Since the original electronics from the skateboard included a large battery, I decided to implement it in the fan so as not to waste it. I also included a power supply to run the fan off of wall power, and an inverter/USB charging hub to make use of the battery otherwise. There was also toggle switch to change from battery to wall power, a battery indicator, a switch for the fan ESC, and a speed control knob. 

The design of the fan was relatively arbitrary besides for the actual blades, which I attempted to design to make the best use of motor power. I had no fan blade design experience at this point however, so the first version of the blades was not well designed. I should have used an odd number of blades to reduce vibrations and balance the airflow. I also used a very aggressive blade profile in an attempt to move as much air per rotation as possible, but this created a lot of noise and inefficiencies. Another issue was the balance of the blades, since I had to print them in two parts due to the size of my 3D printer. 

The biggest problem with the first version of the fan was the fan blades, as they created so much vibration and noise that it was terrifying to put the fan above even ~30% power. To try to solve this I changed the design when I got to school and sent it off to be made on a larger 3D printer to reduce some of the imbalance. I moved from 6 to 7 blades, but in retrospect I should have gone from 6 to 5 instead, as I read later that blade counts above 5 generally only result in decreased efficiency. I adjusted the profile of the blades to be more even throughout, which seemed to help increase airflow. The new blades were quieter overall since the vibrations were reduced but did have a more pronounced "whooshing" sound which was almost as intimidating at high RPM. Regardless of the vibrations and inefficiencies, the fan at least succeeded in moving a tremendous amount of air. Putting your face in front of it felt like leaning out of a car window, which was definitely fun if nothing else. 

The challenging part of this project was attempting to convert as much power from the large skateboard motor into airflow as possible. I do not feel like I fully accomplished this, as I feel that better blade and housing design could have seen resulted in better and quieter airflow. However, I did learn a lot over the course of this project and I would be interested in attempting it again with a new design and more methodical testing of the outcome. If I were to try again I would use an anemometer as well as power information from the VESC to try to gauge the fan's true efficiency.