Electric Scooter Motors Guide What You Should Know Real vs Peak Power, Geared…

Electric Scooter Motors Guide [What You Should Know Real vs Peak Power, Geared vs Gearless, Brushed vs Brushless]

The electric scooter motor is a key component. When buying a scooter, deciding on the motor type will be one of the biggest decisions you will have to make.

That’s why I made a complete guide to electric scooter motors to help you understand everything you need to know about them.

Electric scooter motors

Electric scooters usually have motors with real power levels between 250W and 2000W (some can be even more powerful). The most important distinctions about the motor of an electric scooter are: power level (real power vs peak power), hub vs chain-drive motors, geared vs gearless hub motors, brushed vs brushless DC motors.

By any means, you don’t need to become a mechanic or an expert. But just being familiar with the basics of electric scooter motors will help you know what you need, and ultimately, pick a better model and save money.

Let’s briefly answer some of the most common questions, and cover each of the main properties.

  • Electric scooter motors
  • Do electric scooters have motors?
  • Which motor is used in an electric scooter?
  • Electric scooter motor specifications
  • How do electric scooter motors work?
  • Electric scooter motor power
  • Power levels in electric scooter motors
  • Real vs peak power
  • Power in electric scooters vs other appliances
  • Gearless hub motors
  • Geared hub motors

Do electric scooters have motors?

Every electric scooter will have a motor by definition. If a vehicle doesn’t have a motor, it’s not an electric scooter. The same goes for a battery, every electric scooter will have one.

Which motor is used in an electric scooter?

Today, most electric scooters will have hub motors, which are motors embedded in the wheels. Newer models will tend to have brushless DC motors, as that technology provides some benefits over the older, brushed motors.

Electric scooter motor specifications

A great way to know the quality of an electric scooter motor is through the specifications. Usually, manufacturers list the motor’s power (real and/or peak) in Watts, which is the most useful metric to determine the motor’s ability. Other useful specifications are the motor’s voltage expressed in Volts, its rotations-per-minute or revolutions-per-minute, which are expressed as numbers (sometimes followed by “RPM“), and the motor’s torque, expressed in Newton-meters, or Nm.

How do electric scooter motors work?

How motors work depends on their type. In general, the motor listens for your input through a component known as the controller. When you hit the throttle on your handlebar, the controller sends a signal to the motor to start running.

Then the motor draws energy from the battery and starts to produce movement.

The most common motor found in the everyday commuting scooter is a brushless DC, gearless hub motor. This is a very helpful video that explains how it works

Chain-drive motors, on the other hand, live in a separate area of the scooter, usually in the deck. They generate the movement there, and then translate that movement to the wheels through a system of chains and gears.

The advantages of having one over the other are not clear cut. They will usually depend on the specific setup, and the needs the scooter has to fill.

However, in general, there are use cases where one is preferred over the other.

The main advantage that hub motors have is that they don’t have an additional complicated system of chains and gears. That kind of mechanism is prone to defects. Therefore, hub motors break down less often, are easier to repair, and easier to maintain.

Hub motors can be more energy-efficient. Chain-drive motors lose some energy in the friction that the chains and gears create. Hub motors don’t suffer from that.

However, chain-drive motors can be set up in a way so that they are more efficient than hub motors.

Also, even though they are a more efficient technology, they tend to be cheaper than chain-drive motors.

Hub motors are heavier than chain motors. This can be either an upside or a downside, depending on your needs, as weight usually brings more stability to the scooter and it’s not always a bad thing.

The lack of gears, however, can make it so that hub motors provide less torque. That will result in lower climbing angles and top speeds.

Chain-drive motors are also better for customizations. Changing the sprockets lets you tinker with your scooter’s maximum speed and torque levels.

Also, changing the wheel on a hub motor will be more difficult.

Geared vs gearless motors

Hub motors come in two main types: geared and gearless. Gearless hub motors, also known as direct-drive, are motors that use electromagnets to propel the scooter forward by turning the wheel directly. The component that the motor rotates (the axle) is the same component that turns the wheel. Geared hub motors generate movement inside them, which they then translate to the wheel through a gear mechanism.

Gearless hub motors

In general, gearless hub motors can provide greater power. In effect, this will mean higher top speeds and better climbing angles.

Gearless hub motors are typically larger. They need to make one axle rotate very fast, and are kind of built around it. They will add to the weight of the scooter.

Because of their use of electromagnets to generate movement, gearless hub motors can also provide regenerative braking features.

Geared hub motors

Typically, geared hub motors will be less powerful.

The geared system provides leverage, and so a less powerful motor can actually output more power. That can make geared hub motors more energy-efficient.

But also, that will mean more friction, and more moving parts in general. That results in more wear and tear, and could possibly mean a shorter life span and more defects and repairs.

The main advantage that geared hub motors will usually provide is longer range.

The following video goes into detail about the differences between geared and gearless motors. It’s primarily about the motors in e-bikes, but the same principles apply in scooters as well. Take a look if you want to learn more.

Brushed vs brushless DC motors

This is the last complicated motor parameter, I promise :).

DC, or direct-current motors, can come in two types: brushed and brushless.

There are not that many brushed motors anymore, as they are older technology.

They generate power with two sets of electromagnets. The larger one is in the form of an empty cylinder, and the second, smaller magnet is inside of it. The inside magnet is the one that gets rotated. Its movement generates electromagnetic fields between the two magnets, which is then translated into the movement of the parts that rotate the wheel.

The electric current is being carried through carbon or graphite brushes, hence their name. These need to be replaced since they get worn out.

Brushless motors are a similar but simpler mechanism, that eliminates the need for brushes. They are more efficient, more reliable, and don’t require frequent repairs.

Because of that, they have largely replaced brushed motors, especially in electric scooters.

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What is the most powerful electric scooter motor?

The companies that make the most powerful motors for electric scooters today are Minimotors USA and Rion. Their most powerful models (Dualtron X2, Rion2 RE90) use proprietary motors that have power levels in the thousands of Watts.

The most powerful electric scooter today, the Rion2 RE90, likely has a motor with at least 12000 Watts of peak power. Unsurprisingly, it is also the fastest electric scooter in the world, capable of reaching 100 mph / 160 kmh.

If you wanna take a peek at the wildest electric scooters out there, check out the post on the most powerful electric scooters.

How to maintain the motor on my electric scooter?

Just common-sense general maintenance and taking care of your scooter will be enough for most scooters, as the majority will have brushless DC hub motors that basically require no maintenance.

Don’t abuse your scooter by riding it at its maximum speeds the whole time, and try not to force it to climb hills that are obviously too steep for it.

Unless you have a problem with your motor, it will not require any special care. You can take it to a repair shop once a year to make sure everything works smoothly.

As we mentioned, most motors are brushless today, and they don’t need replacements for their brushes.

Also, most motors are hub motors, and frequently gearless ones, which is literally the optimal combination for having to do the least maintenance and still get the longest motor life. In fact, while electronic defects are one of the most common electric scooter problems, hub motors are almost never at fault, and it’s always something with the battery or the wiring or the controller that’s the real issue, and the motors can keep running like well-oiled machines for years.

If your scooter has a chain-drive motor, your only job will be to grease the chains once every few months, to make sure everything runs smoothly. But, out of the 300 electric scooter models today, only a handful of popular ones still have chain-drive motors (most notable the Razor E300, and some other Razor models).

If you want to learn how the motor works in concert with the rest of the parts in the electric scooter, check out the full guide here.

Want to get FREE SCOOTER tips, exclusive discounts and promotions, and unseen scooter hacks? Join the Scooter Secrets club.

Everything You Want To Know About The E-Scooter Motor

In the 1990s, kick scooters with two wheels were famous in various parts of the world. Kids and adults loved the device for different purposes. The good news is that this vehicle has been trending again for some time.

The key difference is that now people use a modified form of kick scooters called electric scooters. They have the same design, such as two wheels, a handlebar, and a deck. However, they differ because the new models are motorized.

If you’re looking for more information about electric scooter motors, your search ends now. Here is a comprehensive guide to help you.

Table of Contents

  • A Brief Look into the Electric Scooter Motor
  • Motor Power: What Is It?
  • Power Range of Electric Scooter Motors Explained
  • 1, Hub Motor
  • 2. Chain-Drive Motor
  • 3. Brushed Motor
  • 4. Brushless Motor
  • 5. Sensored BLDC Motor
  • 6. Sensorless BLDC Motor
  • 7. Geared Hub Motor
  • 8. Gearless Hub Motors
  • Detailed Examples of the Working of an Electric Scooter Motor
  • Working Of A BLDC Motor
  • Electric Scooter Motor Power
  • Power Levels In Electric Scooter Motors
  • Peak Power Vs. Sustained Power: What’s The Difference?
  • What Is The Motor Torque In Electric Scooters?
  • What Should I Do If My Scooter Motor Fails?
  • Can I Tune-Up My Electric Scooter’s Performance At Home?
  • Do Two Motors With Same Wattage Have Equal Performance?

What Is The Electric Scooter Motor?

A Brief Look into the Electric Scooter Motor

Each electric scooter comes with a motor for operating smoothly. Typically, you will find this part in the hub of one or both wheels.

The motor provides power to the wheels so that you have enough force to move. The part also determines the maximum speed, acceleration, and overall performance of the vehicle.

Motor Power: What Is It?

Many people get confused when trying to understand the motor power of an electric scooter. However, the concept is not complex, as all scooters have a power rating. This is a numerical value that is provided in watts.

Each electric scooter will have a different motor rating because of various reasons. The vehicle’s power consumption determines this value. Typically, electric scooters with high power also have a greater wattage.

The wattage is the value that displays how much power your vehicle’s motor can consume. Typically, the motor will produce high mechanical power if your scooter uses more energy. The relation between these two quantities is directly proportional.

It is also better to get an electric scooter with high-listed power. This is because it will ensure excellent overall performance. For instance, your vehicle’s acceleration and hill-climbing ability will be better.

Power Range of Electric Scooter Motors Explained

The power range of an electric scooter motor is essential to understand. This will enable you to get a vehicle with the best top speed and handling. Typically, you will come across scooters ranging from 250W to 3,000W motors.

Some scooters can be more powerful than the earlier mentioned values. Typically, the range is divided according to the types. For instance, budget scooters usually have 250 to 300 watts of motor power. This type is mainly suitable for entry-level drivers.

Meanwhile, premium vehicles such as the Horizon come with 500 to 1,000 watts of power. This type is suitable for people with some scooter driving experience. Lastly, performance electric scooters have 1,200 to 3,000 watts of motor power. Advanced drivers mainly use them.

All standard electric scooters come with one motor. However, the high-performance type has two. This is why they have an exceptionally high power rating.

Electric Scooter Motor Types

Here are all the motor types you will come across when buying an electric scooter:

1, Hub Motor

Most electric scooters you will encounter in today’s era will have one or two hub motors. As the name suggests, this part will be located in the vehicle’s wheel hub(s). The best thing is that this type is lightweight and simple.

The hub motor also has low manufacturing costs. This is why scooters of this type are relatively inexpensive. Furthermore, the system of this part is also not complex, so this motor does not face technical issues often.

  • Energy-efficient design
  • Cheaper than other types
  • Simple system
  • Easy to repair and maintain
  • Lower climbing ability and maximum speed due to lack of gears
  • Offers less torque
  • Changing a flat tire will be complex because of the hub motor

Chain-Drive Motor

This type is also called a mid-drive motor. So you should never get confused when seeing the two terms being interchanged. The top feature of this type is that it is not located in the wheel. Instead, you will find a chain-drive motor in the deck.

This motor develops power in its locating region and transfers it to the wheels. Chains and gears help with transportation. Typically, this part drives the crank of the scooter instead of its tires.

It also increases the vehicle’s power. The primary purpose of the chain-drive motor is that it helps you maximize the scooter’s gear benefits.

