openCortex: ARTICLE: Team Stanley (Stanford-Berkeley) Sunrayce 99 Proposal




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Team Stanley (Stanford-Berkeley) Sunrayce 99 Proposal
by Alex Tung
created 3/15/1998
submitted 4/25/2003 07:37:52 AM

The Team Stanley (Stanford University - University of California - Berkeley) Sunrayce 99 Proposal

TABLE OF CONTENTS
Introduction
Technical Innovation and Content
Organization and Project Planning
Vehicle Testing and Training
Curriculum Integration and Special Considerations
Fund Raising and Team Support
Conclusions

INTRODUCTION

The Stanford-Berkeley Solar Car Project, formerly Team California, has participated in all four Sunrayces with four different vehicles: the Sunsurfer, California Dreamin', the Sunburner, and the Afterburner. Our new car, the Third Degree Burner, will be essentially a four-wheeled version of the Afterburner. The car will have the same outer shell and solar array, but the rest of the car will be built from scratch. The general principle behind the design will be to keep the parts of the car which were reliable, while redesigning the weak parts and adding a fourth wheel.

TECHNICAL INNOVATION AND CONTENT

Chassis, Battery Boxes

The chassis will be constructed in the same way as the Afterburner chassis, but it will be roughly 22 inches longer to accommodate two rear wheels. We have secured two large carbon fiber sandwich panels out of which we will make the chassis. (One panel is an extra.) After routing grooves into the panel, we will fold it into a box, and the folds will be made permanent with carbon L-brackets bonded with Hysol EA 9460. The two major changes from the last car are in the shape of the cross strut by the driver's shins and the interface between the rear of the chassis and the rear suspension. The cross strut will be widened so that less of the suspension loading is concentrated at the intersection of the strut and the chassis walls. The rear part of the chassis will need to pinch down slightly to fit inside the tapered shell; the pinching will require a slightly different pattern of cutting and folding.

The battery boxes, which were previously integrated into the carbon chassis, will be constructed so as to be removable. They will be made from Kevlar panels rather than carbon fiber. Our hope is that we can build snug custom boxes for each battery configuration.

Tires, Wheels
We'll be using standard equipment in Sunrayce '99: NGM aluminum wheels and Bridgestone Ecopias. Our rolling resistance will probably be higher than it would be with the Michelin tires we have used in the past. The smaller Ecopias (19.1" diameter) will allow more jounce in the suspension without contacting the array.

Brakes
The Enginetics calipers we used in the last race were quite reliable, so we'll be using them again. Our Airheart master cylinders will be replaced with Enginetics master cylinders.

With redundant braking systems on the front wheels and regen on the rear wheel, we had trouble passing the brake test at the '97 qualifier in Arizona. Now that we have four wheels, we'll have mechanical brakes on all four wheels, with the front and rear run off of separate master cylinders. On top of that, we'll have regen from the hub motor on the right rear wheel. We're looking into the possibility of using brake discs that are lighter than the steel ones we used in 1997.

Suspension, Steering
The double wishbone front suspension, machined from 7075 aluminum, will remain virtually unchanged. The rear suspension will be similar to the front suspension, though the geometry will need to be altered slightly to accommodate the tapering of the rear of the chassis and the lack of a steering linkage. We may attempt to eliminate the threaded rod ends from both systems as well.

The steering linkage will remain identical, though the attachment to the upright will be redesigned.

Electrical System
The electrical system will be rebuilt with an emphasis on standardization and reliability. Essentially, it will be the same system housed in a sturdy, easily accessible Kevlar box. The instrumentation will be similar, though we'll be adding a diagnostic LED system to detect blown fuses. Depending on efficiency tests to be carried out in the spring, we may decide to rearrange the peak power trackers.

Drivetrains
We plan on running predominantly with an NGM SC-150 hub motor during Sunrayce '99. However, we are not able to afford a back-up hub motor, so we will be using our old Solectria with a chain drive as our back-up. The Solectria will mount to the back left upright, and sit behind the chassis.

Aerodynamics
Rebuilding the shell for the '99 race is not feasible given our tight schedule, and the improvements we could make would be slight. The shell will receive a sanding and polishing, and the bottom of the car will be rebuilt with a four-wheel cutout. The seam between the shell pieces will be smoothed. We will be designing a new bubble to encase the driver's head. The front wheel fairings will remain the same, but we will be adding rear wheel fairings to shield the rear wheels. Space will be included in the left rear fairing for the alternative chain drive.

