Make it Move: Electric Racer

In this design challenge from the National STEM Learning Centre and Network, students build an electric racer powered by a super-capacitor. Students must construct the racer and choose which pulley ratio will enable it to cover the greatest distance.

Students decide on the pulley ratio following observations of the in-air wheel speed. It is tempting to equate faster in-air wheel speed with greater travel distance but this does not take account of the additional torque needed to move the vehicle mass and overcome friction.

The super capacitor can be charged from a USB socket to deliver a fixed amount of energy. The motor converts the stored energy into movement and the distance moved by the vehicle will give a measure of the efficiency of the system.

Students must consider:

* Is speed or torque the most important factor in determining the optimum speed reduction ratio to make a system run efficiently?
* What factors are likely to influence the efficiency of a racer design?
* How the circuit works.