[CR]Long answer to Super Record BB question, drifts OT.

(Example: Racing:Beryl Burton)

Date: Wed, 1 Jun 2005 13:08:28 -0700 (PDT)
From: "Tom Dalton" <tom_s_dalton@yahoo.com>
To: JohnThompson@new.rr.com
cc: classicrendezvous@bikelist.org
Subject: [CR]Long answer to Super Record BB question, drifts OT.

John Thompson wrote:

Zeus was never as widely popular as Campagnolo, and this surely explains at least part of why you don't hear much about Zeus Ti breakage problems.

I think you have a very good point here, John. Zeus 2000 failures were very, very rare indeed, for the obvious reason that the group was very, very rare. I've heard tell that the groups were actually more expensive than SR, and I know they were neither widely available or widely sought after (for whatever reason). I doubt very strongly that the ti hub axles, for example, were significantly more reliable than the Campy ti hub axles that were deemed to fragile to even bring to market.

Even looking at Campy SR ti parts, which were probably maufactured in numbers exceeding the total of OMAS, Stronglight and Zeus production (by OMAS), we don't have much to go on when we make generalizations about a propensity toward catastrophic failure. I have never seen a failed ti bb or pedal axle of any brand in the flesh (am I starting to sound like Parker?). I have seen two NR steel BB axles that failed in a spiral fracture outboard of the non-drive cup, though I'd wager that the bikes were laid down good and hard at some point prior to the "sudden" failure.

The thing I do know about ti BBs is not that they failed (though surely some did, like Fignon's 2nd gen SR) but that many users complained that they were too flexy. One guy I know who was not very big or strong, but who loved to buy the best stuff, went through Campy and some other brand of Ti BB, and deemed them too flexy, before settling on Stronglight. It is interesting, and news to me, that the Stronglight spindle was thicker in the middle, but it makes sense. I think that there was/is nothing wrong with using titanium, or carbon, or magnesium or whatever for bike parts. The problem seems to arsise when manufacturer's retain a conventional design features and possibly even all the dimensions (form factor?) while changing materials. This is a particular problem when a manufacturer takes a less dense material (ti vs. steel) and machines it to the same size and shape as the denser material to lighten the part in proportion to the density difference. This seems to be exactly what Campy did with the 1st gen SR BB. and they were said to be super-duper flexy.

I think you're correct that not boring out the material in the center of the second gen axle wouldn't increase bending or torsional strength as much as going to an OS center like Stronglight did. As for the nutted design, I have always assumed that this was done to retain as much material as possible at the outboard ends of the axle, rather than boring and tapping for bolts. I suspect that this attachment worked just fine because it the 10mm stud end of the spindle retained the 1.0mm thread pitch typical 8mmx1 fixing bolt. Cheapie BBs use a coarser pitch on this fitting which means less compression of the arm onto the spindle at a given torque.

As for titanium use predating the SR group, consider that the SR-71, which was conceived in the era of the Chevy Bel Aire was made primarily from titanium. 40+ years later it's also still the fastest jet ever in service (that we know of). Cold War tax dollars allowed Lockheed to learn all sorts of stuff about Ti fabrication, some of which may still be secret. (Check out "Skunk Works" by Ben Rich for more).

Drifting a bit closer to topic, I think Campy still suffers from this "retain the basic design, apply the cool new material" approach. In fact, they are worse than ever, replacing aluminum with carbon all over the place with little revision in design. I guess it's good for marketing, but I refuse to accept that this does not lead to either weaker parts, or parts that are stronger (heavier) than necessary. Looking back at the second gen BB, you can see where Campy's inability or unwillingness to really change the basic BB design lead to a part that did not best exploit the properties of a new material. By the time they made it solid, the weight benefit was significantly reduced, and it was still said to be a more flexible part. A more common example would be "early" aluminum frames, like Alans, that retained lugs and the basic dimensions of a steel bike. Compare this to a Klein, and the far better bikes that this would lead to, in which the wall thickness, diameter and profiles of the tubes were much better suited to exploit aluminum's characteristics. Look also at Shimano's current crank and BB, which totally revises the entire design, but still uses the steel spindle and alloy arm. They are pursuing the best designs with the established materials while Campy is reusing old designs on new materials, which seems pretty stupid to me. Of the old square taper BB, for example, the faithful will say "tried and proven design, backward compatible, etc...." To which I respond "outdated, not opitmal for the material, thinking inside the box." Yikes, I spoke "office."

Tom Dalton

Bethlehem PA

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