One important thing to remember when attempting to do this is that motor have a very high startup current spike that would most likely trip some sort of current limiter/overcurrent protection in your power supply. What this looks like is that you hook up the motor, it twitches or might even start turning, but then immediately coasts to a stop. If you're lucky, it's a self-resetting fuse and the PSU works again after unplugging it. However, if you have a speed controller, you can bring the motor up to speed slowly and have a smaller spike. They also (usually) have built-in capacitors that smooth out the inrush current.