Benefits and perspectives
The wheel motor is not at all a new product on the market, as many customers might imagine. The history of the creation of motor-wheels dates back to the middle of the 19th century and is not much behind the age of the invention from the electric motor itself.
Indeed, what could be simpler and better than a motor-wheel: an electric motor, without any gearboxes, the armature of which is at the same time the axis of the wheel.
High efficiency of the structure, which can reach 97 percent, manufacturability, maintainability, low cost, high power density, saving space inside the vehicle for use by passengers and luggage: these are the main advantages of a wheel motor.
The use of motor-wheels in the late 19th and early 20th centuries did not lead to their “victory” over the internal combustion engine, due to problems with energy supply: there were no capacious and lightweight batteries capable of withstanding several hundred charge-discharge cycles at that time. Therefore, motor-wheels were used to a limited extent, for example, in mining dump trucks, where electricity for them was generated by powerful diesel generators located on board.
Now motor-wheels are experiencing a rebirth and are used for a wide variety of land transport. from electric bicycles to electric vehicles.
Environmental friendliness and efficiency. these are the distinctive features of electric transport that inexorably lead it to the leaders in the 21st century.
Wheel motor device
The bicycle wheel motor is a valve synchronous brushless DC electric motor, the armature of which simultaneously serves as the wheel axis and is attached to the motor housing using a pair of bearings. The valve synchronous electric motor is based on the principle of frequency regulation with self-synchronization, the essence of which is to control the vector of the stator magnetic field depending on the position of the rotor. Valve motors (in the English language literature BLDC or PMSM) are also called brushless DC motors, because the collector of such a motor is usually powered from a constant voltage.
The stator of the wheel motor, like any electric motor, is made of electrical steel. The winding is made of copper and is laid in the slots in the stator. The winding design is designed for three-phase operation, which is provided by three Hall sensors.
The sensors are connected to the controller, which generates control pulses to supply voltage to the windings. The high efficiency of such an engine (efficiency up to 95%) is also due to the use of rotors made of alloys with the use of rare earth elements “neodymium-iron-boron”, “samarium-cobalt”.
The absence of a large number of parts, including collectors and brushes, provides the wheel motor with reliability and durability. Heating of wheel motors due to overloads is less pronounced than in traditional electric motors, moreover, the power circuits are usually protected by fuses. Thus, the service life of the wheel motors is largely determined by the quality of the bearings. Of course, the wheel motor cannot be immersed in water and subjected to other extreme tests, but many years of everyday driving in various conditions, including rain and mud, such motors can withstand without problems.
Everything you need to know about motor-wheels in Kiev.
10 reasons why it is better to buy motor wheels from us:
1) A large assortment of wheel motors of different power and design: for the front and rear wheels, as well as outboard motors with a gearbox.
2) The best manufacturers providing consistently high quality.
3) Loyal prices, one of the most competitive in Ukraine.
4) Optimal set of the kit: you buy only those components that you need to convert the bike.
5) Availability of all necessary components and accessories: batteries, rims, tires, cassettes with asterisks, bike computers and much more.
6) All motor wheels are checked and “run in” before sale to exclude hidden defects.
7) Fast repair or replacement in case of failure during the warranty period.
8) Availability of post-warranty service.
9) High qualification of our staff (company experience. 4 years)
10) On-line consultations for our clients
Everything you need to know about wheel motors.
Which wheel motor to choose?
If we consider the wheel motor as an auxiliary motor that helps to pedal when climbing hills, strong headwinds and calm (up to 25 km / h) driving on a flat road, 250 watts of power is sufficient. The advantages of such a motor-wheel are its low weight (2.5-3.5 kg) and low energy consumption. Motor-wheels with a power of 250 watts of gear type, usually available for voltage of 24 or 36 volts. In the case of using lead-acid gel batteries, with a voltage of 12 volts, the number of batteries, a multiple of the voltage, is connected to the wheel motor in series: that is, for a motor with a voltage of 24 volts, 2 batteries are used, for 36 volts, respectively, 3 and for 48 volts. 4 batteries.
In the case of using lithium batteries of different types, the most common are models with a voltage of 24 and 36 volts. Two 24 volt lithium batteries can also be connected in series for 48 volts.
A bicycle with a 250 watt motor-wheel is thus more a bicycle than more powerful models and is less burdened by the additional load of the engine and batteries. Therefore, the layout of a bicycle with a 250 watt wheel motor can be different: both with a front and rear engine. Two or three batteries (depending on voltage) can be placed on the trunk or inside the frame if its design allows. The weight of the converted bike (with 12 amp batteries) will increase by 12-17 kilograms.
Motor wheels with a power of 300-350 watts can also be installed in place of the front or rear wheel of the bicycle. Wheels of this power are slightly heavier (3-4 kg) and are usually produced under a voltage of 36 volts, which means they must be equipped with 3 lead-acid batteries or one lithium-ion with the corresponding voltage.
The dynamics of a bike equipped with a 300 or 350 watt geared motor-wheel is naturally slightly better than that of weaker models and practically corresponds to the dynamics of a 500-watt direct-drive motor-wheel, but is inferior to it in maximum speed. Such wheel motors can be recommended for a wide range of applications, as the most versatile.
