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Date: 28 Sep 2007 04:43:24
From: !Jones
Subject: Bolt hole circle
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In G-code programming, the parameters to the bolt hole circle (bhc)
procedure are radius, angle from vertical to first hole, and number of
holes. My point is that when anyone but a cyclist talks about a bhc,
he or she universally specifies a *radius*, not a diameter.
So, a 110 bhc should be 55!!!
Jones
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Date: 28 Sep 2007 20:41:33
From: Hank Wirtz
Subject: Re: Bolt hole circle
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On Sep 27, 9:43 pm, !Jones <p...@off.com > wrote:
> In G-code programming, the parameters to the bolt hole circle (bhc)
> procedure are radius, angle from vertical to first hole, and number of
> holes. My point is that when anyone but a cyclist talks about a bhc,
> he or she universally specifies a *radius*, not a diameter.
>
> So, a 110 bhc should be 55!!!
>
> Jones
But cyclists don't talk about BHCs. They talk about BCDs.
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Date: 28 Sep 2007 04:56:21
From: Ryan Cousineau
Subject: Re: Bolt hole circle
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In article <241pf3psdgqd58acljhkel84jcknhs5ujt@4ax.com >,
!Jones <piss@off.com > wrote:
> In G-code programming, the parameters to the bolt hole circle (bhc)
> procedure are radius, angle from vertical to first hole, and number of
> holes. My point is that when anyone but a cyclist talks about a bhc,
> he or she universally specifies a *radius*, not a diameter.
>
> So, a 110 bhc should be 55!!!
>
> Jones
Well, that's fair, but the actual most useful in-the-field measure, as
Sheldon points out somewhere, is the distance from bolt to bolt for a
given BCD and bolt pattern*.
Bolt-bolt centres are an easy thing to measure, while the diameter is
hard to directly measure.
Also, BCD feels relevant to cyclists because it constrains the smallest
number of teeth a ring on that bolt circle can have (about 39 for 130 mm
BCD, barring heroic efforts).
*bolt pattern being a distinction that was hardly necessary until the
advent of 4-bolt MTB cranks
--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos
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Date: 28 Sep 2007 22:08:17
From: !Jones
Subject: Re: Bolt hole circle
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On Fri, 28 Sep 2007 04:56:21 GMT, in rec.bicycles.tech Ryan Cousineau
<rcousine@sfu.ca > wrote:
>Well, that's fair, but the actual most useful in-the-field measure, as
>Sheldon points out somewhere, is the distance from bolt to bolt for a
>given BCD and bolt pattern*.
Oh, I agree. If I ever had to solve a BHC, I'd start with that as the
easiest measurement to take; then I count the holes and pull out my
calculator. My point is that, mathematically, a circle is defined by
a radius. I was cutting a chain ring the other day and I accidentally
plugged in 110 is what brought it to mind. I hadn't ever really
thought about it, but we're the only bunch I know of to use a
diameter.
Jones
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