How 2 Guys Turned A '69 Cadillac Into The World's Fastest Hot Tub

This drivable DIY project gives new meaning to the term "carpool"

The Carpool Deville

This vehicle gives a whole new meaning to the term "carpool." Engineers Duncan Forster and Phil Weicker converted a Cadillac DeVille into a working hot tub on wheels. According to Forster, "You haven't really lived until you've sat in a hot tub and watched the world roll by."Photograph by Jeff Newton

Duncan Forster and Phil Weicker built their first tub-on-wheels as undergrads at McMaster University in Ontario, Canada. With a fellow student, they transformed an abandoned 1982 Chevy Malibu into a pool. “This thing was hideous,” Forster says. “The car barely ran, but we were really proud of it.”

"You haven't really lived until you've sat in a hot tub and watched the world roll by."

Twelve years later, living in Los Angeles, they bought a 1969 Cadillac DeVille and one-upped their beloved jalopy. The “Carpool DeVille” ran so well, Forster and Weicker set an even more ambitious goal: world’s fastest hot tub.

A successful Kickstarter campaign funded a trip to Utah’s Bonneville Salt Flats for Speed Week 2014. But after arriving in the desert with their mobile pool, a flooded track—of all things—canceled the race, and with it, their shot at an official record.

Undeterred, Weicker raced the car off the track. The extra mass on the rear axle caused it to accelerate so quickly that a Dodge Ram chase vehicle couldn’t keep up, and hitting a small bump led to scary side-to-side oscillations. “It was exhilarating and terrifying at the same time,” Weicker says.

Video courtesy of Tanner Thomason

Building the Carpool DeVille

  • Vehicle: Forster and Weicker gutted the car's interior. Then they reinforced the steel frame to support the added weight from the water and swapped the shock-absorbing springs for airbags to create a custom air suspension.
  • Tub: Using plywood and fiberboard, the duo made a mold of the car's interior. To make the pool, they covered the mold with gel coat and then layers of fiberglass. A heat exchanger warms the water with heat from the engine.
  • Detailing: Maintaining the Cadillac's look was a high priority, Forster says. They had to totally waterproof the car's interior, sealing the edges of the fiberglass tub and customized dashboard with marine-grade silicone caulk.

This article originally appeared in the December 2014 issue of Popular Science, under the title, "Hot-Tub Drive Machine."