  • Offers more power
  • High range
  • Easy to service
  • Makes troubleshooting simple
  • Improves the scooter’s handling
  • Experiences some energy loss due to friction
  • Difficult to repair
  • Maintaining the motor is tough

Brushed Motor

Before diving into the specifics of this type, you should note that electric scooters can have brushed or brushless motors. They both are DC motors but differ in operation. The former works mechanically while the latter functions electrically.

Brushed motors have been in being since the early 1800s. They are one of the oldest technologies you will come across. The top feature of this part is that it produces power through two electromagnets. One of them resembles an empty cylinder and is larger.

Meanwhile, the second magnet is within the larger one and generates magnetic fields between the two. This is used for producing power which is then transferred to the wheels. The brushed motor transport current through graphite/carbon brushes. This is the reason behind the name of this type.

Most electric scooters these days have brushless motors. This is because they provide more benefits as they are a recent technology.

  • Older technology
  • Wears out with time
  • It becomes hazardous after prolonged use
  • Production in this era is limited

Brushless Motor

This type is also known as BLDC in the industry. The top feature of this motor is that it is made of recent technology. Therefore, the part has a simpler operating mechanism. Besides that, it also does not use brushes for current transfer.

In this type, a digital circuit is found instead of mechanical electromagnets. The power also alternates between the motor coils for efficient functioning. Most scooters in this era will have a BLDC motor instead of the brushed part.

  • Better power to weight ratio
  • energy efficient
  • Operates silently
  • It does not overheat often
  • Highly reliable

Sensored BLDC Motor

BLDC motors come in sensored and sensorless versions. The key feature of all brushless parts is that they get power from the ESC (electronic speed control). Typically, the control requires information about the rotor position for smooth motor acceleration.

The sensored BLDC contains built-in parts called the Hall Effect sensors. The controller uses them to determine the rotor position and maintain optimal speed. The sensors send information to ESC to let it know the rotor’s position.

Once the ESC understands the information, it instantly begins synchronization from zero RPM. Sensors play an integral role in the operation of this motor type. If they fail, the controller will not receive essential information.

Typically, power is transferred to the motor through three wires known as phases. These phases must be in harmony so that the scooter can operate without issues. When the sensors fail, the cables will be out of sync, and the motor will be stuck.

  • Produces higher torque at lower speeds
  • Excellent performance
  • Widely used for vehicles that need more torque at low speeds
  • Applications included electric scooters, RC cars, and much more
  • Sensor failure will cause the motor to be stuck and make a grinding sound
  • Sensorless BLDC will not work with this type’s controller
  • Mainly useful for vehicles with high torque needs

Sensorless BLDC Motor

Sensorless BLDC is simply a motor that lacks brushes and sensors. This part does not contain the Hall Effect or other sensors for monitoring the rotor position. Instead, the controller uses different mechanical methods to receive essential information.

One of the top ways a sensorless BLDC controller knows rotor position is through the motor’s back EMF. Back electromotive force is simply the voltage produced by the motor. This mechanism is widespread in generators.

The top feature of sensorless BLDC motors is they are used in vehicles with low torque needs. For instance, you may find this part in multiple boats. Besides that, many airplanes also have this motor for a smooth flight. This type will also only work in vehicles with a sensorless BLDC controller.

  • Longer life due to lack of Hall effect sensors
  • reliable in some cases
  • Best for low torque needs
  • Only provides rotor position information when the scooter is moving as no back EMF is produced in stationary vehicles
  • complex structure

Geared Hub Motor

Hub motors come in geared and gearless types. They are mainly used in e-bikes, but the exact differences and principles apply to electric scooters too. So let’s discuss the geared hub motor first.

A vital feature of this motor type is that it has a set of gears outside the small motor. The part is inside a casing while the gears remain outside. This motor type is relatively smaller than other hub versions and is compared with climbing motors.

The motor generates power within the casing and transfers it to the wheels through the gear system. Typically, this type is less powerful than other motors. However, the mechanism makes this part more efficient.

The geared system also tackles the common torque issues and encourages the weak motor to produce more power. Another use of this type is that it offers a higher range.

  • Long range
  • Power output is high
  • Maintains good speed
  • Highly efficient

Gearless Hub Motors

The final motor type you will come across in electric scooters is the gearless hub motor. They are also called direct-drive parts and use electromagnets to cause the scooter to move forward. Firstly, you must note that the axle is the part that a motor causes to rotate to turn the wheel.

The electromagnets cause the axle to move so that the scooter can operate smoothly. The top feature of direct-drive motors is a simple inner structure.

The motor only has two essential parts called the rotor and stator. They spin automatically on one side of the component. The primary benefit of gearless type is that they also offer regenerative braking options. This motor is also called a speed motor.

  • Higher maximum speeds
  • Better hill-climbing angle
  • Maintains speed efficiently
  • Provides braking features
  • Overall efficiency is low
  • It makes the scooter heavy as the motor size is larger
  • Wears down quickly in stop and go traffics

How Does An Electric Scooter Motor Operate?

An electric scooter’s motor operates by using the information provided by a component called the controller. This part is present in all e-scooters for efficient operations. Firstly, you have to hit the throttle on the handlebar of the vehicle.

The controller signals the scooter’s motor to work when you push the throttle. After that, the component will use energy from the battery to produce power and cause the wheels to move.

Detailed Examples of the Working of an Electric Scooter Motor

The earlier mentioned description is a simple overview of how the motor operates. However, the mechanism differs significantly depending on the motor type. This is why you may be looking for a comprehensive description.

So here is an example of how the brushless gearless DC motors work. This is the most common type you will come across in electric scooters.

Working Of A BLDC Motor

Typically, the gearless motor contains the stator and the rotor cylinders. One of them is inside the other component. The rotor is the outer part and a permanent magnet. Meanwhile, the stator is the inner cylinder and has a copper coil arrangement.

The motor works by using an interaction mechanism between the electromagnet and the permanent magnet.

When DC power is applied to the copper coil, it becomes energized and this energization of the coil causes the stator and rotor to attract each other, the rotor starts to rotate.

As the rotor turns, the energized coil loses its energy, but its neighbor coil gets energized.

The process repeats continuously so that the rotor does not stop rotating, ensuring that the motor operates smoothly and generates sufficient power to move the wheels.

Specifications You Need To Know About The Motor

The top way you can understand the quality is by knowing the motor specifications. Typically, most manufacturers list power as an essential metric. This value is the best way to determine the motor’s abilities.

Besides that, motor voltage is another functional specification represented in volts.

You will also come across revolutions or rotations per minute. Typically, companies list this metric using its abbreviation, RPM.

Torque is also a helpful specification with a Newton-meters (Nm) unit.

Electric Scooter Motor Power

As we mentioned, motor power is the top way to understand a motor’s abilities. This value determines the various performance features of your scooter.

It also impacts some of the things significantly. Here are the features that the motor power determines and affects:

  • The maximum speed of the electric scooter
  • Top incline angles your vehicle can climb
  • The maximum weight the scooter can hold
  • Range of the vehicle

Power Levels In Electric Scooter Motors

The power of adult electric scooters ranges from 80 to 12,000 watts. This range determines the maximum speed your scooter can reach. If you want a faster bike, you should choose a model with a high power level.

Most standard commuting electric scooters have a power of 200 to 500 watts. These models are best for people with a tight budget. The maximum speed for this type ranges from 25 km/h to 35 km/h. typically, half of the electric scooters today have this range.

However, heavy-duty scooters used mainly for performance and off-road driving have dual motors. These range from 1,200 to 3,000 watts. This range is for each motor in this scooter type and not a cumulative figure.

Here are other prevalent power levels that you should know:

Power Level Maximum Speed
250 Watts 25 km/h or less
350 Watts 25 to 35 km/h
500 Watts 40 to 60 km/h
1000 Watts 50 km/h or more

The most powerful electric scooter model in today’s market is the Rion2 RE90. This model has a motor with a peak power of about 12,000 watts. The scooter can reach up to 160 km/h. This feature makes this model the world’s fastest e-scooter.

However, brands can mislead you when reporting the different power levels. This is why you must understand the concept of peak power. It will allow you to make a fair real vs. peak power comparison.

Peak Power Vs. Sustained Power: What’s The Difference?

Power generated by electric scooter motors varies because of various factors. These include motor temperature, external environment, road obstacles, and much more. The component’s temperature affects its performance considerably. Typically, a motor becomes less efficient when it overheats.

You must understand that peak power is the maximum power a motor can take in indefinitely for a short period before overheating. The scooter will operate using full power in a perfect world with no road obstacles and optimum temperature. This is what the peak power indicates.

Of course, we don’t live in a perfect world. This is why using peak power as a metric is misleading. Typically, the levels your scooter consumes on the road are its real or sustained power. The actual value is mainly 30% to 90% of the peak figure.

On average, the real power of most scooters is 57% of the peak value. Unfortunately, most brands list the peak levels in their specifications to mislead customers. They also don’t mention the term “peak,” so you can never accurately know what the power value indicates.

Continuous or sustained power is the better metric to help you decide when buying an e-scooter. It is the maximum power your vehicle can consume when operating for an indefinite time. This value indicates how much energy the scooter’s motor can handle continuously.

What Is The Motor Torque In Electric Scooters?

The motor torque is the twisting force your scooter’s motor produce to rotate the wheel and help you move forward. In some countries such as the UK, this value is measured using the imperial system in a pound-foot unit (lb-ft).

Meanwhile, the US and other North American countries use the SI unit system. This means that the measurement unit for these places is Newton-meters (Nm). The torque plays an integral role in determining your scooter’s maximum speed and incline angle.

Besides that, the torque also determines the amount of work an electric scooter’s motor can do. Unfortunately, most brands don’t provide this useful metric in their specifications list. However, you can still calculate it using a simple physics formula.

Typically, you should multiply the vehicle’s power by revolutions per second. Simply put Torque = RPS x Power.

Why Should You Not Use Motor Power For Determining Scooter Efficiency?

Many of you may be considering only the motor when buying electric scooters. However, this part does not tell you the whole story. You will have to consider other factors to make an informed buying decision.

The motor power or wattage only indicates how much power the component can consume. Generally, a motor that uses high energy quickly produces more mechanical power. This means that the part will have a high wattage.

Typically, high wattage means the scooter will accelerate faster, hold higher maximum weight, move more quickly, and climb hills easily. However, the value will not tell you the efficiency of the motor. This is why power is not the best metric for determining the performance of electric scooters.

You should never expect motors with similar wattages to have the same performance. This is because one of them can be more efficient. For instance, two motors with a 250 watts rating will consume the same electric power. However, that does not mean that their outputs and efficiency will be the same.

A test by the ESG has proved this conclusion. In the study, Xiaomi M365 with a continuous power of 250 watts was compared with XR Ultra and Segway Ninebot ES motors. Both the models had a capacity of 300 watts.

However, the results showed that Xiaomi M365 is faster than the other scooters. It covered 15 miles per hour in 6.3 seconds. Meanwhile, XR Ultra covered the same distance of 7.8 seconds, and the Segway model took 7.1 seconds.

So you should note that motor power will never give you an accurate performance indication. Most brands also don’t mention the vehicle’s efficiency in the specifications, and you cannot calculate it.

Today, most electric scooters have a maximum efficiency ratio of not more than 50 to 60%. So you should not use wattage to make a direct comparison between two scooters.

The best way to make a fair comparison is by considering other factors. For instance, you should consider the motor powers, maximum speeds, and accelerations to get a better idea.

How Does Motor Affect Other Electric Scooter Components?

Motors with high power will increase the battery size of your scooter. This means that the model will be heavier than those with low power. Besides that, bigger batteries also mean that the scooter will take more time to charge.

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Besides that, you should ensure that the motor type and controller type are the same. For instance, a sensorless BLDC motor will only operate in a device with a sensorless BLDC controller.

Factors to Consider When Choosing the Motor Type of an E-Scooter

Do you require an electric scooter for everyday commuting needs? If so, you should not choose a model with less than 300 watts of power. This is because you will not be able to travel on steep hills.

