AYER -- They came in all sorts of shapes and sizes. Human-powered vehicles overtook both the Nashua River Rail Trail railhead and Main Street in Ayer. It was the third annual Human-powered Vehicles Festival organized by the Friends of the Nashua River Rail Trail.

Bill Brandt of Groton was there with the homemade "thing" he built last year, inspired by the drifting-style Big Wheels tricycle. Brandt cobbled together a front end from an adult-sized tricycle and made a hind end fashioned from PVC and plywood, with a seat borrowed from a fishing boat.

And voila -- Brandt's contraption was a hit. "You just get on and ride it and you don't get off till you get dizzy," said Brandt. Brandt spun around and around in the rail trail parking lot before hopping on a more traditional bike to participate in the Main Street parade.

Rich and Ann Pinto of Atkinson, N.H., split their time between the Granite State and St. Petersburg, Fla. Rich Pinto designed the recliner, or recumbent, bicycles the two rode.

Pinto is president of Bacchetta Bicycles, sold locally at Belmont Wheelworks. It's the first year the couple had participated in the festival.

Another self-styled innovator on hand for the event was Gary Webster of Westfield, riding his American Eagle Tricycle, which he said was "custom designed for an older audience -- baby boomers." The distinctive red seats are manufactured in Vermont and the aluminum chassis is built in Westfield. The tricycle sports a continuously variable transmission, making for a smooth biking experience.

Jim Ellis of Hubbardston is a cross-country skiier in the winter. On Sunday, Ellis strapped on his roller skis and took off down Main Street with ski poles in hand. Ellis figured he could reach speeds of 8 to 9 miles per hour. For speed's sake, Ellis said, he also rollerblades at speeds of up to 12 miles per hour.

Joann LeClair of Goffstown, N.H., and Sue Rockwood of Auburn, N.H., sailed like kites atop their supersized Trikkes -- three-wheeled "carving" vehicles. By swaying atop raised footrests while holding handlebars, the two swooped left and right across the road in a wide path.

Event organizer Tim Leonard said he was thankful the weather held out. The event is held mainly to help raise awareness of the trail and "get out and enjoy healthy exercise and fresh air," said Leonard.