Hey, Ali, didn't someone already patent the idea of a ball movnig throught he tube with some velocity? Smith or Colt or someone like that.
I thought it was Sir Humphrey Twelve-Gauge who had the first patent?
Anyway Tom, it seems as if Jeff is going for Marce's hinge idea.
No suggestions as how to actuate it though; so I think sticking a wee plastic duck on the end of each hinged thumper, and shooting it over with a Colt 45 would be a good diplomatic solution.
Ali.