Besides that, low power also means that your scooter will not operate well on rough terrains. Another thing you should consider is your weight when choosing the motor type. You should get a scooter with a high power rating if you are a plus-sized individual.

Typically, a high power rating ensures that the scooter will need a bigger battery. This contributes to the vehicle’s weight and increases its maximum holding capacity.

FAQ

Here are the answers to the most frequently asked questions about electric scooter motors:

What Should I Do If My Scooter Motor Fails?

A motor is the most reliable part of an e-scooter. If it is not rotating, your vehicle may be experiencing a battery issue. A problem with the controller can also cause your motor to fail. Typically, you should get the scooter checkout by a technician.

Can I Tune-Up My Electric Scooter’s Performance At Home?

In today’s digital era, you can easily find hacks to adjust your scooter’s controller and improve its performance. However such tune-ups reduce your vehicle’s battery life. It will also decrease the maximum distance you can travel. So while you can tune up the scooter, it is not advisable to do so.

Do Two Motors With Same Wattage Have Equal Performance?

The sustained power rating is an excellent way to determine the performance of your scooter. However, it is not suitable for comparing two different models. This is because the mechanical power output of both scooters will vary depending on various factors.

A prime example that will help you understand is our test between the Turboant X7 Pro and Apollo Light scooters. Both models have a power rating of 350 watts. However, the latter can reach a maximum speed of 36 km/h. Meanwhile, X7 Pro’s top speed is 31.4 km/h.

Besides that, Apollo Light can cover a 0 to 15 MPH distance in 5 seconds. Meanwhile, the other scooter requires 7.3 seconds to cover the same distance. So you should never consider two models with the same wattage to perform equally.

Typically, you should consider various factors to get an idea of the efficiency. For instance, you must understand each scooter’s acceleration, maximum speed, and motor power.

Final Words

This is everything you need to know about the motors of electric scooters. When buying your best model, you must consider various factors to make an informed decision. These include the motor’s power, maximum capacity of the scooter, weight, and much more.

Once you understand the motor system of an electric scooter, you can easily choose the suitable model for your commuting or racing needs. So be sure to read this guide thoroughly.

For The Unbreakable

Designed for the dreamers and built for the unbreakable, MIHOS is developed with the latest and more efficient technology. Built with Poly DiCycloPentadiene (PDCPD) or industrial rock, this beauty with strength combines comfort, technology and top-notch mechanics.

Battery

With an improved battery of 74 V, 40 Ah that gets fully charged within 4 to 5 hours, you will be able to travel an approximate of 130 km in a single charge, enjoying its ease of riding.

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The ARAI standard battery pack comes with anti-dust, water-proof, vibration-withstanding abilities and can resist water jets of extremely high pressure.

Combi Brake System (Hydraulic disc brake)

MIHOS is equipped with a combi brake disc system that guarantees a smooth ride as well as the correct handling of the vehicle when reducing speed or avoiding collisions. In short. a combined braking system for a safer speed control.

Suspension

Adaptive suspension for the Indian roads.

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enhanced security

Turn on the ignition with your phone. This allows you to remotely and smartly operate the ignition of your e-bike.

Define your area of travelling by setting up the Geo-fence and get an alert when the bike travel beyond the Geo-fence.

Ride carefree. This super cool feature helps you to plan your trip in available charging.

Retrace your steps! Now with Joy e-connect app, you can check all the places your bike has travelled.

Turn on the ignition with your phone. This allows you to remotely and smartly operate the ignition of your e-bike.

Define your area of travelling by setting up the Geo-fence and get an alert when the bike travels beyond the Geo-fence.

Ride carefree. This super cool feature helps you to plan your trip in available charging.

Retrace your steps! Now with Joy e-connect app, you can check all the places your bike has travelled.

full specification

Range 130km/charge
Motor Power 1500 W
Motor Type BLDC
Charging Time 5. 5.5 hours
Front Brake Disc
Rear Brake Disc
Body Type Tubuler monocoque
Curb weight 110 kg
Ground clearance 175 mm
Max Speed 70 kmph
Max Troque 250NM
Gradability 10.2 degree
Max Acceleration 0-40kmph 7 sec 1.5m/s2
Drive Type Hub Motor
Motor Type BLDC
Motor Power 1500 W
Starting Main key start
Transmission Hub Motor direct drive
Braking Type Combi Brake System ( Hydraulic disc brake)
Charging Point Yes
Speedometer Digital
Smart Battery Yes
Ladies Footrest Yes
Connected features Vehicle Tracking, Geo Fencing, Remote Disabling
Mobile app feature Navigation on, Bluetooth connectivity
Electric Sound System Vehicle sound simulator while riding, bluetooth music playing
Smart connected component CAN Based Communications : Smart BMS CAN based battery, CAN based Smart charger, CAN based Smart charger, CAN based instrument cluster, CAN based controller, CAN based IOT VCU
Headlight LED
Tail Light LED
Turn Signal Lamp LED
Battery Type NMC
Battery Capacity 74 V, 40 Ah
Low Battery Indicator Yes
Tyre Type Tube less
Wheel rim Size Front : 12 Rear: 12
Wheels Type Alloy
Front Brake Disc
Rear Brake Disc
Front/Rear tyre 90/90-12

Introduction: Make Your Own Miniature Electric Hub Motor

In-wheel electric drive motors represent an effective method of providing propulsion to vehicles which otherwise were not designed to have driven wheels.

That is, they’re great for EV hacking and conversion. They’re compact and modular, require no support of rotating axles from the parent vehicle, and can be designed around the vehicle to be propelled. Pure DC electric hub motors, in fact, were used in some of the first electric (and hybrid electric) cars.

They are also not as complex and mystical as one might think. The advent of my project RazEr, a stock Razor scooter with a custom built electric conversion, has raised many questions from amateur EV builder looking to construct their own brushless hub motors. Until now, I have not had a single collective resource to point anyone towards, nor have I been confident enough to understand what I actually built to write about it for other hackers.

Hence, I will attempt to show that a brushless DC permanent magnet hub motor is actually relatively easy to design and build for the hobbyist, resource access considerations aside. I will first exposit some of the details of brushless DC motor theory as applied to hub motors. I will provide some thoughts and pointers about the mechanical construction of the motor itself and how to source major components. Finally, I will briefly glean over ways to control your newfound source of motion. The arrangement of this Instructable is designed for a readthrough first. because it relays theory and advice more than specific instructions on how to create one particular motor.

This is intended as a basic primer on DC brushless hub motors. Many assumptions, shortcuts, and R/C Hobby Industry Rules of Thumb and Hand Waves will be used. The information is purposefully not academic in nature unless there is no way to avoid it. The intention is not to design a motor that maintains above 95% efficiency across a thousand-RPM powerband, nor win the next electric flight competition, nor design a prime mover that will run at constant power for the next 10 years in an industrial process. Motor theoreticians avert thine eyes.

I will assume some familiarity with basic electromagnetics concepts in order to explain the motor physics.

Below is an exploded parts diagram of a prototype motor that I am in the process of designing and building. Let’s clear up some of the vocabulary and nomenclature immediately. The can (or casing) hold a circular arrangement of magnets (electrically called poles) and is supported on one or both ends by endcaps. This whole rotating assembly is the rotor. Internally, the stator is a specially shaped piece of laminated iron pieces (the stack) which holds windings (or coils) made of turns of magnet wire on its projections (teeth). It is stiffly mounted to the shaft (a nonrotating axle) which also seats the bearings for the rotor assembly.

Step 1: Hub Motor Design Considerations

Is a hub motor the right choice for your electric vehicle? Answer these few simple ques.

I mean, read these few pointers which highlights some design tradeoffs and considerations involved in the use of hub motors! They are not perfect solutions to every drive problem, and some of the shortcomings are dictated by the laws of physics.

Hub motors are inherently heavier and bulkier than driven wheels.

Until we make magic carbon nanotube superconductors en masse, motors are essentially chunks of steel and copper, both very heavy elements. What happens when you increase the weight of a wheel two- or.threefold is a drastic increase in th e unsprung weight of a vehicle, or weight that is not held up by a suspension. For those of you in the know about vehicle suspension engineering, unsprung weight negatively affects the ride and comfort of a vehicle. If you just drop hub motors into a vehicle previously endowed with indirectly driven wheels, expect a change in ride performance.

This is more of a concern for passenger cars and sport vehicles than anything else, as most small EVs such as bikes and scooter won’t have suspensions at all. However, the keyword here is small. You might have gathered from my other instructable that some times it’s all but impossible to simply fit a larger motor in an enclosed space. A hub motor will inevitably take up more space in the vehicle wheel. This matters less for larger wheels and vehicles. The MINI QED and Mitsubishi MIEV are example of car-sized hub motors that have been well-integrated into the vehicle design through some pretty serious re-engineering of how the wheels attach to the car frame. You might have to do the same for your scooter, bike, or couch.

A hub motor powertrain will generally produce less torque than an indirect-drive system

Don’t expect any tire smoke from your hub motors. An indirect drive motor, such as one geared to the wheels through a transmission, has the advantage of torque multiplication. This is how a 400 horsepower diesel engine in a semi truck can haul itself and 80,000 more pounds up a mountain road, but a 400hp Corvette could not do the same. the semi engine goes through a painstakingly complex arrangement of gears to transmit many thousands of foot-pounds of torque at the drive wheels. A Corvette is light and fast, and hence the 400 horsepower in its engine is mostly speed.

From physical mechanics, power output is a product of both torque and speed. Due to curiosities in the laws of nature, it is much easier to make a fast but low torque motor than a slow and high-torque one, power output levels being equal.

As it relates to motors, this is why your typical drill motor spins at upwards of 30,000 RPM, but you only get a few hundred RPM out at the screwdriver bit. The drill motor has been engineered to produce maximum power at very high rotational speeds, which is sent through a gear reduction to crank your drill bits hard enough to do this.

But your hub motor is direct drive. There’s no bundle of pointy steel things to convert its rotational velocity into torque. A hub motor can only lose mechanical advantage because the wheel essentially must be larger in diameter than the motor. Comparatively few in-wheel motors have internal gearing. these are most often found on bicycles, since they have a large diameter, and hence loads of space, to work with. It is not that much more difficult to incorporate a gearset into your hub motor, but it is beyond the scope of this Instructable.

The bottom line is, while a 750 watt DC motor on your Go-Ped might let you perform a wheel-spinning launch, a 750 watt hub motor will probably not.

Hub motor drivetrains will generally be less electrically efficient than an indirect drive system

It is certainly true that hub motors bypass practically all the mechanical losses associated with a clutch, transmission, axles, and gears that you typically find in a vehicle powertrain. In fact, drive components alone can eat up 15 to 20% of the power produced by the engine. Imagine if that were gone. what could you do with 15 to 20% more power?

A hub motor will typically have a torque-produced to force-on-the-ground transmission of almost 1. The torque of the motor only has to go through the tire, with its rolling friction and deformation forces. But what hurts the hub motor is electrical efficiency.

A motor is a transducer. Input electrical power and out comes mechanical power. usually. Electrical power is defined as

where V is the voltage across the motor and I is the current flowing into the motor. V has unit volts and I has unit Amperes. Mechanical power is

Pm= T ω

where T is the torque output in Newton-Meters and ω is rotational velocity in radians per second (units 1 / time, because radians are unitless!)

It is perfectly within reason to be inputting electrical power to the motor but get no rotation out. This is called stall or locked rotor condition, and it kills motors. This occurs when T is not enough to overcome the forces pushing back against a motor. think of driving up a really steep hill.

In this case, your efficiency is precisely zero. Zilch, nada, nihil, nothing. Mechanical power out is zero, but electrical power in is nonzero.

While it is true that both motors must start the vehicle from standstill, and thus have zero efficiency for a split second, the fact that hub motors must operate continuously at high T and low ω is the distinguishing factor. Other laws of physics dictate limits of torque output, which I will get to shortly. A\ hub motor has to draw a higher current for the same torque output, and current is what causes heating in wires (not voltage). The more current there is, the more heat is generated.

