It's a sunny afternoon in McLaren Park in San Francisco's Excelsior District. Throngs of people are gathered on either side of a roadway that snakes down a steep hill. As they watch, a person riding what looks like a giant black Converse sneaker whooshes past. Coming up close behind it, a cast-iron bathtub whizzes by on what could’ve been the frame of a lawn mower. Then another driver — this one clinging for dear life onto what looks like a torpedo — hurtles by, inches off the ground. This was the first Artists' Soapbox Derby held by the San Francisco Museum of Art — what we now know as SFMOMA — on May 18, 1975. It was a race for homemade cars. No engines! You just needed to be able to roll, steer and stop. On April 10, SFMOMA is reviving its Soapbox Derby in McLaren Park. Homemade cars that can coast under the power of their own gravity will have their turn in the spotlight, careening down an 800-foot hill. It’s free and open to the public. This week, we’re airing an episode from KQED’s Bay Curious that takes us back to the first Soapbox Derby in 1975 and it’s surprising twists in the road.