This video shows details and operation of a drive mechanism for the Newton's Cradle (or clacking balls). Rather than have the balls suspended by wire, I had to use a section of hollow fishing pole (could have used carbon fiber rods) so that I could have a lever to push the drive ball back with. This drive could be used with any number of balls but I had a hard enough time aligning just two balls with the basic hand tools I had available. This would be a nice project for someone with real machining skills.
I had wanted to do this project for sometime and had tried various methods with wire suspended balls but no joy. Then it occurred to me to use rods to suspend the balls. I'm not sure how the rods affect the efficiency of the balls transfer of momentum but they seem about as effective as using wires. I'm sure with good machining the efficiency would go up.