Humans have an innate thirst for adventure and an instinctive desire to expand their knowledge through first-hand experience. By testing the limits of personal strength and endurance, we obtain a better understanding of ourselves. One aspect of adventure is the art of competition, both head-to-head and in the pursuit of new records. This thirst is never more pure than when we’re on the hunt for ultimate speed. Team AeroVelo is comprised of professional and student engineers, all striving to set the world human-powered speed record.
Every year, teams gather from around the world to compete at the World Human-Powered Speed Challenge (WHPSC) in Battle Mountain, Nevada. Team AeroVelo has been a regular fixture at the event since 2009, each year edging closer to their desired achievement. AeroVelo is an elite design and innovation lab that pursues engineering projects that foster a sense of adventure and passion in scientific development, challenge the norms of conventional design, and focus on a healthy, sustainable future.
“We’re very small and right now our main activities are the student summer projects, public speaking & outreach and limited consulting on wild engineering projects,” states Cameron Roberston, co-founder of AeroVelo, Inc. AeroVelo partners with the University of Toronto’s Human-Powered Vehicle Design Team (HPVDT) and shares the team workspace full-time during the summer.
HPVDT, comprised of the most accomplished undergraduate students in aerospace, materials, and mechanical engineering, focuses on the design and construction of innovative, high-performance human-powered vehicles. AeroVelo’s goal from the partnership is to provide students with hands-on, practical engineering design experience that promotes efficiency and sustainability while encouraging the reduction of society's impact on the environment. Each year the student team has 4 months to engineer and build a human-powered vehicle.
AeroVelo’s latest speed bike, ‘Eta’, is named after the Greek letter used in engineering as the symbol for efficiency. When it was first designed in 2014 it represented the team’s goal of building the world’s fastest human-powered vehicle, capable of breaking the ground level speed record – which was 133.8 km/h (83.1mph) at the time.
While the striking aerodynamic design may be the most visually stunning aspect of the bike, its internal components are equally as fundamental to its performance. A portion of Eta’s transmission is designed to use a more efficient chain than that typically used in bicycles.
“Most bicycles have a free-wheel which allows the wheel to rotate even when the pedals and chain are stationary. In our front-wheel drive design we are not using a standard bike chain and cannot use an off-the-shelf bicycle free-wheel.” says Alex Selwa, a member of the student engineering team, explaining why an overrunning clutch solution was required.
After careful research, the team contacted Formsprag Clutch in Warren, Michigan to request an overrunning clutch solution. As part of Altra Industrial Motion, Formsprag has access to the product catalogue of its sister company, Stieber Clutch. It donated a Stieber CSK25 PP overrunning clutch to the AeroVelo team as part of its Student Support Program.
The CSK clutch was a clear choice to accommodate the size and load requirements of the unique hub. “The front hub design involved fitting many different components into a small and efficient package. The clutch needed to be as small as possible in order to fit inside the sprocket and stay within the width requirements of the hub,” explained Selwa. “The clutch is press-fit onto the hub body and then pressed inside of the sprocket. It is responsible for driving the wheels at speeds up to 145km/h or 90 mph.”
Stieber’s model CSK25 PP is a bearing-supported sprag-type clutch, delivered grease-lubricated and protected against dust particles as small as 0.3 mm. It provides instant locking/engagement when the clutch shifts from overrunning to engagement, with a maximum overrunning speed of 5,000 RPM and a 77.5 lb. ft (105 Nm) torque capacity. The sprag-type backstop keeps the shaft from turning backwards with keyways on both the inner and outer races that prevent the bearing from rotating on the shaft. All CSK clutches feature Formchrome® sprags with chromium-infused steel that produces an ultra-hard surface to maximize wear resistance, which results in extra-long clutch life.
With the help of Stieber Clutch, Team AeroVelo’s Eta speed bike reached a top speed of 139.45 km/h (86.65 mph) at the 2015 World Human-Powered Speed Challenge, breaking the world record for the third time that week.
“Our goal with Eta was not simply to break a speed record. Our goal was to reach such unbelievable speeds that it gets people to think twice about preconceived limits of what is possible,” stated Todd Reichert, cofounder of AeroVelo, Inc. “We want to give a huge thanks to all of our sponsors, volunteers and supporters, who have put in their time and money to help us pursue a dream and take on a true engineering adventure.”