Jim Ready asked for help setting up his porta catena, to which Rodney Handsfield replied:
The Porta Catena is an elegant solution to the small problem of where to put the chain when transporting your bike. A problem solved by Dave Moulton by brazing a nail head to the right seat stay of his frames. The spacing of the rear hub and maybe the wheel dish will need to be fiddled with in order to have clearance for the chain when it is on the smallest cog. Once you have made these changes it works quite well.
Here's my opinion:
Elegant might be the wrong word. A complex solution to a trivial problem is the opposite of elegant. Inelegant? A bit. This is not to say that P-Cs aren't cool, and quintessentially Campagnolo. I have one in the factory-sealed package, and that's exactly where it will stay. I put it alongside the Delta brake in the cool-but-ridiculous Campy Hall of Fame. Not gaining entry are the uncool-but-similarly-ridiculous pneumatic saddle, Biodynamic water bottle, and Euclid brake-shifter set. All this stuff is part of what makes Campy, Campy, but none of it is elegant. The Record crankarm... now that's elegant, imho.
As Chuck already mentioned, the PC is not simply a chain hanger. It is intended to allow the rider to derail the chain from the FW to the dropout-mounted hanger, by way of the shift lever stop release. It requires one big concession that is a deal breaker in most applicatons. It takes up space between the dropouts. This means either loosing a cog, or adding dish and axle length. Dish makes the wheel weaker, axle length leads to more bending stress and breakage. If you are willing to get by on a 5-speed (or Ultra-6 and the attendant problems of narrow spaced cogs), the PC had it's place. If you raced criteriums and didn't need a lot of gears and were really, really concerned with fast wheel changes, it might have been useful. Of course, this assumes that you didn't mind removing the hanger and changing FWs anytime you wanted that last cog.
The PC shares conceptual attributes with first gen C-Rec rear der. That unit had an upper spring that carried no benefit for shifting, and existed solely to hold the rear der body back during a wheelchange. A minor problem was that the body didn't return to position on its own, and you could ride off with your der at a crazy angle. The bigger problem was that they all broke. They are big coin on Ebay these days. This complex feature was deleted within a year or so, and replaced with something useful in the form of a tiny setscrew that controlled body angle.
Anyway, to set up the PC, assuming you have a 126 mm frame, and assuming you don't want to respace to 130 mm, you need to go to a 5-speed or narrow-6. If you go to 130 mm, or are already there, you can use a 6-speed or possibly a narrow-7. The hanger bolts onto the dropout in way that is pretty obvious. The shifter stop plate and lever are replaced with special parts that come with the kit. The rear der high gear limit screw is set to line the chain up on the hanger. The shifter is set to the non-released position, and cable "tension" (actually it's cable length) is used to position the der beneath the small cog when the shifter is fully forward against the stop, but not in the realesed position. As you can see, another drawback of the system is that it makes cable adjustment more critical, like on an indexed system.
Tom Dalton Bethlehem, PA, USA
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