How to Control Speed of One Wheel in a Table Tennis Ball Serving Machine?

[Cowzer]

For my leaving cert project (Ireland) I have to build a table tennis ball serving machine. I'm settling on a design that uses two spinning rotors to fire the ball out as it passes between them, but I'm wondering is there any way to automatically adjust the speed going to one of the rotors (each one will have a different motor)?

Design is like this

http://www.blackwatersports.net/blackwatersportsb2b/images/b2b_Titan.jpg

Is there any way to control the speed of one of the wheels?

Cheers

 

[Danger]

Is the intent to impart various spins to the ball? If not, I see no reason to have different speeds on the two rotors.

 

[Cowzer]

Yeah various spins is the intent as that will increase it's functionality without sacrificing design like a having it on a pivot would make it a bit "clumsy" nearly. There's marks for functionality and design along with other stuff. Is there a way to do it? If not I have a nice way for pivotting it I might use

 

[berkeman]

This wikipedia.org page should get you going:

http://en.wikipedia.org/wiki/Adjustable-speed_drive