E-bikes for steep roads: mid drive and hub drive motor efficiency comparison

Abstract

Power input, speed, and efficiency concern people when selecting a transportation means. This study compares multiple e-bikes configurations and presents to the reader scientific criteria to choose the one that fits best for non-trained cyclists, who want to use e-bikes for everyday transportation in cities with steep roads, assuring that the cyclist takes effective part of the power input. Power development, speeds, energy consumption and efficiency result from a mathematical model and experimental data. Configurations vary in motor placement, assistance level, cyclist cadence, wheel type and transmission sets. Results indicate that the motor's placement is the most determining factor in the efficiency of the entire system. Placing the motor in the bottom bracket, allows both the cyclist and the motor to range in the most efficient rpm. As efficiency for the middle drive motor is higher than the hub drive motor, energy consumption in the hub drive motor is 18% higher.