Originally Posted by
unterhausen
I think if you look through the NAHBS tandems, that most of them are using a larger, round, 4130 tube. I love the way the old reynolds oval boom tubes looked, but they aren't as stiff. People are used to it now that tandem builders have been doing this for decades. You aren't bending the boom tube in the major dimension of the oval all that much. I think they did it that way so they would fit a larger tube on a bb shell, and that's an issue with a round tube of similar section. You have to remember that when the Reynolds tandem tubing set came out, it was the only set of tubing with oversize tubes on the market. We were so set in our ways that Klien actually sued Cannondale over using larger section tubes, it was so unheard-of. I find it hard to get over the old ways, but I usually manage to force myself if the new ways are better or even just easier to source.
U-Man; No argument on your points. Spot on. I am well aware of the bow-wave caused by the advent of the Taylor Bros driven Reynolds 531 butted tandem tube set. Was there then and wanted them bad (for all the good it did me to want). And as a student I couldn't come close to the cost of a built Taylor tandem.
I built my first bike frame (a full sloping top tube tandem for personal use) in 1974-76 from a mix of available tubes; a 1 3/8" chromo downtube, a 1 3/4" round chromo straight gauge boom tube, two 531 HD seat tubes, 531 HD double butted single bike downtubes for all the rest of the tubes, a full sloping cinelli cast crown and the strongest set of Reynolds stays and blades I could get.
I built my first set of bike wheels for that tandem; Phil Wood 48-spoke bolt-on hubs, 27 x 1 1/4" Weinman A129 concave rims and stainless 14g spokes. A Shimano disk and a brace of Mafac canti's provided the stoppage via a set of dual pull levers.
Even though #1 build was an XLg/Lg (25"/23" seat tubes) with maximum length top tubes it was very stiff in all dimensions and tracked perfectly even of steep climbs and descents.
Some regrets looking back were;
1) Setting aside my math results and going with the trend of 130mm rear OLN instead of 145mm (Phil would have made the hubs for 145 at the same cost as 135mm);
2) Not following my instinct which told me a direct lateral tube was the best reinforcement adnd instead going with the trend in running the lateral tube line to the rear dropout. Proud to say that I didn't use the typical 1/2" 'sketti tubes, instead I used 531 HD butted single downtubes back to the stokers seat tube and then an extra pair of HD Reynolds chainstays back to the dropouts with the extra CS length employed to overlap the ST and the rear lateral tube by about 3 inches (lots of brass used at that joint).
3) Letting the bike go and losing track of the jig when moving on from college to the real world... once in a while I will still take out the faded and smudged full scale drawings and stare at them... but enough memory and history for today.
/K