"How do you stop a skateboard going 25 miles per hour with a wheelchair on top?" After anyone sees my brother skateboarding in his wheelchair, this is the typical reaction. Following a hiking accident in 2016, my 18-year-old brother suffered extensive injuries that left him paralyzed from the waist down. My family and I searched for a way for him to maintain his previously active lifestyle, and he quickly found a passion for monoskiing. Unfortunately, there is no snow in the small farming town that we're from, and living in Utah year-round to monoski was not an option for him. This dilemma sparked one of the most time-consuming yet rewarding projects of my life. After tons of research, my brother and I settled on attempting to design an adaptive electric skateboard. I had design and electrical experience from being on the school Robotics team, and my brother was familiar with 3D design software — I set out to custom design a skateboard for him. I broke down the project into three main components: the 3D printed bindings that connect the wheelchair to the skateboard, the custom-built battery, and the drivetrain. The purpose of the bindings is to provide enough pressure to hold the wheelchair in place while turning but still preserve the ability to load and offload with ease. To achieve this precise fitment, I used calipers to sketch dimensioned orthographic projections of the tire's cross-section. We then used SolidWorks to design a 3D model of the binding and printed it using our 3D printer. After many failed attempts, we created a binding that achieved exactly what we hoped. Once we had this functional prototype of the binding, I started building the battery. On the Robotics Team, I'd had extensive experience working with lithium-ion cells. I used 48 21700 size cells spot-welded into a 12S4P configuration to supply the 50.4 volts necessary to power the skateboard's motors. To ensure the battery pack would operate safely, I wired a charge-only battery management system to the pack to monitor cell voltages. Once the battery was completed, we moved on to constructing the drive train. We wanted a comfortable yet stable ride, so I opted for a flexible bamboo double-drop deck to provide shock absorption. We selected 110 mm, super soft, 72A urethane wheels to maximize grip and capitalize on my custom battery's extra power output. I then chose double kingpin trucks to minimize the board's turn radius and allow for fluid carving. To finish off the drivetrain design, I coded the Electronic Speed Controller (ESC). For the ESC, I opted for a fully programmable Focbox Unity to allow for complete customization. Using knowledge gained from Robotics, I programmed in exponential relationships for the throttle and braking. These curves let us preserve smoothness in acceleration and braking while maintaining high power output. The ESC also enabled me to create three different speed and brake profiles with varying intensity levels, all of which can be user-selected using the handheld remote controller. The last step was to piece everything together. I soldered the motors and battery to the speed controller and bolted up the enclosure, and the board was ready to ride. Fast-forward four months, and our adaptive electric skateboard has gained over 100 million views across social media platforms. At the end of November, my brother headed to Burbank for an interview on The Ellen Show, showcasing his skateboarding in person. He skated alongside Tony Hawk, challenging what it means to be paralyzed. We hope to extend the freedoms he enjoys to other paraplegic individuals, hopefully within the next year. I see my brother soar on something I helped create, and for the first time since his fall, I am completely happy. See our paralysis defying board: https://youtu.be/sQ4ylC7zPvI