It turns out the only problem with Knuckles is that we broke one of his gears! Whoops! It turns out we were putting a pretty extreme load on this little gear and it sheared right off into three pieces!
The shaft and the key were pretty badly damaged, but we managed to figure out what happened. Our key didn’t line up well on the inside of our gear, leaving almost half of the tooth length of the gear unsupported. The key way on the shaft was a little large, so they key could wobble. And finally, our gear had been made with the key way corners cutting through the thinnest part of the gear material. All this came together into a perfect storm which took down our gearbox. After discussing the issue with a number of esteemed professors, including our favorite, Q Jane Wang, we’ve determined that if we get a gear with a better cut key way (which we have), and redesign the shaft and the key to fit well with each other and the gear, we should we good to go.