One more reason to ALWAYS carry a chain tool
This morning I opted for the 1982 peugot road bike I picked up at a thrift store last week. About 5.5 miles into the commute, the rear der. simply broke off. The friction shifting had been acting up for a couple of miles but I had no idea it was self destructing. I had no problems with it on longer rides this weekend. As near as I can tell, there had been a hairline fracture for years and it finally failed today in the cold air (25 degrees).
As I sat there evaluating my options, it quickly became clear that I had to make a single speed out of the drive train. I took about 8 inches out of the chain and put it into my favorite gear (which luckily was pretty straight back) before sliding the axel as far back as possible into the semi-horizontal drop-outs and tightening the crap out of the QR. I only had another 4 miles to work but so far it has worked like a charm. Life would have sucked if I hadn't had my topeak hummer in my pack. Lesson learned.....always carry a chain tool or you may be walking to work. With enough miles, each of us will loose a deraileur at some point.