> >>but 7/10 always has been the
>>>standard.
>
>Just a further comment. I'd read Jan identifying tubes this way and didn't
>question it because he almost always writing about the technical trials bik
es
>which I assumed would use specially drawn tubing and a 1mm butt would make
>sense. That's where the stress is concentrated and a thick end would
>make a good
>deal of sense, especially as most of those bikes were fillit brazed. Thanks
,
>Jan, for clarifyhing this.
>Phil Brown
>San Rafael. Calif.
After talking with some people offlist, I am having more doubts whether these designations are to be taken literally. Certainly, 7/10 mm in the center of a tube would be quite heavy a gauge for 531, yet these frames aren't heavy at all.
The old builders really designed bikes based on experience, not calculations. They did not care whether a tube was 0.7 mm or 0.5 mm in the center, but they knew what type of ride they would get out of that tube, and that was all that mattered to them. So the tube was known as "Sept-dizièmes" (Seven-tenths), but nobody cared what the actual measurements were.
Sort of like 2 x 4" lumber today - nobody is too bothered by the fact that it measures neither 2" nor 4", but 1.75 x 3.75" or something like that. -- Jan Heine, Seattle Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com