This is called Joule heating and is governed by the power law Pj = I² R. It is a square law: double the current, quadruplethe heat.

Now you see why hub motors are less efficient electrically than indirect drive motors. Hub motors are low speed creatures, and will inevitably spend much of their lives at or near stall condition. This occurs whenever the vehicle is moving at low speed or accelerating. A hub motor will see more moments of low or zero efficiency than an indirectly driven, geared motor.

The bottom line is, prepared to see a decrement in battery life if you swap your existing drive system with a hub motor.

Now that I have told you the reasons to not build and use hub motors, let’s get on to how you can build and use hub motors.

Step 2: The Brushless DC Motor

At the heart of most hub motors is a brushless DC motor. To build a hub motor right, you need to understand some basics of brushless DC motors. To understand brushless DC motors, you should understand brushed DC motors. If you’ve taken a controls class, chances are that you’ve used brushed DC motors as a plant to test your controls on.

I’ve highlighted and bolded the juicy stuff that you’ll need, but for the sake of continuity it’s probably good to grunge through all of it anyway.

Brushed DC Motor Physics

Perhaps the best DC motor primer I have seen (I’m not biased at all, I promise guys! Pinky promise! ) is the MIT OpenCourseware notes for 2.004: Dynamics and Control II. Take a read through it at your own leisure, but the basic rundown is that a brushed DC motor is a bidirectional transducer between electrical power and mechanical power that is characterized by a motor constantKm. and an internal resistanceRm. For simplicity, motor inductance L will not be considered. Essentially if you know Km and Rm, and a few details about your power source, you can more or less characterize your entire motor.\

Update10/06/2010: The original 2.004 document link is dead, but here’s one that’s roughly the same content-wise. Also from MIT OCW.

The motor constant Km contains information about how much torque your motor will produce per ampere of current draw (Nm / A) as well as how many volts your motor will generate across its terminals per unit speed that you spin it at (V / rad / s, or Vs / rad, or simply Vs). This back-EMF constant is numerically equal to Km, but some times called Kv.

In a DC motor, Km is given by the expression

where N is the number of complete loops of wire interacting with your permanent magnetic field of strength B (measured in Tesla). This interaction occurs across a certain length L which is generally the length of your magnets, and a radius R which is the radius of your motor armature. The 2 comes from the fact that your loop of wire must go across then back across the area of magnetic influence in order to close on itself. This R has nothing to do with Rm, by the way.

As an aside, I will be using only SI (metric. ) units here because they are just so much easier to work with for physics.

Let’s look at the expression for Km again. We know from the last page that

Pe = V I and Pm = T ω

In the ideal motor of 100% efficiency (the perfect transducer), Pe = Pm, because power in equals power out. So

V I = T ω

Where have we seen this before? Swap some values:

V / ω = T / I

The takeaway fact of this is that knowing a few key dimensions of your motor: The magnetic field strength, the length of the magnetic interaction, the number of turns, and the radius of the armature, you can actually ballpark your motor performance figures usually to within a factor of 2.

The Brushless DC Motor

BLDC motors lie in the Awkward Gray Zone between DC motor and AC motors. There is substantial disagreement in the EE and motor engineering community about how a machine which relies on three phase alternating current can be called a DC motor. The differentiating factor for me personally is:

In a brushless DC motor, electronic switches replace the mechanical brush-and-copper switch that route current to the correct windings at the correct time to generate a rotating magnetic field. The only duty of the electronics is to emulate the commutator as if the machine were a DC motor. No attempt is made to use AC motor control methods to compensate for the AC characteristics of the machine.

This gives me an excuse to use DC motor analysis methods to rudimentarily design BLDC motors.

I will admit that I do not have in depth knowledge of BLDC or AC machines. In another daring act of outsourcing, I will encourage you to peruse James Mevey’s Incredible 350-something-page Thesis about Anything and Everything you Ever Wanted to Know about Brushless Motors Ever. Like, Seriously Ever.

There’s alot of things you don’t need to know in that, though, such as how field-oriented control works. What is extremely helpful in understand BLDC motors is the derivation of their torque characteristics from pages 37 to 46. The short rundown of how things work in a BLDC motor is that an electronic controller sends current through two out of three phases of the motor in an order that generates a rotating magnetic field, a really trippy-ass thing that looks like this.

The reason that we consider two out of three phases is because a 3 phase motor has, fundemantally, 3 connections, two of which are used at any one time. Here’s a good illustration of the possible configurations of 3 phase wiring. Current must come in one connection, and out the other.

In Mevey 38, equation 2.30, the torque of one BLDC motor phase is given by

T = 2 N B Y i D/2

where Y has replaced L in my previous DC motor equation and D/2 (half the rotor diameter) replaces R.

If you do it my way, it becomes

T = 2 N B L R i. replacing D/2 with R.

Remember now that two phases of the motor has current i flowing in it. Hence,

T = 4 N B L R i

This is the Equations to Know for simple estimation of BLDC torque. Peak torque production is (modestly) equal to 4 times the:

number of turns per phase strength of the permanent magnetic field length of the stator / core (or the magnet too, if they are equal) radius of the stator current in the motor windings

As expected, this scales linearly with current. In real life, this will probably get you within a factor of two. That is, your actual torque production might be between this theoretical T and T/2

Wait, 4? Does that mean if I turn my brushed DC motor into a brushless motor, it will suddenly have twice the torque? Not necessarily. This is a mathematical construct. a DC motor’s windings are considered in a different fashion which causes the definition of N and L to change.

Next, we will see how to use this equation to size your motor.

28 July 2010 Updateto the definition of T

In the equation T = 4 N L B R i, the constant 4 comes from the derivation of a motor with only one tooth per phase, assuming N is the number of turns of wire per tooth on the stator.

The full derivation of this constant involves each loop of wire actually being two sections of wire, each of length L. This is due the fact that a loop involves going across the stator, then back again. Next, in a BLDC motor, two phases are always powered, therefore contributing torque.

We can observe that in a motor with only 1 tooth per phase (a 3-toothed stator), there are no more multiplicative factors. However, for each tooth you add per phase (2 teeth per phase in a 6-tooth stator, 3 teeth per phase in a 9-tooth stator, etc.) the above constant must be multiplied accordingly. The constant in front of the equation essentially accounts for the number of active passes of wire, which is 2 passes per loop times 2 phases active times number of teeth per phase.

So, what I actually mean is that T = 4 m N B L R i where

m = the newly defined teeth per phase count.

As the windings themselves have yet to be introduced, keep in mind the number of teeth per phase in the dLRK winding is 4.

Step 3: The Brushless DC Motor and You

T = 4 m N B L R i. otherwise known as T = Km i

affect your motor design, and why am I viciously pounding on torque so much? Because torque is ultimately what hauls you around, and is one of the components of mechanical power Pm. Once you determine roughly how much mechanical power you will need, you can size wires and components appropriately.

Notice some key characteristics of the equation and how they affect motor performance:

Torque increases with number of turns N and radius of the stator R and strength of the magnetic field B and length of the stator L and winding current i.

What we observe here is that to a degree, you can linear scale motor characteristics to estimate the performance of another motor.

This is R/C Hobby Industry Hand Wave number one. The concept of turns and motor sizes.

A 100mm diameter motor will, all else being equal, produce twice as much torque as a 50mm diameter motor.

A motor with 1.2T permanent magnetic field will likely be 20% more torquey than a 1T motor. And so on.

This has its limits. you cannot reasonably assume that you can quintuple your windings and get 5 times the torque. other magnetic characteristics of motors, such as saturation come into play. But, as will be shown, it is not unreasonable to extrapolate the performance of a 25 turn-per-stator-tooth motor from a 20 turn one, and such.

The LRK Winding

At the bottom of it all, what I am designing and making is a fractional-slot permanent magnet three phase motor. What the frunk does that mean? The fractional slot just means that (magnet pole pairs phases) / (number of teeth on the stator) is not an integer. If you understood that, you know it more than I do.

A brief explanation is that the ratio of number of stator teeth to number of magnet pairs strongly affects the physical characteristics of the motor. A magnet pole pair is defined as two magnets, one with the North pole facing radially inwards, the other with the N pole facing outwards.

This ratio, commonly called T : 2P (for teeth to 2 total poles), affects the cogging of the motor, i.e. its smoothness.

Get a DC brush motor and twirl the shaft. there is a minimum amount of torque required to ‘click’ it over to the next stable position. This is cogging. It causes undesirable vibrations and high-order electrical system effects, and we don’t like it.

A type of motor winding with T : 2P close to 1 (but not 1 exactly. that results in a motor which doesn’t want to move) substantially reduces cogging (to near zero) and is the most popular small BLDC motor winding around. It is called the LRK winding, after Messrs. Lucas, Retzbach, and Kuhlfuss, who documented the use of this winding for model airplane builders in 2001. Not only does it offer low cogging, but also ease of winding and scalability.

Here are figures of the basic LRK winding and a variant called the DLRK (Distributed LRK).

The takeaway here is that using a stator with 12 teeth (or slots, the area between the teeth) and 14 magnets (that is, 7 pole pairs) will give you a pretty decent motor to start with and use in your fledgling motor engineering career.

The difference between the two winding styles is subtle. The distributed LRK winding has a smaller end-turn effect. An end turn is the wire that has to wrap around outside of the magnetic field in order to close the loop. It contributes no torque, but does have a resistance (all wires have nonzero resistance. we’re not talking superconductors here). The dLRK avoids bunching the end turns up excessively, which results in a slightly more efficient motor. Slightly as in one or two percentage points. nothing to win a Nobel Prize over.

Below is a picture of Razer’s motor core with a full dLRK winding.

Step 4: The Stator: Obtaining, Care, and Feeding

For the past 4 pages I’ve said stator stator stator stator. What IS the stator, and where do you get one? The stator is the number one most painful specialized industrial component to acquire for a motor build, generally speaking, and is usually what you end up designing your power system around just because you have one and by Robot Jesus you are GOING to use it.

The stator is difficult to just make because it requires the stacking and fitting of many layers of very thin, electrically insulated steel sheets. Not just any steel sheet either. no Home Depot galvanized roof patches here. Motor steel is called electrical steel or transformer steel and are special alloys that contain high silicon. This enhances the magnetic characteristics of the steel and reduces its conductivity.

So why does it have to be laminated. and especially insulated ones? This is due to the phenomenon of eddy currents. The short story is that moving magnets over conductive materials cause the material to dampen the magnet’s motion. In a motor, that means your motor is trying to brake as hard as it’s trying to go. Those eddy currents get turned right into heat. If you take the method that most new motor builders go:

Well, I’ll just cut it out of some thick steel plate or a block or something. I have a milling machine, it’ll work, right?

It will, but you’ll make a heater that occasionally twitches, rather than a motor which heats up as it runs.

Having laminated, low conductivity sheets of material means that the eddy currents are neutralized to a large degree. For low speed motors, this eddy current loss or core loss can be negligible. For high speed motors, it can eat up as much as 15 to 20% of the power.

So where do I get a stator?

This will be the only how to get section that’s not in the Resources page, because you generally don’t just go and get one.

Because they require the punching, stacking, and otherwise processing of hundreds of little steel sheets, stators tend to be designed once and then mass produced by the thousands. This mass production is why they are hard to get new if you are a hobbyist or motor hacker.

Fortunately, the appliances and implements that these thousands of mass produced stators end up in are commonly available secondhand, for free, or as scrap.

Laser copiers and printers

My #1 favorite source for stators, as they tend to get junked by the dozen as departments and institutions get new equipment. Canon, HP, Xerox, and Ricoh tabletop copiers tend to be rich in 12 tooth stators in the 50 to 55mm range. In this case, older and bigger is always better. Project RazEr’s motor came from a gigantic (floorstanding, needs-its-own-room-in-the-office style) laser copier, which not only yielded the one large motor, but several smaller AC motors and a bucket of gears, shafts, and pulleys. Printing equipment is always a good bet for electromechanical components, though new units tend to use stepper motors, which are not suitable for conversion.

