Donnie knows that grin. It's a tiny reflection of his own whenever he's ready to see the results of something he's put some hard work into. Usually he's playing to an audience of himself, and while there's still always the satisfaction of a project coming to fruition, ultimately he still knows what should happen. Watching someone else's project come alive is a new dimension of eager anticipation.

He steps back, quickly estimating how much space will keep him well clear of the motor's range, a little more hastily with the added warning from Dustin. Talk about unpleasant!

A minor moment of disconcertment as the motor hums from the obvious activation and intake of power. True, it doesn't seem to display much, but nothing sounds like it's grating or threatening to overload, no telltale whine even from its small movements to suggest that something might overheat. The quiet is an acceptable quiet so far as Donnie can tell, and it's evident that he's listening from the slight tilt of his head, and the approval from the smile pulling across his face as his eyes rove across the motor in its entirety.