At 5:03 PM +0000 11/3/08, billydavid13@comcast.net wrote:
> On the one p
>oint of the pro peleton's lag in adopting cotterless cranks - where Jan has
> asserted the reason [or, at least, a reason] being a wider Q-Factor -
> which Steve Maasland says is unsupported by evidence - It seems pretty cle
>ar that there was a lag. Even a casual perusal of '50s race photos shows a
>huge preponderance of cottered cranks 'til late in the decade.
During the 1930s, there was great concern among racers with respect to mechanical resistances. It was thought that having a straight chainline was crucial. Bending the chain in a figure-8 was considered adding too much friction. Even a spring-loaded chain tensioner was considered adding friction. These concerns lasted into the 1950s, as you can see from many derailleurs that either automatically adjusted the chain tension as you shifted, or even had a secondary lever that allowed you to adjust the chain tension. And the width of pedaling was one other concern.
Even though we may find it hard to believe today, weight was not a major concern. A racing handbook in the late 1920s said that only the weight of the rear wheel was of slight concern, because it was powered, but that the front wheel mattered much less.
The adoption of aluminum cranks went in stages. In the 1930s and especially after the war, weight became more of concern. Rene Vietto rode the 1948 Tour de France on an aluminum Barra that is light even by today's standards. The bike is featured in our book "The Competition Bicycle," so I had the opportunity to examine it in detail.
Many riders began to ride aluminum cranks during mountain stages, where weight presumably mattered most. At the same time, you often see the same riders on steel cranks for flat stages. During the days when switching bikes was not allowed, this meant that the mechanics had to change cranks and BB overnight! A logical reason for the cottered cranks on the flat stages was that weight did not matter, and so the racers preferred the narrower tread (Q factor) of the cottered steel cranks. The alternative, widely accepted explanation used to be that racers were concerned that their cranks might break. However, this does not make sense. Cranks were more likely to break during mountain stages than during flat stages, yet the same racers used aluminum cranks in the mountains.
The concern for tread (Q factor) continued into the 1960s. Campagnolo's cranks had their breakthrough when they were redesigned with narrower arms and without the raised pedal lip. Again, in Le Cycle, I found this regarding breakage of Campagnolo cranks in the 1962 Tour de France (rough translation by me):
"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, 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 note the perfect track record of the Stronglight cranks and TA rings."
Source: Le Cycle, July/August 1962, p. 33
Note that in 1963, despite the rash of broken cranks the year before, more riders than ever used Campagnolo cranks. Campagnolo equipped more than 90% of the Tour de France racers that year.
I apologize to long-term members for digging this out of the archives again...
Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
http://www.bikequarterly.com