Mechanical Testing: Motor and Prop Testing

After creating our testing tank and our setting up our sensors (for volts, amps, and newtons) we started to actually test the motors. It took about an hour to test each motor with the corresponding props in both forwards and reverse. Although the whole process took much longer because we had to try motors multiple times and we were often distracted by other parts of the project.

To test the motors we put them into our (not so much) waterproof container. We ended up flooding this container because some of the motors moved to much and caused flooding. Therefore, we had to create a constant (which was our container) to test the motors in. It was a challenge to get some of the motors into our container (particularly the Rule 1000GPH and Rule 800GPH, which we had to "carefully" force in). Another complication was making sure that the wires were fed up through the pipe to the surface of the water and were not too twisted or submerged. The rod in the top of the tank was then threaded through the pipe to act as the fulcrum of our lever. We then connected non-stretch fishing line that ran from the force plate, through the pulley and to the pipe, we had to tie it so that it was continually pulling on the container (because it would have been very hard to zero it perfectly by tying it...). We then zeroed it using Logger Pro. Lastly we connected the motors wires to the motor controller and then the controller to the battery.

The first picture below is of our testing tank from a ground perspective. The Raspberry Pi is in the foreground and the tank with the our motor controller and battery are in the background. The second picture is a front view of the tank we used for testing:

After that we had to set up the equipment for reading the data. We connecter the Vernier force plate we were using to our computer through a Lab Pro and into LoggerPro, from this we got force readings to the nearest newton (setup pictured above). To get amperage readings we used a Blue Point CAT III amp clamp connected to a Vantage graphing voltmeter. Finally for voltage we used another more basic voltmeter. We had to record our data in a google spread-sheet and then transfer it to Logger Pro because of some program limitations.

To test we needed to SSH into the Raspberry Pi and used Pi-Blaster (a PWM program) to control the motor through our motor controller. Setting PWM duty cycle signals to 25%, 50%, 75% and 100% to get a quarter, half, three-quarters and full power respectively. At each of these presets we took readings of voltage, amperage and force. We then switched out the propellor which was easy thanks to our propellor attachment design. After we had finished using all ten of our chosen propellors we would switch the direction of the entire container by switching its direction on the rod in the other direction and switching a double pole, double throw switch to change the direction of the electricity. We than ran through all of the propellors in forward and reverse giving us twenty-four data points for each test. We tested 10 different props and 3 different motors giving us a total data point set of 720.

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