Most hard drives will spin continuously if you just connect power, all of the older ones did. You can also drive the spindle motor with a brushless ESC made for RC models, I did that once with a dead 3.5" server drive that had about 8 platters. Spun it up to probably 20,000 RPM before I ran out of voltage from the bench PSU. I was starting to get nervous that it might fail catastrophically, it sounded like a jet engine spooling up.