Pamela Daly was on vacation in New York City, when she paused to look up and admire the skyline. Suddenly, the whole world started tilting to the left. "I actually thought maybe we were having an earthquake," she recalled. It wasn't an earthquake, but it was a disaster for Daly. One of the small, front wheels had fallen off her wheelchair. A passerby helped her put the wheel back on. But a few blocks away — in the middle of the road, in busy Manhattan — the wheel came off again, and Daly fell. A broken wheelchair and, just like that, a broken hip. Pamela Daly at her home in Charlestown. (Robin Lubbock/WBUR) Many wheelchair users have a story like this, Daly said, often more than one. Researchers estimate that more than 50% of wheelchairs break down in a typical six-month period. One study found that among veterans the number is as high as 88%. When a chair breaks, it can take a long time to get it fixed. Experts put the average at two to four weeks, but stories of people ...