California Bicycle Museum

The period from approximately 1980 to 2000 was a turning point in the materials used in bicycle frames. During this period, lightweight steel was continually refined to be lighter and stronger, while still maintaining excellent riding characteristics and durability. Also during this period, new materials including aluminum, titanium and carbon fiber gained respectable acceptance among cycling consumers. During this period, manufacturing improvements in these new materials resulted in frames with consistent performance advantages, and now steel frames are rarely used by professional racing cyclists.

In 2004 a handful of mechanical engineering students at UC Davis started the design for this bike to compete in the World Human Powered Speed Challenge held annually at Battle Mountain, Nevada. At the 2007 competition, while still familiarizing himself with the bike, UC Davis student Steve Dey piloted the bike to 50.8 mph. Unfortunately, it never reached its full potential due to a crash on the following run after trying to pass a competitor in a cross wind.

Standard spoked wheels at high speeds churn the air like fans. These disk wheels have smooth sides that avoid the power losses of spokes. Their small size allows the bike to be lower and therefore more aerodynamic. The wheels were custom manufactured by the UC Davis team. The bike features front wheel drive to avoid efficiency losses from a long chain to the rear wheel. The intermediate gear set between the cranks and the wheel allows for the high gears necessary to reach world record speeds. This unconventional drive train design was necessary to fit all components between the riders’ knees. Many of the components were built or modified by the Davis team, including the bottom bracket, intermediate gear set, and front hub.

Aerodynamic drag is the biggest limitation on top speed for bicycles. HPV fairings allow for smooth airflow over the bike, reducing drag to about 1/10th that of a typical bike at high speeds. The fairing on this bike was based on a NACA airfoil to be as efficient as possible in real world conditions. Using CAD modeling, the airfoil shape was then custom fit to our pilot so as to be as small as possible. So as to preserve non-turbulent airflow for as long as possible along the fairing, the split for the front and rear halves was positioned as far aft as possible. This fairing was constructed from carbon fiber, fiberglass, and Kevlar composites in a honeycomb sandwich structure.

With a mostly sealed HPV fairing, overheating can drastically reduce the potential power the pilot can put out. A NACA air duct, visible immediately forward of the canopy, is placed directly in front of the pilot’s mouth to allow for adequate breathing and cooling without disrupting the airflow over the fairing

Manufacturer: UC Davis

Location: UC Davis

Museum Collection

UC Davis College of Engineering

Temporary loan to California Bicycle Museum