Why are most electric bicycles rear-wheel drive and why don't they use front-wheel drive?
Yesterday I read this question: The electric bicycle motor is on the wheel, and the front drive consumes less energy, so why is the electric bicycle not designed to be front wheel drive? Actually, there are front-wheel drive e-bikes, but they are more often rear-wheel drive. The choice of front drive or rear drive depends mainly on the type of e-bike.
Front drive is more suitable for light assistance
For example, the picture above is a front-drive electric bicycle, which is a common type of electric bicycle in Japan and rarely seen in China. This type of bike basically retains the structure of a traditional bicycle, but with a very small electric motor on the front wheel axle. The motor power is small and the battery capacity is not large, so it is not suitable for long distance and long continuous driving. It is more suitable for daily short-distance travel assistance. Even without power can also ride like a bicycle. The small motor and battery do not add too much extra burden.
Most of our electric bicycles are rear wheel drive, in fact, after the release of the new regulations, this kind of car has been included in the ranks of electric motor. This kind of electric bicycle battery is big enough, the motor power is also sufficient, the power is very good, the speed is also very high. The battery is fully charged and can run a long distance. The reason why this kind of car is more popular is essentially more in line with the domestic use of the situation. For example, to carry people, cargo, run long distance, bad roads, climbing, these do not matter.
In order to adapt to the relatively harsh conditions of use, rear drive is the only choice, mainly the impact of these factors.
1, the bearing capacity of the front shock absorber
Front-wheel drive power can only be transmitted to the body through the two shock absorbers, the transmission force arm is very long, resulting in a large shear force on the shock absorber. Then your shock absorber should be strong enough, and the durability should be good enough. And the rear wheel is directly attached to the frame, and the force is applied by the frame when driving.
Whether it is an electric bicycle or a motorcycle, the center of gravity of the vehicle moves backward when accelerating, and the rear wheel has more adhesion at this time. The rear drive is less likely to slip when the motor power is high, so the drive efficiency is higher. I once rode a front-wheel drive e-bike, which was an old age pedestrian tricycle. When turning on the concrete road, I could obviously feel the front wheel slipping slightly, and the driving force was wasted.
3、The front wheel drive direction changes frequently, not as stable as the rear wheel
The front wheel is responsible for turning, if the front wheel drive, when you turn the direction of the driving force will also change with. The rear wheel drive is always the same as the body, more stable.
4、Rear wheel adhesion is better
Two-wheeled vehicle driving when turning or changing lanes, the body is bound to tilt, and the front wheel to turn a certain angle, so the rear wheel landing area in the turn is larger, and the adhesion of the ground is also greater. For example, in the above picture, it is very easy to encounter this posture when driving an electric bicycle, and the front wheels are obviously not as attached as the rear wheels.
The low energy consumption of front wheel drive is relative to that of a car
Because the majority of car engines and transmissions are located in the front of the car, the use of front-drive structure does not require too complex transmission system, the transmission directly output two drive half-shafts to transmit power to the drive wheels. A rear-wheel drive vehicle requires a driveshaft to transfer power to the rear axle and then to the two drive wheels through the differential and drive half-shaft. Obviously the rear drive structure is more complex and the system has more running parts, which will definitely increase the running resistance and thus lead to higher fuel consumption. In contrast, the wheels of an e-bike are themselves electric motors, which do not increase the resistance of the drive train whether mounted in the front or the back.
Since the vast majority of our electric bikes are relatively powerful electric motors, and the frequency of daily use is high and the conditions of use are relatively harsh, rear drive is definitely the best choice.