This appeared on the iBOB list yesterday and I thought this might be an interesting subject for discussion on the CR list. Anyone want to add their comments?
On Apr 20, 2007, at 7:22 AM, Jan Heine wrote:
> More importantly, we (Bicycle Quarterly) put the history in
> perspective. Many of our readers don't care when a logo on a crank
> was changed, but they are fascinated by finding out why old bikes
> were designed in certain ways and what we can learn from that. For
> example, why did racers continue to use heavier steel cranks for
> almost 25 years after the Stronglights were introduced? In various
> web forums, you read that it was because the racers feared that the
> aluminum cranks broke. BQ showed that many racers in the early
> 1950s used aluminum cranks in mountain stages - if they were afraid
> of failure, they would not have used them on stages where cranks
> suffer from the highest loads. However, these racers switched to
> steel cranks for flat stages. Combined with other evidence, we
> concluded that on the flats, where weight matters little, the
> racers preferred the lower tread (Q factor) of the steel cranks. In
> the mountains, they were willing to pedal with their feet apart in
> exchange for almost a pound less in weight. Suddenly, you realize
> that there was a method behind this, rather than just "racers
> always are conservative." And of course, it illustrates that racers
> believed tread (Q factor) was very important, something that many
> people still believe today, even though many crank manufacturers
> don't care about tread at all.
Jan writes, "BQ (Bicycle Quarterly) showed that many racers in the early 1950s used aluminum cranks in mountain stages - if they were afraid of failure, they would not have used them on stages where cranks suffer from the highest loads. However, these racers switched to steel cranks for flat stages."
Aluminum cranks were first used by professional racers in the early '50s on mountain stages because of their light weight. Even though aluminum cranks were introduced in the mid 1930s, pro racers were too conservative to try them since they were new and unproven. Also aluminum's lack of a fatigue limit was well known (aluminum bike frames date back before 1900), so what better reason not to use aluminum cranks on flat stages since weight wasn't an issue on the flats. Also bear in mind that WWII interrupted the 25 years that it took pro racers to ride with aluminum cranks (no racing of any significance for the ten years between 1939 and 1948).
Jan writes, "Combined with other evidence, we (Bicycle Quarterly) concluded that on the flats, where weight matters little, the racers preferred the lower tread (Q factor) of the steel cranks."
I think what the pro racers preferred was the piece of mind of racing on their race proven steel cranks. In all my reading and talking to geezers that raced I have never once heard a concern for the different tread dimension (Q factor) of steel and aluminum cranks. I think your conclusion that racers didn't use aluminum cranks because the tread dimension was slightly wider, not because they didn't trust them, is highly suspect given the overall conservative nature of pro racing back in the thirties and forties.
Incidentally I measured the distance the pedals are moved outwards, comparing a 1950 Bianchi Folgorissima equipped with steel Magistroni cranks and a 1979 Bianchi Superleggera equipped with aluminum Campagnolo Super Record cranks: it's a pretty insignificant 8.5mm on each side!
Chuck Schmidt
South Pasadena, CA