The largest copier motors I have seen (before they enter the realm of AC induction) have 70mm stators.

These things show up for free all the time on Craigslist, or free stuff drives at institutions. Electronic recycling stations are also worth a call.

Junky old DC and AC motors

Old motors with burned windings or worn out bearings get thrown out all the time. DC motors are hit-or-miss. DC motor armatures tend to get designed with odd numbers of teeth because the lack of symmetry contributes to smoothness. While stators with tooth numbers that are an odd multiple of 3 can be turned into motors, they cannot use the LRK winding.

Because DC motor armatures spin internally, they have teeth that project outwards, which makes them ideal for BLDC conversion if the tooth count is correct.

AC induction motors and especially AC three phase motors are usually good bets for useful iron, except they tend to be conventionally shaped. that is, rotor on the inside, stator on the outside. We want the opposite, but if you just want a motor, this is a good place to start.

Junky old motor includes junky old kitchen appliances, which often use a variant of the brushed DC motor called a universal motor. These tend to have 12, 18, or 24 tooth armatures, especially large multispeed blenders, usually under 50mm diameter.

You know how I said you can’t buy them? I lied. Hobbyists have recently become such a large market that a few companies actually make stock stators that are empty of windings and already surface coated to accept your own.

For the widest selection, see GoBrushless’ motor stators. Check out the 65mm, 18 slot one!

For the monetarily endowed, many shops specialize in short-run and prototype lamination cores, including the aptly-named ProtoLam. Be ware. just one stator made to your design can cost several hundred dollars, but if you’re just totally obsessed with rolling your own, the resource is available.

How large of a stator do I need?

Remember the torque equation

T = 4 m N B L R i

For most reasonable operating conditions, you can consider:

T to be a design goal. A goal for acceleration or hill climbing both require minimum force-at-ground figures, which translates to a torque at the motor.

N to be the primary variable you can control. This is mildly coupled to i, which is dependent on your battery voltage.

R and L are the parameters set by your stator. In a way, m is also determined by your stator. after all, it has a fixed number of teeth that have to be divisible by 3 for this type of motor.

B is is the strength of the permanent magnetic field that the stator acts upon, set by your magnet strength (and a mechanical factor to be discussed)

Clearly this is a multivariate optimization problem. If you have a choice of how large your stator can be, the answer is the largest. The more L and R you can pack into the expression, the less N and i you need. Remember that motor current i is the biggest contributor to heating and efficiency loss.

If your L and R are already set because you have a pulled stator and want to use it, then the only realistic variables you can fiddle are N and B.

Step 5: Magnets and Magnet Wire

Until now, I’ve just been hand-waving the existence of MAGNETS. End of story. There exist permanent magnets.

Yes, there definitely are, and you can actually spec and buy them according to your needs. The type of permanent magnet used in most small BLDC motors today are Neodymium Iron Boron chemistry magnets. They lie within a group of magnetic materials called rare earth magnets, because Nd is a rare earth metal. These are not actually all that rare, which helps explain why NIB magnets don’t cost you an arm and a leg.

Actually, back up. They can. NIB magnets can be so powerful that they leap across a foot or more or open air and slam together. if you are trapped in between, you could be in for a world of hurt. Everybody by now has seen the aftermath of someone’s hand being caught between two colliding 4 inch square NIB magnet blocks. I’m not linking that. As a tip for the future: Take extreme caution around magnets!

A typical NIB magnet is rated as Nxx, where xx is a number between 28 and 52 (as of this writing). The number is that magnet’s magnetic energy product. Without diving into EM physics, higher is better.

At a cost, of course. NIB magnets are notorious for being high temperature sensitive. The Curie Point of a permanent magnet is the point at which stops being a permanent magnet. No, they don’t regain their magnetism after they cool down. For ultra high strength NIB magnets, this could be as low as 80 degrees Centigrade (or about 150F).

That’s not very high at all. you can easily trash a motor by running it too hot.

Here’s a link that explains magnet ratings pretty clearly. The same person is also a reputable dealer of all sorts of magnetic mayhem.

A typical NIB magnet as used in a motor will have a remnant surface flux of 1 Tesla. If you get the Good Magnets, it is safe to assume that B in the torque expression T = 4 m N B L R i is equal to 1.

Hence, the equation reduces to T = 4 m N L R i.

The takeaway fact for magnets is that stronger is better until your motor gets too hot. It doesn’t hurt to have a stronger B-field. Getting the latest and greatest in N52 magnets can boost you B to 1.1 or 1.2.

I will address how to spec our your magnets shortly, but meanwhile.

Magnet Wire

A permanent magnet sitting there doesn’t do anything. It’s not very interesting to watch. What makes the motor work is switching electromagnets. If you’ve been through a physics class with any gusto, you’ve made an electromagnet out of wire and a nail.

Do not plug this into the wall like yours truly.

Each of the 12 teeth on the stator function as an electromagnet. From the same physics class, recall that for every turn of wire you wrapped around the nail, the electromagnet got stronger. Same deal with the stator teeth. this is why N is a factor in the equation.

So you can just make a 20,000 turn motor and be done with it, right? Sure, if you want to run 10,000 volts to actually push enough current through your windings to mean something.

There are a few constraints to consider when designing your windings. Magnet wire takes up physical space. essentially, given a set of space constraints, the more turns you want to wind, the smaller the wire has to be. This makes sense from a physical perspective. Eventually, when you use nanowires, you can have a 10 billion turn motor that packs all the slots to near 100% fill for maximum magnetic mayhem.

Except your motor resistance Rm would be astronomical. This is another constraint. Choosing the number of turns is a careful balance between getting the Km that you want but minimizing Rm. The motor resistance can only contribute to loss. It can only hurt you. Therefore, the goal of almost all hobby motor winders is to minimize the resistance.

This means using as few turns of the biggest gauge wire you can to get the Km that satisfies you. The One Wiki has a great table of AWG copper wire resistances.

Magnet wire comes in many flavors. they are all, at the end, conformally coated solid copper wire. This coating can be enamel, polyurethane, epoxy, or in exotic / high temperature motors, fluoropolymers and wound fiberglass sheaths. The cheapest grades are generally enamel insulated and will work up to about 150 degrees Centigrade.

By this point, your expensive N52 magnets would have vaporized already. unless you are dead set on taking your motor to the limits (which means this tutorial won’t help at all), don’t splurge on expensive HT wire.

Can you physically handle it?

Don’t underestimate the strength of a strand of copper. You might be used to 28, 24, or 20 gauge magnet wire, which is small enough to be negligibly soft. Maybe annoyingly soft. Now try bending a 16 or 14 AWG solid wire, which is pretty close to the thickness of a piano’s bass strings. Now imagine you have to bend this around a corner only millimeters in radius, possibly 100 times or more.

If you are having a hard time with one stand of monster wire, you can consider splitting it into equivalent parallel strands of smaller wire. RazEr’s motor was wound with double 22 gauge after I had difficulty wrestling 18 gauge around for 25 turns. Use the wire gauge table to compare diameters!

Step 6: Actually Winding the Motor

If you’ve never wound a motor before, the diagrams of LRK windings are probably pretty meaningless. This is a time when you need to learn the nomenclature of motor hobbyists.

An example would be the dLRK winding:

electric, scooter, motors, guide, know, real

What? Did you just sing the alphabet song or something? Kind of. The three phases of the motor are referred to in this case as A, B, and C.

A capital letter indicates one winding chirality, a lower case means the other. For instance, if A is designated make a loop of wire in the clockwise direction, then a means wind the loop of wire in the counterclockwise direction. And a dash or space means an unwound tooth.

The general convention is capital letter equals clockwise loop, lower case equals counterclockwise loop. But, what is more important is consistency. If you do it one way, stick with it.

So what does the above string of gibberish mean? Starting at any tooth (mark this as your index!), begin making loops of wire around it according to the designation. To wind two teeth Aa style, wind one of them clockwise, and the other counterclockwise (or vice versa. keep track of this.)

There is no right method to obtain clean windings, but the last thing you want to do is just bundle wires around the tooth with reckless abandon. For large motors, use latex gloves to ease hand abrasion and a wooden dowel to wrap wire around for extra leverage.

Unfortunately, I don’t currently have any pictures of video of me winding a motor. This might change in the near future to save a thousand words of explanation.

Perhaps one of the most valuable resources available is the Combination Table. Input your number of stator teeth (nuten) and your number of magnets (pole) and it will automatically generate the correct winding pattern! The above table was generated by one of the Crazy German R/C Airplane Dudes, who seem to be the source of all technological advancement in the model motor scene.

Single Layered, Multi Layered

You may find that you can’t get the N number you want by only winding one layer of wires on the stator. Simple solution: Keep winding and make a second layer.

Two to three layer windings are generally the limit of heating cooling unevenness for small motors, and the Rm gets ridiculous as well. As more layers are added, the end turn effect will become more and more of a factor.

If you find yourself having to wind many layers, perhaps switching down a size of wire will alleviate that.

How many turns (N) do I need?

The other killer question of small motor design. Given other motor parameters, you can backsolve easily for the minimum N needed to achieve a certain design goal, usually torque. Accounting for losses and assumptions, N should be above this number by a comfortable margin explained shortly.

Example(Updated 3/28/2012 to correct the math which has been wrong for over 2 years! I keep meaning to fix it, then never getting around to it. Ultimately, enough of you called me out on it, so congrats. Here’s the fixed math using also the new torque constant factor m).

Let’s say that I want to design a motor inside a 12cm (0.12m) wheel that will let me climb a 10% grade (or about 5.5 degrees inclination) at velocity v = 5 m/s (about 11mph), and I weigh m = 65kg. The force of gravity F pulling me back down the hill is

F = m g sin 5.5° = 61N, or thereabouts. I

I want to climb the hill at 5 m/s. Mechanical power is torque rotational speed, but it is also linear force linear velocity.

Thus Pm = 61 5 = 305 W

Seems reasonable, right? Assume the motor is a perfect transducer (it’s definitely not). The electrical power required is also 305 watts.

Assume my battery is 28 volts, so i = 305 W / 28 V = 10.9A

To exert a linear force of 61N at a radius of 0.06m (wheel radius), the torque T is 3.66Nm.

Two variables, T and i, have now been established. The motor is a 12-tooth, 3 phase motor, so m is 4 (there are four teeth per phase). You can now reduce the equation to

T / (4 m i) = N L R B

R is ultimately limited by the size of my magnet rotor and inner diameter of my tire. a topic which is forthcoming. Let’s say that my wheel choice has forced a maximum stator diameter of 70mm, and the motor can’t be more than 30mm wide to fit in my vehicle.

B is my magnetic field strength. Let’s assume it is 1 Tesla for now. we will see soon that this is not a bad guess if your motor magnets are reasonably thick.

T / (4 m i L R) = N

Let’s see what this comes out to.

3.66 / (4 4 10.9 0.03 0.035) = 19.98 = N

This value is a reasonable first approximation for the number of turns per tooth you need. Since hundredths-precision turn fractions aren’t possible, take the closest integer: 20.

Fiddle Factors and Hand Waves

Every nonideality and inefficiency in the world will work to make your motor faster (read: less torquey) than what the number of turns alone would indicate. Therefore, it is good sense to consider this as the absolute minimum number of turns per tooth. The torque constant value derived from using NIBLR is generally 20 to 33% too high for average fractional-slot, permanent-magnet motors like the type we are considering.

Remember also that motors are not perfect transducers. The average efficiency of a decent BLDC motor is somewhere around 90%. So, if I want to perform this hillclimb at maximum efficiency, that’s much different than attempting it at maximum power output. The efficiency of a motor at maximum power output is always less than 50%. This is something to be well aware of. if you are using this ‘target output force’ method to design your turn count, then you should take the speed to be somewhere close to your anticipated cruising speed. This makes sure that, if anything, you overdesign the motor for torque as nonidealities only take it away from you.

