In the home-electric vehicles. We can assist or help or strengthen riding all-electric mode. Vehicle bicycle high rate, maintainability, wearing parts and a bike maintenance is very convenient. Also unique advantages can be achieved mechanical multistage shifting, double speed (the rear axle with an ordinary bicycle, as the installation of mechanical transmission, which is the hub electric bicycles can not be achieved) such that motor efficiency is always at the highest efficiency work area. In different road conditions and wind can shift day shift driving, avoid large current impact. Mechanicallow gear when climbing power will be greater, can bring people climb overpass. No wonder people call it double shift "climbing king", "double universally day."