Re: [CR]Re: broken bike components revisited (part 387)

(Example: Events:Cirque du Cyclisme)

Date: Tue, 30 Apr 2002 11:47:15 -0700 (PDT)
From: "Tom Dalton" <tom_s_dalton@yahoo.com>
Subject: Re: [CR]Re: broken bike components revisited (part 387)
To: classicrendezvous@bikelist.org
In-Reply-To: <ea.26dcfb79.2a00394e@aol.com>


Just had yet another look at Ric's images of failed arms. I saw one common denominator; all the arms looked thoroughly trashed, with lots of dents, scratches, abrasion, and corrosion. Except for the freaky longitudinal failure on the Campy arm (a real defect???) all these arms look like they've been pushed too far. Another interesting aspect is that many of the failure surfaces have black oxidiation half way across, or more. This suggests that the cracks existed for some time prior to the "catastrophic" failure. If the riders had their eyes open, these cracks could be spotted before a serious incident. Instead, the owners of these parts were pedaling around on cranks that were cracked half way through. Naturally, the last bit fails suddenly. Tom NortonMarg@aol.com wrote: In a message dated 4/27/02 12:57:36 PM Pacific Daylight Time, GPVB1@cs.com writes:

<< I think you may have just pointed out that any manufacturer's BB axle can break! If you ride long enough and far enough, you may end up with a total of zero manufacturer's axles that you will trust.

IMHO, if you had an Engineer's inside view of the Automotive or other major Manufacturing business and saw the details of exactly what gets sold to the public, I fear you might never drive another car or use another toaster oven! Engineering and Manufacturing something for use by humans is always a compromise.

Bottom line: any part/component/machine/thing can break. Some do fail; the vast majority don't. Most (yes, not all) that break do so after hundreds of thousands (or indeed millions) of cycles of use. Some break due to exceeding Design loads and/or stresses. Some finally fatigue due to old age at many times Design life (how long does anyone think that Tullio's Engineers intended a 1958 Record crankarm to last?). There are a zillion other reasons why something can fail. Ask Laurent Fignon if his infamous SR BB axle failure in the TdF was "catastrophic" or not. Ti (and many other "exotic" materials) fail that way. One of the best things about steel is that it rarely fails suddenly and catastrophically. Steel is real!

You may want to see Damon Rinard's website for pics. of various manufacturers' broken bicycle parts (http//pardo.net/pardo/bike/pic/fail/FAIL-001.html for cranks and spindles, for example).

What I noticed about the better BBs that were contemporary to and followed the Campy Ti axle (I always thought that one looked too skinny to not flex like crazy) was that the axle diameter increased. It may not be exact, but a principle of tubing is that as diameter increases, strength increases pi times faster than weight. Some of the cartridges used a skinny axle with relatively larger bearings. The ones I like have larger diameter axles and hence smaller bearings with a larger id. Nadax made one that was bullet proof and I think a little adjustable for any play that developed in the bearing itself. Clearly some manufacturers paid more attention to sound engineering principles than others. I have chosen carefully and have had no further failures and I check my parts regularly. A clean bicycle is a well inspected bicycle. I may not have the lightest bbs in the world, but they're plenty light enough if they have alloy cups and a Ti axle, although even the steel axle version isn't so heavy I won't use it. At this point in my "career" I'm not riding so many miles that it's an issue, and I'm not using Fignon size gears. I'm not at all surprised he broke one of those early Ti axles. Stevan Thomas Alameda, CA _______________________________________________

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