At the end of my senior year of high school, my entire class was given the option to take the month of may to complete a project instead of going to classes. So, I and five of my friends spent the month building a custom electric go-kart. 

It features a fully custom gusseted steel tube frame, somewhat functioning steering, and a motor that is supposedly 3000W, but is definitely significantly less than that. While it didn't end up being as awesome of a vehicle as we envisioned, it did work enough, and we had a great time building it, so I still count it as a success.

I did all of the CAD for this project, which turned out to be much more difficult than expected, as many of the components were purchased from amazon, and did not have drawings or dimensions provided. This meant that I had to guess about a lot of dimensions, design adjustability into place, or just make the part myself. This was overall fine, but the steering rack in showed up and was significantly different from what we expected, so we had to adapt quickly. It still worked, but a little bit less than we were hoping for.

Part of my job for the past couple summers has been running the rocketry program at the camp I worked at. Most of this involved helping young children build the same couple rockets over and over again, so I got very good at building a couple of specific model rocket kits (I've built over 300 Estes gnomes). However, a few times a week, a kid would make a mistake that couldn't be easily put back to the way that it was supposed to be. So, I also got very good at making anything vaguely rocket shaped fly. Some of my favorites are pictured here, and with the exception of the soda can rocket, they all flew at least a little bit. 

The sub-minimum diameter rocket in particular had one of the best flights I've seen, because it weighed so little it accelerated hard and got a lot of altitude. The custom firework executed its mission beautifully: it flew quite high on an E motor, then instead of deploying a chute, it ignited a non-trivial amount of gunpowder and blew up at apogee.  I've actually built several hot rod rockets, because sometimes just attaching a motor to the bottom of a kid's rocket was easier than putting one in the intended spot, and they all flew better than you would expect. 

The soda can rocket did not work. I tried to put two motors in the bottom and light them simultaneously, but only one lit. This caused the rocket to spiral in the air, hit the ground, light the second motor from the wrong side, and burn straight through the cans. It was fun to build and still a fairly spectacular launch though.

One summer a while back, I really wanted to build a potato cannon, but I didn't want to deal with combustion or fuel, so I decided to make it powered by compressed air. I would clip a bike pump to a valve on the storage chamber, pressurize it, and open a large diameter ball valve, launching whatever you could fit down the 3 inch barrel well over a hundred feet. 

There wasn't really a lot of value to this project other than me having fun, but I enjoyed the process and have no regrets.