>I think it is reasonable to assert that mountain bike needs lead to some
>important experimentation and the re-discovery that you can make a lighter
>stronger frame by increasing the diameter of the tubes. It is fundamental
>mechanics theory but long overlooked/ignored/unknown by the craftsman
>builders.
>
>Todd Teachout
>Hercules, CA
Todd,
From a 1970s perspective, I think you may be right. The lovely racing bikes of that era were all pretty similar, and lacking innovation.
However, if one goes back in time, there was a lot of experimentation with tubing diameters - and I don't mean the super-skinny tubes of American department store bikes!
To get some data, let's compile a list of the makers who experimented with oversize tubes on single bikes (let's not include tandems for now. Here is a start:
- Bates: Cantiflex tubing was OS in the middle, but standard diameter at the ends. - A. S. Gillott: Tapertubes were OS at BB end - Herse: 30 mm OS down tubes on request (appear to have been thinwall. - Singer: singles built from OS tandem tubing, found to be harsh-riding and not much fun according to Ernest Csuka. Tandem tubing has relatively thick walls. - Schulz in 1930s France used a very OS central tube. The design apparently inspired the Paris Galibier (which added two very small diameter top tubes).
Who else? Anybody in Italy? If somebody knows, the wall thicknesses of Bates' Cantiflex and Gillott's Tapertubes would be of interest, too.
I think assuming the craftspeople building bikes in the old days were ignorant is a bit arrogant. Many of them worked with serious riders, who gave excellent feedback, and they put a lot of thought into their machines. The bigger makers - sure, I am willing to believe that there wasn't much analysis going on there. But people like Gillott, Herse, Bates and others had a very good grasp on things - certainly more so than many of the early mountain bikers, who started with junky bikes and could not build upon much of a cycling culture.
When we don't understand something, we often assume it was done without much thought. The same applied to the front-end geometries of old French bikes. If you believe that "more trail = more stable handling," their geometries make no sense at all. I remember a post by an "expert" on the framebuilders' list claiming that "they didn't think much about front-end geometry back then."
However, after much study and analysis, we found that nothing could be further from the truth. Especially Rene Herse bikes clearly had a front-end geometry adapted to their intended purposes. In fact, Peter Weigle recently told me about the front-end geometry he plans to use for his next "sportif" bike. It came as little suprise that it exactly matches that of a 1951 Rene Herse sportif (Peter did not know what geometries Herse used on his sportifs). Both bikes are intended for the same purpose and the same tire size... Once you understand the complex dynamics involved (low-speed vs. high-speed stability, weight of handlebar bag, pneumatic trail, etc.), you realize that there was a lot of thinking behind it. You may disagree, because you prefer a bike to handle or feel different, but that does not mean they were ignorant when they did what they did.
And a final note regarding the viability of OS tubing: The often quoted 50:1 rule for older steels really makes little sense. Reynolds offered (in France, not in Britain) 531 in 3/10 mm wall thickness. For a 28 mm down tube, this comes out to a ratio of about 1:93. Sure, Those frames were fragile, especially when dented, but many held up for years of hard riding. Tours de France were won on them - for example, Ocana's Gitanes were reported to be made of the stuff.
For comparison, a modern 1 1/4 down tube in a 0.4 mm wall thickness had a ratio of 1:79. So I don't see a reason why the same steel that could be made into 0.3 mm wall standard-diameter tubes could not be made in 0.4 mm OS tubes. So it was less a question of "could not be done," but "would not be done." I doubt it was ignorance. I believe it was that they tried it, and at the time, they preferred standard diameters. Times have changed, riding styles, distances, components, road conditions. All these factors influence the feel we want in a bike. So OS may make sense now when it did not decades ago.
Jan Heine
Editor/Publisher
Vintage Bicycle Quarterly
c/o Il Vecchio Bicycles
140 Lakeside Ave, Ste. C
Seattle WA 98122
http://www.vintagebicyclepress.com