Captains log, supplemental. You may have seen our first dry test in a previous log and you were probably thinking "C'mon, there wasn't even a mechanical load on that thing!?" Well this clip is for you. We built an inertial test rig, which is basically a 10lb 10" flywheel enclosed in a protective screen to prevent it from decapitating us. Considering that angular momentum is proportional to the square of radius, and that this wheel is almost double the combined mass of a bench grinder drive train, it's a big test. Check it out.