I have completed my model of a speed controller, and am now attempting to make the fan nicely come up to speed and spin. However, I can’t seem to figure out how to do it. I’ve tried using reactor stuff, but it doesn’t work. I’m sure there is a relly simple way to do it using animation constraints, but I need some help to find out how to do it! Any ideas are appreciated! 
Look into using the Curve Graph.
And under your rotation, and set a nice curve.
Thanks, works like a charm! I really need to work on that curve editor…