> Date: Thu, 3 Jun 2010 23:18:34 -0700
> Subject: Re: [RBW] 67cm AHH double top tube inquiry
> From: cyclofi...@earthlink.net
> To: rbw-owners-bunch@googlegroups.com
>
> > to type a few words about it? Maybe post a picture or two?
>
> I'm definitely not in your frame size range, but the double top tube
> approach is pretty valid - particularly for taller frames which are flexing.
>
> The tall Hilsens were the first to get the twin top tube treatment from Riv
> - the Bomba design came together after that. About the same time, GP was
> writing about truss structures in the Readers, and how they distributed
> forces and created appropriately rigid structures. I think that was the
> genesis of that twin top tube approach when appropriate.
>
> There are others who have reached the same conclusion - Bernie Mikkelsen as
> an example:
>
> http://www.flickr.com/photos/jimg/403130063/
>
> Obviously, you have to get your mind around it, but as evidence in favor,
> I'd point out that if your Salsa is flexing and you are in love with your
> Bomba, it sounds like you're already there.
>
> The actual weight of a top tube and the two half-lugs is pretty danged
> minimal. If you plunked 'em on a balance scale with a water bottle on the
> other side....
>
> The resultant ride is going to be what a smaller sized rider gets with a
> single top tube frame - riv comfort and superb handling. Just what you want
> for your next brevet.
>
> - 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
>
> "That which is overdesigned, too highly specific, anticipates outcome; the
> anticipation of outcome guarantees, if not failure, the absence of grace."
>
> William Gibson - "All Tomorrow's Parties"
>
>
Maybe this is a better question for a frame builder but would wider tubes solve
the problem just as well as a double top tube? My steel tandem uses slightly
oversized tubing to add some rigidity. Given the size of the bike the wider
tubes look appropriate. On something like a 66 or 68 frame I would think that
31.8 tubing might allow a standard diamond frame to be used.
Larry Powers
Get a bicycle. You will not regret it if you live. - Mark Twain
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