Motor-wheels with a capacity of 500 and 600 watts turn the bicycle into a full-fledged electric vehicle, since they allow you not to pedal at all, with the exception of steep climbs. Motor wheels of this power can only be mounted on sturdy frames with reinforced or double rims and thick spokes (3 mm). Motor-wheels with a power of 500. 600 watts are usually designed for a voltage of 48 volts, so they need to be equipped with 4 lead-acid batteries. If the motor-wheel of such power is located at the rear, then the batteries should be placed inside the frame, and if in front, the batteries located on the trunk will balance the additional load on the front wheel of the bicycle.
The weight of such a set (with batteries with a capacity of 12 amperes) will be approximately 24 kilograms. If you add the bike’s own weight to this, it becomes clear that lifting it up the stairs or riding only on pedals, without the help of the engine, is not the easiest thing to do.
The advantages of such a set are that in terms of its operational characteristics it is not much inferior to 50-cc scooters, allowing you to reach speeds of up to 45 kilometers per hour.
Electric bicycles are better than gasoline scooters, not only because of their environmental friendliness: they are also the most economical mode of transport. the cost of electricity to move an electric bike for 1 km is less than 1 kopeck. For comparison, the cost of gasoline for a passenger car to cover the same distance in the city will be at least 1 hryvnia.
Motor-wheels with a capacity of 800-1000 watts leave only its shell from the bike, turning it into an electric scooter. Such an electric bike can easily drive almost all the uphills on which the roads are paved, but due to the increased weight and deterioration of the roll-forward, riding such an electric bike with the help of pedals will no longer bring pleasure.
In terms of increasing the power-to-weight ratio of the bike, you can go even further and put on it two motor-wheels with a capacity of 500-600 watts in front and behind. If such a set is powered by four 20-amp batteries, then a mileage of 40-60 kilometers can be provided. This kit can be recommended for trips in mountainous areas.
We hope that we have provided comprehensive information for thought. If you still have questions, you can read the answers to the most frequently encountered in the sections “articles”, “questions-answers”, or consult our specialists.
How to choose a motor-wheel for an e-bike, geared or direct drive? Or better take a closer look at the carriage motor?
Which wheel motor to take? This is the question most people ask themselves when they decide to convert their bike to an electric one on their own. On request in the search bar, you can find many different articles on this topic, but very often there are many contradictions in them. To the choice of the wheel motor. however, as well as the choice of other components must be approached thoroughly, because the wrong choice of components can be critical and spoil the impression of the electric bike as a whole.
In fact, there is nothing difficult in choosing the type of electric motor, you just need to understand the basics. And in this article, I will try to make it as simple as possible, but informative to help you make the right choice.
At the moment, there are three of the most popular and efficient types of motors for electric bikes, these are: gear motor-wheels, motor-wheels with direct drive and carriage electric motors.
All of them have both strengths and weaknesses. In some situations it will be better to use one type, in some other.
In order not to waste your time, I will immediately tell you about the golden rule of choosing motor-wheels:
If you do not need a speed higher than 40 km / h, then your choice is a geared motor-wheel. If you need a speed of more than 40 km / h, you need a direct drive wheel motor. All.
A wheel motor is an electric motor that is installed in place of a conventional wheel. There are both rear motor-wheels and front ones. The engine itself looks like a very large bicycle hub spoked into a regular rim. In turn, wheel motors are divided into geared and direct-driven.
An important point: the controller, not the motor, determines the power of the e-bike. The motors indicate the rated power that they are able to “digest” without harm to themselves.
This type of wheel motor is the most common and is used most often. And this is no accident.
These motors are distinguished by the presence of a gearbox, as the name suggests. The gearbox is needed to increase the torque. And also, to ensure the free roll of the bike when the electric motor is turned off. Thus, it is possible to obtain more power output from the motor with less power consumption. Due to this, gear MK are small in size and light in weight.
An important point: with the same declared power, the thrust and acceleration of a geared wheel motor will always be better than that of a direct drive wheel motor. For example, a 500w gearbox MK in terms of thrust and acceleration will be approximately equivalent to 1000w MK with a direct drive.
The gearbox requires maintenance in the form of a lubricant change and inspection as a whole, as well as replacement of gears. The resource of the gears is on average 7-9 thousand km! I want to emphasize this point, since there are a lot of myths on the Internet about the unreliability of geared motor wheels. Direct drive wheel motors are slightly more reliable than geared motors. that’s true. But this does not mean at all that geared wheel motors are unreliable. They are just a little less reliable due to their more complex design, that’s all. No need to be afraid of it.
Blame for the “unreliability” of gear motor-wheels, first of all, “plastic” gears. The gears in the gearboxes are made of nylon. They perfectly withstand loads and do not make noise, as if there were metal gears in the motor. Manufacturers do not use metal gears not so that your motor breaks down faster and you buy a new one, but because it makes no sense. They will make noise, weigh more and wear out the permanent crown on the motor cover.
