Please don’t judge [Alan] on his choice of vests. This project is from 1999 when it was common to see people rockin’ these threads. Anyone who has ever spent time on the University of Minnesota campus in Minneapolis, Minnesota will know that parking is at a premium. [Alan] had a 12-15 minute walk from his parking garage to his office and was considering a cheaper parking location that would balloon that to 20-25 minutes. But engineers don’t see problems, they see project ideas. He started work on a tiny electric scooter that could slim down his commute. Obviously he did find some success, but it was interspersed with failures that make his scooter the Fail of the Week.
After doing some research on existing electric scooters [Alan] headed to Ax-Man Surplus, a hacker’s paradise of engineering supplies spanning the electronic, mechanical, and chemistry disciplines. He picked up a 130V DC motor which draws 1A with a 1/8 HP rating. He built a rectifying DC power supply to test it and was laying down rubber in the basement of his building. But you can’t get very far running on an extension cord so the natural progression of the project moved to prototyping a battery for the unit; a dozen 10.8V 1700 mAh NiCad batteries. He figured it would be good to add in a fuse. His “testing” of a 20A fuse was done by shorting the connections which is how he discovered that the cells themselves have an over-temp cutoff built-in. We’d call that fail number 1.
The next issue resulted in all the cells in the battery going dead. There’s a great description of this that culminates in [Alan] realizing he probably charged them with reverse polarity. He swapped out for another pack and took the finished scooter for a rather scary test drive. He hit the accelerator and the thing took off.. with no way to stop it. Flipping the switch did nothing as it heated up and began to melt. And he only had the front brake installed which was no match for that powerful motor. We start shaking our heads when [Alan] kept repeating the same mistake, moving to a mains light switch with the same results, then adding a flyback diode also with the same results. So what’s going on with this fail? Why were the switches unable to cut power even after he moved them to the off position? Let us know what you think by leaving a comment.
We love the idea of building your own electric transportation. But electric scooters are getting to be a bit too common. We’d recommend a commuting tricycle. You might think that you’ll be made fun of, but not with the way this thing tears up the track!
Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story – or sending in links to fail write ups you find in your Internet travels.