I know that a lot of work has been put into determining the shape of the top of coal loads to cut down on loss of product, dust abatement and even wind resistance… but the other day I was on a walking trail that has a bridge over a mainline and watched a coal unit train pass directly beneath me (a scary experience, to say the least!) and I noted that the center of the coal loads were mounded above the sides of the car, and the “roundness” of the surface was such that the sides of the load were a couple of inches below the sides of the car.
This is all well and I supposed good, but the “ends” of the coal load were rounded down to the point where I could see the start of the sloped ends of the car itself… and that appears to me to be about 2-ft of the ends of the car with no coal against it!
There was enough room at EITHER end to easily contain the amount of coal that protruded above the sides of the car at the middle.
I am sure the car is filled to its weight capacity, even though by volume there is plenty of room to spare, but, it seems to me, in my muddled mind, that if the coal were to be leveled off to fill the cavernous cavities the present system of loading leaves at each end, that the wind resistance would be lowered considerably… Not only reducing the size of the hump of the load protruding above the car upper edges, but the cavities at each end must present some additional friction as the train passes through the air. (I get better gas mileage on my car if I drive with my windows up… The smooth (relatively) sides of the car with the windows up reduces the wind resistance of the car enough to produce a noticeable improvement in fuel consumption.)
Unless this hump in the load provides some sort of airfoil shape that creates lift on the whole car making it easier to haul them at speed! How come the load is mounded above the top of the car such as to present a larger cross-sectional area?
I would imagine they do not dump the coal between the cars. My guess as to why the coal is so low at the ends is that there is a period of time in stopping the flow of coal and again in starting the flow where the flow is not at 100%, therefore not much coal ends up at the ends.
Just like a box of cereal, the product settles and tamps itself down during shipping. Trimming or packing at loading would be a waste of time and money since it will happen automatically and at no cost during movement. In fact, I am sure that if it were trimmed and tamped at loading, transit would only pack it in harder and make it more difficutl to unload. These guys know what they are doing.
Flood loaders at coal mines dump the coal into the hoppers as they move under the loader at a set speed. The loader cuts the loading off at a precisely set weight, so most hoppers have the trailing end of the load shorter than the beginning end.
It would be interesting to view a ships hold as it was loaded at the coal pier and then as it was received at destination…I suspect they would present totally different views after several thousand miles of ocean motion mixing.
1.) Where I view the coal cars, the train has traveled at least 800 miles so any “shake down” would be well done by then.
2.) I vaguely remember articles in Trains Magazine (and elsewhere) about how the coal is “groomed” after being loaded, specifically to reduce dust in the 1st 50 to 100 miles to reduce severe wear on the rails, wheels and bearings caused by the dust blowing off the moving train. Several different types of “coatings” have also been tried to reduce the dust being blown off the surface. If you look at the coal load you can see that is appears to be smoothed and all stuck together (kind of like asphalt).
So that still leaves me wondering how come the load isn’t dropped lower (by filling the ends of the car) to reduce the overall profile of the car?
If you are viewing the train after an 800 mile journey, then you haven’t seen what it looked like out of the loader! It probably is piled as high and wide as you speak of!
I am a conductor for the BNSF railway, and have worked recently on the Powder River division on the Orin and Cambell subs(where the Powder River coal is loaded for the BNSF an UP rr’s). I work on the Southwest Divsion(Arizona and New Mexico). I have also worked the the majority of the route PRB coal goes from the mines to the utilities. Coal is semi crushed prior to loading in a teeple to the hopper car and wetted down to control dust as it’s loaded. The actual piece that loads the coal into the car is called a chute and it goes up and down and flow is also controled. As previously stated, the car set is moved at a controled speed (either called pace setter or slow speed depending on type of locos used). The loadout operatorer plunges the chute into the car at a set height and and opens the flow from the beginning of the car to the end of the car, stopping in between cars. These sets are loaded as quickly and efficiantly as possible to avoid delays. PBR coal is in high demand and sets arrive as quickly as they depart. The average set is about 130 cars verying from 105 to 150 cars. There is not a “preferred profile”, cars are loaded to weight capaciety ranging from 141 to 143 tons per car. The BNSF is currently testing to determine how much ladding is lost due to “blow off”. The cars are weighed prior to departing the mines and also when they reach their final destination at the utility. There is some lost, but not tons per car. In a business and environmental sense, it would be better to keep this lose to a minimum. Hopes this answers your questions.