--- Richard M Sachs <richardsachs@juno.com> wrote:
so, when you ask:
> "...what can't I measure with fair accuracy to
> double-check what
> the builder promised?"
> i assume you meant to write, "...why can't i...",
I meant as I asked, Richard, which should or could have elicited a simple response like, "dimension A and B," or, gee Joe, I guess I can't think of anything. But you rehashed what I already know about framebuilding. I'd rather you'd acquiesced to the abilities of "lay people" on simple addition and subtraction, that's all.
Joe Starck
> snipped:
> " can't I measure with fair accuracy..."
>
>
>
> when i fixture a frame, (CR content: even tho it's
> not a 1" top
> tube frame...), i cut the tubes to fit the fixture.
> once the frame
> is brazed, i refixture around it and double check
> against the
> precsribed numbers. if any at all, the only changes
> occur in
> the front center measure - it can shrink .5mm, and
> in the head
> angle - it can come by by a minute or three. this is
> due to heat
> expansion and contraction.
> after i refixture around the finished frame, i
> record the numbers
> and write them in the book.
> to tell you the truth, i can't remember any client
> ever addressing
> these numbers and saying either 'yea' or 'nea' to
> what i describe
> the frame's numbers to be. if i tell a guy it's a
> 42cm chainstay
> and he wants to measure it, why does it matter if he
> uses a rule
> and i use my fixture? if i measure a 42cm chainstay
> on a frame
> and the book says i wrote down 41.75cm, i usually
> buy myself
> a pink guitar and listen to adrian balou.
> ya' know what? there are no guitars here. why?
> because i went
> to high school and if the discrepency example i cite
> here were
> ever a reality, i would not have finished making the
> frame.
> so, when you ask:
> "...what can't I measure with fair accuracy to
> double-check what
> the builder promised?"
> i assume you meant to write, "...why can't i...",
> you can measure
> it. if you're not clear on why a difference may
> exist, ask the frame's
> builder. if he tells you his numbers are the
> centreline ones we've
> discussed, that will explin why they differ from the
> ones yielded
> from the tapemeasure.
> e-RICHIE
> chester, ct
>
>
>
> On Fri, 13 Aug 2004 12:17:44 -0700 (PDT) Joe Starck
> <josephbstarck@yahoo.com> writes:
> --- Richard M Sachs <richardsachs@juno.com> wrote:
>
> "...typically, all measurements on a bicycle are
> center to center. fwiw, measuring the key dimensions
> after it is assembled will not always replicate the
> 2D
> ones that were in the frame blueprint."
>
> Richard,
> I asume you do, as I and others did and/or do, i.e.,
> incorporate every parts variable into the frame
> design, i.e., lower stack heigth, tire size, rim
> radius, etc., such that when it's all assembled,
> tires
> pumped up, tape shellacked, and what not, THAT A
> FINAL
> MEASURING INSPECTION SHOULD JIVE WITH THE BUILDER'S
> AIM, ELSE HE ERRED.
>
> As earlier discussed with chainstay length, the
> "effective chainstay length," as Don called it, or
> the
> "virtual length," to paraphrase, as you called it,
> can
> be double-checked by measuring the actual chainstay
> length, i.e., hypotenuse, and add half a centimeter
> or
> so, ON AN ASSEMBLED BICYCLE. The third dimension
> isn't
> at play here.
>
> The only third dimension measurements that aren't on
> your 2D drawing of note are dropout spacing and all
> that that entails.
>
> So if I positioned my newly assembled
> summumbonumboojum bicycle upright on a level
> surface,
> approached it from the side(2D as in your drawing)
> and
> went to town on it with my tape measure, I'd expect
> all my measurements taken by me, someone with basic
> math skills, to jive with da plans.
>
> That said, what can't I measure with fair accuracy
> to
> double-check what the builder promised?
>
> Joe Starck
> summumbonumboojum bicycles
> Madison, WI
>
>
>
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