Buy some cheap wall mirrors ($5 in Walmart here in the US) they flex a little bit (I've made funhouse mirrors with them. Broke a few in the process too so be careful.) so you could experiment by fixing the ends of the mirror to a stiff board and trying different sizes of wedges in the middle to...
Alrighty then... I did it. Fixed mine. Works great now. Was very hard to turn a couple hours ago. I gently tapped out the center 'spindle' from the roller that the adjustment knob fit on. (I was lazy and use a Phillips screwdriver that was near me, thus the dents in the end of the spindle). No...
We are having similar problems. I'm excited to find this discussed on a physics forum of all places. I, too, think I need to pull the center rod out of the outer roller but I'm hesitant to do so as the machine still works but it's very hard to crank. I don't want to totally break it. I would...