Pluses of geared motor wheels:
– Free roll, just like on a regular bike
– Light weight
– Small size
– Acceptable efficiency in all speed ranges, show themselves well on climbs and starts
Cons of geared motor wheels:
– You cannot get high speed (above 40 km / h) with standard equipment
– Cannot get high power (above 1000w nominal) with standard equipment
– Less reliability, require gear replacement
This type of wheel motor is only needed for high speeds and high powers. With it, your bike will become more like an electric scooter or even an electric motorcycle.
Direct drive motor wheels have the simplest design. They only consist of a rotor and a stator. This makes them more reliable.
But it should also be said that hall sensors are installed in all electric motors. They are needed to work more efficiently. And more often than not, it is the hall sensors that turn out to be the weak link. If at least one of the three fails, the motor will most likely stop working. This problem is solved by simply replacing burnt-out sensors with new ones.
Due to the lack of a gearbox, direct drive wheel motors have poor efficiency at low speeds. They are not as good at lifting as geared or bottom bracket motors.
In addition, these motors have resistance to movement. This means it will be more difficult for you to pedal when the motor is off.
And I really feel sorry for the people who, through ignorance or after reading the wrong information, have chosen a direct drive motor wheel for themselves and use it with weak controllers and a battery. As a result, they get a speed of only 30-35 km / h and low power. The motor simply cannot reveal its potential in such a configuration, and the owners have to put up with the enormous weight of the motor and the resistance to movement when pedaling.
The advantage of direct-drive MKs is often the possibility of recuperation. That is, the return of energy when braking from the motor back to the battery. In other words, the ability to use the motor as a generator.
In fact, recuperation on an e-bike is extremely inefficient and almost meaningless. The percentage of recovered energy is very low and does not make up for the disadvantages that a direct drive MK has. Large manufacturers such as MXUS, for example, do not approve of recuperation and disable this feature by default.
Advantages of direct drive motor wheels:
– High speed can be obtained (above 40 km / h) with standard equipment
– You can get more power (above 1000w nominal) with standard equipment
– reliable, do not require maintenance
Cons of direct drive motor wheels:
– Resistance to movement, harder to pedal
– Big sizes
– Large weight
– Poor efficiency at low speeds
– Requires a powerful battery and controller to function properly, as well as a sturdy frame
Bonus: which wheel motor to choose, front or rear ?
In fact, everything is quite simple here. If the design of the bike allows. a rear motor-wheel is always preferable.
The bike fork is not designed for this kind of load. If you install a front wheel hub motor, the fork wear will increase. And fork dropouts (mounts) can simply break or twist, such cases occur very often. Dropouts have to be reinforced with special amplifiers Another disadvantage is the slippage of the front motor-wheel.
When does it make sense to install a front wheel hub motor? In the event that the design of your bike does not allow you to install the motor-wheel back. For example, if your bike has a planetary hub or foot brake in the back. Or if you have a very complex and expensive transmission that you do not want to interfere with and you plan to install a low-power motor.
Such motors are rather narrowly directed and are much less often used for converting ordinary bicycles into electric ones. They are needed, as a rule, for movement in very hilly or even mountainous areas. In addition, these motors are installed by owners of two-suspension bicycles for extreme off-road riding. In these cases, a bottom bracket motor will be preferred. The thing is that such motors are installed in the bicycle carriage and transmit the torque through the chain to the rear wheel. This means that you yourself can adjust the amount of torque using bicycle gears, thereby getting either very good traction or a fairly high speed.
Unless you live in a very hilly area and do not practice extreme off-road driving with steep climbs and difficult routes, then you should not consider this type of engine, as it has significant disadvantages compared to motor wheels. For infrequent arrivals on forest roads and off-road, a powerful geared motor-wheel is sufficient.
If you still plan to purchase a carriage motor, then you need a good, reliable transmission that will accurately work out every shift.
Cons of carriage electric motors:
– Wear of the bicycle transmission when the electric motor is running
– Have measurable pedaling resistance when the battery is low
– Less reliability and more expensive to repair, compared to motor-wheels
– You need to constantly use gears, you need a good transmission
– High price
On this, perhaps, everything. To summarize, we can say that in most cases it is better to take a closer look at geared motor-wheels. This type of motor continues to improve, more and more lighter and more powerful models appear. The main thing is not to miscalculate with the required power when choosing! But this is already another story, which cannot be told in a nutshell and which should also be carefully understood.
Which motor wheel to choose for a bike
Which motor-wheel of an e-bike is better, front or rear?
There are already many articles on this topic, I will write my own vision of this issue.
Firstly, there can be no unequivocal answer to this question, because if the best was the front or rear wheel drive of an electric bike, then there would be no choice, only one option would be sold, which is observed in powerful motors from 1000 W. Less powerful motors are available both front and rear, so each option has its own advantages.
What are the advantages of the front and rear wheel motors? Why powerful e-bikes with only a motor in the rear wheel?
A powerful motor-wheel of 1000 watts or more is likely to damage the front fork of a bicycle. Dropouts can be broken, they will not hold the motor-wheel axle during a sharp start, even with a dropout amplifier. You can break the fork itself with too strong recoil from a heavy wheel with a motor, moreover, this recoil will go into the hands of the cyclist himself, no shock absorber will extinguish the impact of a 7-kilogram motor. That is why powerful motors are installed only in the rear wheel.
