OK, convince me!
I noticed today that the deraillier on my peugeot rubs on the spokes when im in a low gear Seeing as the only time the bike comes out of its very highest is when I want to burn away at the lights, I reckon its a good candidate for getting rid of the blubbery bits. How much money? How much effort on an old french non-standard racer?
Most likely a threaded freewheel. Youll want to have a shop remove it, or get a tool and do it yourself. Replace it with a bmx freewheel. Notice that your chainline is nuts. Take bike to shop and have them redish the wheel and move the axel so the chainline is better. This will also have the consequence of making your wheel stronger as it removes dish.
If youre a bit crazy, thread on a track cog with locking compound. Tada! Youve got a fixed gear. Yes you can potentially unscrew the rear cog as theres no provision for a lock ring, but after a hard ride, itll be dang tight and difficult to move.
If its a cassette, remove, get some spacers, slap on a Shimano DX cog somewhere in the shuffle, tighten down wiht lock ring.
Get bmx chainring bolts, remove large ring, put small (42) on outside, attach with the new shorter bolts.
Put on your new chain. Whatever you want short of a 10 spd chain. Cheap bmx chains are fine, as are inexpensive derailleur chaings. Single speeds dont care much.
42x16 is virtually perfect for everybody for street riding, but do change as needed. I sometimes rock a 17T rear in winter.
So the short list
1. Make rear wheel into single speed wheel
2. Remove derailleurs and cables.
3. Convert crank into single speed.
4. String up new chain.
5. Adjust chain tension, not crucial on a single, but essential with fixies
Cost in dollars:
15 redish and move axle, labor.
15 bmx freewheel
10 new cheap chain
5 chainring bolts
bout fifty clams and you get a virtually maintenance free ride.