At the club ROBOTICA we create every year a special project:

Last year (feb. 2000) We made Ball-Collector-Robots.

There for we needed a machine  That puts the balls back in the field.
This ping pong ball shooting machine has an autofire. 

One new Technic motor drives the whole machine.
Load, shoot, turn (limited 120 degrees), and even the ball lift to load the balls in the top.

A seperated machine, like a forklift transsport band loads the BSM.
This one is not on the picture.
By just making a tube filled with balles on top the machine can shoot lots of balls without human interaction.

for more info take a look at the robotica web site or contact:

Martyn Boogaarts at:  mjr.boogaarts@usa.net