At first glance, it looks like Tom Whalen is riding a quiet minibike. He’s certainly cruising along fast enough.

Despite the green racing suit and full-face helmet, however, Whalen is riding a bicycle, albeit one with a few key parts missing. In a warehouse in Massachusetts, eight teens are watching in awe, via television, as he flies down a hill.

“These aren’t your average bikes,” Whalen said Wednesday. “These are gravity bikes, which are basically stripped down BMX bikes. No pedals, no chain, and no gears.” Whalen is from Brownfield but now lives in Portland.

Whalen is serving as a client for the PBS show “Design Squad,” and has a job for the eight engineering enthusiasts located two states away: build and ride one of these bikes. The fruits of their labor will be the subject of the fourth episode of the show’s second season, airing Friday at 5 p.m. on Maine Public Broadcasting.

Whalen, 20, studies manufacturing at Southern Maine Community College in Portland. While attending a street luge competition as a 14-year-old student at Fryeburg Academy, Whalen saw gravity bikes on display and was intrigued.

“It was within a couple of months after I went to the first event that I started competing,” he said.

The bike’s features can include a lowered frame and added weights. Racers have a marked area to push off with their feet, and gravity does the work for the rest of the way. Whalen said a good race speed is 55 miles per hour, although he has been clocked at 70.

Not surprisingly, racers also wear an armor of pads and other protection.

Since he started, Whalen has become a professional rider for Gravity Sports International while maintaining his activities on the street luge and dirt surfer, which looks like an odd cross between a skateboard and mountain bike.

Whalen said WGBH-TV in Boston, which produces “Design Squad,” contacted him last summer to take part in the show.

“I was excited about it initially,” he said. “I didn’t know anything about the show, and once I looked into the show and found out what it was all about, it was pretty cool.”

In the show, eight students, ages 17 to 19, compete in teams of four to design and construct a product for a client introduced at the beginning of the show. Assisted by mechanical engineer and host Nate Ball, the teams have two days to create a project before the client chooses a winner.

The same teens are present throughout the season, although teams rotate each week. After all of the episodes are completed, the cast member who has won the most challenges gets a $10,000 scholarship from the Intel Foundation.

Producers at WGBH found out about gravity bikes much the same way Whalen did.

“I wanted to do a high energy sport that was out of the box. And we were looking at street luge but then found gravity bikes,” said Dorothy Dickie, senior producer and director of the show. “It was decided to do bikes because it was doable in two days. To say that the cast freaked with excitement is an understatement.”

“Tom was very cool and extremely knowledgeable as a racing veteran even though he was only 19,” she added. ” The cast really respected him, and justifiably so.”

Whalen said the crew filmed his challenge to the cast, but he was unaware of what the teams were working on in a warehouse in Cambridge until the final showdown. This took place in New Hampshire on the hay bale-lined driveway of Dean Kamen, founder of For Inspiration and Recognition of Science and Technology and inventor of the Segway Human Transporter, among other devices.

“They were both pretty good,” Whalen said of the final bikes. “I mean, they each had their high points that were better than the other. But overall, they were pretty well-designed.”

Whalen said he’ll continue with all of the gravity sports he participates in.

“I’m pretty much in it for the fun at this point,” he said.