Article Courtesy of Qualisports
THE CORE OF THE ELECTRIC BIKE: AN ANALYSIS OF THE DIFFERENCES BETWEEN THE MID-DRIVE MOTOR AND THE HUB MOTOR.
As the core of power output, the motor, one of the four key components of an electric bike, has the ability to convert kinetic energy into mechanical energy. What are the advantages and disadvantages of these two types?
The motor is placed in the center of the rear wheel
The hub motor is a motor assembly that integrates a reducer directly assembled in the hub. Electric bikes in the market usually use the brushless hub motor. The structure of it is simple-- under the action of current, a magnetic field is formed between the two magnetic steel sheets, so as to make the shaft inside start to work. And the failure rate is low due to the simple structure.
The hub motor has poor heat dissipation, and the temperature of the tire will also be transmitted to the motor, especially in Summer, when the temperature of the road is super high, and then, the heat will be transmitted to the motor from the tire.
The hub motor is exposed to the outside environment, unlike the mid-mounted motor, which is normally covered by the frame. That is say, when an e-bike is parked in the sunlight, with the black metal cover of the motor, the temperature of it can easily increase to 50℃.
With its mature design and relatively low price, the hub motor e-bikes occupies more than half of the market of electric bicycles. However, since the motor is integrated on the wheel, it will break the balance of the front and rear of the bicycle, and it will be greatly affected by the bumps during the mountain off-road. For the full suspension model, the rear hub motor will also increase the unsprung mass and the rear suspension.
In response to greater inertia impact, large-sized sports bicycles usually use a mid-drive motor.
As the name suggests, the motor is placed in the middle of the frame (or at the crank set)
The advantage of the mid-drive motor is that it can maintain the balance of the front and rear weight of the whole bicycle as much as possible, and will not affect the movement of the shock absorber. The impact of the motor on the road is also smaller. The ultra-high integration can reduce the unnecessary exposure of the cables. In terms of off-road handling, stability, and passibility, it has a better performance than a bike with a hub motor. At the same time, the rider can also freely choose the wheel set and transmission, and the daily disassembly and maintenance of the hub is also simpler.
In fact, the mid-drive motor is not that ideal. Since the driving force needs to be transmitted to the rear wheel through the chainring and the chain, it will aggravate the wear of the chainring and the chain compared with the hub motor, and the pedaling needs to be slightly changed during shifting. Be gentle to avoid the terrible squeaking of the chain and the flywheel.
The structure of the mid-drive motor is more complicated than that of the hub motor. In addition to the motor, the whole structure also requires clutch, transmission shaft, transmission chain, transmission, differential mechanism and other components to work together to output power to the rear wheel. These components not only increase the complexity, but also the difficulty of maintenance. It requires regular maintenance, and the modification is much more difficult.
Which motor is best for your needs? It depends. If you're looking to do casual city street biking, a hub-motor will be fine. If your looking for off-trail or mountain biking, a mid-drive motor would work better overall.
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