At 5:55 PM -0700 5/11/09, Kurt Sperry wrote:
>Now I have
>no idea whatever how to tell a prewar 49D from a postwar example of
this cycling icon,
The shape of the groove in the middle of the arm is different. The pre-war groove ended in a perfect semi-circle, the post-war groove was more pointed.
I am not positive that the change appeared exactly in 1945/46, because it is impossible to date cranks, and some builders may have used pre-war materials after the war, and other bikes may have had their cranks replaced.
However, based on my observations, all original pre-war bikes with Stronglight cranks (such as the Caminargent in "The Competition Bicycle") have the round groove end, and no post-war bikes with original cranks do. (In "The Golden Age of Handbuilt Bicycles," there is a 1930s Reyhand with a post-war crankset... which was duly noted in the appendix with the changes to the bikes.)
Now all you need to do is go to a swap meet and find one of the pre-war cranks... or outbid all the others on e-bay, who think they are bidding for a run-of-the-mill post-war crankset!
However, upon thinking about it, the pre-war arms don't appear to be quite so rare after all. I have seen a number of them on bikes here and there. They probably are like the first generation Campy cranks with the raised lip around the pedal hole. Super-rare until people started looking in their garages, and quite a few appeared.
Jan Heine
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Bicycle Quarterly
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