Its the driveshaft. Still working on it. Made two didfferent ones today didn't work. Haven't found the best material yet but still working on it. The ones that I did make weren't small enough to have some flexibility they did turn but one twisted and the other wouldn't stay in place. I have made one for a ho scale years ago but since this one is so small not sure if I will be able to do it. Only time and testing will tell.