I only have seen one or two Rebour drawings with 4 chainrings. I think it was a publicity stunt, more than anything else. Back then, every builder made something amazing for the Paris show, hoping to catch Rebour's eye, and then get free publicity by being included in the magazines. Usually that was a novel solution for racks, internal derailleur cables and such.
The drawings show cross-over gearing. From memory, it may have been 50-44-36-26 or something like that.
Also, there was some event where more gears got you extra points. But that was in the 1940s, and people stretched the imagination by using triples and 6-speed (gasp!) freewheels. These were made by brazing extra cogs onto 5-speed freewheels.
Finally, I have heard rumors that some people used 4 chainrings on tandems. However, I never have seen a machine with that setup.
If VBQ had an April 1 issue, I might include a techical article on "double half-step" - half-step is nice, but with a granny, you get very large steps in the smallest gear. By using four rings, you could use a 50-47-28-25 or so, and get half-step the second time around!
Jan Heine, Seattle
Editor/Publisher
Vintage Bicycle Quarterly
c/o Il Vecchio Bicycles
140 Lakeside Ave, Ste. C
Seattle WA 98122
http://www.mindspring.com/
>I've heard that some Alex Singer and other French touring bikes came
>with 4 chainrings, and I know that it is possible to fit 4 chainrings on
>a TA Pro 5 Vis crank. I'm curious, what chainring sizes were used on
>the quad cranks, and what freewheels?
>
>Thanks
>Sean Smith
>Huntington Beach, CA