One day I woke up with an idea in my head—several months later, I was riding on a self-designed and assembled work of engineering—an electric skateboard. With my experience with remote control cars, I knew it was the next project for me. After weeks of research and persuasion of my parents to give me the go-ahead, I began my project.
I used a computerized design program to create a 3D model of the board I was going to build. It was important to consider safety, durability, ease of use, appearance, top speed, and maximum distance. The length and width of the deck was designed to provide stability when riding at high speeds.
I designed a motor mount to be cut out of a sheet of aluminum and welded to the trucks, finding a welder and machinist to provide assistance. They were impressed and delighted to see a young student pursuing something as complicated as this project.
Choosing the right motor and gearing were important since the skateboard needed to have enough torque and acceleration for hills, and enough speed to make it an efficient mode of transportation. The motor is a brushless motor, and can spin at a maximum of 6,370 rpm with the batteries—lithium-polymer, a lightweight but powerful option. I used a smaller gear on the motor and a larger gear on the wheel to keep the speeds of the board safe, not overheat the motor, and provide enough torque.
The board is controlled by a handheld remote, which can also control the regenerative brake that recharges the battery powering the board. I thought it would be beneficial if I could charge my phone while riding the skateboard, so I created a charging system that uses the motor as a generator. This required changing the AC coming from the motor into DC to charge a phone via a three-phase rectifier. I needed only 5 V to charge my iPhone; the motor generates from 12 to 24 V, so I used a transformer that converted that to 5 V.
During a number of test rides around a high school track, I registered a top speed of 25 mph and found that the board has a maximum range of about 4 miles. If more distance becomes necessary, I could use batteries with a higher capacity or add two more batteries wired in parallel. One full ride on the board can boost an iPhone’s battery level by 40%. Riding the board is an exhilarating experience where I can carve up hills, cruise on flat ground, and coast down hills.
I entered this project in a local science and engineering fair and received many awards. Looking back, I think about how much I learned about mechanics, electricity, and so much more. I am so grateful for the assistance and wisdom from the people I met along the way. The board is a blast to ride, and every time I hit the throttle and zoom uphill, I put one more person in awe.
Ryan Needle • Potomac, Maryland