Do You Know Electric Bicycle Motor

On the market there are a wide variety of electric bicycles, pedelec, power assisted cycle, PAC bike, and the most concerned question is whether the motor is reliable. Today, let's sort out the motor types of common electric bicycle on the market and the differences between them. I hope it can help you clarify the misunderstanding and find the electric bicycle suitable for your intended use.

Power-assisted bicycle is a new type of two-wheeled vehicle, belonging to a bicycle. It uses battery as auxiliary power source, is equipped with electric motor and power auxiliary system, and can realize the integration of human riding and electric motor assistance.

What is hub motor?

The hub motor, as its name implies, is to integrate the motor into the flower drum. After being powered on, the motor converts electrical energy into mechanical energy, thus driving the wheel to rotate and driving the vehicle forward.

Generally, designers will install the hub motor on the rear wheel, especially on sports vehicles, because compared with the front fork, the rear triangle is more stable and reliable in structural strength, and the transmission and routing of the torque stepping signal will also be more convenient. There are also some small and exquisite city cars with small wheel diameter on the market. In order to take into account the internal speed change drum and the overall shape of the vehicle, it is also OK to choose the front wheel hub scheme.

With its mature design scheme and relatively low price, hub motors account for more than half of the electric bicycle market. However, because the motor is integrated on the wheel, it will break the front and rear weight balance of the whole vehicle, and at the same time, it will be greatly affected by the impact of bumps when off-road in mountainous areas; For the full shock absorber model, the rear hub motor will also increase the unsprung mass, and the rear shock absorber needs to cope with greater inertia impact. Therefore, the large brand sports bikes usually use the central motor.

What is a gearless hub motor?

As shown in the figure above, the internal structure of the gearless hub motor is relatively traditional, and there is no complex planetary reduction device. It directly relies on electromagnetic conversion to generate mechanical energy to drive the bike.

There may be no clutch device inside the gearless hub motor (this type of motor is also known as the direct drive type), so it is necessary to overcome the magnetic resistance during power-off riding, but because of this, the hub motor with this structure can realize the recovery of kinetic energy, that is, when going downhill, convert kinetic energy into electric energy and store it in the battery.

The gearless hub motor has no reduction device to amplify the torque, so it may need a larger housing to accommodate the permanent magnets, and the final weight will also be heavier. The 500W direct-drive hub motor on the electric bicycle in the figure above. Of course, with the progress of technology like powerful Neodymium bicycle magnet, some high-end gearless hub motors can also be very small and lightweight.

What is a central motor?

In order to achieve better sports performance, high-end mountain electric bicycle usually adopts the scheme of central motor. As the name implies, the mid-mounted motor is the motor placed in the middle of the frame (tooth plate).

The advantage of the central motor is that it can keep the front and rear weight balance of the whole bike as much as possible, and will not affect the action of the shock absorber. The motor will bear less road impact, and the ultra-high integration can reduce the unnecessary exposure of the line pipe. Therefore, it is better than the bike with the hub motor in terms of off-road handling, stability, and traffic ability. At the same time, the wheel set and transmission can be freely selected, and the daily disassembly and maintenance of the flower drum is also simpler.

Of course, this is not to say that the central motor will be better than the hub motor. There are different grades of any brand products. When comparing, it is also necessary to integrate multiple dimensions such as performance, price, use, and so on. You should be rational when selecting. In fact, the central motor is not perfect. Because the driving force needs to be transmitted to the rear wheel through the gear disc and chain, compared with the hub motor, it will aggravate the wear of the gear disc and chain, and the pedal needs to be slightly gentle when changing speed to prevent the chain and flywheel from making a terrible popping sound.