlier posts, the coupled car rotary dumper requires a design that pivots on the cars center sill alignment. Depending on the design of the dumper, one car only or more than one car can be dumped at a time. I know of one and two car dumpers, but in theory, the entire train could be dumped at once if the dumper is long enough. Being the visual person you are, you can quickly see that dumping an entire train at once is not practical, but what a sight that would be.
Uncoupled car rotary dumpers rotate on a ring that centers on the middle of that ring, and aligns with the track structure when in the upright position. An engine or off-track car mover shoves one or two cars into the rotary, carefully spots them (mass and its location are important with these dumpers), clamps come down from the “top” to hold the car(s) in place, and “around they go”. When the dumping has been completed and the car(s) is(are) upright, the clamps come off, and the next cut of cars is pushed against those in the dumper, shoving them out the other end onto a descending slope track where they roll away by force of gravity.
You can do the visualation by taking pieces of paper, cut “small” and in rectangular shape to look like the end of a car, then poke a pen or pencil into the appropriate spot fo
Those “really tall towers” with men in them watching the trains go by are not rail-fan observation points. They were interlocking towers where men, working for the railroad, operated switches and set signals to control train operations. In the days prior to CTC, they were the only practical methor of controlling railroad crossings and locations where trains could change tracks on multiple track mains.
Those little houses where the towers used to be are equipment sheds (aka relay boxes) where the electronics are housed so that the dispatcher can do the same thing as the interlocking operator. Those people spending time in those little houses are signal maintainers doing their repairs and preventive maintainence.
Any design shape or capacity you could desire or imagine. Two basic arrangements - center (between the rails) and side (outside the rails). Also, cross dump (between and outside at the same time!) Can be very messy, depending on design. If you need to clean the rails before the next car is dumped, you have a real lemon of a system.
Glad to help, Madam Da Mook. Bottom dump cars are sometimes used to spread ballast with a crosstie sliding under the wheels to keep it even with the rail tops. Also, bottom dumps would occasionally open in switching it they coupled too hard. You can visualize that, can’t you Mook? Those towers, in an earlier age, were the locations of guys who made the nice green signals red so we couldn’t move. Then we’d have to go to the lineside telephone and call these same guys to ask why the signal was red.
Muddy owes Mook a picture of the rotary coal dumper at Holcomb, KS (This rascal not only dumped coal cars, but ripped horns, lights, antennae and air conditioners off the tops of unsuspecting locomotive cabs!)
Central axis of the coal dumping cylinder = drawbar/knuckle of the coal hopper…The colored end of the coal car is generally the rotary knuckle end…
and all for the same price, I imagine! [^]