INFUSION REPORTS

The following report was written by Scott Loh, 2006-2007 Mechanical team leader.

“Infusion” has three wheels: two in the front and one in the rear.  Low-coefficient of rolling resistance electric vehicle-racing Bridgestone “Ecopia” tires are used.  The vehicle’s rear wheel is run by an electric motor powered by the Ballard “Nexa” hydrogen fuel cell module.

The chassis of “Infusion” includes five bulkheads perpendicular to the length of the car.  From the front, the first three, at the feet, knees and waist of the driver, are made of 1/8” thick sheet aluminum.  The fourth bulkhead rises above the driver’s head and serves as a roll bar.  This, and the fifth bulkhead, are each composed of one sheet of 1/16” thick aluminum and another of 1/8” thick aluminum bonded to the sides of a layer of Nomex honeycomb composite material, which is sealed using microbubble composite material.  The space between the fourth and fifth bulkheads holds the fuel cell module, the metal-hydride storage canisters, batteries, regulators, gas lines and valves.  The fourth and fifth bulkheads are bolted together at the ends of four steel tubes that run across this space.  The structure of the first through fourth bulkheads is likewise strengthened by a monocoque of 1/16” thick sheet aluminum riveted between the bulkheads.  The first four bulkheads are bolted to a heavy steel tube that runs from the first bulkhead to the fourth parallel to the two torsion bars of the vehicle’s suspension.

The vehicle’s front suspension has a double A-arm (wishbone) setup and is located in a small space below the monocoque.  The torsion bars are necessary because the small space allowed for the front suspension does not allow for shocks and long A-arms.  The lower A-arms bolt to the torsion bars, providing stiffness.  Two small dampers damp the the suspension movement.  All of the A-arms, anti-roll bar, uprights, brake mounts, and other components of the front suspension are machined aluminum.  The rear suspension of “Infusion” consists of a single swing arm on which the vehicle’s motor, which runs the rear wheel by belt, is mounted.  Two bicycle dampers are used as shocks to provide the swing arm with stiffness.

Because of the small space available in “Infusion,” a compact steering setup is used.  The steering shaft runs forward under the monocoque from the front suspension to a set of gears connecting the first shaft to a second shaft that runs toward the driver’s steering wheel.

“Infusion” has two braking systems.  The brake pedal compresses two master cylinders when pressed.  One master cylinder activates the bicycle braking caliper on each of the two front wheels.  The second master cylinder provides the redundant braking system required by the Shell Eco-Marathon, in which “Infusion” is competing, to the caliper on the vehicle’s rear wheel.

In the space between the vehicle’s fourth and fifth bulkheads containing the fuel cell module, the ferro-titanium alloy metal-hydride hydrogen storage canisters chemically react hydrogen gas at high pressure with the metal-hydride pellets inside them to store the hydrogen at a nominal pressure of 147 psig.  This low pressure of the gas in the metal-hydride canisters compared to the high gas pressure in aluminum-fiberglass gas cylinders (2000-3000 psig) that were originally intended to be used allows the hydrogen fuel for “Infusion” to be filled in the canisters in the LAAE workshop.  In the vehicle, the metal-hydride canisters release hydrogen gas through a series of valves and regulators connected by 1/4” OD high-pressure stainless steel tubing to the fuel cell module, allowing the module to generate electricity and power the vehicle.