--- Anvil Bikeworks <ojv@earthlink.net> wrote:
> Joe wrote:
> "(Is this within Don's 6-9 mm axle/hanger edict?)"
>
> I'd just like to point out that it is not *my*
> edict, but it is a range
> called out on Campagnolo, Shimano, and SRAM frame
> specifications.
Right on Don, for if dropout dimensions didn't matter to component manufacturers, there would be no dropouts on the planet stamped with "Campagnolo" or "Shimano." The dimension had never been an issue for me though, as my employers were responsible for parts procurement.
The
> amount varies with hanger length; the shorter the
> hanger, the more narrow
> the window. Based on my own experience with DS
> MTB's (sorry Dale), it seems
> to be widely disregarded, but since CS&S see fit to
> call it out, I think
> it's probably worthwhile to keep in mind especially
> considering todays 9 &
> 10 speed cassettes.
>
> Also, I think it's almost universally accepted that
> when talking about frame
> geometry, chainstay length is called out as the
> straight line distance
> between the BB center and the axle center (not
> parallel to the ground).
Si. I'm just used to and comfortable with measuring either way given the varied requirements of my employers due to differing frame fixture methods of measuring coupled with employer-designed computer software
The
> terminology used to describe the dimension is
> confusing. A horizontal
> measurement is always parallel to the ground. A
> vertical measurement is
> always perpendicular to the ground. A "Parallel"
> dimension is one that
> travels from point to point and may include both
> horizontal and vertical
> elements e.g., measuring along the hypotenuse of a
> triangle.
>From whence does the term originate to label a
hypotenuse measurement as a "parallel" dimension, and
how often and by whom is it used this way? The
spectrum of the usage of "parallel," when describing
things relative to each, as in parallel lines or
parallel computer hardware or parallel plots in
literature, etc., makes instinctual sense, but to
label a hypotenuse measurement "parallel" just because
it can be thought of as measuring in both a vertical
and horizontal direction is silly. Don, if you
said,"The parallel dimension of the top tube length is
56 centimeters," I don't think one would get the
picture from your usage of "parallel" that the tube's
centerline is a hypotenuse, meaning it slopes up as a
compact-style frame does. "Confusing" indeed.
>
> When considering balance while designing a frame,
> it's easier, for me, to
> determine the required chainstay length by
> considering only the horizontal
> distance from BB center to axle center. That
> horizontal distance is what I
> like to call the "effective" chainstay length.
Likewise with "effective" top tube length on that 56 above, eh?
To
> illustrate my point, a
> 420mm chainstay length as parallel measurement (the
> way it's typically given
> in frame specs)
As a hypotenuse, si.
puts the axle in a different
> position depending on BB drop.
> As drop increases the chainstays effectively shorten
> and vice versa.
Si. About a millimeter horizontally per centimeter vertically? I'm guessing; I don't have my calculator handy.
Thanks Don, Joe Starck, Boojum Summumbonem Bicycles Madison, WI
> Cheers!
> Don Ferris
> Anvil Bikeworks, Inc.
> Littleton, Colorado
> Ph: 303.471.7533 / 303.919.9073
> Fax: 413.556.6825
> http://www.anvilbikes.com
>
>
> -----Original Message-----
> From: classicrendezvous-bounces@bikelist.org
> [mailto:classicrendezvous-bounces@bikelist.org] On
> Behalf Of Joe Starck
> Sent: Wednesday, August 11, 2004 3:02 PM
> To: classicrendezvous@bikelist.org
> Subject: Re: [CR]Re: measuring stay lengths
>
> -- Richard M Sachs <richardsachs@juno.com> wrote:
>
> "my way of measuring (measuring along the centerline
> of the frame's central plane) yields the half cm
> diff
> that you note, not the 1 ephgrave mm that you not
> after the fact. "
>
> Richard,
>
> Let's consider a 42 cm chainstay length and 8 cm
> drop.
>
> Side view of the frame:
>
> The designated chainstay length is 42 cm measured
> from
> center of bottom bracket to center of rear axle,
> PARALLEL TO THE GROUND, and the rear axle position
> is
> achieved by default on a vertical dropout, whereas
> with the use of a horizontal, it's anywhere the
> builder prescribes, in my case, it was always to the
> midway position that the axle could be positioned in
> the dropout, using primarily 1010B or shorter
> horizontals (Is this within Don's 6-9 mm axle/hanger
> edict?)
>
> Now then, this above set-up on a frame jig means
> that
> the measurement along the somewhat centerline of the
> chainstay, I say "somewhat because the dropout
> center
> is 'neath it, measured from center of BB to center
> of
> axle position, should be set at a bit less than 42.7
> mm, being the hypotenuse of the 42 cm leg of the
> triangle.
>
> So, say 6 mm difference there.
>
> Now then,
>
> Top view of the frame:
>
> Same 42 mm length, and yet the hypotenuse leg is a
> wee
> bit shorter, by about one millimeter. And when
> measured from outside of crank bolt to outside of
> skewer the differnce is less, as the measurement is
> now close to being parallel to the plane of the main
> triangle. But who cares about the top view, right?
> It
> was this dimension I was thinking about when I
> stated
> the one ducky difference, and so I yes, I
> contradicted
> myself , but in err' only. My bad.
>
> Still, I would think that if a Sachs owner (Is
> Richard
> Cielec a Sachs owner?) were to measure his chainstay
> length from outside of crank bolt to outside of
> skewer, center to center, and came up with 42.5 on
> an
> 8 cm or so BB-drop-designed frame of yours,
> subtracted
> 5mm netting 42 cm, he has indeed measured his
> chainstay length quite nicely and precisely.
>
> Starck,
> Joe
>
>
>
>
>
>
>
>
>
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