Effect of propeller size on thrust produced
The materials required for this science fair project:
- A 12V dc motor
- 1 piece zinc sheet (thickness 0.5mm, size 750mm x 600mm)
- 1 pair of scissors
- 3 cubic wooden blocks measuring 20mm x 20mm x 20mm
- 1 electric hand drill and drill bits
- 1 set of needle file
- A protractor
- A sscrew driver and some screws
- A shoe box
- 4 toy car tires with 2 metal rods for support
- A DC12V battery
- A stopwatch
- A ruler
- Black masking tape
1. For this science fair project, the independent variable is the size of the propeller blades. The dependent variable is the speed at which the boxes move as a result of the thrust that is generated by the propeller. This is measured by recording how long it takes for the shoe box to travel 2 meters. The constants (control variables) are the power of the motor, the angle of the blades, the size of the box and the distance covered by the box.
2. Using a hacksaw, slots at 20 degrees are cut into the sides of 3 wooden blocks. The propeller blades are then slotted in as shown in Figure 1. A hole is drilled in the center of the wooden block. The dimensions of the hole are modified with a needle file to ensure a good fit for the shaft of the propeller.
3. 4 holes are made at the bottom of the shoe box. 2 metal rods are inserted and 4 tires mounted. The masking tape is used to mark lines 2 meters apart for testing the speed of the box.
4. 4 blades are cut out according to the dimensions shown in Figure 1C. The blades are mounted onto the wooden block with screws. The motor is placed with the propeller onto the box. Secure them in place using duct tape. The DC12V battery is connected to the motor. The time taken by the boxes to move 2 meters is recorded and the results are shown in the table below.
Ensure the blades are properly fixed to the wooden block so that they do not come loose when they rotate.