The porta-catena was a direct copy of the Nivex chainrest. When Tullio Campagnolo bought two Nivex derailleurs in 1948 from Alex Singer, he probably got the dropouts to go with them. Campagnolo turned the Nivex 90° to work with a bolt-on derailleur hanger and so create the first Gran Sport - the first parallelogram racing derailleur. After showing it at a few trade shows, he must have realized that the Nivex-style desmodromic twin-cable actuation would scare off many race mechanics, so he incorporated a return spring like Simplex already had on their archaic plunger-type derailleur. The immortal Gran Sport was born, which is the direct ancestor of all modern derailleurs. You can read the whole story here
http://www.bikequarterly.com/sample_articles.html (first link under "History"). It appears that during the mid-1970s, Campagnolo's R&D didn't have much to do. Their components were made unchanged year after year. The biggest change, in the early 1970s, was to substitute a few steel bolts with titanium, and paint some parts black, to create the Super Record group. After that was done, somebody must have found those Nivex dropouts in a drawer, and thought: "Wow, that is a great idea!" Instead of making a new dropouts, they just drilled three holes into their existing ones, and created a bolt-on chainrest. Why wasn't it a success? I can only speculate that Campagnolo introduced it at a time when "more gears" was becoming the mantra. People just had moved from 5- to 6-speed, and 7-speed was on the horizon. Were they willing to give up one of those hard-won cogs? Neutral support could be another - the days when Campagnolo could dictate the equipment choices in the peloton were over, and with a Portacatena, you need a 126-mm-spaced rear wheel with a 5-speed (instead of the common 6-speed) freewheel. How does the chainrest work? Very well. I have a Nivex on my bike, and *Bicycle Quarterly's* second tester Mark uses a hand-made chainrest on his machine. Even though I've only had one flat in the 18 months I've ridden the bike (thanks to the Grand Bois Hetre tires, which flat very rarely), it was great to shift the chain to the chainrest while rolling to a stop, then remove the rear wheel like a front wheel... There is no risk of ripping the chainrest off the dropout - in fact, the way to get the chain back off is to mount the bike cyclocross-style, and then pedal with the chain on the chainrest and shift back onto the cogs. (The cogs must be turning to allow the shift.) My bike has a Nivex shift lever with a lockout for the chainrest, but Mark uses a standard Ultegra downtube shifter, with nothing to prevent an accidental shift onto the chainrest. I have ridden his bike, and done that on a fast downhill. Nothing much happens. You just shift back to the smallest cog again. Now if you sprinted out of the saddle and used STI to shift onto the chainrest, that might be a bit more dicey, but even there, I suspect it wouldn't be a huge problem. And of course, engineering a lockout into an STI/Ergo lever wouldn't be hard, if one of the big makers decided to resurrect the system. Jan Heine Editor Bicycle Quarterly <http://www.bikequarterly.com> Follow our blog at http://janheine.wordpress.com/ On Sunday, January 13, 2013 8:56:37 PM UTC-8, Eric Norris wrote: > > I suspect one problem with the PC was that if you parked the chain while > riding (or when stopped( and then started pedalling, it would rip by the > holder off of the dropout. I haven't tried it, but that's my theory. > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To view this discussion on the web visit https://groups.google.com/d/msg/rbw-owners-bunch/-/bTXkbBtHoNIJ. To post to this group, send email to rbw-owners-bunch@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
