Jim This is a fun law of sines problem. As we all know the theoretical top tube length is the one that tells you about fit, since it's the level distance from the seat tube to the head tube. But since you asked, here's how you set it up:
We've got a triangle with three sides with lengths a, b and c. It has three angles: A, B and C that are opposite each of the three sides. The law of sines tells us that: a/(sin A) = b/(sin B) = c/(sin C) What this means is if you know a few of these, you can calculate the rest. The triangle I'm drawing has two top tube lines that intersect at the head tube: a = the THEORETICAL TT, and b = the ACTUAL TT . The third side is c = the short line along the seat tube that connects the two top tube sides. Angle C opposite line C is the slope of the actual top tube = 6 degrees Angle B opposite the actual TT is the seat tube angle = 71.8 degrees Angle A opposite the theoretical TT is the rest = (180 - 71.8 - 6) = 102.2 degrees Since we know A, B, C and a, we can plug into the law of sines and solve a/(sin A) = b/(sin B) b = (sin B) * a/(sin A) b = (sin 71.8) * 57.5cm/(sin 102.2) = 55.88cm On Friday, June 27, 2014 7:55:51 AM UTC-7, Jim Bronson wrote: > > What's the (non-theoretical) TT on this frame? The TT listed on the > Rivendell geometry charts is theoretical. > > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
