Re: [CR]Mandaic Frame

(Example: Books:Ron Kitching)

From: <Wdgadd@aol.com>
Date: Sat, 4 Aug 2001 22:14:02 EDT
Subject: Re: [CR]Mandaic Frame
To: Philcycles@aol.com, classicrendezvous@bikelist.org


Columbus Genius was a top of the line Nivacrom alloy product in the early 90's (introduced in '91). Wall thickness is .7/.4/.7 for top and downtubes in "standard oversize," and either single butted .8/.6 or double butted .75/.4/.6 seattubes. There is also an outside butted seattube available, as well as a 33 mm O.D. downtube with .8/.5/.8 walls and a 31.7 mm O.D. seattube with single butted .8/.5 walls.
      The unusual thing about Genius is what Columbus calls Differential Shape Butting. The headtube end butts on the top and down tubes are longer on the top and bottom, respectively, and the BB end of the downtube and seattube (except the D.B. seattube) have butts that are longer in the horizontal plane than the vertical plane. The idea, as I understand it, is to remove materiel from the less highly stressed areas of the butted portion of the tube. There are little raised bumps inside the ends of the tubes so the builder can orient them correctly (I scrapped a Genius downtube by assuming that the notch on both the toptube and downtube were to be on the underside of the tube-wrong!)I've also heard from reliable sources that some well regarded builders (none of them Listmembers!) had downtube failures when using Genius-has anyone else heard this? Regards, Wes Gadd