A shower of sparks exploded from the tip of the welder that 17-year-old Mang Sang was wielding as he touched it to one of the metal gears attached to the Workshop School's mobile structure for the Kensington Kinetic Sculpture Derby.

"Can you do the other ones, too?" asked Jared Lauterbach, the adviser for the team. He had been standing to the side, keeping a watchful eye on Sang as he worked on the vehicle.

This year is the second that the Workshop School, a project-based public high school in West Philadelphia, has participated in the derby, a  quirky annual celebration of art and sculpture in Kensington.

The human-powered vehicles at the center of the event must successfully navigate a three-mile urban obstacle course that includes a messy mud pit at the end. The rules? A vehicle cannot have stored energy, motors, or electricity. Walking, pulling, or pushing also are not allowed. On top of that, a vehicle must move at a minimum of 3 mph, so competitors have to get creative with their designs. Rain is expected this year, which makes the race even harder.

This year's competition starts at noon Saturday at Trenton Avenue and Dauphin Street and snakes its way to the finish line at Trenton and Dreer Street. Taco and ice cream vendors will be on hand to refuel spectators. Attendees can also pop over to the Trenton Avenue Arts Festival for local art vendors selling items such as jewelry and ceramics.

The Workshop School won the prize for best engineering last year, and Lauterbach said that made his students more ambitious about this year's project.

"There was a brewing company at the competition last year that just had the coolest Star Wars-themed vehicle," he said. "We really want to beat them this year, so we amped everything up."

The team members started working on this year's design three months ago. They built their vehicle from a stripped-down 2000 Chevrolet truck, recycling the steering column they used last year as well as the emergency brake before adding gears and pedals. The team ordered parts online with the help of sponsorship by the Philadelphia Federal Credit Union, and built the rest in-house. (Because the structure weighed 2,000 pounds, Lauterbach said, he is going to drive it Saturday, much to the disappointment of the young engineers.)

To win a prize at the derby takes more than structural integrity — competitors have to be creative with how the entries are decorated as well. The competition gives prizes for best costume design, best breakdown, and best/worst pun in design. The Workshop School's vehicle is Egypt-themed this year, which it is hoped will win the crowd over.

Jalen Adderley, 16, helped with the art for the vehicle, drawing huge panels of cartoons featuring mummies and pyramid builders.

"I designed four panels, and they each took me a day or so to make," Adderley, who has been drawing since second grade, said. "It wasn't that hard, because I knew a little bit about Egypt, so I just drew upon that to make my own designs."

Rasheed Pittman, 17, who helped build last year's vehicle, also assisted with construction this year.

"This year's vehicle is much more complicated," he said, watching Sang work on the gears to which the pedals would be eventually be attached.

Lauterbach acknowleged that the team was working on a very tight timeline because of how complex the vehicle is. "We're really down to the wire," he said. "But it's because the problems that we encountered with this are all real problems. Sometimes you don't know if they can be fixed, but we work them out together."

Kensington Kinetic Sculpture Derby and Arts Festival