They are competing in the city's first Kinetic Sculpture Race, a course covering 11 miles of blacktop, mud and water. Also entering the fray, coming from as far as Crystal Lake, Ill., and Greenville, N.C., are the Bartmobile, the Leaping Junkyard Beaver, Rosie the Dragon, Chainsaw Wilber, and other contrived contraptions.
If all goes as planned, some may actually finish the one-day event, said Theresa Segreti, director of design and education at the American Visionary Art Museum, the race's sponsor.
``This is part of our educational mission, to find genius in our own backyards,'' said Segreti. In its search, the museum has showcased everything from lawn-ornament art to towering whirligigs made of cast-off farm implements. Why not a race featuring traveling trash bins and aquatic hot rods?
``It's going to be a wonderful spectacle,'' she said.
And an engineering challenge, said Curtis Anthony, 40, a South Philadelphia bike-shop owner who has donated his workshop to the cause. In late February, he and some fellow members of Philadelphia's Dumpster Divers, recyclers who never met a trash pile they didn't like, began fashioning their seesaw-in-a-box from discarded parts.
``I think we can finish the race,'' Anthony said this week, as he and others hustled to complete their entry.
Michael Yozell, 30, owner and operator of the floating hot rod from Manayunk, has his sights set a bit higher. ``Winning an award would be nice,'' he said.
His three-wheeled creation, whose name, Hot Rod Lincoln, comes from a song made famous in 1972 by Commander Cody and His Lost Planet Airmen, is a testimony to the mind's machinations. It has 63 forward gears and a reverse, enclosed in a gleaming, 7-foot-long version of a chopped-top coupe. The body is made of papier mache and covered with a dazzling coat of waterproof black paint. A painted flame job, the hallmark of '50s cool, covers the hood in red and yellow tendrils. The only thing missing is a pair of fuzzy dice on the rear-view.
And it floats. On each side of the body, next to the gears, are pontoons. When it's time to hit the water, Yozell outfits his rear wheels with a series of paddles that propel the machine in much the same way that a stern wheel pushes a riverboat.
It propels very well, too. In 1994, in a kinetic race in Arcata, Calif., Yozell finished four hours ahead of the nearest competitor - the hare bounding far ahead of the tortoises.
The trash bin? As of Tuesday night, it remained a work-in-progress, a series of sprockets and cogs and chains and steel and plywood, looking curiously like something dropped from a second-story window.
``We should have it ready in two weeks,'' Neil Benson, a Dumpster Diver helping to build the rolling refuse container, said Tuesday - three days before the crew was to load it in a van for the trip to Baltimore.
The ``Dumpster,'' which is nothing more than a box masquerading as a blue trash container, will work on roughly the same principle as the hand-operated mechanics' cars that were common sights at railroad yards. But instead of relying on arm power to pump levers that turn gears that spin wheels, the bin will use the force generated by four guys on two seesaws with bicycle chains attached. As they bob up and down, the chains will engage cogs that turn bicycle wheels. That's the theory, anyway.
The designers have chopped up an estimated 20 Schwinn bicycles to create the moving parts and skeleton that fit inside the 16-foot-long, 8-foot-wide box. Their frames are a tangle of yellow and blue and red and green, reaching in all directions under the twin seesaws.
The builders have installed bands of Styrofoam along the trash bin's bottom edges to keep them out of the harbor's cold waters. According to calculations, they have enough to keep the 600-pound creation, plus its four occupants, reasonably dry.
If you can't stay dry, have fun, said Hobart Brown of Ferndale, Calif., who founded the first kinetic race 30 years ago. Like Noah with an arc welder, he built something fantastic while others, not seeing the future, laughed.
``We're not really in this to see if you win or lose,'' he said. ``That's an important lesson in life, when you think about it.''
Yet Brown, an artist who works in metal, didn't set out with such lofty goals that summer day in 1969. He sat down to repair his son's tricycle.
``By the end of the day, it was seven feet tall,'' said Brown. ``And it had five wheels.''
Five wheels! His friends hooted. Neighbors peeped over fences. Brown put the thing in the front yard, where motorists slowed to gawk.
``Naturally, someone said, `We've got to have a race,' '' said Brown, 65. ``It was the stupidest thing.''
It took place on Memorial Day that year and stretched one block, from the street in front of Brown's home to Main Street in Ferndale, a city 270 miles north of San Francisco. Five machines competed. The winner: a polka-dotted turtle that blew smoke, made a mating call, and laid an egg.
That humble procession has since grown into a three-day, 38-mile event that begins in Arcata, crosses part of Humboldt Bay, and ends in Ferndale, and attracts scores of machines. Other municipalities, including Sacramento and Ventura, Calif., Boulder, Colo., and cities in Poland and Australia, have mimicked that event with their own kinetic races.
``People say, `Why do you do this race?' '' Brown said. ``I haven't a clue.''
Yozell does. ``Events like this bring out creative minds,'' said Yozell, a roofer and competitive cyclist.
``It ought to be fun,'' said Benson, 46.
He won't be seesawing - ``I don't want to have a heart attack,'' he said - but will be trailing the trash bin on its land route, propped atop a shopping cart powered by an electric motor. Benson sees his role as cajoler and cheerleader, briber of judges, and searcher for shortcuts.
He's not worried about that hot rod, either. ``We've got better bribes than he does,'' said Benson. ``We've got our T-shirts printed, and they say we won.
``A year from now, who's going to argue with that?''