In-wheel hub motors might be uncommon, but they are not a new idea.

The very first in-wheel hub motors were first designed around the end of the 19th century. The first patent that featured a wheel hub motor was filed in 1884 by the inventor W. Adams. This design was much more complicated than what you will see from modern wheel-hub motors. The device included a brushed DC motor along with a planetary gear.

It might not be a surprise that this design was not successful commercially, but it was an important machine nonetheless, as many solutions and ideas regarding electric drives have been inspired by it.

Combine today's high performance in-wheel motors with increased uses of scooters in urban areas for last-mile personal transport, thanks to companies like Lime and Bird, and there is the potential for immense innovation.

In-wheel electric scooter motors

There has been a huge increase in people who now use electric scooters as transportation. The motor that powers these scooters is the heart of the machine, giving the user the force to move themselves forwards, at whatever speed they desire.

All electric scooters feature at least one electric motor. The electric motor will typically be a direct current brushless (BLDC) unit that will be built into the hub of the front, back or both of the wheels. Brushless motors are preferred here rather than brushed motors, due to their better durability, efficiency and performance in general. Brushless motors also run quieter and do not overheat as much.

The power of these motors is designated by the power consumption (watts), and in general the higher the wattage on the motor, the more powerful it will be. This will allow the scooter to carry more weight, go faster, accelerate quicker and go up hills with ease.

[Learn more about DC motors on GlobalSpec.]

Hub, mid-drive or hubless

The majority of electric scooters will feature hub motors, typically on the rear wheel. These motors deliver power directly to the hub of the wheel. However, other configurations for the motor are possible. Scooters with dual hub motors will have a motor at both wheels, with a typical setup featuring two 2,700 W BLDC hub motors that will send power to both wheels seamlessly. Generally, the rear motor will start up first, with the front motor engaging once the operator requests more speed

A mid-drive motor does have a lot of benefits over the traditional hub motor. The mid-drive motor powers a crank shaft instead of the wheel, and this multiplies the torque it can deliver to the wheels, albeit at the expense of speed. The mid-drive option also provides more range and power due to the gearing change. It is also much easier to maintain and service than the hub motors. Two bolts hold the motor in and taking it out does not affect the rest of the scooter. The placement of the motor is closer to the center of gravity, and this improves the weight distribution and handling of the scooter.

This custom-made hubless motorcycle wheel illustrates the concept. Source: binsalim/CC BY-SA.40This custom-made hubless motorcycle wheel illustrates the concept. Source: binsalim/CC BY-SA.40

Hubless wheels have no center material. Instead of a hub, a solid wheel cover seals the backside of the tire. The power is delivered to the wheel perimeter via wheel cover instead of the center axle. This type of motor is not currently available on mainstream electric scooters, but there are some significant reported advantages to using them. Improved braking and steering are two of these benefits as the forces applied are closer to the wheel and ground than the other motor types. The rotating inertia of the wheel is also reduced, and its sleek and unique look is an added benefit.

There are some drawbacks to a hubless design, as there is more strain on the components when compared to the other designs. Without the strength of the hub inside of the wheel, the wheel can also be more susceptible to damage from impacts to the rim from potholes or otherwise. Hubless wheels are also more expensive than the others and require higher-precision ball bearings. Due to these drawbacks, hubless wheels are an unconventional choice for e-scooters.

The first hubless DC motor for scooters

Engineers and designers at AKTIVO have come up with a design for a new hubless wheel motor that they claim is the first and only hubless wheel design in the world. They worked for over 10 years on integrating the motor for the electric scooter into the wheel, giving a simpler and lighter technical solution than other designs.

This new electric scooter design features a 350 W hubless electric motor that utilizes a set of 60 magnets that controls the speed and torque output. This system also features high-efficiency ceramic brake, braking and position lights. It is claimed that this new scooter can tackle 20° hill climbs, has extremely high steering accuracy and requires little maintenance. This nimble design would make it perfect for more difficult locations where other scooters might not meet the challenge - say, San Francisco.

Hubless wheels have been featured and discussed at length before, but they have not been implemented into mainstream vehicles due to the number of issues the design presents. This new hubless electric motor hopes to bring hubless wheels to the mass market by using quality materials like ultra-light magnesium alloys, ceramic brakes and lithium batteries. It is a feat of engineering that has not been achieved yet, and time will tell if it can bring hubless technology to the mass market!

So, what are your thoughts on hubless electric scooter motors? Do you think they are a viable option for electric scooters moving forward, or just a design that exists because it looks cool? Enginering360 would love to hear your thoughts in the comments below!