Real world challenge

Teams across the nation get closer to unveiling their designs for hydraulicpowered bicycle

There's nothing quite like a summer ride in the park, and several students are gearing up for a wild ride at the Cleveland Metroparks in Brecksville, Ohio, for the first-ever Parker Hannifin hydraulic bicycle competition.

Cal-Poly's bike utilizes regenerative braking to charge an accumulator.

Last September, Parker challenged its partner universities to come up with a useful and successful design of a human-and hydraulic-powered bicycle. Below are four of the nine designs student teams have developed.

Regenerative braking

At Cal Poly - San Luis Obispo, regenerative braking is the key technology the team is working on. Rather than applying brakes, this technique will use a break lever to operate a hydraulic motor. In turn, the hydraulic motor will charge an accumulator to provide energy.

The concept includes a pump or hydraulic cylinder that is hooked up to a crank. The cylinder pumps in both directions — when extending and extracting. The students also replaced the normal chain sprocket with a cam follower.

A piston pump will drive the hydraulic motor on the back of the bike, while the gear motor drives an internal 15-speed transmission for speed control.

Different teams, different styles

Murray State's computer-rendered bicycle features a simple hydrostatic system with hydraulic motor, pump, and accumulator.

Students at University of Illinois have created two teams, each working with the same hydraulic technology but with different bike styles — upright and recumbent. These teams are using a simple system that does not include an accumulator. The system will have a geared input to a pump in the front and a direct closed link to a motor in the back. The students created renderings of the bikes on ProEngineer and are using standard frames for the actual bikes.

University of California, Irvine's engineered schematic.

Sticking to the basics — Students at Murray State University are sticking to the basics with a simple hydraulic motor and pump. This system utilizes a hydraulic circuit, pump, accumulator, and gearing system. The rider will pedal the bike on the downhill, charging the accumulator for traveling uphill. This hydrostatic system will be fitted onto a three-wheel recumbent bike.

A pneumatic alternative — They're doing things a little differently at University of California, Irvine, where five students have opted to build a pneumatic-powered bike. Two 2-in. bore cylinders connected to the pedals generate pressure, while a 5-liter reinforced accumulator and 2.5 in. bore cylinder on the back turn the rear wheel. Solenoid valves, a microprocessor, and Hall-effect sensors were also included to time the air supply to the rear piston so the bike will move forward. A rear rack holds the bike's pistons, plumbing, and accumulator. The students chose a pneumatic system because it will keep the bike lighter than with a hydraulic systems, and it is environmentally friendly.