Jim I think some of the compounding confusion comes from the Riv site. There, they claim a 100mm dirt drop stem has an effective horizontal extension of 82mm. I think that should simply read 'extension' with 'horizontal' removed. That's what my 100mm dirt drop stem measures to, and only then does the trig make any sense. Every vendor that sells both the dirt drop and the Technomic call them +35deg and -17deg, respectively. Take a glance at the dirt drop stem installed on the bike and it is obvious that the rise on the bike is >>35 degrees from horizontal. It's about 54 degrees (35 degrees in stem rise plus the complement to the headtube angle which in this case is 19 degrees).
So, by my reckoning, the 100mm Dirt Drop stem does in fact have 82mm of extension and ~86.5mm of reach. That I've measured By that same approach, the 80mm Dirt Drop stem has 65mm of extension and ~69.4mm of reach. That I have not measured Using that fact, it turns out that a 80mm dirt drop stem which has 35 degrees of rise in the stem and ~65mm of extension, is within a mm or two of a 7cm Technomic Deluxe in reach. On May 19, 7:54 am, CycloFiend <cyclofi...@earthlink.net> wrote: > on 5/19/10 12:24 AM, happyriding at happyrid...@yahoo.com wrote: > > > > > > > On May 19, 12:36 am, CycloFiend <cyclofi...@earthlink.net> wrote: > >> on 5/18/10 9:57 PM, happyriding at happyrid...@yahoo.com wrote: > > >>> On May 18, 8:38 pm, CycloFiend <cyclofi...@earthlink.net> wrote: > > >>>> I'm not quite following your math (geometry?) on this. When they > >>>> describe > >>>> the horizontal extension as 65 mm, wouldn't that be the just 5 mm longer > >>>> than a 6 cm Technomic stem? > > >>> If you have two stems: an 80mm Dirt Drop (with 65mm extension) and a > >>> 6cm Technomic, it will be impossible for you to get the bars in the > >>> same spot--no matter what you do. Additionally, you will never get > >>> the bars to be within even .5 cm of each other. > > >> That's the statement I'm not following. > > > Here's a picture: > > >http://www.flickr.com/photos/49416...@n00/4620513517/ > > > The next picture shows the trigonometry/math. > > Ok. So, I think we were both making the same error, though on different > aspects of the problem. > > In your photo, you are showing the 6.5 _extension_ as a 6.5 _reach_ > > The extension would be at a 90 degree angle from the quill, as shown in the > Habenero diagram, or the alex w. tool that Seth shared. > > I was thinking of the Technomic as having a 6 cm extension, when it actually > had a 6 cm reach. > > Thanks for creating that image. > > - Jim > > -- > Jim Edgar > cyclofi...@earthlink.net > > Cyclofiend Bicycle Photo Galleries -http://www.cyclofiend.com > Current Classics - Cross Bikes > Singlespeed - Working Bikes > > Gallery updates now appear here -http://cyclofiend.blogspot.com > > "There were messengers who named their bikes, but Chevette never would have > done that, and somehow because she did think about it like it was something > alive." > > William Gibson - "Virtual Light" > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to rbw-owners-bu...@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > For more options, visit this group > athttp://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
