> > 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/
The illustration shows a standard set of ROSA chainrings, which were made by the Cyclo derailleur company. The BCD is the same as the Stronglight cranks.
Don't use the Data Book to date anything. It was compiled from a rather incomplete collection of old magazines. For most items, there are no captions. It's a nice source of inspiration, for example, today's builders can get great ideas about various ways that things were done.
To figure out what happened and when, you need to go to the original
literature. For example, the illustration of the chainwheels probably
was taken from an ad published in 1935. The same illustration was
used in 1933 ads by Cyclo as well (Le Cycliste Feb./March 1933). So
the ROSA chainwheels weren't introduced in 1935, but before 1933.
>This eventually became extremely popular on Stronglight
> > (mod 49) cranks during the 1950s - 70s
>the stronglight 5 pin cranks came out in 1934-1935.
1933.
>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.
It was a standard BCD, used by many companies. The Rosa chainrings
appear to predate the Stronglight cranks (see above). Rosa/Cyclo did
not make cranks, but there were other cranks that used this BCD.
>''Cyclo Tank'' is this the original name for Cyclo?
Tank was a separate company. They made pedals and freewheels, as well as hubs and cassette hubs. The latter were marketed under the Cyclo-Tank name.
Note that one of the drawings shows a triple chainring setup. Those were available already before 1930...
Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
http://www.vintagebicyclepress.com