|Anywhere on-line to find old bike geometries?||MeDotOrg|
Aug 6, 2001 8:41 AM
|As people are probably sick of hearing, I crashed my Bianchi Veloce a few weeks ago. Until I get a new frame, I'm riding my 1983 Fuji S-12-S-LTD. It is fascinating to experience the difference between it and the Bianchi. I would love to find the geometry for this frame. Does anyone know of anyplace on-line (or anywhere else for that matter) I could find the geometry for an old Fuji frame?|
|you don't need it||ET|
Aug 6, 2001 9:34 AM
|Take out a tape measure. Anything you measure, you know. In addition to BBH and top tube, measure the seat tube c-t of top tube (call this side c), the vertical drop from top of top tube to (center of) BB (side a), and from center of intersection of seat tube and top of top tube until point on top tube vertically above BB (side b). Repeat a few times to ensure accuracy. Given the age of the bike, many of the dimensions will probably come out exactly to a full, half-, or quarter-inch. Let the seat tube Angle (i.e. the angle opposite side a) be designated A. Then by the Law of Cosines,
a^2 = b^2 + c^2 -2bc cosA
Just solve for cosA, then find the arccosA. This is your seat tube angle. Betcha it's a nice number (after a little rounding due to measurement error), and then you know it's right. If you also want head tube angle, form a triangle which contains the head tube angle either by projecting tubes or by measuring an imaginary side (e.g. from top of fork to intersection of seat tube and top tube). You now again have three sides of a triangle, and repeat formula, where A is head tube angle.
If you don't have a clue what I'm talking about, post the measurements and I'll calculate it for you.
There is a device called a frame angle protractor you can buy or which an LBS might have, but you really don't need it.