the only thing on bikes i don't work on are the derailers,not because i'm not mechanically inclined,just because i raced bmx when i was much younger and never learned how to adjust drerailers by the time i started to ride bikes that were equipted with them. any way to get to the point my fathers early '70s model px-10 that is in excellant shape needed the front simplex derailer adjusted-i brought it to the local bike shop and $27.00 later got it back,i test rode it and the chain came off the front sprocket, i returned it to them and he again adjusted it while i waited,took it home it again threw the chain off. i brought it back left my phone number with them and 6 days later after not hearing from them i go by to see if its ready. the young man tells me the old derailer broke so they installed a new one. i checked the bike and it had some new scratches in the frame and a cheap derailer that he rounted the cable under the bottombracket with .. afetr they removed their derailer i brought it home and now im in search of the collar piece that hold the derailer on the tube as mine is broke on the very end,it is hard to see in the pictures.anyone have one of these?the circled part is broke in the pix