The above motor example is the motor for Project RazEr. In actuality, RazEr’s motor has 25 turns per tooth. overspecified by roughly 25%.

To wrap up, R and L are mechanical constraints dictated by your vehicle’s mechanical parts while m, B, N, and i are electromagnetic constraints dictated by your choice of magnets, wire, and coil layout.

Step 7: Magnet Layout and 2D Design

What were we talking about? Oh, yeah, hub motors. With a preliminary electrical specification for your motor, you can now proceed onto the early stages of mechanical work.

By now, you should have stator dimensions available to you. The goal of magnet rotor layout is to size 14 magnet poles to fit around the stator until you have enough information to spec out or purchase magnets.

The process is constrained bidirectionally. The minimum diameter of your circle of magnets clearly has to be larger than the stator. However, you may find yourself additionally constrained if you have already picked a wheel. Then, the maximum inner diameter you can use on your wheel tire becomes the other mechanical constraint: your magnet circle’s outer diameter plus a certain can thickness is limited by the wheel.

Using online tools

It used to be that you had to whip out a calculator and a pencil and hash out some serious trigonometry to lay out the magnets, or use a 2D computer aided design program. or, if you have machine shop access, just making the motor can bigger until it fits. Below is an image of my initial layout for Razer’s motor in Autodesk Inventor’s sketch environment.

Rotor design tools have now emerged on the Intergoogles. The most prominent of these is the GoBrushless rotor calculator, which conveniently packages all the layout into a form. Heck, it even draws what your rotor will look like. Let’s go over what the terms on the page mean. All dimensions are millimeters:

Stator Diameter: The maximum outer diameter of your stator.

Rotor Diameter: The minimum INNER diameter of your rotor

Magnet Width: Assuming square magnets, how wide your magnet is.

Magnet Thickness: How thick your magnet is. A magnet you would select for your motor is almost always going to be magnetized through its thickness.

Magnet Poles: How many magnets there are in total. There are going to be a multiple of 14.

The Air Gap(Updated 28 March 2012 to include air gap factor for the magnets)

The one thing I left out of the above list is Air gap, because the subject warrants its own discussion.

The tightness of your air gap determines how much of the magnetic field is linked to your stator. The EM term is coupling. A tighter airgap yields better coupling between magnet and stator. You know why the B rating of the magnet is called remnance? Because that’s how much field remains at its surface if the magnet is in open air, with no magnetic materials to surround itself.

A motor is a magnetic circuit, and there are a whole set of laws that govern them. For practical purposes, it boils down to the more coupling you can ensure in your magnetic circuit, the stronger the field in your airgap. The Gap Factor equation is:

Ba = B0 (t / (t g))

where t is the thickness of the magnet, g is the radial thickness of the airgap, and Ba is the flux density at the surface of your stator. This is the flux that will actually generate torque, so really it is the value that should be used in the NIBLR equation! B0 is the surface remnance rating of your magnets. for high N grades like N48 and N50, this could be as high as 1.3 to 1.4. But if your airgap is loose, or the thickness of the magnet is small compared to the gap, then you will lose a substantial fraction of it before the stator radius.

For example, if you have type N42, 3mm magnets but a 1mm airgap, the multiplier is 0.75! That means the B value you thought was close to 1 (since N42 magnets have roughly 1 Tesla of remnance) is more like 0.75. This can really throw your motor design and make it clock high speeds (thus less torque) than you expected.

Now you see why you can’t just glean the first torque equation off the intro page and be done. The updated torque equation is:

T = 4 m N B0 (t / t g) L R.

So, the tighter the airgap the better. to a limit, as with everything. If you are running tenths of millimeter airgaps, you had better be well-versed in machining, or have a computer controlled machine do it for you. Wobble in your can from machining tolerances and irregularities can throw off your airgap measure and could cause your magnets to collide with your stator!

I try to shoot for an airgap of 0.5mm or thereabouts. 0.4, 0.6, whatever. The wide the airgap, the more fiddle space I have if something turns out to not fit correctly.

Magnet fill percentage

This describes the fraction of the rotor circumference on the inside of the magnet ring that is occupied by the magnets. This number should be somewhere between 75% and 95%, generally. Square magnets can never achieve 100% fill unless you are truly lucky. Numbers below 75% will hurt torque and efficiency because the B-field in the airgap becomes irregular.

Oddly enough, very high fill percentages actually have a slightly negative effect towards motor performance, because the magnets become so close together they leak to eachother. The effect is minimally noticeable for low speed hub motors, however.

While fill percentage isn’t calculated on the GoBrushless rotor designer, you can easily calculate it by

Fill = (14 k Magnet Width) / (pi Rotor Diameter) using consistent units, like millimeters.

What’s that k I stuck in the equation there? Another random constant to keep track of? AAAAHHH

Not really. Let’s say you can’t get good fill and an acceptable airgap number using single-piece square magnets, and you can’t change the rotor diameter.

It is allowed to use two smaller magnets side-by-side to emulate a single large magnet. This also has the advantage of better conformity to the round walls of the rotor. Smaller magnets are a better approximation to the game of squaring the circle. The less your airgap deviates from the average, the less torque ripple your motor will exhibit.

Hence my reference to multiples of 14 earlier. GoBrushless’ rotor designer will space all the magnets out evenly, but as long as they fit evenly, there is no reason you can’t group them into larger metamagnets, as seen in Figure 3 below.

In the extreme case of RazEr, I used four mini magnets to make one magnet pole. Two side by side, and two rows deep. The fill factor was incredibly close to 100%!

Magnet Length

Up until this point, your design has been exclusively 2D. Once you get the profile of the magnets right, you need to make sure they are available in the correct length.

The magnet length can be fudged a little. Optimally, the magnet length is equal to the stator length (L). That is because the steel in the stator is what focuses the magnetic field generated by the motor windings into the magnets. Shorter magnets will result in suboptimal performance. try to avoid this, because part of the stator field will be essentially shooting off into empty space.

It is also not advisable to spec out magnets which are too much longer than the stator. This causes interaction with the end turns of your windings, which is undesirable. A small amount longer, such as the next millimeter or two up in order to achieve a stock magnet size, is fully acceptable.

In RazEr’s motor, I had a 35mm wide stator, but no 35mm magnets. I thus spec’d out for twin 20mm magnet stacks, which brought the magnet width to 40mm. I decided to live with the stickout, so to speak.

Rotor Thickness

One of the constraints you will face is the OD of the rotor. In the best possible situation, the ID is set by the magnets and you have free reign over the outside. However, if you already have your prospective wheel and tire picked out, you might face limits here.

This is problematic because you cannot make the rotor can too thin in the walls. Not only does structural strength suffer, but the magnetic field of your permanent magnets won’t be properly contained. If it leaks out, then the airgap field strength B will suffer, because what goes out of the motor doesn’t come back in, so to speak.

The rule of thumb is to make can more than one half the magnet thickness. Going under this will cause quick flux containment loss. It does not hurt to go over. in fact, if your rotor is very thick, it can actually be part of the motor structure. Most commercial hub motors for bikes and large (road-legal) scooters and mopeds are made in this way. The only potential downside to a massive rotor is weight.

Step 8: Mechanics and Materials

Now we’re getting to the mechanical design. Let’s lay the ground rules for what you might need or have access to.

Rotor Material

Your magnets would like to be contained in a material which offers low resistance (reluctance) to the magnetic field, and also does not magnetize itself permanently in the presence of the magnets. Many high performance alloys of nickel, cobalt, iron, and trace metals have been invented to optimize the magnetic properties of a motor. They’re expensive, require specialized heat treatment, and even specific machining processes to conform to the geometry of a magnetic machine.

We’re not going to bother with that. The most common rotor material for hobbyists is just plain steel tubing. It does a good enough job, and the best part, it’s cheap and readily available. I will list sources of steel tubing in the Resources section, but as a general rule, the tubing you purchase should be:

low carbon or mild steel. High carbon and heavily alloyed steels have significantly worse magnetic properties.

seamless or at minimum DOM style tubing. This is the majority of steel tubing, but keep an eye out regardless. DOM tubing has a more uniform wall thickness and no ugly weld seam to affect the roundless. It is generally made to tight tolerances. Avoid cast iron pipe.

plain finished. A precision ground or machined and polished finish will not do you any good unless it’s already precisely the diameter you need.

Oversize (OD larger than your rotor’s outside diameter) AND undersize (ID smaller than your magnet mounting surface) so you can machine it to suit and not worry about hitting the limits of your materials’ physical manifestation.

Since the only thing which has to support a magnetic field in your motor is the rotor, the endcap and other structural elements only have to be mechanically sound. That means you have way more choices here. Generally, it’s some kind of nonferrous (not steel) metal.

Aluminum is the number one choice. It’s light, strong, easy to machine, and common. Not exactly cheap in big, however.

Plastics! Engineering polymers such as nylon, polycarbonate, acetal, and polyethylene in high density and high molecular weight varieties all exhibit high strength and lightness. Plus, plastic machines like. well, plastic. Easy to shape, especially if you are new to machining.

Some plastics let your motor have the magical see-through effect. The BWD Scooter uses Lexan (polycarbonate) side plates so you can see the robot in disguise.

If you are into that stuff, you could conceivably craft endplates out of fiberglass or carbon fiber panels. The ultimate in light weight and stiffness, but be aware of the fact that you have to attach it to the can somehow. This will be addressed shortly.

Center Shaft Material

The most important trait of the shaft is that it can’t bend. I’ll address shaft design shortly, but you should expect to make the shaft from some kind of metal. Larger hub motors use steel, smaller ones may be aluminum. I used an aluminum shaft on Razer’s motor for weight savings and ease of machinability.

Aluminum should be limited to the aircraft alloys: 6061, 2024, 7075, and similar. These offer higher strength than other aluminum grades.

You can get away with a mild steel shaft such as the low 10xx alloys (e.g. 1018, 1020), but if you are already using steel, moving up to a medium carbon or alloy steel shaft wouldn’t hurt. Very low alloys (1006 and similar) do not machine well. they are actually too soft to finish machine finely.

Let’s be honest: a motor is a precise alignment of opposing magnetic fields. Invariably you will need access to machine tools to make them. Unless you are very crafty with your shop drill press and Dremel and can make things conceptric to within 5 thousands of an inch (0.005, or around 0.1 millimeters!) constructing the endcaps and rotor (and shaft, and stator mount. ) will require access to.

A metal lathe. Not a wood lathe, where you hold the tool yourself, but a metal lathe. If you have made it this far, I assume you know how to operate such a machine already, because giving machining lessons over Instructables is slightly troublesome.

You will need the ability to precisely bore an inner diameter. Boring bars, or something which can function as them, are a must.

A milling machine, or at minimum, a drill press with X-Y table and fixturing indexing abilities. This can be a full size Bridgeport or similar, or a miniature hobby mill like those found at Harbor Freight. Basic tooling should be available. You should have a spindle drill chuck to precisely drill holes with at the least.

Some kind of vise. Handy to have for pushing in bearings and cans, and also for holding the stator while you wind it! Extra leverage will only help in winding.

Measuring calipers, micrometers, dividers, etc. Because several parts need to fit closely with one another, you must have metrology tools. I get by with a single digital caliper.

Step 9: The Center of the World

Your entire motor revolves around its center shaft.

Inside-out motors like hub motors have the advantage that their shaft is actually stationary. It is also the only mechanical connection to the outside world, because. well, everything else is moving around it. So, the shaft must be stout and resistant to deformation or bending. An off-axis, bent, or otherwise incorrectly constructed used shaft will cause wobble, stress the bearings, and with your weight on it, could exceed the strength of your fasteners.