Motor-wheels with an average power of 500 W can be made for both the front and rear axles of the bicycle. The advantages of front-wheel drive motor wheels include:
- Easy to install, even for people who do not need to maintain or repair their bikes.
- Improved e-bike handling especially at high speeds.
- The all-wheel drive of the bike, if you pedal to help the motor, helps to move on sand or other off-road. Even motorcycles do not have this, in fact, an all-wheel drive bicycle is a new mode of transport.
The disadvantages of front-wheel drive are also present:
- “Heavy steering wheel”. if the 500 W wheel is gearless, then it weighs more than 3.5 kg, which becomes very noticeable on a bad or unpaved gravel road. Recoil is felt, hands get tired quickly, ride comfort is significantly lost. For light motor-wheels, for example, a gearbox 350 W, the discomfort is much less, and the effect of all-wheel drive remains.
- shoveling out the soil. the pressure on the front wheel is much lower than on the rear, and accordingly, the grip on the road is less. You can row sand from under the front wheel for a long time while almost without moving, in addition, this sand flies onto the cyclist and onto the chain, after such a sand shower, it is necessary to do at least a chain transmission.
The rear wheel motor is more common on e-bikes. Almost imperceptibly changes the balance of mass of the bike and its handling. The installation of the rear motor-wheel is not much more difficult, and if you buy an electric kit together with the installation, then there will be no problems at all. Several limitations should be noted:
- than 8 gears will not fit on the rear axle together with the motor. Inexpensive bikes with thick (not lightweight) dropouts and 7-8 rear hubs are better suited for conversion.
- Loading batteries, especially lead-acid SLA AGMs, on the trunk will significantly impair the handling of a rear-wheel drive electric bike, at high speeds the rear will wear from side to side. If you are going to buy lead-acid batteries, take a front-wheel drive.
For low-power motors 350 W and below, there is not much difference, front-wheel drive or rear-wheel drive, but for an easy trip around the city or a forest walk this power is quite enough.
Which motor is the best wheel: geared or direct-driven. Part 1.
Bicycle gear motor: advantages and disadvantages.
Motor wheels for bicycles are divided into two main types: direct-drive and geared. Each type has its own advantages and disadvantages. In order to find the Volta bikes motor wheel that suits you best, below we give detailed information on geared motor wheels. An article about direct drive motor wheels is HERE.
Gear motor wheel design:
Inside the body made of light alloy, a permanent neodymium permanent magnet (BLDC) electric motor with Hall sensors (its device is described in part 2 of the article), through a planetary gearbox and a freewheel clutch, rotates the output shaft, which serves as the axle of the wheel motor. If the wheel motor is not supplied with current from the controller, and the bicycle wheel is pedaled, then the electric motor disengages from the freewheel clutch in the gearbox and does not rotate when the bicycle is moving. Therefore, the gear motor of the wheel does not worsen the roll and on an electric bike with the motor off, you can ride on the pedals as easily as on a regular bike.
Possibilities of geared motor wheels:
Volta bikes wheel geared motors with a rated power of 350 watts, accelerate the electric bike to 32. 34 km / h. An electric bike with such motor wheels can drive up to 13. 15% inclines, and from acceleration, you can overcome steeper inclines. If the power of the wheel motor is not enough to overcome the slope, a little assistance with the pedals is required. as if driving on a straight road.
Volta bikes wheel geared motors with a rated power of 500 watts can accelerate an electric bike up to 45. 50 km / h. An electric bike with such a motor wheel drives up slopes with a steepness of about 20. 22%. almost everywhere where roads are laid. From acceleration. you can overcome the steepest climbs.
Volta bikes gear motor with a rated power of 1000 watts also accelerates the electric bike to 45. 50 km / h. An electric bike with such a wheel motor can drive up slopes with a steepness of about 25. 27%. The thrust of the kilowatt gear motor of the wheel is more than enough in any road conditions.
Advantages of geared motor wheels
Limitations for geared motor wheels:
It is not recommended to exceed the specified maximum speed, forcing for this gear motor wheels of any manufacturer, using controllers with a higher operating voltage. In order to achieve the highest possible speed or to develop a large tractive effort, a high current is applied to the windings of the electric motor. The maximum power of the gear motor of the wheel is limited by the possibilities of its cooling during operation, the cross-section of the power cables and the ability of the gearbox to operate at a high speed, or transmit a large tractive effort. Exceeding the capabilities of the electric motor, the wheel motor and the power cable, is expressed in their overheating. In severe cases, overheating leads to a short circuit of the windings or cable and their failure, and the gearbox, with increased loads, wears out intensively. Therefore, for e-bike rides in scooter mode, at high speed, without pedaling, it is better to install a direct-drive motor wheel
The axle and bearings of any wheel motor are designed for loads of a certain magnitude. The ability to withstand certain loads determines the quality of the steel from which the axle is made and its diameter, as well as the type of bearings and their quality.
