I've got a 1983 Bianchi Nuovo that I converted to a fixed gear a couple of years ago. I kept the two existing chainrings on the front as I didn't see any need to remove them. I just used one of them for the chain.

I took a good spill (about 30MPH) and a couple of the chainring bolts broke and the rest loosened up quite a bit. I decided I'd buy single-speed chainring bolts and use my existing crankset/bb/etc. with the single chainring. I tightened the bolts down until there wasn't any play in them and everything was fine for a few days. But today on my ride home from work, I noticed some play in my pedals.

I pulled over and noticed that all of my chainring bolts were loose. I tightened them back up and they were just fine about two miles later when I got home.

Should I replace my crankset, bottom bracket, and all that? Should I go back to using two chainrings like what was originally on the bike (I have both chainrings and a brand new set of "normal" chainring bolts). Is there anything I can do to keep the chainring bolts from loosening?

Lastly, what are the recommended tools for tightening chainring bolts? I normally just use my Park Tools allen wrench and a screwdriver, but the screwdriver rarely spans the entire back side of the bolt. Is there a tool specifically designed for this, or do I just need a really big screwdriver?

Thanks so much!