Single Supported vs. Double Supported

There are two top-level arrangements, and they have some implications with respect to vehicle compatibility and shaft design.

overhung, single supported, or car style. The most common style for large hub motors, like those used on. cars. Only mounted on one side. The shaft is thus used in bending. Shafts and bearings for motors of this style need to be much thicker and stronger to avoid damage than.

double supported, or bike style. The most common for small hub motors. The vehicle weight bears down on both sides of the stationary shaft, and the bearing loads appear between these two points. For short distances between supports, the shaft is used in shear. This is a better arrangement for stiffness, but its not as serviceable because the motor is surrounded by vehicle on both sides.

I will FOCUS on double supported shafts for now, since the single supported designs are quite literally just half of the former.

Single Bearing vs. Double Bearing

Uh oh. There’s even a distinction here? Yes! The rotor assembly can be supported only on one side, that is, one endcap, or have two endcaps and be fully enclosed.

Single bearing systems represent the vast majority of your average R/C outrunners. While most of those use a live shaft, the principles are the same: the rotor is supported only on one end, and the other is open to air.

Besides exposing the internals of your motor to weather and debris, knowledge of some intermediate mechanical engineering principles is needed to correctly design a single-bearing system. I will not consider single bearing motors, because they are mechanically less durable than an equivalent sized double bearing motor.

You CAN have a single bearing motor with double frame attachment, but then it’s just pointless, no?

Double bearing, or two-endcap rotors are what essentially all production hub motors are. Even if they are single-supported (car style), there is still a front endcap and a rear endcap, both of which hold bearings. These provide the idea symmetric loading that prevents rotor deformation and magnet-stator collisions.

General overview of shaft design

Refer to Figure 1 for a basic cross sectional diagram of a generic hub motor center shaft.

the External Mounting Surface is the main means of attachment to the vehicle. This may be an externally threaded bolt-like protrusion, or a square clamping surface, whatever. This may not be present in compact motors, but are almost always found on bike-style motors, because they are designed to drop right in place of the nonmotorized rear wheel.

the External Mounting Clearance is a shoulder to provide spacing between the vehicle frame and the rotor surfaces. May or may not be the same physical diameter as.

the Bearing Seats are precision-machined surfaces onto which the motor bearings are fitted. Tight tolerances (1 to 2 thousandths or less!) are required for proper bearing use.

the Internal Bearing Clearance serves as a backstop for the bearings so they cannot shift axially.

the Stator Mounting Surface may directly couple to the stator, or can support a hub or other mechanism to retain the stator. Generally the largest diameter the shaft occurs here.

the Internal Mounting Surface performs the same function as the EMS, but is on the interior of the shaft. This typically takes the form of a threaded hole into which you can tighten a screw against the vehicle frame. Any practical combination of EMS or IMS features can be used. this is a matter of design.

However, there is one very important aspect of internal features that you have to be aware of.

Getting the wires out

Without an electrical connection to the outside world, your motor cannot operate! At the minimum, you need provisions for running three heavy gauge wires out from the internals of the motor. If you plan on using Hall Effect sensors, this could increase to eight total wires: 3 large and 5 small signal wires.

Most generally speaking, two methods exist for running conductors to your windings:

Through the shaft center. The shaft is hollow, and the motor mounts using external features. This requires drilling out the center of a shaft while remaining concentric and on-axis. A cross hole or slot is drilled internal to the motor, usually near the stator mounting surface, to bridge the interior of the motor with the outside. Then, wires are run through this center hole.

Besides the shaft. In RazEr’s case, I elected to use this method of cutting a small keyway (actually a flat) and just running the wires out through it. While easier, this method causes wires to run very close to rotating surfaces, and also means that a section of the motor bearing has no shaft contact. This is mechanically suboptimal.

Examples of each method are in figures 3 through 5 below.

Yeah, I know, we have to talk about this eventually. The fact that you have to provide enough space to run cables means the motor shaft cannot be too small in diameter. Small diameter shafts are also nonconducive to stiffness.

For hub motors, the old adage rings true: Bigger IS better. Use the largest diameter you have available to you, or the design allows!

Both iterations of RazEr’s motor used 15mm diameter shafting. I found this adequate for the roughly 2 inch span they had to bridge.

Shaft size directly correlates with what bearings you can use. Speaking of bearings.

Step 10: Get Your Bearings!

Smooth bearings make a world of difference for an electric motor. In a hub motor, they are even more important, because they have to support the full weight of a vehicle whereas a standard indirect drive motor might only have to put up with chain tension.

General Bearing Knowledge

In all likelihood, you’ll end up using miniature metric single row deep groove ball bearings in your design, because they are the most common types around. Such bearings are rated using the 6000 system.

Bearings are rated by their Dynamic Radial Load Capacity. Dynamic means moving, and radial load is any direction orthogonal to the shaft axis. which is to say, any way you can think of loading it. Ball bearings are generally not rated for Thrust loads, which are coaxial to the shaft.

An average 6001 type bearing has a 12mm bore, a 28mm outer diameter, is 8mm wide, and has a DRL rating of about 1000 pounds. That might sound like alot, and it is. if your application is applying constant loads with little to no shock, like in an industrial motor running a pulley or something. This is never true for hub motors.

What kills ball bearings is shock load. You hitting a pothole, the sidewalk, a small animal, etc. Even just sidewalk seams can exert impulse forces of thousands of pounds for a fraction of a second. Force is proportional to acceleration, and hitting something solid imparts very high accelerations into the colliding masses. Bearing failure is called by brinelling, or the balls putting divots into the bearing races from shock loads. This results in the crunchy bearing sound.

In the worst case, you can deform or shatter a ball, and your bearing usually seizes up. Hence, it never hurts to use the biggest bearings you can design into the motor. The above 6001 bearing is a good choice if you don’t mind the limited shaft diameter.

Thin Profile Bearings

The 6800 and 6900 series describe thin section bearings which have a minimal difference between the bore and the OD. Bigger ones are some times called ring bearings.

They are convenient because they offer large shaft diameters, good for wire clearance, but without being excessively large in outer diameter or width. After, you don’t want your bearings eating up all the precious space between your mounting surfaces.

However, the 6800 and 6900 series are thin section for a reason. They are designed for very light loads. The minimal difference in the outer and inner dimensions means that steel thickness is sacrificed for space saving. These bearings usually have DRLs no more than a few hundred pounds.

Yeah, that still sounds like alot, right? But the steel outer and inner races may be just two or three millimeters thick. Thin section bearings brinell easier than their beefier brethren because the thin steel races have less resistance to forceful incursions, like an overloaded ball.

I would caution against using the 6800 series at all. The 6900 series is slightly heavier in construction and represent a good intermediate between ring bearings and normal bearings.

For instance, a 6802 ball bearing has a 15mm bore and is only 24mm across. A 6902 bearing has the same bore but is 28mm in diameter, and has over twice the rated load in general purpose ABEC-1 style. Peace of mind for 4 more millimeters?

Sealed or Shielded?

When spec’ing out bearings, you will often find them in myriad flavors, regalia, and trim levels. The question usually boils down to open, sealed, or shielded?

Open bearings are open to the air. There’s nothing covering the bearing races from dust, grit, and contamination. They also cannot retain lubricant. Open bearings will be destroyed very quickly in hub motor duty. You find these more inside motors or engines where they’re bathed in oil and enclosed from the outside.

Shielded bearings are the next level of grime protection. A thin metal shield over the ball races keeps out most everything. However, metal shields do not contact the inner race, so over time, things still do get in. These are by far the most common ball bearings, though, because they represent a good compromise.

Sealed bearings use a rubber seal to accomplish the same goals with more security. The downside of a sealed bearing is more free-running drag, because the rubber seal rubs on the inner race as it moves.

If I had a choice, I would just go with sealed bearings. The price difference between them and shielded is usually minimal, they retain lubricants better, and generally speaking, metal shields can be deformed or damaged easier than a flexible rubber seall

Bearing fit Ball bearings are precision devices, and thus need precision to be correctly mounted and used. Never use a hammer or mallet to install ball bearings. If they do not slip in, use a proper arbor press! Even a vise is better than nothing (and no, I don’t mean vise grips).

Bearing installation must be straight (not crooked) and the difference between the bearing’s OD and your mounting surface’s bore should be less than 1 thousandth of an inch. That’s 0.001 inches, or.02 millimeters. That’s really precise.

Too tight fits will cause crunchiness and a hard to turn bearing. Using the bearing like this can destroy it quickly.

Loose fits, if under 5 thousandths, are generally rescuable using a retaining compound such as Loctite 609. Very loose fits are not recommended at all.

Step 11: Boundary Conditions for Your Motor

We have reached the last and most important part of the motor: the endcaps.

Okay, I lied. EVERYTHING on your motor is the most important, but this one is the MOST important!

The motor endcaps are what bridges your motor shaft and the rotor can. Because they are large in diameter and disc shaped, they are often the most difficult parts to get right on a motor. They have to stay concentric and without axial wobble. Usually, they’ll have rotor attachment features machined in them too.

Referencing figure 1 on the bottom, there are a few characteristics of every endcap design.

The Bearing bore is a precisely machined surface, that is, /- 0.001 or less, into which the bearings fit. Usually, this is a press fit, but can be a tight slip fit if one side needs to be removed for servicing.

The Bearing shoulder might or might not be present. If it is, it’s usually just a small extension that brings the thickness of the bearing bore to the width of the bearing. It might not even be needed if the bearings are press fit into the bore. It can be on the outside or the inside.

A winding relief cut is usually made so the magnet wires bulging out from the stator don’t interfere with the rotation of the endcaps. If your motor is sufficiently wide, this is unnecessary, but space-constrained motors like my scooter motors needed the endcaps to sort of conform around the stationary internals.

Making the winding relief results in a dish-shaped endcap.

Can mounting surface and provisions. The surface is the broad cylindrical face that mates with the magnet can itself, and provisions is just my term for describiing how the can is held in place. Regardless of how the can is physically mounted, the surface itself should be smooth and well fitting: unless you are purposefully going for the permanent press method, leave this a smooth slip fit, which indicates a diametrical difference of.002 or less.

In terms of how to actually mount the can, there are a few approaches. Shown in Figure 1 is radial threaded holes which go through the can and into the endcap.

Shown in the other pictures of my scooter motors are axial holes which either let me bolt through the can or around it.

Through-can axial screw holes, which make the can itself structural, are the most common method for large bike and car motors. If you have the space available, it is also the strongest!

The BWD scooter is a great example of through-can axial screw mounting. The endcaps also prominently feature an external bearing shoulder.

You have the option of integrating wheel mounting facilities into your endcaps, which is what I did for RazEr. Speaking of which.

Step 12: Wheel Mounting

Hey, since this IS a hub motor, there ought to be a way to mount a wheel on it or something. You might have picked a wheel out already to build your motor within, or are building the motor to eventually mount a tire to.

Let’s clear up some terminology first. The tire is what contacts the ground. The rim is what the tire is mounted to, just like in a bike or car. The hub is what the rim mounts to. We are building a hub motor.

It is perfectly reasonable to integrate rim and hub in a small motor. We will see that the integration was my choice for RazEr.

Wheel mounting generally comes in one of several flavors, just like everything else. The exact method you might end up using depends strongly on your available space and existing wheel specifications.

Car style. The hub is distinct from the rim. If you literally are building a hub motor for a car (why are you reading this?) then it offers the most flexibility in terms of wheel placement and choice. Welded or stamped studs usually emanate from one endcap so you can mount the rim.

Bike style. In the case of bicycle motors, the rim is still distinct from the hub, and radial spokes emerge from flanges on the case of the motor, usually the endcaps.

Scooter style. A degenerate case of the bike motor, the rim is small enough to be directly bolted to the endcap projections. The rim is still distinct and removable.

My style. Illustrated below in Figures 2 through 4, this just puts the tire (in my case, a chopped and screws push scooter wheel) directly between the endcaps, sitting on the motor can. Not serviceable without removing a motor endcap, which really constitutes taking apart the motor. Thus, RazEr’s motor isn’t very suited for public release.

A modified version of chuxx0r style is removable rings that are logical (but not physical) extensions of the rotor endcaps, which are now completely inside the can, and attach using radial screws. This means I can undo one of the rings, slip the wheel off, put a new one on, and reattach everything.

