Mechanical Engineering Department
BS in Mechanical Engineering
James Widmann, John Fabijanic, and George Leone
California Polytechnic State University has been invited to compete in the Parker Hannifin Chainless Challenge Competition in 2014-15. Cal Poly has chosen a team of mechanical engineering students to take part. We have named our team “Bike Under Pressure” and all references as such refer to the team.
The challenge is to build a bicycle which does not have a solid mechanical connection between the power input of the rider to the power output of the wheel(s). After conducting research into different previous designs and brainstorming designs of their own, Bike Under Pressure developed two conceptual designs. One design featured a hydraulic pump and motor system which uses fluid power from the pump to cause mechanical rotation at the motor. The other design incorporated a set of linear actuators coupled together to create linear motion from the cranks, transmit the pressurized fluid to the other actuators, and create rotational motion at the back wheel. After careful deliberation, the team pursed the pump and motor conceptual design.
A detailed design was iteratively created. This design features a front drive unit and rear drive unit to efficiently utilize two F11-5 pumps. A custom bicycle frame provides the mounting points and strength necessary for the hydraulic circuit. The hydraulic circuit also incorporated valves and an accumulator and reservoir for energy storage and regenerative braking. In addition to these features, the bicycle has a clutch which allows efficient coasting and ease of walking the bicycle.
The bicycle was manufactured and assembled by Bike Under Pressure in total except for the frame. The frame was manufactured to Bike Under Pressure’s specifications by the Cal Poly Frame Builders club. Custom components were machined in the Cal Poly Mechanical Engineering and Industrial Manufacturing Engineering departments’ machine shops. Standard components were donated by Parker and purchased online and in San Luis Obispo.
The resulting prototype is capable of a maximum speed of 23 mph, a sustained average speed of 11 mph, weights 125 pounds, can exceed 60% efficiency at top speed, and cost $4600 to build. On competition day for the Chainless Challenge hosted by Parker Hannifin in Irvine, California, Bike Under Pressure placed first place overall.