AutonerdI know of M-K from some locomotive rebuilds, but what would they have needed with coal hoppers?
They didn't. They were for track ballast (rock), not coal.
They would have been leased or contracted for track construction/maintenance activities like Herzog hoppers today.
Chris van der Heide
My Algoma Central Railway Modeling Blog
One use would have been Interstate Highway construction. At least one company had its own C-C GEs for that!
Bear's picture of the M-K hopper looks to me as more of ballast car, as the discharge gates are over the rails, rather than between them.
I used to get hoppers which came with those plastic "loads", but later opted to use "loose coal".
This train shows some loads of loose Black Beauty sand-blasting medium...
...which gives each loaded car a weight of about 8oz.
This car is loaded with fine coke breeze (from the making of coal into coke)...
...it's somewhat messier than the blasting medium, and does create a "prototypical" cloud-of-dust when loading or emptying the car. A loaded car weighs-in at 5.5oz.
While loading and/or emptying loose loads can be time consuming, I much prefer it to my attempts trying to remove those one-piece plastic coal piles.
Depending on one's point of view, a loose load of "coal" in a derailment does look somewhat more prototypical than a dislodged heap of plastic coal.
Wayne
https://commons.wikimedia.org/wiki/File:Morrison-Knudsen_ballast_hopper.jpg
http://www.rrpicturearchives.net/showPicture.aspx?id=2743364
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
Morrison-Knudsen was primarily a large construction company (think Hoover Dam), so the hoppers may have been for construction material like aggregate.
I bought a few 3/4 bay, 70-ish ton hoppers on eBay for a coal train I'm building, and I picked up one painted in yellow for Morrison-Knudsen (primarily for the coal load which, alas, only fits one other car I have... which ahs a load). I know of M-K from some locomotive rebuilds, but what would they have needed with coal hoppers?
Thx!
Aaron