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INstructables build-a-tool contest
INstructables build-a-tool contest
Me and a friend took part in the Instructables Build-A-Tool contest, by building a functional wind tunnel. The idea came about in November 2023, and was fuly realised in June 2024. As part of this, we had to plan, design, manufacture and test the tool. It took months of researching existing wind tunnels and trying to understand the physics behind them; we had to understand concepts including the Bernoulli effect and the Venturi Principle.
A wind tunnel consists of 3 main parts; the diffuser, test section and intake. Each of these had to be designed meticulously and by considering multiple physics concepts. For the diffuser, we found that the angle of elevation couldn't be more than 5°. We decided on 4°, in order to have a good ratio of the fan area and test section area, while still having a large enough angle. For the test section TODO. Finally, for the intake, we found a 5th-degree polynomial that provided the right curvature so air could flow cleanly into the test section. Another ratio we had to try and implement was that the test section cross sectional area to the intake cross sectional area had to be between 1:6 to 1:10. We decided on a ratio of 1:8, to avoid the intake being too large while still having a suitable amount of air pulled through.
Electronics
Electronics
There was a large electronics side to this wind tunnel; we wanted to go all out. We decided to have multiple microcontrollers, each connected to one of the required sensors, and streaming data to the cloud. We were going to initially have 4 sensors; one to measure downforce, one for drag, one for conditions such as temperature and air speed, and one to control the power of the fan. In the final decide, we removed the drag sensor, due to not being able to measure it.
I had to think carefully about the design of the electronics; it had to be done in a way to ensure each data reading could be matched and we could tell which air speed linked to which downforce reading. I put together code for each of these microcontroller by programming in C++ and creating standard code which could be used by each of the 3 sensors. All my code is available on GitHub if you're interested!
We measured downforce using a load cell; this is a metal sensor that detects how much a rod deforms when a force is applied to it, and measures this as a voltage, which can be read as a weight value. We had to calibrate the load cell carefully, which we did using 100g masses. After working out the calibration value, we were set; we could measure accurate values for the downforce felt when air flows over the test model.
The build
The build
The actual build was stressful! We gave ourselves little time for the actual build, meaning we had to ensure it worked first time. We constructed the entire thing in around 4 days, plus 9 days for 3D printing the intake section. We fell into many issues; the diffuser started to fall apart, we had alignment issues with the intake and had issues with some of the sensors. Naturally, this only happened as we approached the deadline! Fortunately, we overcame these issues and everything came together at the end; we had a working wind tunnel that streamed data to the cloud, and had somewhat accurate values for the downforce.
The competition
The competition
We entered the wind tunnel into the Instructables Build A Tool contest. The brief was simple; we had to build some form of tool. We built and wrote up the whole thing with steps for someone to recreate it. We won the first student prize, called the Judge's Prize, and won a $300 gift card. If you're at RLS, feel free to pop into S9 to have a look at the completed project!
Overall, the project was largely successful and while we fell into many issues, we managed to learn loads about engineering, the design process as well as theoretical concepts in physics and electronics. Hopefully this project will inspire someone else in the future!
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