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"E-Bike", a popular term in recent years, originates from "Electric-Bicycle", which refers to electric-assist bicycles. The market for electric-assist bicycles has been growing rapidly in recent years and has become a major driving force in the bicycle industry. The core technology of electric-assist bicycles includes motor technology and its associated sensors and transmission components. Mastering these core technologies can help manufacturers gain an advantage in the market.
In electric-assist bicycles, the mid motor is a design that has received widespread attention in recent years. Unlike traditional hub motors, the mid motor is installed at the bottom bracket of the frame, replacing the traditional bottom bracket and is equipped with a gearbox structure. Mid motors offer several significant advantages over hub motors:
Mid motors directly act on the bottom bracket, requiring the cooperation of components such as clutches, drive shafts, and differentials to transmit kinetic energy to the chainring, assisting the rider's pedaling.
The motor is only responsible for direct mechanical transmission, affecting the part of the vehicle exerting force during pedaling, with a general energy conversion efficiency of over 80%. The mid motor's internal clutch ratchet design allows the motor to be completely disengaged from the bottom bracket ratchet when not powered, eliminating magnetic resistance. Hence, riders can continue to ride unimpeded during fitness rides or when the battery is depleted.
Mid motors use an internal gear combination mechanism, comprising multiple clutch gears inside the motor casing to improve output torque, providing higher power for load and climbing. Additionally, the torque sensing is more sensitive, directly responding to the changes in the crank's pedaling force, resulting in faster acceleration.
Since the overall basic gearing and transmission structure of the bicycle remain unchanged, riders can still use the mechanical rear derailleur system in conjunction with mid-drive assistance for higher riding efficiency.
As the name suggests, “mid-drive” motors are placed at the center of the frame, keeping the vehicle's center of gravity near the middle, which does not affect the balance during high-speed riding. There is no need for additional battery weight for counterbalancing. Therefore, most new models on the market place, or even hide, the battery in the downtube area of the frame.
On the other hand, since the power is applied only to the bottom bracket-crank-chainring, it simulates normal riding force without altering the rider's habit of using the mechanical gear system. Thus, they can still choose different gear ratios to match different road conditions and riding environments——which is why mid motors are more suitable for sports bicycles.
Additionally, they do not add extra burden to the braking system, and the wheel mass of the front and rear wheels remains unchanged, having no impact on conventional braking performance.
Integration, unibody, and consolidated design are advantages of mid motors. All sensors are integrated into the mid-drive box, with only one wire extending out and connecting to the handlebar controller. Even the battery connections use an internal wiring plus contact concealment method. This streamlined integrated design makes mid motor bikes easier to maintain, cleaner in appearance, and more convenient for users.
Typically, mid motors boxes have very high defense capabilities, generally achieving an IP65 or higher protection rating. The motor, when in operation, can completely resist external objects and dust intrusion, as well as low-pressure water jets from any angle.
sales@syimotor.com
+86-512-65975022
+86-512-65963935
No.588, Liupu Road, Wuzhong District, Suzhou/215124, JiangSu Province, China
