One of the reasons for which motors in scooters and other electric vehicles are large and bulky is that they have to be designed to last a long time in real world environments.<p>The motors being used for this project are hobby model aircraft motors. These motors put out a lot of power per unit volume but are most definitely not designed for continuous duty at anywhere near to full output. They are also not sealed against the elements and have bearings selected for reasonably balanced loads with relatively low radial loads.<p>I have piles of these on my workbench ranging from cheap Chinese units to top of the line German designs. I use these on our planes, helicopters, multi-rotors, boats and cars. At the top end you have amazing hand-crafted quality with a prohibitive price (unless you want to pay $8,000 for a skateboard). At the low end they are cheap and they are junk. I've seen everything from magnets coming off, coils burning out, power leads coming off, bearings going bad prematurely and shafts bending.<p>In short, while the design process is interesting, I think the most fundamental flaw is being ignored: The motors are not designed, nor are they suitable for, this kind of an application.