Motor variations

The wide variety of standalone motors in the last 15 years made developing hub motors hard. The standard outrunner with opposing shaft is perfect for mounting a tire & encoder. With home built flying machines just about replaced by DJI, the future of standalone motors is in doubt. DJI's gigantic, top end copters use their own custom motors. They're equivalent to what hobbyists used to make, with extremely marked up prices, so it's surprising no-one still makes their own.