Young Engineers of Today Spring Lab 4: PVC Trebuchet


For lab this week we have one more final ancient engineering challenge. Students have been studying all sorts of CAD programming. The last few weeks in webinars they have been studying TinkerCad, SketchUp, and Inkscape.

While they develop their learning and start to craft their new skills we cannot really do a 3D Printing lab. It is only exciting to watch the printer for about 5 minutes. As they get ready to design their 3D prints for a materials lab coming up in Lab #6 we are working through another engineering project.

We launched into PVC trebuchets. Students were not given instructions. We want them to design their device. The challenge is who can be the King of Fling?

You can see from the slides that I did give them some parameters. I shared with them the measurements to make a trebuchet that looked like the one in my room. I had built a much larger version, but if they wanted to use the measurements to build one that assembled like the one I built they could.

However, students did not have to use those measurements. We started lab with paper and pencils. Students had to sketch out their plans with measurements before anything could happen. Even if they used my measurements on the slides they still had to map out all the pieces.


Second, students then had to figure out the proper cuts. They were given 2 x 10ft pieces of PVC. They had to figure out which pieces fit to get them all cut out using only those. If you do the math of all the pieces suggested we are over 16 inches. I had already precut 2 x 2 in and 1 x 12 inch pieces for them. The rest they had to figure out. They were told if they mess up, then they will have to problem solve to make it work as they would not get any extra pieces. I gave the hint that the solution to a bad cut or not thinking it through would result in a much smaller trebuchet. This was enough for the to plan.


What I was most impressed with was how many took this serious. This proves that the classes and labs are starting to sink in with proper thinking, problem solving and prototyping.

Now, I know you are thinking that this seems like an easy project. What you need to understand is something I am learning. Students do not know how to use tools. This is why YEOT is vital. We are forcing students to take their ideas and knowledge that they are learning whether in this class or at school and bring it to life. Students rarely get this chance. They learn some formulas, they design on paper or computers, but it typically stops there. Students in YEOT are taking it to the next step to actually make their ideas. Students had to be taught how to use a hacksaw, how to handle the PVC, how to measure with a yardstick, etc.


A perfect example is this situation. This is not a knock to the student, but to the lack of real world application taking place in education. One of the pieces needed to be 42 inches. I only provided students with yardsticks. A group came up to me and said it was impossible to cut a 42 inch piece. I asked why? They told me that it was impossible to measure 42 when “the stick” only went to 36. I told them there was a solution and honestly they brainstormed for a few minutes and could not figure it out. I had to show them how to mark 36 inches and then measure another 6. These are intelligent kids, but this shows how minimal their life application of their knowledge is in their lives.

People fear mistakes. They fear tools. They fear that students might get hurt. This is part of self discovery and growth.

As the nights went on we made some great headway. Most groups have the frame completed. Most have the throw arm ready. We are now left to make the sling, test the trebuchets to dial them in, and then glue them together. This will most likely be a two lab project because without instructions they must problem solve.


In the end we have about 6 different designs. Some will work and some won’t. I have not told the ones who will not work that they have issues. They need to learn on their own. I have questioned their ideas and gave hints, but in the end they might just surprise all of us and have the best. I have seen this happen more times than not.


It was a great two days of labs with so much learning and hands on experience. Despite the chaos and mess this might be my favorite lab so far. I cannot wait for two more weeks to launch these bad boys!


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