Brooks Solar wins 2006 Solar Drag Race!

The second annual Solar Drag Race was held at the Confluence Technology Center in Wenatchee, WA on June 24th, 2006. This event is a head-to-head drag race competition, over a 1/4 kilometer straight course, of vehicles powered only by solar energy. See http://users.applecapital.net/~jim/solardragrace.htm for details and race rules. The competition was conceived by Dr. Jim White, Chelan County PUD, who won the event in 2005. This year Jim graciously loaned other entrants solar modules, electric motors, and ideas while focusing on coordinating the event.


A team of volunteers worked on the Photon Phantom, the Brooks Solar entry in the Open Division. In addition to those listed, Nick Pascoe, helped with testing, troubleshooting, and race day.



Although construction began only weeks before the event, planning and design ideas were developed over several months. A go cart kit was purchased and it’s parts were used for steering, braking, seating, etc. A 16.5’ long, square tubular aluminum frame was built to hold the solar array.



Final design details and assembly was a rush project the week before the race.



A unique transmission was built, based on design suggestions of Jim White. Like a large cassette tape, the transmission consisted of a “supply reel” attached to the rear axle and a “take-up reel” attached to the electric motor. With the “tape” spooled up on the supply reel, and the other end attached to the take-up reel, the electric motor rpm would initially be high, and the rear axle speed low, allowing for high torque during the start of the race. As the vehicle moves ahead, tape accumulates on the take-up reel, and reduces the spool diameter on the supply reel, resulting in faster rear axle speed while keeping the motor rpm in the “sweet spot” throughout the race. The tape is just long enough to complete the race before it comes off the supply reel and flaps around the take up real. At that point the electric motor is shut off, and the brake is applied to stop the vehicle.

Theoretical top speed was calculated at 50 mph. With the vehicle on jack stands under no load, under the noon day sun, the rear wheel speed was clocked at 52 mph with a bicycle speedometer!


Fortunately there was time for road testing on a deserted, newly paved, housing development road. The first test revealed the webbing being used was too narrow and slipped off the spool, jammed, and the vehicle wouldn’t move! Wider webbing was used to correct the problem, and bearings were added to the transmission “take up” reel to reduce friction. The second test revealed the plywood cassette transmission spools were too warped and rubbed on the frame. Maximum speed during testing was 10.5 mph. The cassette transmission was completely rebuilt the evening before the race.



Race day was sunny and hot. The crew made last minute preparations, looking down the race course, while other teams worked feverishly to complete assembly of their entries.


Icing the modules just moments before the race began helped reduce the power loss that occurs when crystalline solar modules get hot. Next year we’ll use a canopy to also shade the modules until just before the race.

We were in the second heat, racing against the winner of the first heat. At the gun we quickly pulled away from the competition and finished well ahead. The tape on the continuously variable, one shot, cassette drive transmission came off the supply reel exactly as we crossed the finish line. Top speed registered on the bicycle speedometer was 14.5 mph. Disappointing compared to the winning top speed last year of 17 mph, but enough to win.

The winning team! (Not shown: Carl Madison and nephew David.) The Photon Phantom is loaded on the transport trailer, ready to head home, with numerous notes for improving performance next year!