Overview and Background

Overview

As part of a Higher Level Physics IB project a student wanted to investigate how the angle of a propeller blade affected the lift.
The propellers were designed in Fusion 360 and the blade angle altered from 0 to 90 degrees in 15 degree steps.

Lesson Plan and Activity

Method

The propellers were printed out in PLA at 65% scale in order to fit the motor axle that we were using.

Each blade is attached to the motor which is then mounted on an electronic balance.

If the blade is mounted 'upside-down', as the propeller rotates it pushes down onto the balance. The resultant measurement can be converted to a force using F=mg.

A graph of Force vs Angle can then be produced.

An interesting extension is to devise a method to measure the speed of the rotation and repeat the experiment at different speeds. One of the more creative solutions to this was to attach a small piece of paper to one end of a blade. As it rotates, the paper hits against a microphone and the frequency of the registered 'taps' was analysed using Audacity.

Likewise the experiment could be carried out as a "Wind Turbine" investigation and e.m.f. induced measured from the motor.

Safety Note: A safety screen was used when carrying out this experiment as some of the propellers had sharp edges

Materials Needed

Equipment

7 printed propellers
d.c. motor
electronic balance
variable power supply
safety screen

Propellers with different blade angles