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Help with arithmetic concerning circles

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Help with arithmetic concerning circles

Postby 9fingers » 06 Sep 2014, 13:04

I know even some very capable woodworkers sometime struggle with the arithmetic and trigonometry concerning circles.

This link maybe well help with terminology and the calculations.

http://www.1728.org/circsect.htm

Bob
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Re: Help with arithmetic concerning circles

Postby Froggy » 05 Oct 2014, 20:24

Thanks Bob. Have added this to my favourites, I'm sure it will come in useful (if only for the kids homework :D ).
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Re: Help with arithmetic concerning circles

Postby TrimTheKing » 06 Oct 2014, 08:31

Cool, thanks Bob

Cheers
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Re: Help with arithmetic concerning circles

Postby Rod » 06 Oct 2014, 09:00

Having spent 50 yrs designing roads, roundabouts, bridges, etc as well as managing a land survey section - I'm trying to forget all that stuff?

Nice link though Bob.

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Re: Help with arithmetic concerning circles

Postby RogerS » 06 Oct 2014, 11:15

Rod wrote:Having spent 50 yrs designing roads, roundabouts, bridges, etc as well as managing a land survey section - I'm trying to forget all that stuff?

Nice link though Bob.

Rod


Ooh...you can probably answer this question, then? Why are car parking spaces so narrow? Did whoever come up with the British Standard parking space drive one of these?

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Re: Help with arithmetic concerning circles

Postby Rod » 06 Oct 2014, 13:00

The standard used to be 2.4m x4.8m with a 6m "lane" between opposite rows to allow manoeuvring. Less if it's a herringbone parking arrangement.
I think authorities have been allowed to ignore this as I'm sure many are much smaller than this? There's one car park in Winchester that I will not even attempt to use. I keep meaning to measure some to see the difference?

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Re: Help with arithmetic concerning circles

Postby bugbear » 06 Oct 2014, 14:02

The length-sagitta-radius relationship is important; sagitta is a much more intuitive measure of flat curve segments than radius, but being able to interconvert is very handy.

It crops up in arched alcoves, the theoretical hollow a plane will cut for a given blade projection, and even what the radius needing to mark out a scrub plane blade is.

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Re: Help with arithmetic concerning circles

Postby Andyp » 06 Oct 2014, 14:25

RogerS wrote:Ooh...you can probably answer this question, then? Why are car parking spaces so narrow?


Dunno, but having now had too cars with sliding rear doors I can't ever see me going back to hinged doors.
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Re: Help with arithmetic concerning circles

Postby 9fingers » 06 Oct 2014, 14:37

bugbear wrote:The length-sagitta-radius relationship is important; sagitta is a much more intuitive measure of flat curve segments than radius, but being able to interconvert is very handy.

It crops up in arched alcoves, the theoretical hollow a plane will cut for a given blade projection, and even what the radius needing to mark out a scrub plane blade is.

BugBear



Thanks for dragging back on topic BB :lol:

I too find the sagitta calculation very useful. In woodwork for defining curves/arches etc and in metal work to answer the question, "how much do I machine off a round bar to give a flat of a specific width?"

At school it was not a formula I paid much attention to but now in combination with the solution of quadratic equations (created by the formula) are in quite regular use in my hobbies and interests.

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Re: Help with arithmetic concerning circles

Postby bridger » 22 Nov 2014, 05:56

I was never a whiz at mathematics, and now that autocad can give me the numbers I need without my needing to know the names of the math functions I doubt I'll ever have to...
Occasional musings on my blog:
bridgerberdel.wordpress.com
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Re: Help with arithmetic concerning circles

Postby Andyp » 22 Nov 2014, 10:48

Hi Bridger and welcome to the forum.

If you have a mo why not introduce yourself in the Welcome Board, tell us about the type of woodwork you do etc. Oh, and we love pictures so any project images or workshop tours always go down well.
cheers

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