System Fan

how can you make a fan spin continuously using a system of weights tied to a shaft or pulley system?

i am making a rude goldberg machine for my project and i am stuck on trying to make a system of weights move up and down to spin a shaft or pulley to rotate a fan in one direction for airflow. i understand you cant have perpetual motion but is there anything close to it? if anybody has any ideas i would love to hear them. thank you

Examine the clockwork in an old style mechanical clock. Use a ratchet w/ small return spring to wind the mainspring with the falling weight. Use a spring coupling between the drive shaft and the propeller to even out the jerky motion caused by the escarpment.

Chevelle-Family System VERSION 1(FAN MADE)