Greg,
Sure modern cranks will break in time. But my comments earlier regarding the choice of alloy that Campi chose for the NR arms, and that this alloy was not the best available is I believe true. One reason I say this is that I had the chance to design cranks for Specialized during the 1980's. We worked with Sugino in Japan. Their engineering staff told me that the alloy Campi used was not the best for this application. I don't remember what the alloy was, but we used something else. I also asked Shimano engineers and they said the same thing. I personally turned in more broken NR arms for warrantee when I was building frames than I ever saw returned of the Specialized cranks.
I got to see NR arms being made in the Campi factory around 1982. The forging blanks were larger than the finished part. These arms were machined all over, giving the distinctive square shape. This method could reduce the advantage of forging, depending on where the metal is removed. The Japanese arms were forged to near net shape, only flash cleanup and polishing was done. The blank forging finish was very nice on the Specialized arms I designed. We also did extensive testing.
Some comments regarding carbon fiber. I also worked on the designs of carbon fiber frames and the Specialized/Dupont wheel. One of the things that I learned was that the design element that is hardest to achieve is stiffness. So if you try to duplicate the stiffness of a nice steel frame using carbon fiber the resulting frame will be much stronger than it needs to be. This is especially true on the wheels. Most disk or strip carbon wheels are not as stiff laterally as a 32 hole spoke wheel. When you get a wheel like the Specialized/Dupont wheel (which is made from carbon fiber) as stiff as the normal spoke wheel it is very strong. In fact if designed and built correctly carbon fiber parts are vastly stronger and safer than metal. Race car chassis made with this material are orders of magnitude safer than the metal ones they replaced. And they are lighter and stiffer to boot. UV resistance is a design detail that any good part will address.
Jim Merz Bainbridge Is. WA
-----Original Message----- From: classicrendezvous-admin@bikelist.org [mailto:classicrendezvous-admin@bikelist.org] On Behalf Of GPVB1@cs.com Sent: Thursday, August 29, 2002 3:12 PM To: classicrendezvous@bikelist.org Subject: Re: [CR] New Equipment Failure Rate
Tom D. wrote:
<snip>
> Bob, 9-speed Ace has been around since 96 IIRC, and the new Record
group
> rolled out in 1995, though there have been annual changes, as is now
> standard for Campy. Six or seven years is a long time. Under an
elite/pro
> rider, a season or two is all that can be expected of this stuff, as
was
> the case with NR/SR stuff.
>
>
<snip>
Tom:
Six or seven years is definitely *not* a long time in terms of major bicycle component durability IMHO! 20 - 40,000 miles (based on your 1-2 year figure) under a pro-level rider should do less damage to a set of cranks than the same amount of miles from an equivalently-powerful amateur (the pro should have a more consistent and smooth cadence and power delivery - less load
fluctuation).
The Campy Record cranks that many say are so crappy have been around since 1958 - that's forty-four years, or nearly seven times as long.... The vast majority of 'em still ain't broken yet!
What's the predicted useful life of the glue in carbon-fiber cranks if they're exposed to Southern California levels of Ulraviolet light exposure eight hours a day? Five years? Ten?
As far as the machined aluminum cranks that are out there on the market are concerned - intuitively, a crank arm CNC'ed from raw aluminum will likely not be as strong or durable as an equivalent-section forged aluminum one - think about it for a moment..... Do racing engine manufacturers use CNC'ed crankshafts? No - they are forged. Same goes for the crankshafts of 18,000 horsepower diesel ship engines.
Again, I think folks have a ton of 20/20 hindsight regarding vintage bicycle part design. We all enjoy being armchair quarterbacks, but you can't re-design something in the 1970s while sitting in the 21st Century (well, at least not without a time machine...).
The new bikes are often worn as a fashion statement, and changed frequently, along with the jersey, shorts, helmet, accessories, SUV, etc. This is because many of the "new age" roadies come from a motorcycle/MTB background, where spending big bucks often to "upgrade" your ride/equipment is considered part of the game. Nothing inherently wrong with that; the Marketing folks have a field day with it, but it is certainly unnecessary, and encourages the spread of our growing "throw-away" society (e.g. frames / components that only need to "last one or two years").
Cheers,
Greg "No user-serviceable parts inside" Parker A2 MI USA Where we are "Recycling old Campy parts for a better tomorrow"
(heeheehee.......)