bob, the stronglight 5 pin cranks came out in 1934-1935. They were on the Carminargent. The Cyclo 5 pin chainrings were the same BCD as the Stronglight and TA. Williams(british company) had been doing the 5 pin back in the 1920s, maybe even before. I think I remember asking why it was adopted many years ago, and the response was sufficient, but it escapes me now. joel ralph flood philadelphia, PA
On Fri, Jan 30, 2009 at 9:02 AM, <Stronglight49@aol.com> wrote:
> Here is a scan showing one of the earliest depictions I've seen
> of a classic "5-pin" chainring set. It is shown in The Data Book
> among a page of Cyclo-Tank innovations, dated 1935.
>
> http://farm4.static.flickr.com/
>
> This eventually became extremely popular on Stronglight
> (mod 49) cranks during the 1950s - 70s and on TA's Pro
> 5-vis cranks introduced in 1963. But the design had
> already been quite commonly used on many different
> manufacturers' steel cranks throughout the 1940s and
> was clearly used earlier.
>
> There is really no way of accurately determining the bolt
> circle diameter used on the example pictured. Later
> cranks and chainrings from MANY manufacturers had
> settled on 50.4 mm. for the smaller circle connecting
> rings to cranks. This is an extremely odd size, which
> also has no obvious direct decimal or fractional BSC
> (British) equivalent.
>
> Does anyone know why that diameter first adopted...
> and who had first used it? Was it perhaps simply carried
> over from other machinery completely unrelated to bicycles?
>
>
>
> BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA
>
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