Getting Raspberry Pi or Arduino to control three clock hands separately
You can use 3 successive hollow shaft stepper motors like this one: 
http://www.ebay.com/itm/CNC-Hollow-Shaft-28-2-phase-28HB3302K-Dual-Shaft-1-8degree-33mm-Stepper-Motor-/271809907038?hash=item3f4922095e:g:hwoAAOSwJkJWjO1P

Then use successively smaller shafts through the center of the one in front like this: