Reference to the Pennick & Ford plant in Cedar Rapids brings back a memory from the early 70's. The P&F plant used an unusual machine to unload boxcars, it was a car rocker, but nothing like the car shakers we associate with unloading open top hoppers. The boxcar was placed on the rocker platform, the side doors opened and the grain doors cut (if paper) or removed (if wood) after the doorway area drained the rocker would be activated and the platform on which the car rested would start rocking back and forth, it wasn't a huge movement maybe 3 or 4 inches on each end, but the back and forth up and down movement caused the grain in the ends of the cars to move to the center of the car and drain into the unloading pit. It wasn't real fast taking maybe 15 to 20 minutes to empty the car.
One day I witnessed a Rock Island stockcar that had been converted to grain service by lining it with plywood being unloaded on this contraption and after a while as the rocking cycle got going the roof of the car was moving in one direction as the floor was going in other directions, parts were dropping off in all directions I actually stepped back about 50 ft as I was concerned the car would disintegrate right before my eyes. I am sure that was the last revenue move that car ever made.
I think the car rockers were made by Straight Engineering of Iowa who also made car dumpers, the rocker was really a poor mans version of the car dumper as they were a lot cheaper than installing a full car dumper. They were expensive to maintain for the plants as just as they shook the cars apart they tended to shake themselves apart. Railroads eventually banned them by refusing to serve any plant that used them I only ever saw one other one at a soybean processing plant in Indiana an d it had not been used in many years.
So much for old memories, I want to see the first operating model of one of these contraptions.