ORGANIZATION AND PROJECT PLANNING

While registering as a single team for Sunrayce, students from Stanford and Berkeley work as two separate teams collaborating to build a single car. Each team has its own team leader and is subdivided into similar divisions. All major systems (the chassis, the electrical box) have at least one person from each school working on them. When several people are working on a system, one person is designated system leader. Smaller systems are assigned to one person only. These arrangements will change when we're on the road-- the well-being of each system will be assigned to one person, so that there can be no confusion about responsibilities. See Appendix A, Organizational Chart, for details.

The two schools are 44 minutes apart by car, and we are just finishing construction of a trailer that will allow us to transport the car between the schools easily. Communication between the teams is facilitated by an email list, as well as a phone list.

The project is governed by oligarchy and dedication. The team leaders make the large decisions in consultation with the rest of the team and team alumni; the smaller decisions are delegated to systems leaders as their dedication warrants. Our philosophy tends toward the conservative and reliable.

Most of the previous year has been devoted to organizational and preparatory activities: renovating our workshops, recruiting new members and funding for the '99 race, and obtaining tools and equipment, including a CAD workstation and an arcwelder.

We are currently in the midst of building the vehicle. Our overall plan calls for the vehicle to be completed by April 4, in time for qualifiers in Arizona. The weeks between the trip to Arizona and the race will be dedicated to testing of the vehicle and rebuilding of components that give us trouble in Arizona. Unfortunately, it is likely that some of the less essential components, such as wheel fairings, will not be constructed until after the qualifiers. See Appendix B, Timeline, for details.

VEHICLE TESTING AND TRAINING

We plan to spend the time between the April qualifiers and the race testing our car and training more drivers for Sunrayce. Before the qualifiers, we'll be testing the car on the road outside our workshop and on the local roads in Palo Alto and Berkeley. The post-qualifier tests will take place in the Central Valley of California. In preparation for the past few races, we've been testing the car on a particularly flat stretch of road three hours south of San Francisco. We'll have three of these valley drives, leaving Friday night, testing Saturday morning before the wind picks up, and returning Saturday night. They will have the major purpose of measuring the performance of the car in different conditions. The drives will have the secondary purpose of getting the team comfortable in racing situations-- working under pressure with a limited set of tools to deal with emergencies.

The trip to the East Coast will be no small challenge. In the past, we've traveled with a school bus, a van with the trailer, and a moving van. In '99, we will travel in several smaller vans. We will bring a smaller amount of tools and supplies. Team members will pay for their own food, and we will bring tents and sleeping bags to cover our accommodations. It is our intent to recruit a cook, but thus far our search has been unsuccessful.

CURRICULUM INTEGRATION AND SPECIAL CONSIDERATIONS

Both Berkeley and Stanford allow students to earn credit for their work on solar car in general electives: ME 191, "Engineering Problems," at Stanford and Engineering 198, "Directed Group Study" at Berkeley. Furthermore, various engineering classes work on class projects that use the solar car as a case study or application of concepts learned. Recent studies have included analyses of the front and rear suspension systems, and the design and construction of a battery charger. This year, two Berkeley students have received President's Fellowships, one for analyzing solar cell efficiencies under different conditions, and one for implementing a more extensive telemetry system. We make a general effort to teach our new recruits what we have learned about electronics, aerodynamics, CAD, composite design, and the like. The team also foots the bill for 9 shop licenses each year, so members can learn to machine while benefiting the project.

FUNDRAISING AND TEAM SUPPORT

The project has three major costs to cover for Sunrayce '99: hub motor, batteries, and travel expenses. By reusing our array from 1997 and securing donations of materials from various companies (notably two carbon fiber panels from Hexcel, a CAD workstation from the Stanford student shop, and aluminum stock from Robin Materials), we will be able to cover our three major expenses with money supplied directly from the schools. Inevitably, many small expenses will pile up: tools, mold materials, shipping, publicity, phone bills, and such. The Stanford team has received $30,256 from the student government for the year, while Berkeley has just received an $8000 grant from the College of Engineering. For more details on the financial aspects of the project, see Appendix C, Team Stanley Budget 98-99.

A large part of the 97-98 school year was spent preparing the Berkeley and Stanford sites for the construction of the car this year. The team currently occupies four buildings, two at each school, and has built up a good supply of power tools and materials. Our relationship with the schools is good.

CONCLUSIONS

While we still have a large amount of work ahead of us, the Berkeley-Stanford Solar Car Project has a learned a great deal from the efforts of our predecessors. Our hope is that by building on the success of our past vehicles, we will build a solar vehicle capable of winning Sunrayce '99.

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