In the old hacker fashion I decided to repair the wheel and the treadle myself. A whole new world with a whole new lingo opened up to me today, thanks to youtube. So far I've only managed to rip off the thread of the back-wheel rod, everything else looks still intact. I'm a bit late for this years cycling season, but it's immanent for my health and well being, that this thing rolls again. Tomorrow I'll try to recut the thread on the rod and the day after I'll receive some special tools for repairing bikes. The cost was about half of a home improvement store bike, but I want to learn this stuff and see if I can fix it by myself.