Just glueing rubber to the outside of the can. Yeah, it can be done. You’ll make steamroller tires and you better be sure the glue is strong!

Wheel gutting

If you’re building small motors like me, it’s usually hard to find just a tire for the motor. You’ll have to cut it out of another wheel.

This is a tricky machining operation because you can’t fixture to rubber tires- they’ll just deform. If you can securely clamp the wheel to a machine surface, then by all means, cut away.

If the wheel is sufficiently small, you can use a machininable fixture collet on a lathe to grip the entire outside at once. That will usually gain enough stiffness to let you cut the center out. These things are made up to 6 inches or so for common, import-grade fixtures.

Make a mandrel that bolts through the center of the wheel. Now you have the wheel secured by its strongest point.

Casting your own tires

Certainly an option, and for the truly hardcore DIY addicts, the most productive. I have no experience with urethane or rubber casting, so can only tell you to read Instructables more.

Step 13: Fabrication Notes and Conclusion

That’s it. I have just written 12 Instructable pages without actually telling you how to build anything. I think few can beat that.

This is only intended as a guide and primer on what you could do. I did not include directions on how to fabricate one specific motor because it assumes too much engineering knowledge to tell someone to follow my lead, at least in my opinion. In a future Instructable, I might go over the specifics of building RazEr’s motor. But, in the interest of modularity, I elected to keep things separate this time.

Maybe you guys can take up my slack by talking about how you made your hub motor!

What I can do now, though, is put in a few fabrication notes for when you embark on your hub motor adventure.

The elevator pitch in terms of motor design here is to stuff in the strongest magnets and the largest stator using as many turns of the largest wire running across the highest voltage battery you can get your hands on. Maximize ALL of N, R, L, i, and B. But wait, I thought earlier you said as few turns as possible was the best? Not necessarily: I said that just enough turns to get a workable Km contributes to lower motor resistance. There is no need to constrain yourself to low turn numbers. In fact, high turn numbers running at high voltages are almost always better than low turns and high current!

Use a good high temperature 24 hour epoxy to glue the magnets in. Cheap hardware store 5 minute epoxy has inadequate time to set, and the chemical crosslinks are not nearly as strong. Thin laminating epoxy (for fiberglass and carbon fiber layup) is recommended, with a microsphere filler. The filler shortens the working time of the epoxy, but causes it to be stronger and more tenacious.

Speaking of gluing the magnets, you may notice that they have a tendency to snap towards eachother in your can. To avoid this, cut up some popsicle sticks into wedge shapes and push them into the gap to separate the magnets.

GoBrushless’ rotocalc also generates a magnet placement guide image. Print this out at full scale on a piece of paper and perform your magnet gluing over it.

As long as you have machine access, make jigs and fixtures to help you glue the magnets. Try not to let them float as you’re gluing.

While on the subject of epoxy, sealing your motor windings with high temperature enamel or epoxy will keep them together (prevent unraveling or jiggling) and make them more heat resistant. Do this AFTER you make sure your motor works and winding is correct.

Never wind wires on a naked stator. The metal edges will pierce the magnet wire’s thin enamel coating and result in a phase short to the core. You are bound to make more than one, so the phaes will short to eachother!

If you cannot avoid winding on a bare stator, liberally apply heatshrink or electrical tape to the inside corners of the stator, and wind carefully. If you create a short, you MUST rewind that phase.

Pull your wires tight. Loose windings are more likely to be damaged, and they are longer than they need to be, so your motor has extra resistance.

Insulate, insulate, insulate. You have wire running past high speed rotating surfaces which will abrade the insulation if allowed to rub.

Use a good, flexible wire. Silicone high strand count (HSC) wire, including the popular Wet Noodle from W.S. Deans, are the best choice.

Use high quality hardware. On Razer’s motor, I made the mistake of using stainless steel screws because they were cheap and already at the hardware store (instead of ordering high quality socket head cap screws). Bad mistake. they sheared and stripped one by one, leaving the motor wrecked.

A Note on Motor Control

BLDC motors can either be sensored or sensorless.

Sensored motors have Hall Effect sensors which react to magnetic fields. There are at least three of them inside your average sensored motor, and they function as a very crude position encoder. A sensored motor controller reads the state of these sensors and correlates them to the position of the motor through a lookup table. It then outputs the proper voltage levels to the motor according to this state table. This is called Space Vector Modulation.

Yours Truly has build a fully hardware (logic chips, op amps, no microcontrollers) SVM motor commutator for a class project. And it actually worked.

Sensorless motors are operated by controllers which sense back-EMF. Remember from the page about DC motors and their ability to be used as generators? Every time the brushless motor moves, it puts out a sinusoidal (or trapezoidal) waveform on its 3 connections. A Smart controller can actually read these voltages and have an idea of which direction the motor is traveling. It can then sequence its output to encourage the motor to keep rotating, generating torque.

What is the difference? One has 3 more parts and the other doesn’t?

Sensorless motors cannot operate from standstill unless the controller is very sophisticated. If the motor is not moving, the controller has no way of know where it is. There do exist controllers which can sense motor position based on the effect of the motor’s magnets on the phase inductance. However, those are ungodly expensive and are a new industrial technology (which makes them even more expensive.

Hence, if you keep your motor sensorless, you may find yourself kick-starting your vehicle.

The vast majority of inexpensive R/C airplane motor controllers are sensorless.

Sensored motors can operate from 0 speed, but require a controller that can read them. These tend to be more expensive than their sensorless brethren.

Additionally, if you add sensors to your motor, you have to place them in the correct spots. Hall sensor placement is a quasi-nontrivial process that requires knowledge of the motor’s electrical slot ratio.

Two popular Hall Sensor placements exist: 60 degrees and 120 degrees. I glean over this on my website, but the degrees refers to how many electrical degrees apart the sensors are.

To place Hall sensors properly in your motor, you have to know how many electrical degrees each slot (or tooth) occupies:

°elec = 360 p / t

where p = number of pole pairs. For a LRK motor, this is 7. Likewise, t, the stator slot count, is 12.

For a LRK motor, the electrical degree of one slot is 210 degrees.

Now that you know the °elec of your motor, you can technically place the first sensor anywhere. Let’s call this the A sensor. I have just wedged it between the Aa winding of the first phase.

You must place the B sensor in a slot that is °elec ahead of sensor A. This may or may not actually end up in the middle of a slot, and it is an iterative process. Each slot is 210 electrical degrees, so start adding. Begin at 0 degrees, the position of sensor A. Keep track of the number of times you add, wrapping around 360 degrees for each result, until the result is equal to 120.

1) 0 210 = 210. No need to modulo 360. The number of additions is 1.

2) 210 210 = 420. Subtract 360. The result is 60. The number of additions is 2.

3) 60 210 = 270. No need to modulo 360. The number of additions is 3.

4) 270 210 = 480. Subtract 360. The result is 120. The number of additions is 4. You win.

Thus, sensor B should be 4 slots away from sensor A, and sensor C a further 4 slots away.

Conveniently enough, in a LRK motor, a 120 degree hall sensor placement actually results in the sensors being physically 120 degrees apart. Isn’t that awesome?

Sensors complicate the wiring issue because you need at least five more wires: Logic power, ground, and the three outputs A, B, and C.

However, I believe that sensored motors (or the wacky inductive sensorless jiggymabob) are the best for small EVs. And EVs in general. They allow you to take full advantage of the massive torque capabilties of BLDC motors by using them at 0 speed!

DIY electric vehicles are fun and exciting, as well as a treasure trove of learning opportunities. Engineering your own motor is no small feat, especially one destined to be operated in a vehicle of your own design.

Here’s hoping that future regulations over the nascent electric vehicle industry and laws over their operation grant amnesty to, or even encourage, DIY mechanics, hobbyists, and experimenters.

The virtually rendered motor seen in the opening page is a motor for my next crazy EV project: Deathblades. I’m aiming to do what alot of people have been peer pressuring me to do, and drop RazEr’s technology into some foot trolleys of certain head trauma. See my YouTube page for a snazzy animation of how the hub motor goes together. If you’ve been confused by my thousand-word explanation, this should help clear it up!

If you’ve never seen RazEr in action, check out its test video here.

I’ll be updating, editing, and changing things around as I go, so if you see any glaring omissions or errors, absolutely point them out to me!

And good luck. See the next page for a list of resources!

Step 14: Resources, Links, and Knowledge Base

GoBrushless These guys mainly deal in small aircraft motors, but their rotor designer is a godsend. They also sell stock stators in the 50mm and 60mm size range.

Super Magnet Man Reputable dealer of stock AND CUSTOM! neodymium high strength magnets. All of my motor magnets have come from him. George is a friendly person to deal with and chock full of all kinds of magnet information.

Custom magnets from George generally take 3 to 4 weeks to manufacture and are priced only slightly above stock magnets. This is absolutely phenomenal: For a bit more cash, you can have a full circle of magnets customized to your motor.

Protolam These guys supplied the iron for the BWD Scooter gratis. They have in house punches and LASER cutters and will make small quantities for your experimentation

Your local motor shop Got a local electric motor rebuilder? Give them a visit. They’ll be glad to see a motor which doesn’t require a forklift and 8 guys to handle. High-grade magnet wire and potential harvestable motors.

A certified legit hobby products dealer out of Hong Kong. Mind-blowing pricing on everything, and they make no attempt to hide the fact that their products are Chinese in origin. You can put together an entire EV hacker powertrain just from the parts on this site. Stock up on lithium batteries before the Fed regulate bare Li packs out of existence.

Their large outrunner motors are inexpensive enough to consider cannibalizing for stators.

I shouldn’t even have to mention these guys. If you can think of it, they probably carry it, else it’s not worth buying. Magnet wire in huge and holy crap gauge, raw materials, bearings, adhesives, and hackable wheels are just a few motor-relevant things I can think of that you can find there.

Purveyors of fine (Chinese) motor controllers in sensored, sensorless, both, and neither (DC). Their KDS line of mini-controllers will be perfect for your small sensored hub motor. You can also be lazy and just buy one from them.

Because all legit bearing manufacturers have 3 letter names. Inexpensive bearings for your motors. I’ve gotten all my bearings for everything I’ve built from here. Everything I’ve built since discovering them, that is. Speedy Metals

Where I got my Giant Steel Death-Tube from for Razer’s motor. Get raw materials for the mechanical structure of your motor here.

Contains one the best brushless motor primer I have seen. Electric Motors part 1. 5 is worth a read to get more background on the matter.

Everything I just said and more wrapped up in a handy spreadsheet style calculator! Forget 4 N B L R, it will give you everything from back EMF profile to torque ripped to phase voltages and inductances. To use it properly, you MUST know critical dimensions and materials of your motor. But it’s about as close as you can get to building it and throw it on the dyno.

This site is a veritable platinum mine of motor information and theory. if you can read German. Alot is lost in translation if you use an automatic translator, so find your nearest German guy and press him into service? Dr. Okon is the progenitor of the famous and useful Kombinationstabelle.

Always welcoming of newcomers and people with questions. The Crazy German R/C Airplane Guys here represent a vast majority of all motor limits-pushing that has occured in the hobby.

Learn more about the background of the LRK winding here.

Not to be one to self-plug, but I have a bad good habit of keeping detailed build logs about EVERYTHING. Documented are all the rebuilds of RazEr, its predecessor Snuffles, and my most famous creation, the LOLrioKart.

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6 Комментарии и мнения владельцев

Thank you very much for all the applications you have provided to us, and we all benefited from them, especially me. I hope you are always in constant bidding. Is it possible for you to help us in designing a motor like this?Yasa Axial Flux Electric Motorhttps://www.yasa.com/products/yasa-p400/OREVO Axial Flux Electric Motorshttps://avidtp.com/product/evo-motors/Thank you very much

Hai all. I have queries about bldc hub motor. I want to design a stator I have stator diameter, speed, voltage. I need How to find number of teeth and it’s dimensions, plse reply sir

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