Chuck,
I don't mean to be snide at all. I'd like to find out more about these things. Where did you read that pros didn't use aluminum cranks because they feared breakage? For example, I'd love to know what the Italian literature had to say about that...
I agree with you that Rebour isn't always 100% reliable, but he was very interested in racing (a racer himself in the 1930s), and he was at the Tour and talked to the riders, mechanics, team managers, etc. I haven't seen any better accounts, but I'd love to know what others wrote.
To back up my claims, I looked through the CR archives, and found this message (below) I posted a long time ago. Once again, Rebour may be wrong, but it seems logical that Campagnolo redesigned their cranks after only 4 years on the market to reduce the Q factor, while working hard to make the new ones look almost indistinguishable from the old. From what I have read, the early ones don't break, it is the second, thinner design that does. This seems to be confirmed by Rebour, who suggests going back to the earlier design.
So that makes it two references to Q factor with respect to racers, one from the 1950s, one from 1962. There are two designs that seem to strive to reduce Q factor: TA's first crank (and TA rarely made something just to be "hot and new," but usually to be better), and Campagnolo's second generation crank.
It is interesting to note the in the Tour 1963, more than 80 riders switched from steel and other non-Campy cranks to Campy (110 of the rides rode Campy, whereas there were only a handful in 1962) - the year after there had been a rash of crank breakages! If they really were concerned about alloy cranks breaking, why did they adopt them the year after their concerns had proven correct?
Anquetil won the 1962 Tour on Stronglight (alloy) cranks, but in 1963, he won on Campy. Clearly, the pros had confidence that Campy had solved the problem. A cynic might say they were paid to ride the cranks, and that it was hard to say no to hard cash... but it is hard to imagine Anquetil risking a tour victory for some product endorsement money (which wasn't a huge amount back then, I am told.)
Speaking of metallurgy, I doubt there were huge advances between a 1950s Stronglight 49D and the 1962 Stronglight model that Anquetil used to win the Tour. From what I've heard, the metallurgy of Campagnolo cranks in fact increases the risk of breakage, compared to other crank alloys. (Check the CR posts, it was some tests Specialized had done in the 1970s.) So racers adopted aluminum cranks that were more likely to break than the ones they had echewed years before.
I do not doubt that Q factor then fell by the wayside, and that is why you didn't hear about it. Everybody was riding Campy cranks, and they all had the same Q factor, as did the others on the market. So there was nothing to talk about.
Design concerns in cycling are cyclical. When I started racing seriously in the late 1980s, C-Record was the hot stuff. Everybody was concerned about aerodynamics, hardly anybody talked about weight - that came in the mid-1990s. But to conclude that before the mid-1990s, nobody was concerned about weight would be wrong, as evidenced by Merckx' bikes and many others! It just wasn't a concern for a while (which is why Campagnolo replaced their Super Record ccomponents with a group that weighed significantly more.) It's just that I entered the sport during a period when weight was not of concern.
-- Jan Heine, Seattle Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com
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From the aforementioned 1962 Le Cycle, by D. Rebour on the technical side of the Tour de France:
"In fact, there were some Italian cranks made from light alloy that broke. In my opinion, this is due to the material used in a particular series, no doubt by the subcontractor who supplied the raw forgings, who might have mistakenly used an alloy that is too "dry," and not the one usually used, which until now, had given perfect satisfaction.
Knowing how reputable this brand is, without a doubt the necessary has already been done, but it is very difficult to retrieve a defective series after quality control could not detect this hidden flaw.
Perhaps, if the manufacturer had retained the original cross-section (of the crank arms), this problem would not have occurred.
But it is obvious, that because of demands of the racers, who always want to reduce the width of the pedaling (what we call Q factor today), the manufacturer was moved to reduce the thickness of the cranks by 2 mm. Even though the wise decision was taken to augment the width of the part by the same measure, the reduction was made in the direction of the maximum load, where flex can occur when the pedal is pushed. I think it would be good to return to the original cross-section.
This does not keep us from admiring the precision and finish of the Campagnolo cranks, and also remark the perfect record of the Stronglight cranks and TA rings."
Translation Jan Heine (rough, sorry, no time to polish). Translator's notes in parentheses.
Source: Le Cycle, July/August 1962, p. 33
Jan Heine, Seattle