I've got app inventor and have tried this many different was but kept coming up short so I eventually gave up. Maybe someone here can help me out. I work for a garage door instal and repair company and a big part of a job is calculating the amount of turns to put on the torsion spring. . It basically just goes the door height divided by the circumference of the drum that the cable attaches to. I was hoping to make the app work by selecting door height and drum size by menu to get the answer. This would be great for training new guys and save time too. I've got more ideas but I guess I wanna see if anyone is interested first. Thanks