Drive Motor Selection

Assuming a flat road with minimal inclines and declines, the factors that need to be considered when determining the power required from the drive motor are mainly the drag force and all the firctional forces that affect the propulsion force generated by the front wheel BLDC motor. The following figure shows a 2D FBD that outlines the dynamics of the system in an ideal scenario. Please note that the third wheel cannot be seen on the 2D FBD, but it is accounted for in the force analysis.

After assuming all values for friction, drag, and weight distribution, the propulsion force (Ft) required for the front wheel to move the tricycle was determined. The power of the front wheel can be determined using the following equation:

Using the propulsion force, the power required for the front wheel was determined to be 418W at max conditions, with an assumed lumped efficiency of 80%. Therefore, we purchased an electric bike conversion kit with a 36V 500W 26" front wheel BLDC motor with an assumed efficiency of 80%. The conversion kit was purchased on amazon at $525.29 CAD.