Our team used a hoop-ish system, where the balls are driven in by sand belts powered by a window motor, then locked into individual hoops. Each ball pushed the previous ball up and out into the next hoop. The balls were locked in by steel bands, each tightened by a cam. Balls were pushed out by running the system in reverse, gravity would push each hoop down into the belts. It worked out rather well in competition, even though we didn't use it too much. Most of our strategies involved capping and hanging, neither of which worked as well as our ball sucker...
Here's our file photo
I'll try to get some screen grabs of it's use in competition.