In this series of posts, I will present my adventure of building a self balancing scooter, similar to a Segway.
This has become significantly easier in recent times because of the easy availability of the crucial components:
- Electric motors powerful and fast enough to carry a human
- Batteries with low cost and high energy density
- Reliable electronics and sensors
- Custom mechanical components
Choosing a Brushless DC Hub Motor
Earlier hobbyists have used brushed DC motors, coupled with gearboxes and custom-machined hubs/wheels to build their scooters. These were typically expensive, had limited availability, and required expertise with a machine shop to put together.
Today, you can find inexpensive brushless hub motors meant for use with electric bicycles. Here is the one I picked from the wonderful Taizhou Quanshun Motor Co. in Taizhou, China:
They cost around $250 USD per unit. For that price you get a motor with plenty of torque, high speed, and a convenient mounting shaft. These motors just use standard bicycle tires, which makes the process even simpler.
Of course, you need two of these motors to make a scooter.
These motors have a top speed of around 440RPM when running at 48V. With a 20 inch wheel, that converts to around 25 MPH. Peak torque is over 100 Newton-meters. They are rated for a continuous input current of 30amps, which means 1440 continuous output watts of power!
With two motors, that means you can sink 3kW, or 4 HP into the drive train of this scooter. This will be fun :)
The only concern I have now is the weight, they are quite heavy at around 10kg per motor.
These motors come with a single sided, 28mm diameter output shaft with an 8mm square keyway. The next step will be to make a motor bracket that will fit this shaft and accept an 8mm key. From there, the bracket will be mounted onto some aluminum T-Slot extrusions, making the frame of the scooter.