When LJ Wilde and his family approached the trailhead at Grand Teton National Park, he felt a bit nervous about what park rangers might say to him. After all, Wilde was pulling along his paraplegic daughter in a prototype hiking cart that he’d designed and built. It was the first time testing it in the wild, and he didn’t know how the rangers might react to him taking this one-wheeled contraption into the park. Still, ranger comments or not, he’…