energy chain - owntech-foundation/Tutorials GitHub Wiki

In this page we give you the general consideration in order to understand how to select the right parts for you skateboard. If you are only interested in the making process, go directly to the Bill of Material.

graph LR;  
  style ESC fill:#ED7D31, stroke:#000000;
  style Motor fill:#A5A5A5, stroke:#000000;
  style Battery fill:#4472C4, stroke:#000000;
  style Pulley fill: #00694C, stroke:#000000;
  style Wheel fill: #4E4A7C, stroke:#000000;

  Battery --> |Provides power|ESC
  ESC --> |Control Speed|Motor["Electric Motor"]
  Motor --> |Drives|Pulley
  Pulley --> |Drives|Wheel

Select a motor

BLDC motors

Start from your top speed : let say 20km/h Divide it by 3.6 to get it in m/s = 5.5m/s

Measure your wheels diameter and calculate the perimeter for 70mm wheels, perimeter is about 220mm. It means that in order to move for 5.5m, the wheel need to spin 25times. At max speed, the wheel shaft need to spin 25times in one second. Or 1520 times in one minute.

The wheel shaft spins at 1520 RPM at full speed.

Now lets pick a sensible pulley ratio. In practice it is hard to have a pulley diameter ratio greater than 4. Lets start from here:

A 4 ratio gives a motor shaft speed of 6230RPM

The speed the motor can deliver depends on two things :

• The voltage applied
• Its parameters, namely the kV rating.

kV rating is an essential metric to consider when choosing a BLDC motor for an electric skateboard. The kV rating represents the motor's speed constant and indicates how many RPM the motor will rotate per volt applied. A higher kV rating means the motor will spin faster per volt, providing higher top speeds. On the other hand, a lower kV rating will offer higher torque for better acceleration and climbing capabilities, but it may result in a lower top speed.

It means that the top speed of the motor will depend on the battery voltage we choose. In our case we have a 18V battery around, lets use it !

At 18V, we need a kV of around 350 in order to reach 6300RPM at full speed.

Last thing, it is way better if the motor has a sensor with it in order to ease the startup of the skateboard. Otherwise at very low speed, the skateboard acceleration won't be smooth.

The presence of a position sensor in a BLDC motor can enhance the startup performance of an electric skateboard. Position sensors, such as Hall effect sensors or encoders, provide feedback about the rotor's position within the motor. This information is crucial during startup as it enables the motor controller to determine the rotor's initial position and apply the appropriate commutation sequence.

DC motor

The second option, less common is to use a regular brushed DC motor. Any motor able to run at 6000RPM, with a peak power rating above 100W will do.

Select Belt and pulleys

You now have to find two pulleys with a diameter ratio of 4. One of the criteria is that the small pulley must fit on the motor shaft.