Disadvantages of geared motor wheels:
Reliability of geared motor wheels
Volta bikes wheel motor warranty. up to 3 years! As our 10-year experience has shown, during normal operation, most of the gear motors of Volta bikes wheels, produced in 2007. 2008 (at that time, in Ukraine, except for us, no one sold gear motor wheels!), Until now work for clients, without any repairs. The most common failure that occurs in all types of motor-wheels, of any manufacturer, is not mechanical. This is a failure of the Hall sensors. During the warranty period, no more than 1-2% of Volta bikes motor wheels are required to be repaired. Breakdowns not caused by improper operation (external mechanical damage, overheating) are repaired free of charge, under warranty.
The main mistakes in the operation of geared motor wheels
In order for the motor wheel to serve for a long time, it must not be overheated. The safe temperature of the wheel motor body is up to 60 degrees Celsius. When this temperature is exceeded, the neodymium magnets in the electric motor begin to gradually demagnetize and the efficiency of the wheel motor gradually decreases. At a case temperature above 70 C, Hall sensors may fail. At a case temperature of more than 100 C, (the temperature of the windings is above 120. 130 degrees C), the insulation begins to melt at the windings and an interturn short circuit occurs. Overheating breakdowns. not repaired under warranty.
Do not overload the motor wheel in excess of the norm. According to the permissible load, each type of wheel motor is designed for a certain type of transport: electric bike, electric scooter, electric motorcycle, electric vehicle. If a bicycle motor is a wheel, used on an electric scooter to ride it together and with a bag of potatoes on the trunk, then it may not withstand such experiments.
The e-bike can be ridden in the rain, but the wiring must not be damaged and the motor wheel must not be immersed in water. Even if you lubricate the wheel motor housing cover with sealant, there is always the possibility that water will seep through the hole in which the cable is inserted, or through the bearings on the axle.
Correct use of geared motor wheels
When starting off on an e-bike, you should always help the motor to the wheel with the pedals. The greatest load goes to the engine when it starts moving. By helping the motor to the wheel with the pedals, you will increase not only the resource of the wheel motor, but also the distance from one charge, since the battery consumption at the moment of starting the movement is also the greatest.
To prevent the gear motor wheel from overheating, you need to use a standard controller. Its current is designed for the maximum that the motor wheel can “digest” even during intensive operation in hot weather. Under difficult operating conditions, for example. overcoming a long climb in hot weather, or a long drive at maximum speed, we recommend stopping and checking the temperature of the wheel motor housing by hand. Safe case temperature. up to 60 degrees Celsius. If it is higher, you need to turn off the motor wheel and let it cool down.
Do not drive at maximum speed all the time. The optimum cruising speed is 2/3 of the maximum. So you will increase the resource of the wheel motor, increase driving safety and provide a greater mileage from one battery charge.
Riding an electric bike in the rain through puddles is quite safe for an electric drive, but you need to make sure that water does not flow into the wheel motor, for example, through a cable, through a hole in the axle. For this, the cable must come up to the axle of the wheel motor slightly from below. When it rains, it is best to wear bike covers that protect not only the cyclist, but also largely the battery if it is located inside the frame or under the saddle.
Myths about gear motor wheels and reality
“The gears of the planetary reducer are made of plastic to reduce the cost”.
This is not true. Plastic gears are used to:
“Gears made of plastic have a short service life: a year or two”.
“It is undesirable to ride an electric bike in winter”.
“The low power of the geared motor of the wheels provides a longer travel distance compared to direct-drive”.
E-Bikes Part 1. Front Hub vs Rear Hub vs Central Motor. What Works Best?
“The gear motor wheels can be boosted to increase top speed.”. The manufacturer, through tests, determines the nominal and maximum power of the wheel motor. These data are indicated in the technical specifications. Exceeding the maximum power, and for the gear motor of the wheel. also the maximum rotation speed, is fraught with increased wear of the gearbox. With a strong overheating of the electric motor, the wheel motor may fail from the turn-to-turn closure of the windings. Overheating is considered to be the case temperature above 60. 70 degrees Celsius.
Maintainability of gear motor wheels
Over time, wear and tear of the plastic gears of the gearbox and bearings will still require replacement. Other parts are also subject to wear: the freewheel clutch, bearings on the axle. A new gear assembly with a bearing costs less than 100 UAH, and the operation to replace them is simple and accessible to any person who repairs his bicycle on his own. Of course, Volta bikes service centers perform any wheel motor repairs.
Maintenance of geared motor wheels
Volta bikes gear motor wheels do not require any maintenance (for example, lubrication, or adjustment) throughout the entire period of operation. The estimated service life of all types of Volta bikes wheel motors is 10 years, but with careful use, it can be much longer.
Gear motor wheels are slightly inferior in reliability to direct-drive ones; at the same time, they are smaller, lighter, more high-torque. Gear motor wheels are recommended for installation on a bicycle, if a high speed of movement is not required (up to 32. 50 km / h. depending on the power of the wheel motor), it is desirable to maintain a good roll and the ability to ride on pedals, without an electric drive.
Drawings by A. Galova, specially for TM Volta bikes
Advantages of a geared wheel motor:
When choosing a wheel hub for your e-bike, follow these guidelines:
Remember that the correct choice of the type, performance, and power of the bicycle motor-wheel determines in many respects the reliability, safety and durability of the entire electric bike.
