Yea, i built a LEGO fan. What? What pun? I have no idea what you are talking about! 😛
It features a crank, but can also be equipped with a motor. It has three adjustable blades, some gears, a stabilizer beam and more,
The hardest part about anything that spins around fast is obvious. Balance. Each of those blades is carefully designed to match the weight of the others.