Reflections on Final Project

(L to R, Christina and Kat with the Wellesley Energy Bike)

Last week, my partner Kat Roche and I finished our final design of the Wellesley Energy Bike display and got to show it off in the science center during the exhibition. In general, I think the project came out well despite all the difficulties: participants really felt the difference between bulb types as they were pedaling and viewers saw the difference in effort.

To summarize the design process:

• We sketched out all our ideas of how to bring sensors into an interactive display about energy.
• We broke down the design into three parts: works-like, looks-like and learns-like.
• Then, we began building and experimenting with different mechanical/electrical functions:
• Back wheel was raised off the ground using a bike stand and placed flushed against the PVC wheel attached to the permanent-magnet motor 
• The axle turned along with the wheel and transferred mechanical energy into electrical energy from the spinning to the motor, where it was transformed into electrical energy to power the circuit.
• The board's circuit consisted of incandescent and fluorescent bulbs, a hair dryer and an outlet for additional appliances, as well as featured some fun facts about US energy consumption. 

We made an extra instructional/promo video (below) to demonstrate how the energy bike is educational and interactive. I couldn't be prouder of the final design of our Energy Bike Project, though the final days leading up to it were definitely a doozy with last-minute touchups.

 FACT REFERENCES:

https://www.dosomething.org/facts/11-facts-about-energy

http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3

The Night Before the Exhibition:

We painted the motor brace and leg stands for the display board. (To attach the legs, we nailed them to smaller pieces of wood and then screwed the wood flush against it.) We also added a voltmeter, in order for participants to see their output from pedaling and better maintain their output between 12 and 15 volts (the necessary range for the inverter).

Lastly, we printed out and glued all the fact and instructional text to the board and painted more flare onto the display for aesthetics. (We carefully planned the positions of each text bubble before permanently gluing it all -- taking into account eye-level, relative importance, etc.)

Somehow, we managed to finish the entire project early that night before the presentation -- and even found a hairdryer with a power requirement low enough to be supplied by our bike. Not to mention, we still had time to test everything and correct any malfunctions. We were able to get back to the dorms well before dark and rest up.

Judgement Day:

The Evolution of Kat

Overall, I think our presentation went well. Unfortunately, halfway into the event, our small wheel mechanism came apart and never quite stayed on correctly after that. We had thought beforehand that the glue was melting due to the heat caused by the friction/resistance from the bike wheel -- and so we used heat-resistant glue the night before. Since it didn't last, our next conclusion was that, rather, the tape was melting. We tried using aluminum tape, but the heat-resistant glue did dry fast enough before we attached the wheel again. 

For a short term solution, we used lots of duct tape and a small piece of wood to brace the wheel on the open-ended side where the wheel kept falling. It worked for a while, until, eventually, the glue and tape If we had more time, we would have liked to try some different wheel options. For example, a Delrin wheel might have worn down eventually but, if we directly glued it to the axle, the motor wheel might not have fallen off as easily.
stopped holding together again. Though the wheel was staying in place,the axle wasn't turning and, hence, the lights were not being powered.

Nonetheless, we had lots of fun and our users did learn about the importance of energy efficiency when the bike was working. The
ones that got a chance to pedal felt the difference between powering the incandescent and powering the fluorescent lights -- and even those who just watched commented on the difference in consistency between the two. It seemed our message was clear, and I couldn't be prouder of what we accomplished in the short amount of time we had.

I'm glad I was able to finally pursue a goal I've had in my mind for a long time and I'm really glad that I was able to fall back into my passion for electrical engineering and circuitry. I didn't leave the mechanical skills I learned behind me and I did learn quite a bit from Kat on the subject. I think the success of our project is due to how well Kat and I both got along and how dedicated we both were to the project.

Sad to say "Goodbye" to ENGR160 but looking forward to my next journey in engineering. 

Hope you've enjoyed the ride as much as we both have!