Saw this tweet last week and, despite my technical skills being in the micro-Hayes-Golding range, I just had to try it!
We ordered the cars from Kelvin LP:
and started building the cars when they arrived on Friday. Here’s what the boys thought at the beginning of the project. My younger son first:
and then my older son:
We built for about 45 min and got about 1/2 way there. The building is not that challenging, though I’d guess our 45 minutes with a 5th and 7th grader would be closer to 15 min with high school kids.
Here’s where we got to after the work on Friday night (the main tools that you need for the build are a glue gun and a soldering iron) :
After about another 30 min of building this morning we’d finished the cars. We used some spare lego pieces to help the solar panels tilt up.
Our first test out in the street didn’t go as well as I was hoping because it was a little cloudy, but at least the wheels still ran and the boys seemed pretty happy:
Later in the morning, though, we got enough sun on our porch to do a nice demonstration:
So, not really a math project but still really fun. Thanks to Megan Hayes-Golding for this great idea!
Mike's Math Page 
Check this out. The girl on the right played ultimate for UCLA so obviously I’m biased, but it was super fun to follow their trip: http://www.cycleforscience.org/
Thanks Anna. Wish I would have known about it at the time – could have added a 3rd UCLA player to my favorite list 🙂