Electric bicycles can be equipped with two types of brushless electric motors: direct drive and geared.
Direct drive technology can greatly simplify the design of the bicycle electric motor and improve the accuracy of spatial movement. Direct drive bicycle electric motors consist of a ring-shaped steel stator with three-phase copper windings and a permanent magnet rotor. Direct-drive bicycle motor-wheels work without additional transmission elements and provide high torque due to their rather rational design. A large number of pole pairs, with a rather large rotor diameter, optimizes the generation of output torque and contributes to an increase in the efficiency of the magnetic field. From the technical point of view, these engines are the most reliable and durable, since there is nothing to break in them. In addition, it is generally known that any direct drive electric motor provides optimal conversion of electrical energy into mechanical movement.
Due to the absence of gearboxes or other mechanical elements of the transmission, direct-drive motor-wheels have zero backlash, which in turn provides a high indicator of their control efficiency and high rigidity under loads. Also, wheel motors of this type have a low noise emission threshold.
All direct-drive motor-wheels during braking are characterized by the ability to work in the mode of a generator that generates regenerative energy, which is dissipated in the drive or again goes to the energy supply source. batteries (energy recovery function during braking). It is only necessary that the controller be provided for the performance of this function by the bicycle electric motor. Gear motor-wheels, in turn, exclude the possibility of operating in the generator mode, since the coefficient of friction of their elements is quite low during braking.
Gear motor-wheels weigh less than direct-drive ones, and are characterized by fairly good torque indicators. These motors provide less resistance to motion than direct drive motors.
Unlike direct-drive motor-wheels, electric motors with a gear mechanism do not develop speeds above 25-30 km / h, therefore this type of motor-wheels is suitable only for those people who do not expect high speed performance from their electric bike.
Due to energy losses in the gearbox, gear wheel motors are characterized by a lower efficiency than direct drive motors.
Multi-piece assembly makes geared wheel motors less reliable in operation. As a rule, plastic gears are the fastest to fail in them (teeth are erased). The use of a different material in the manufacture of gears (for example, metal) for gear motor-wheels is not advisable, since metal gears will significantly weigh down the design of the engine and make its operation rather noisy.
For a better perception of the above information, we will summarize the advantages and disadvantages of both direct-drive and geared bicycle motor-wheels.
Disadvantages of direct drive wheel motor:
Advantages of direct drive motor wheels:
Which wheel motor is better: direct drive or geared?
We are often asked, “Which is better, a direct drive bicycle electric motor or a geared motor?” It is quite difficult to answer unequivocally, since both types of bicycle motor-wheels have their pros and cons. It would be wrong to impose your opinion on the buyer, since he himself must figure out which purchase option will be the best for him, and which will most of all meet his needs, having analyzed the technical parameters of the motor wheels provided for sale. Let’s just say: there are several factors that must be taken into account when choosing, only for each person the priority of this or that factor
depends on his individual needs.
The motor-wheel, which is a brushless synchronous DC electric motor, as an element of the complete set of an electric bicycle, is an executive electromechanical system that provides spatial movement of the entire bicycle structure. Traction, speed characteristics, as well as the duration and reliability of an electric bike are largely determined by the choice of an electric motor-wheel for completing an electric bike.
Disadvantages of a gear motor:
So, we have considered the positive and negative aspects of the two types of bicycle motor-wheels, now we bring to your attention a few key parameters for comparing direct drive and geared motors:
The weight. Reduced bicycle motor-wheels weigh less than direct-drive ones, but those who think that direct-drive motor-wheels have much more weight than geared ones are mistaken. There is a difference in weight. I do not argue, but it is so insignificant that when installed on an electric bike it is practically not noticeable. If we take, for example, a gear motor-wheel 24V 350W, then its weight will be, depending on the brand of the manufacturer, 2.6-2.9 kg, while a direct-drive motor-wheel of the same power will weigh 4.2- 4.4 kg. If we calculate the difference in the weight of these motor-wheels, we get a figure of 1.5 kg. Based on this, I think that weight is not the primary indicator when making a choice in favor of a particular model of an electric bicycle motor-wheel, but the choice is still yours.
The size. The opinion is erroneous that direct-drive motor-wheels are larger than geared ones. If, of course, we compare electric motors of different powers (for example, 250W and 500W), then the difference in size will be clearly noticeable. But if we take electric motors with a direct drive and a gear mechanism equal in power (250W or 350W), then their external dimensions will be identical.
Hub Drive VS Chain Drive BLDC Motor For Scooter And Electric vehicles
Powerful and practical. If you plan to ride mainly on flat terrain, and are not going to accelerate your electric bike over 25-30 km / h, then you should pay attention to the small-sized and compact 250W or 350W motor-wheels (geared or direct drive). If you want to squeeze from your electric bike up to 40-45 km / h, the proposed routes of your trips are hilly, you weigh more than 70 kg and expect the best traction performance from your electric bike. get a 500 W motor-wheel. The power of an electric motor of 500 W is quite enough. so that your electric bike becomes almost an analog of a scooter with an additional pedaling function, overcoming steep climbs without problems.
