The first time you see someone on a Boosted board flying uphill, passing pedestrians and cyclists like they’re standing still, is pretty unforgettable. When you see another rider, racing downhill and then stopping on a dime, you realize something special is at work. Boosted boards have an incredible amount of power – both to accelerate and to brake – and offer an exceptional level of control. It takes a concert of industry-leading motor control electronics, high power density batteries, and precise wireless connectivity to make this happen. And at the core of it all is Boosted’s brushless motor belt drive system.
The Breakdown: Hub Motors vs. Belt Drives
In the electric skateboard world, two main motor architectures are most common: hub motors and belt drives. Hub motors replace the center of a wheel with a motor. Belt drives utilize an externally mounted motor with a belt and gear-like pulleys to create a gear reduction on the motor before transferring power to the wheels. Our engineers spent countless hours analyzing the advantages and tradeoffs of both systems and built and tested prototypes along the way. In the end, the team made a conscious choice to utilize a belt drive, as that system is crucial to enabling the incredible power and clean ride feel our riders have come to love.
The Math Behind the Torque (but in a Fun Way)
When designing a high-powered electric drivetrain, there are two main things we are trying to do: maximize torque and minimize heat. Torque is a measure of how much twisting force something can produce. What we ultimately care about is how much torque is exhibited on the skateboard’s wheels, as this translates directly into how fast a rider can accelerate and brake. Twist the wheel harder forward, accelerate faster. Twist the wheel harder backwards, slow down faster. In short:
Wheel torque = ability to accelerate and brake
With a hub motor, the torque a motor produces is the same as the torque on the wheel since the motor is just part of the wheel. Or:
Hub Motor: Wheel torque = motor torque = ability to accelerate and brake
With a belt drive system, the belt and pulleys amplify the motor’s torque so the wheels produce multiple times the torque produced by the motor. Boosted boards use a gear reduction of over 3X so we get 3X the ability to accelerate and brake. Or:
Belt Drive: Wheel torque = 3X motor torque = 3X ability to accelerate and brake
On top of that, Boosted boards use a dual motor drive system, so you get another 2X the torque compared to that of a single motor.
Why Bigger Motors Are Not Always Better
Ok, so why not just use 3X bigger hub motor then and skip the belt drive system? We could, but then you’d have to carry 3X the motor weight. Motors are already one of the heaviest components in the system; it is far more efficient to add a belt drive than to triple the motor mass. When you’re looking for high torque at the lightest weight, belt drive systems are truly best in class.
Keeping Our Cool (Or the Importance of Heat Dissipation)
As motors produce more torque they produce a lot more heat. Too much heat leads to overheating failure. We have found that belt drives are much more efficient at dissipating heat than hub motor systems. Hub motors are surrounded by wheel rubber, which acts like a blanket and traps heat in the motor. In contrast, the Boosted belt drive system has multiple cooling surfaces all around the motor including the motor cap, the motor mounting plate, the truck hanger, and the outside of the motor itself. Even the belt helps carry heat away from the motor. Our riders keep their boards for years. Keeping the motors cool and efficient is key to the boards’ longevity.
Buttery Smooth Ride Feel
Belt drives have another major advantage: ride feel. Boosted boards are known for their buttery smooth ride and exceptional carving ability. The flexible deck on our longboards is a big contributor, but just as important is the fact that we use an unadulterated (or pure) wheel. What does that mean? Well, it’s important to know that wheel core geometry and selective placement of urethane rubber have major impacts on a wheel’s ability to grip and how smoothly it rides. Hub motors displace both the wheel core and a large portion of the wheels’ urethane rubber leaving only a thin band of rubber surrounding the wheel. That leads to a jarring ride and a wheel that tends to skip across the pavement more easily during a carve. With the belt drive system, we don’t have to compromise our wheel design to accommodate a motor. Instead our wheels feature an H-core geometry that helps support a nice, thick layer of urethane that acts as a shock absorber between you and the road.
Of course hub motors have their advantages too. Hub motors hide in a wheel and create a nice, clean aesthetic. They also turn more freely when the motor is off. We think it’s a great choice for those reasons.
Ten years ago, no one would have believed that electric skateboards would be a viable means of transportation for tens of thousands of people around the world. But now in nearly every major city commuters are trading their cars, bikes, and bus passes for a ride that is efficient, reliable, and fun, but can handle the rigors of daily use. At Boosted, we’re proud to offer a vehicle that’s light enough for practical use with exceptional power and braking capability. At its very core is Boosted’s belt drive system.