Some support for Jan's conclusion about the belief in minimizing tread may come from the expense not just of producing but also stocking crank spindles in lengths that don't vary much. eg 112 vs 115mm. I can appreciate the exquisite rightness of spot-on alignment with a single chainwheel and cog, but tread minimization would be right there with equipment-anorexia to explain why one would put in a different spindle to save 1.5mm per side.
Any reports, Jan, of racers who had bunionectomies to reduce their tread? There must have been candidates who could pare 5mm per side from the procedure.
But, about aluminum crankarm breakage. I'm puzzled about engineering errors about a failure mode I would have associated with fatigue over much longer use.
Harry Travis Washington, DC USA
On Tue, Nov 4, 2008 at 5:56 PM, Jan Heine <heine94@earthlink.net> wrote:
> At 7:46 PM +0200 11/4/08, Amir Avitzur wrote:
>
>> As a kid I read Bicycling!
>> Even then, I could see that a lot of what was written didn't jive with my
>> experience on the road. I'd hate to think that old Bicycling! magazines
>> are
>> being considered historically correct today. (Same goes for a whole slew
>> of
>> bike books from that period.)
>>
>> A lot of the articles in Bicycling! in the 70's seemed to be spoon-fed by
>> the advertisers. I wonder if 40's and 50's French or Italian bike mags
>> were
>> any better.
>>
>> So here's my question:
>>
>> Where do you get your bicycle history?
>>
>
> If you are looking for historic fact (Who rode which bike, etc.), historic
> photos are best. They don't lie. Rebour's drawings, which usually were made
> from photos, are quite useful, too. If a photo shows a certain component,
> you can assume that component existed. If a racer is shown during a race
> with that component, you can assume he rode that component.
>
> If you are looking for dates, the contemporary literature is best. If
> Bicycling showcases the latest Campagnolo derailleur, you know that it
> existed, at least as a prototype. Maybe Bicycling missed the boat, and the
> part has been available for a while, so introduction dates are minimum ages,
> as they say in geology. (The part may have been introduced earlier, but not
> later.)
>
> If you are looking for what people were thinking at a certain time, the
> contemporary literature is my best source. People's recollections change
> over time, so even if somebody remembers something, it may not have happened
> that way.
>
> For technical issues, you have to do your own testing, unless the test
> procedures are described in detail and you find them adequate. Daniel Rebour
> wrote in the 1950s that your bike goes up when you turn the handlebars. The
> opposite is true - it goes down - and that is what causes wheel flop. Rebour
> was considered the foremost expert on bicycle technology, but he made many
> similar errors. So be careful about technical analyses then and now.
>
> To give you an example, in the research about steel cranks vs. aluminum
> cranks, we first went to historic photos (thanks to Aldo for supplying a
> bunch). This allowed us to determine when racers started to use aluminum
> cranks (late 1940s), and during which stages they used them (more in the
> mountains than on the flats).
>
> To find out why they did not switch wholesale to aluminum cranks, I asked a
> number of people, but nobody knew. Ernest Csuka laughed and said "The racers
> were concerned about anything aluminum, because it might break." I am sure
> that was true at some point in the 1930s, but by the late 1940s, things were
> more complex. It made no sense that racers would use fragile aluminum cranks
> in the mountains, but sturdy steel ones on the flats. Sprints back then were
> high-rpm affairs, with the riders staying seated, so that would not stress
> the cranks. If a crank would break, it was during an attack in the
> mountains.
>
> So then I turned to the literature, and found numerous mentions of concerns
> about crank tread (I prefer the classic term over the modern jargon "Q
> factor"). And I also found the references I posted earlier that specifically
> said that racers were concerned about crank tread and thus resisted aluminum
> cranks.
>
> I then asked people about crank tread, and several builders confirmed that
> crank tread was a huge concern of the racers back then. Racers specifically
> asked for frames that minimized tread when they got their custom bikes made.
>
> I also measured the tread of a number of historic racing bikes. Working on
> our book "The Competition Bicycle" gave me access to quite a few very
> historic machines. The steel cranks generally were about 7 mm narrower than
> the aluminum ones - see the chart of various cranks and their tread width in
> a recent issue of Bicycle Quarterly. The reason for that are the tapers:
> aluminum cranks can move up on the tapers each time they are taken off -
> especially with the relatively soft alloys used by Stronglight at the time.
> So you had to have a little extra space. Steel cranks would always end up in
> exactly the same spot on the BB spindle.
>
> For the time being, I am comfortable with the conclusion that racers
> resisted aluminum cranks in the 1940s because they were concerned about
> tread width. I suspect - without any evidence - that in the 1930s, they
> really were concerned about the cranks breaking, but by the 1940s, the
> cranks had proven their worth, even in the Tour de France under some of the
> strongest climbers.
>
> Jan Heine
> Editor
> Bicycle Quarterly
> 140 Lakeside Ave #C
> Seattle WA 98122
> http://www.bikequarterly.com