Take this information into account when making a purchase, since the power indicator of the motor-wheel of an e-bike is very important!
Life span / period of operation. Many years of experience in the sale and operation of bicycle motor-wheels clearly demonstrates that the gear mechanism of an electric motor is more susceptible to wear and tear than a motor-wheel with a direct drive. In all geared motor wheels, regardless of the manufacturer, plastic gears (gears) are used, it is their teeth that begin to wear off over time under the influence of constant friction. The use of metal gears is considered impractical, since it significantly makes the design of the motor-wheel with a gear mechanism much heavier; moreover, the use of such a material in the production of gears would cause the formation of a rather high noise threshold. The gears of the geared motor-wheels, depending on the frequency and distance of the routes traveled on the electric bike, wear out in 1-2 years. However, it is also not worth giving up geared motor-wheels due to wear of the elements of their mechanism, since the plastic gears are quite simply replaced. Each gear can be removed and repaired independently of the others.
In the design of direct-drive electric bicycle motors, unlike geared motors, there are no parts that are subject to wear and friction. The operating period of such wheel motors is more than 5 years.
Torque. It is believed that geared bicycle motor-wheels tend to have higher torque ratings, but this statement is not entirely accurate. Modern technologies make it possible to produce direct-drive motor-wheels, both equal to gear motors in terms of maximum torque, and with a higher expression of torque.
Work under load. If we compare bicycle motor-wheels of equal power, then a direct-drive motor-wheel will stand out for the best performance under load, with the same speed characteristics as a geared electric motor.
To better understand the functionality of wheel motors of different powers, we suggest you compare a 250W bicycle electric motor with a 500W one. The latter is larger and heavier than the 250W motor. But at a time when the 250 W motor-wheel can move at a maximum speed of 25-30 km / h, which is quite enough for a bicycle trip at a moderate pace, the 500W electric motor can accelerate to both 40-45 km / h and limit their speed capabilities electronically to a safer level (25-30 km / h), for example, in a situation of heavy traffic on the road.
Many countries around the world have legal limits on both the power of the motors used in electric bicycles and the maximum speed they can reach. In fact, at the legislative level in these countries, it is prescribed that the electric motor installed on a bicycle should not have a power of more than 250-350 W. If the electric motor is equipped with electric motors of higher power, then a prerequisite is the speed limit with electronics at 25-30 km / h. Considering this moment, many global manufacturers of e-bicycles equip their bicycle products with low-power motor wheels, which allows, on the one hand, to adhere to the law, and on the other hand, serves the purpose of reducing the cost of e-bicycles and reducing their weight. Since the direct drive wheel motors are heavy, electric bicycles for the market in these countries are equipped with geared motors. The legislative base of Ukraine does not establish restrictions either on the power of the engine used by the electric bike, or on the speed it develops. Therefore, in fact, the most Ukrainian cyclists have the right to choose the type of electric bicycle motor-wheel that best suits their needs.
Manufacturers such as Bionx, Bafang prefer to complete electric bicycles with 250W motor-wheels. At the same time, such global companies as Currie, Pedego, Stromer consider equipping their 500W electric bicycles with motor-wheels with a speed limit function more appropriate.
If you decide to convert your electric bike to an electric drive, but do not know which wheel motor (geared or direct drive) is more suitable for you, first of all decide for yourself with the following points:
The type of terrain on which you will move. If your cycling routes run on hilly terrain, a direct-drive motor-wheel of at least 500W is more suitable for you.
The maximum speed indicator is sufficient for you. If 25-30 km / h is enough for you when traveling on an electric bike, then get a 250-350W motor-wheel. In this case, the choice between a direct drive and a geared motor is based on the quality characteristics that are paramount for you. For a faster e-bike you need a more powerful electric motor.
In principle, for you, the difference in weight between these two types of electric motors. As mentioned earlier, a direct-drive motor-wheel weighs more than a geared motor, but in motor-wheels of the same power this difference is very small.
What is a bicycle wheel motor and how to choose it
Many people choose to use e-bikes because they help to ride against the headwind and climb a high hill. Everyone can now assemble an electric bike with their own hands, thanks to the many sets brought from China.
But the electric bicycle only increases the strength of a person, and does not completely replace it. Thus, pedaling while riding an e-bike will still be required, and this is especially necessary when driving up a slope.
Unlike other motorized vehicles, which only have a motor to push the car forward, an electric bicycle combines the power of a motor with the power of the rider. Machines that combine power from different sources (for example, a motor and a person) are called hybrid.
When a person is not sure that a specific set with an electric motor will help climb to the top of a hill, he is lost in thought: what if the hill will be even steeper or longer. And naturally everyone wants the most powerful electric bike kit ever. However, in many cases the most powerful electric motor will be overkill, and you will end up spending too much money and carrying around much more weight than you really need.
You can climb a low hill with almost any motor-wheel for a bicycle. And if at the same time lightly pedal, then you can easily climb a steep hill, even under difficult conditions. strong headwind and heavy rider weight. Compared to conventional bicycles, electric bikes will pleasantly surprise you.
