I have a ten year old decathlon cheapo bike and I wanted to take out the axle out of the rear wheel to see if I could replace it with a quick release mechanism and also learn a bit about how it works (the bike is cheap and not important). I undid a few nuts until I could take out the large axle bolt but when I did, out fell a load of ball bearings from either side.
I don't think I'll be able to reassemble it and a lot of the parts are rusty and probably need replacing but I don't know what to replace them with and like I said, ideally it would be quick release.
As far as I can tell the assembly is a freewheel cassette. Then there was this large bolt going through the wheel with two nuts and another threaded item I cant identify either side. Inside there were the bearings each side with a washer like cover. But they seemed only to be held in place by the presence of the bolt.
Edit: The bike is a rockrider 5.0 from about 2010 or so.