Bike-in-a-Bag

For the past few weeks, students in my Junior STEAM class, Design and Engineering have been learning more about the design process, and put it to action once again. We talked to people from Dyson, Chicago Mobile Makers, and Divvy in preparation for this project. I partnered with DN to design a bicycle using what we had learned. Each person/pair was assigned a fictional person with a set of needs for their bike that we had to design around. DN and I were assigned "Mohammed" who "is" a 16 year old from Accra, Ghana. He has a five mile bike ride from home to school every day, and his main concerns were having space to transport goods from the local market, and theft prevention. The representatives from Dyson stressed the importance of sketching before you commit to a design, so we started by getting pen to paper. The brief said it can get quite rainy in Accra, and when the representative from Divvy came she explained to us that bike seats can crack when exposed to rain and left to dry which is why Divvy bike seats have a hole in them, so we incorporated that as well. After a few dozen poorly drawn bicycles we settled on a design with an extra foldable storage crate in the back, with a large bag that's big enough to hold the entire bike, and has straps for easy carrying. The bicycle folds in the middle which we used pipe cleaner to show in our model. DN and I worked very hard on this project, and we can't wait for you to see it below!

DN, Bike Sketch, 2021

MD, Bike in the Wild, 2021

For the digital sketch below we needed to get an idea of how the wheels would work on our bike so we made a version of it in Geogebra. Since you can't share files on Geogebra DN did it from their computer and I got on a call with them to talk through it. In our model the radius was an inch whereas if we were to actually manufacture the bicycle the radius would be 12.24. We think our bike would be about 20 pounds, and the average healthy 16 year old boy is about 130 pounds. We guess our bike would be going about 16 miles an hour, so with this times the total weight of Mohammed and the bike we can determine the kinetic energy would be 750 joules with the formula (150*10)/2 = 750.

For the gears we weren't really sure where to start but we learned the average bike's gear ratio is 2.75 so to fit that we landed on having a small gear that had 16 notches and a large gear with 44. Since 44 divided by 16 is 2.75 this works great. 

This project was very engaging and challenging to complete. I don't actually know how to ride a bike, so talking to people about them and learning as I went was interesting. The wide variety of guests we got to talk to and the multiple instances for feedback were very helpful in the process. I had a great time completing this assignment with DN and it was a wonderful way to end this class.