When it comes to aging joints, even a robot is only human.
For years, it was hard to imagine a more formidable offensive foe on the basketball court than "Hoops," a 3-ton orange robotic arm with deadly aim that long has entertained visitors to the Carnegie Science Center.
The 8-foot-long gizmo was programmed not to miss a shot, and it seldom did. Children and adults who challenged it one-on-one usually wound up being schooled by a device able to sink free throws and 22-foot shots with accuracy rates as high as 98 percent.
But over time the steel phenom in the center's Roboworld gradually lost some of its edge.
Like an aging basketball star, Hoops had worn down its "shoulder" and "elbow" joints from more than 1 million shots tossed over 45,000 hours of use, sending its accuracy rate down to about 60 percent.
Now the science center is slowly rehabilitating what it calls the world's only professional grade basketball-shooting robot of its kind in hopes of restoring its original glory as it plays out its twilight years.
Replacement parts are hard to come by for a 17-year-old robot, so science center staff long have known that Hoops is one major breakdown away from forced retirement.
That would leave a void not only for a generation of visitors who have marveled at the lanky mechanical athlete, but also for staff who have grown protective of one of the science center's signature exhibits.
In fact, Dennis Bateman, the center's director for exhibit experience, said he sometimes averts his eyes in denial when he walks past Hoops as it misses a shot, quietly telling himself "Didn't see that."
"It's just a piece of equipment, but you get attached to it," he said.
When the rise in errant shots first became noticeable, science center staff tried to compensate by making subtle changes in the software that controls Hoops' aim. When that no longer was enough, they did what most people with a serious medical problem do: They called in a specialist.
A technician who arrived from Detroit diagnosed the problem and performed a joint realignment on Hoops last month. "It was almost like a chiropractor or a doctor who came in and realigned everything and got things working as best he could," said Doug DeHaven, lead robotics technician in Roboworld.
But that caused other complications. The software controlling the aim, which had been gradually changed as Hoops' game worsened, had to be brought back to its original setting by painstaking trial and error. The process, which the center likened to physical therapy, has partially restored Hoops' overall accuracy to between 70 and 80 percent, with even higher rates some days. But Mr. DeHaven said getting the accuracy rate to stay consistently above 90 percent ultimately may require re-teaching Hoops how to shoot off the backboard, a change that would produce more baskets without requiring Hoops to be as precise in its execution as it once was.
"Older guys have to shoot differently," he said.
Still, even in a slump, Hoops outperforms visitors who try their luck shooting at a rim adjacent to the exhibit. At one point last Wednesday, an overhead scoreboard showed Hoops had made 88 percent of its shots that day, versus 27 percent made by humans.
As star athletes go, Hoops has never been much of a prima donna.
While NBA stars command signing bonuses, product endorsements and royal treatment from their teams, Hoops performs day-in and day-out, requiring little more in return than a couple yearly check ups.
"We just made sure we kept up with the lubrication, that we kept proper air pressure in the basketballs and dust it off once in a while," Mr. DeHaven said. "It never talks back."
But Hoops does command celebrity status. Crowds gather around the machine as it uses a fork at the end of its arm to scoop up basketballs to attempt its three bread-and-butter shots: the underhand or "granny-style" free throw, a traditional free throw and a 22-foot behind-the-back straightaway toss.
Spectators cheer when shots go through the net and sometimes even when they go awry, as if reassured by the knowledge that even a robot makes mistakes.
"The little ones just stare," project manager Kim Amey said of the children who approach the netting that surrounds Hoops hoping for a close-up view. "You can't get them to move away. They're mesmerized."
A couple years back, former Harlem Globetrotter Curly Neal squared off in a free-throw contest with Hoops during a stop in Pittsburgh. It ended in a draw as both man and machine sank 11 of 15 shots.
Hoops, built by a European robotics manufacturer in 1995, was the sort of robot often used in the automotive industry for spot welding. But the science center was thinking basketball when it had its robot programmed.
It debuted in Pittsburgh in 1996 and eventually at science centers across the nation where it was loaned out for months at a time, including stints at the New York Hall of Science in New York City, the Museum of Science in Boston and the Franklin Institute in Philadelphia.
In 2009, the Carnegie Science Center brought Hoops in from the road for good and made it a permanent exhibit in time for the opening of Roboworld, a 6,000-square-foot space with dozens of exhibits including the Robot Hall of Fame that help showcase the Pittsburgh region's prowess in robot building.
Mr. DeHaven said people mistakenly assume that because Hoops performs precisely the same moves over and over, the ball should go in the net 100 percent of the time.
But it didn't work that way, he said, even when Hoops was in its prime, because such variables as slight changes in room temperature, humidity and even vibration from heating and cooling of the building that can throw off a shot.
Barometric pressure changes that alter the basketball's size can also affect the shot, as can gradual wearing of the ball's surface and even how the ball happens to land as Hoops scoops it up.
"The ball has those dimples where the seams are," Mr. DeHaven said. "If it comes to rest slightly crooked it can change how it comes off the fork."
Some who visited the science center on Wednesday said they wondered why Hoops wasn't making more of its shots. But they nonetheless marveled at the machine.
Joy and Skip Lancaster of Hampton stopped beside the exhibit with their awestruck 3-year-old son, Matthew, who pointed at it and asked his mother repeatedly "What's that?"
Christopher Nau, 11, of Wheeling, W.Va., gave props to Hoops after shooting baskets alongside the machine.
"It could do stuff I couldn't like shoot behind the back," he said. "I personally think the robot is awesome."
Bill Schackner: firstname.lastname@example.org or 412-263-1977. First Published March 11, 2012 5:00 AM