Tichy has a kit for a modified boxcar that has bottom hopper doors and roof hatches. I am considering using these on my streamline transition era layout, supplying a redi mix plant. My question is how were these emptied, and into what? after the initial gravity flow were they shoveled out by hand? Did the pit have a simple rubber belt conveyor or something else? These days most use air to push the powder through pipes. I'm hoping to model a correct, small redi mix plant on a siding for the mid 1950's. i saw such a plant today, not on rail, that looked perfect for the other details.