After each ascent, there is a descent from the hill. it’s just like the cycle of substances in nature. Downhill, with regenerative braking, the electric motor can charge the battery and extend the range of the e-bike. Electric motor designed by V.V. Shkondina can, when generating, return the maximum part of the energy that was spent on climbing the mountain.
Generating energy slows the bike down, so installing a Shkondin motor would be a good idea if you want to limit the bike’s top speed downhill, naturally without using the brakes.
In addition to regenerative resistance, each electric motor has internal friction, so any drive on an electric bike will somewhat reduce the top speed when coasting compared to a conventional bike.
When changing gear, torque is always lost. Therefore, it is advisable to always start climbing the hill in the appropriate gear or make as few changes as possible when climbing.
Even a geared motor is affected by gear changes. After the rider changes gear, any engine will have to change the speed. In this case, it will be better if the cyclist gives an extra push through the pedals after the gear change.
The front motor wheel also loses torque along with the rider when changing speed, as they are combined into the same gear system.
Analysis of different electrical kits
There are two possible options for electric bike kits:
- A motor installed in a wheel. This system does not take advantage of the bicycle gear system.
- A motor inserted into a carriage (such as the Optibike MBB system) that can be rotated in parallel with your feet. This system is activated through the bike’s chain drive.
In the first case, the chain drive system remains inactive, and you can not rely on the maximum efficiency of the engine when going uphill. In the second case, of course, you will lose a little on friction in the chain transmission, but you will be able to optimize the efficiency of the engine when changing the speed.
Ordinary motorized or geared?
It does not matter if the electric motor is connected via a chain drive (drives in the carriage) or not (front, rear motor, friction gears), the bicycle speed system will still be involved.
The gear motor wheel allows you to move using a reduced gear ratio. It can help a cyclist to climb a very steep hill when using a motor with a highly reduction planetary gear. In this case, the engine will operate close to the highest efficiency point, as it will maintain high rpm. But still, there will be a loss of efficiency in a motor with a gearbox, since such systems are complex and some frictional waste is inevitable in them.
Gearless systems do not decelerate the engine. Consequently, the efficiency of the engine in them is not constant, but very often depends on the speed of the bike. But such systems are simple, so their total efficiency is higher compared to geared motors.
As you can see, there is a problem of choosing between electric motors with a gearbox and without it. On the one hand, the former can maintain the same efficiency of the motor over a wide range of speeds, while the latter have inevitable losses when the speed decreases. On the other hand, electric motors without a gearbox have a high overall efficiency.
When trying to climb a very steep slope or when carrying heavy loads, your average speed drops quite a lot. In this case, a motor without a gearbox will operate at a level with a significantly reduced efficiency. For uphill climbing, gear wheel will be the best choice.
However, it is safe to say that in other riding conditions, a motor without an undershift will do its job better (especially on frequent long trips) than overly complex systems with a gearbox.
Electric motors specialization
The electric bike wheel motor can be specially designed for better uphill climbing or optimized for increased range or increased travel speed. High horsepower engines have a high hill climbing ability (torque), but they reduce the travel range (quickly drain the battery).
The efficiency (efficiency) of the motor in terms of power is not constant, it has a maximum value at a certain speed. Also, its value depends on whether the speed increases or decreases.
Examples from real life situations
Take, for the first example, a standard motor with a maximum power of 250 watts at 10 km / h and a cyclist who can also bring in 250 watts (not trying hard) to maintain a given speed. Together they deliver one impressive 500W of power.
- At a speed of 10 km / h, a rider can climb a hill with a slope of 17.5% with 500 watts of combined power.
- At a speed of 8 km / h, a cyclist can climb a hill with a 17.5% incline with his 250 W and a motor running at 80% at 200 W.
- At a speed of 6 km / h, a cyclist can climb a hill with the same incline of 17.5% with his 250W and 125W motor running at 60%.
At first glance, these results may seem completely inaccurate, because only the efficiency of the electric motor goes down along with the speed, and it seems that the cyclist can still climb the same steep slope.
This inaccuracy will be resolved when we understand how important a person is to the operation of an e-bike. Let’s see what would happen if the cyclist did not press the pedals at all and all 500 watts (as in the example above) came from the motor.
- At 10 km / h, a cyclist would only be able to climb a 17.5% incline with the 500 W engine running at 100%.
- At a speed of 8 km / h, a rider can climb a hill with a lower incline of 17% with a 400 W motor running at 80%.
- At a speed of 6 km / h, the rider can drive up a hill with a slope of 14.5% with only 50% running of the 250 W motor.
These results are taken from the e-bike calculator with the following inputs: total weight. 100 kg; frontal resistance area. 0.4 square meters; friction coefficient. 0.7; lifting length. 100 m; headwind speed. 10 km / h and rolling resistance coefficient. 0.007.
Race around the city on a self-assembled electric bike with a motor wheel:
Rider strength is most important when you need to maintain speed on an e-bike, because when it drops, engine efficiency is greatly reduced. By analyzing this, you will be able to understand how an e-bike is different from any other motorized transport and why installing geared motors is not always the best choice. It is better not to put a motor with a gearbox in the front wheel at all, because it should have a free roll.