In regard to the video Dan posted, a brief comment about the 'internal workings' in these elevators. When the grain flowed down, it exited the center and frequently left a very steep 'wall' of grain from the center 'drain' to the outer wall of the silo. Frequently a person would need to get into the area to rake the grain down. Seemed at least once a year out in the big grain growing areas that resulted in an avalanche of grain (especially wheat), in which the person was trapped and died - just like the the danger from snow bank avalanches.