It’s a performance piece, an abstract sculpture and a roadside attraction all rolled together into one perfectly round and wobbly ball of hay.

It sits atop a Toyota Yaris belonging to Portland artist Michael Shaughnessy.

The Hay Ball, as he calls it, has been a familiar sight in Portland since he weaved it together with twine and rolled it out of his garage two years ago.

Shaughnessy enjoys the puzzlement and amusement it evokes. As he drives around the city, people point and smile.

“Sometimes they burst into cheers,” he said while driving down Congress Street recently. “It’s good to hear that.”

A small crowd gathered when he parked on Exchange Street. Tom Scarpa, owner of Scarpa’s Restaurant, was cooking when he looked out the window and saw it.

He ran outside, shouting to Shaughnessy, “Hey, what’s that for?”

“It’s exactly what we are doing now — a conversion piece,” Shaughnessy replied.

Scarpa poked at the Hay Ball. “Isn’t that cool? A ball of hay. Just to make people go and say, ‘What the hell is that?'”

But is that art?

“I think the answer is definitely yes,” said Bruce Brown, curator emeritus at the Center for Maine Contemporary Art. “It’s a wild and brilliant idea.”

Brown said he saw the Hay Ball earlier this year on Dana Street, while Shaughnessy was standing on a stepladder pretending to give the Hay Ball a trim with some hedge clippers,

“Any material these days is acceptable as an artist’s medium if they say so, and it’s a sculpted object that he has created,” Brown said.

Affable and easygoing, Shaughnessy wears a frumpy Stetson hat and seems more like a laid-back farmer than artist.

But he really is a professional artist. Shaughnessy, 54, teaches sculpture at the University of Southern Maine. He has built a long career making art from hay, which he weaves through bailing twine over a wood substructure.

His twisted and gangly abstract creations — which often take up an entire wall –have been shown at the Bates College Museum of Art, the Space Gallery in Portland, Lehman Art Gallery in New York and Mesa Arts Center in Mesa, Ariz.

Last year, he won the 2011 Portland Museum of Art Biennial Jurors’ Prize for his sculpture, “Cascade, Current and Pool (For the Vanquished Falls of the Presumpscot River),” which featured twisted, tentacle-like dreads of hay crawling up a lobby wall. The piece mimics the eddies of the Presumpscot River.

He said he likes working with hay because it’s an earthy, working-class material associated with agriculture and ancient objects, such as basketry and thatch roofs.

It took him a couple of days to build the Hay Ball, a globe two-and-a-half feet in diameter. On the car, it looks ready to wobble off at any moment. Shaughnessy says it’s secure, and so far police haven’t questioned him about it.

A big part of the project for Shaughnessy is interaction with the public. He likes photographing the Hay Ball in different light — such as under a street light or at a gas station at night. He often photographs people standing in front of so it appears as a kind of corona, or halo, around their heads. He considers the photographs part of this art.

He wants to people to submit their own photographs of the Hay Ball to the project’s Facebook’s page.

Shaughnessy says he’s now ready to introduce the Hall Ball to the nation. This month, Shaughnessy plans to drive the Hay Ball cross-country to the Pacific Ocean and back. He’ll document the trip with video cameras attached to both the sides of his Toyota and compile it all into a video and book.

Like it or not, when he embarks on his solo, two-month journey in two weeks or so, he’ll be serving as an ad hoc ambassador for Maine’s quirky art scene.

“In effect, this is like taking a bit of Maine creativity on the road,” he says.

Shaughnessy plans to roughly trace the journey taken 52 years ago by John Steinbeck, who wrote a book about his encounters with Americans, called “Travels with Charley.”

Steinbeck’s poodle, Charley, served as an icebreaker when meeting with strangers. Likewise, the Hall Ball will serve the same role, Shaughnessy says.

He hopes to raise $14,000 by Aug. 18 for the project using Kickstarter, a crowd-funding Web site for creative projects. He’s raised more than $1,500 so far.

Investors will get email updates and post cards from the road, and they can help shape the journey by suggesting destinations and meeting places.

The goal of the project, Shaughnessy said on the Kickstarter site, is the journey itself and the “wonder and delight it produces, the interactions it enables, and the interesting situations evoked by a simple but perplexing object on a car.”

Dan Porter, an executive of a research and analysis firm, donated $50 to the project. He said he likes the message.

“It’s the whimsical nature of what he’s doing combined with the underlying theme of individuality in an increasingly homogenized word,” Porter said.

Shaughnessy said the Hay Ball tends to develop its own persona and that he sees himself as its caretaker.

“It see it as this thing that I drive around with, and people seemed to be drawn to,” he said. “New insights are constantly being revealed. It shows me about human nature and how people relate to each other. I’m sure on this journey I will learn more and more.”