I recently changed the rear tire and paid no attention to the original working state of the rear derailleur. After a miserable attempt at resembling, I lost what I now think was the Derailleur bolt and nut (one flat side, curved elsewhere) during a short ride. It's since been replaced with whatever nut and screw I could find laying around.
Like the first attempt (with all the original parts still available) at reattaching the wheel, after a hard pedel, especially uphill, the wheel will move from centered. The tire rubs against the frame creating enough resistance to make pedaling feel impossible.
The rear dropout has a small screw hole and a large triangle cutout. I cannot find a configuration that allows the derailleur to screw into the small hole, and so am fastening it using the larger triangle.
Is the placement of the derailleur the problem? Do I just need to turn the nuts holding the axle on a little harder?
after the axle has slipped down: