There is an opinion that a central (carriage) motor is best suited for driving in mountainous terrain. Nevertheless, the Crimean MTB-marathon, which took place in September, showed that the wheel-motor can compete with the central motor.
First, I would like to tell you a little about the marathon itself, so that there is an understanding that the tracks are quite difficult, with steep descents and ascents that not every electric bike can handle.
The marathon lasted 4 days, one race every day. A small circle, the so-called «Light», was defined under the «Electro» category, the participants in this category started 5 minutes before the main start.
At the first stage of the competition, called «Big Gate», the distance was 35 km, the climb was 1013 m, at the second stage, «All Inclusive» was to cover 38.8 km with the climb of 1081 m.
The third stage «Zelenogorsk trail» with the longest distance
The marathon took place in the area of the Kanaka resort, located on the southern coast of Crimea between the cities of Alushta and Sudak.
Two weeks before the start of the competition, heavy rains took place in this area, which washed out the clay and exposed sharp stones. In addition, in some places the route is crossed by rather deep ravines.
The ascents on some sections of the tracks are so steep that the participants had to climb them on foot.
Small free-flowing crumbs of rock added extreme on the slopes, but despite this, most of the participants successfully overcame such sections, although there were quite serious falls.
And of course, not without the famous Crimean «anchorite» thorns, which pierce the tires and remain in them. Their spikes are so small that they are difficult to detect, and the salvation is the use of tubeless tires in combination with a sealant that is poured inside.
When punctured, the sealant begins to come out through the puncture, polymerizes and remains in it, stopping the release of air. But this does not help if you damage the rim on sharp stones at high speed.
Now let’s take a quick look at the winners’ electric bicycles and try to draw some conclusions regarding the engines, the bicycles themselves, and of course, the participants.
The capacity of the quick-release battery used in the race is 816 Wh (17 Ah @ 48 V). The weight of the bike with this battery is about 21 kg, the same as the bike of the winner.
Despite the fact that Alexander came second in the overall standings, he still
Here I would like to emphasize that even an experienced amateur who has assembled an electric bike with his own hands can get on the podium. Moreover, on the first day of the competition, he managed to come second.
Separately, I would like to say about the participant who took
A motor-wheel is a motor that is spoked into a rim, which is most often installed in place of the rear wheel of a bicycle. We will consider a gear motor, it is lighter than a direct drive motor, and thanks to the gearbox, it has a higher torque at the same power.
The central motor is installed in the bottom bracket of the bike, and the torque is transmitted to the rear wheel through the transmission system, which includes a chain and cassette.
The main advantage of the central motor is that the rider can control the torque transmitted from the motor to the wheel by shifting the transmission.
In other words, in lower gear it will be easier for the engine to pull you up a steep climb, and in upper gear it will be easier for the bike to accelerate on the track to a high speed.
In addition, the central position of the engine allows for good weight distribution of the bike, keeping the rear wheel as light as possible.
However, the geared wheel motor has its own advantages, allowing it to compete with the central motor.
The first is the continuity of the transmission of torque. In order to change the gear ratio when using the central motor, that is, to change gear before starting the climb, the cyclist must briefly turn off the engine.
Although professional bikes use shift sensors for this, it still takes some time, which ultimately affects the results of the race. This is not required when using the wheel motor, as it operates independently of the transmission.
Secondly, the wheel motor saves the resource of the chain and cassette, since these elements are not used to transmit torque, and even if the chain breaks or the rear derailleur fails, the wheel motor can continue to move.
The results of the competition show that an experienced amateur on a bicycle assembled in Russia with a motor-wheel can quite successfully compete with an athlete on a professional bicycle with a central motor.
But of course, the design with a motor-wheel must be well thought out and competently assembled — for this, a motor with a high reduction ratio is installed on the Sherpa bike and its thermal protection against overheating is implemented, which excludes shearing of the gears.
In addition, the engine is controlled by a compact Russian-made controller, which was developed with the active participation of Electron Bikes and is assembled in Nizhny Novgorod. There will be a separate article about this controller a little later.
More details on the characteristics of the Sherpa bike can be found in
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