Engineering Design & Development Part 2: Assembly and Testing

Our final prototype! The Expanding Hydraulic Barrier.

WHY did I pursue this project? Where am I getting my inspiration from?

This was the second half of the CAPSTONE course I pursued in my senior year at Clear Springs High School, in Spring 2018. This CAPSTONE course was known as Engineering Design & Development, and it is the final course that can be taken as part of the AP + PLTW Science & Engineering Career Gateway Elective in High School. For this blog post, I will be focusing on the assembly and testing of the apparatus that was designed the previous semester.

To recap, the problem we chose was that hurricanes are causing floodwaters to damage people’s homes. After our research & brainstorming, we settled on building the Expanding Hydraulic Barrier (EHB), which is an apparatus that can be assembled in the doorway of someone’s home to prevent floodwaters from coming in and causing damage.

HOW did I pursue this project? What processes were needed to complete it?

We had to start out by getting more specifics of the design. We had to ask ourselves questions like, “How big do we want this device to be? What should be it’s dimensions? It’s weight? What materials should it be made out of?”

We first decided on the materials. We ended up settling for sheets of galvanized steel, since they are durable and waterproof. We bought 48 x 36 inch galvanized steel sheets from Home Depot, which we then cut to our dimensions described below (we wanted it to extend at least a third of the way up from the bottom of the doorway, so we settled on it being 19 inches tall):

Snapshot from my engineering notebook, showing the steel sheet dimensions

We also bought Carbon Steel Tubing to reinforce the galvanized steel sheets, since they would be flimsy on their own. We bought 6 feet of steel in total, and they will be attached to the galvanized steel sheets via welding.

Snapshot from my engineering notebooks of the carbon steel tubing we bought from Home Depot.

We also wanted to apparatus to effectively seal the doorway, so we bought a roll of weatherstrip. We even bought a 2-ton bottle jack, but we didn’t have enough time to include it in the final assembly.

Now that we had our materials, we needed to run some calculations. The two models we used were the Pressure Prism Model and the Forces on an Inclined Plane Model.

I’ll start with the Pressure Prism Model. This model considers hydrostatic forces that will be asserted on a submerged surface. It is a function of depth and the density of water:

Pressure Prism Model. Source:
on Wikimedia

According to our calculations, our apparatus will need to withstand 0.4338 tons of force to be able to fend off floodwaters.

Our next model was the Forces on an Inclined Plane Model. This model predicts the angles at which a certain object will start slipping:

Forces on an Inclined Plane Model. Source:

While we had a prototype wooden block and weathersrip that weighed 0.06867 Newtons, we weren’t entirely sure at which angles the weatherstrip would start slipping. For those values, we needed to run experiments.

The experiments themselves were, in my opinion, pretty basic. I legit got each material commonly found in doorways, placed the weatherstrip prototype on them, and then measured the angle at which they started slipping.

Snapshot of one of the pieces of test data from our Inclined Plane experiments.

For this experiment, we used dry wood, wet wood, dry painted wood, wet painted wood, dry brick, wet brick, dry concrete, and wet concrete. We ran 6 trials on each, and measured the angles at which the weatherstrip prototype began to slip. The results of our data are outlined below:

Results from the Forces on an Inclined Plane Experiments

From these average angles, we used the tangent function to find the coefficient of static friction between the weatherstrip and each material. We have concluded that this coefficient was high enough for the product to keep from slipping on each material.

WHAT did I learn in this process? What new skills did I acquire (soft or technical)?

This was the more technical part of the CAPSTONE course, and it was even more independent than the previous semester. I learned how to design and conduct experiments that proved our proof of concepts. I learned college-level math and fluid dynamics with the pressure prism model and the forces on an inclined plane model. I learned how to interpret data and apply it to our prototype.

We also had to present our prototype at the end of the year to a board of engineers. That means I also built up my presentation and scientific communication skills. What stood out to me the most is that when I told the engineers about the Forces on an Inclined Plane experiments I performed in my own backyard, they told me that it was the same kinds of experiments they perform at SpaceX to qualify their materials in their rockets. They also told me the math I performed with the pressure prism model was the kind of math only 2nd or 3rd year college students could perform. I took both pieces of feedback to heart, and it showed that this course was the best way possible that I could finish my high school engineering career.

WHAT are my next steps? Do I have another project planned? How have people responded?

The EHB shortly before donation to CNS in Fall 2019

I graduated Clear Springs High School after this course, and then I enrolled at the University of Texas at Austin, majoring in Mechanical Engineering. My college career consists of several projects that I will write about in future posts. Unfortunately, both of my colleagues chose different schools, but I still respect their decisions and am confident that this course has benefitted them just as much as it has me.

In terms of the prototype, I hung onto it for a long time, but I ended up donating it to the College of Natural Sciences at UT Austin. I will reveal the reason why in a future post.

Male | 21 | He/Him | UT Austin ‘22 | Engineer/Entrepreneur | Space City (Houston, TX) | 3rd Gen German-American