> Right Steve - Jon hjertberg of wheelsmith had these jigs for a while -
> there may have been other sets as well. I could think of a way to do it
> with a lathe too. I know several people who have ridden cranks so
> modified. But it scares me a little bit, given what we already know
> about the failure modes of Campy crankarms. The factory campy NR
> "triple" arms had slightly thicker arms in the spider where the
> intermediate bolts went thru, and those arms had a threaded bushing to
> mount the inner ring. The modified arms simply use a bolt that threads
> right into the aluminum.
>
Sorry to disagree, Mark. The Campy #818 triple bolt/spacers are threaded into the aluminum of the crank arm with no such bushing. Stop by and see a couple on my bikes. There is a difference between a factory and a drilled triple though. That is that the milling on the front of each arm of the spider stops short of where the triple bolt hole is, so the arm is indeed thicker there. That said, I have done dozens of them over the years with no failures. Campy cranks do fail, in the crotch near the arm, at one end of the arm milling or other, and sometimes at the pedal threads, but I have not had one fail at the triple bolts. I have though seen triple bolts themselves break in a drilled crank. I think it is from failing to counterbore the holes a little to give relief to the triple bolts which have a slight radius at the end of the threads. If you don't counterbore for this, then the bolt doesn't sit flat against the crank arm and can get wiggled back and forth so it fatigues. I have a jig that we had made many years ago for accurately drilling and tapping Campy cranks for a triple, and I do counterbore them. It is almost a moot point though because you can't hardly find the Campy #818 bolt/spacers any more. I have a stash of Avocet (ofmega) bolts and spacers that accomplish the same thing and are not so sensitive to the counterbore problem, since the bolt and spacer are two pieces. I have offered this service to the list before, and at the risk of being called on the carpet for it, I will just say that the door has been reopened and people may not have known that I do this. I charge $30 per crank arm plus $15 for the bolts and spacers. It will take any 74mm chainring, although some have to have their holes reamed to fit. A tapered reamer does this easily. Send me your tired, your poor, your dirty old Campy cranks and let me turn them into a nice old man's triple. I have a couple favorite chainring combos by the way. I use 32-42-47 and 13-26 freewheel on my old touring bike with a Campy front derailleur and short arm Campy NR rear derailleur and it works great. One my "vintage" titanium bike though I use 32-42-52 and 13-26, with a Suntour XC Pro front derailleur and a NR rear with Rally cages to suck up the extra chain. Those both be factory triples with Merz 32T rings that were made for Campy triples.
Bob Freeman
Seattle