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Author Topic: Calculating Radius  (Read 5573 times)

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Offline fabr

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Calculating Radius
« on: July 05, 2009, 05:05:10 PM »
What formula is there to determine a radius of an arc if you know the distance between the end points and the height of the arc at its' apex above a line connecting the end points?
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"There can be no divided allegiance here.  Any man who says he is an American,
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artie on edge

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Re: Calculating Radius
« Reply #1 on: July 05, 2009, 05:14:34 PM »
Square 1/2 of span.
Divide by rise.
Add rise.
Divide by 2.

 ;)
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artie on edge

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Re: Calculating Radius
« Reply #2 on: July 05, 2009, 05:15:24 PM »
or if you want that in its correct format.....

edge of the circle is b (at a 90 degree angle to a)
then (^2 equals "squared"):
(((a/2)^2)+(b^2))/2*b =radius
or half a squared plus b squared divided by 2 times b.
I think the degrees are (atan(a/2)/(r-b))*2
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Offline fabr

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Re: Calculating Radius
« Reply #3 on: July 05, 2009, 05:17:48 PM »
WTF? is that oz speak? Seriously I didn't understand a bit of that. Thanx for the help but now I need a lot more help it seems.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Rick S.

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Re: Calculating Radius
« Reply #4 on: July 05, 2009, 05:33:27 PM »
I knew there had to be a formula, but not knowing it this is how I would have figured it out before the days of Cad.
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Offline fabr

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Re: Calculating Radius
« Reply #5 on: July 05, 2009, 05:56:16 PM »
Quote from: Artie on edge on July 05, 2009, 05:14:34 PM
Square 1/2 of span.
Divide by rise.
Add rise.
Divide by 2.

 ;)
so,if the span is24" with a 6" rise- we have 12" squared =144"/6=24+6/2=15" radius?
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

artie on edge

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Re: Calculating Radius
« Reply #6 on: July 05, 2009, 06:56:52 PM »
Precisely. In fact I just used your figures and used a piece of cable to check it. It is indeed a 15" Rad. In fact to 'prove' the calc I just measured out your figs on a piece of paper and a piece of cord to check it......

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artie on edge

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Re: Calculating Radius
« Reply #7 on: July 05, 2009, 06:59:05 PM »
Quote from: Masterfabr on July 05, 2009, 05:17:48 PM
WTF? is that oz speak? Seriously I didn't understand a bit of that. Thanx for the help but now I need a lot more help it seems.

Nah...Aus speak is much worse than that... just simple caclulus......  8)
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artie on edge

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Re: Calculating Radius
« Reply #8 on: July 05, 2009, 06:59:55 PM »
Anybody want the calcs for determining just how many more cc's a rebore will gain? Thats easy too.... let me know if you want it...  ;)
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artie on edge

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Re: Calculating Radius
« Reply #9 on: July 05, 2009, 07:00:21 PM »
I think Im a postwhore.... :-\
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Offline fabr

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Re: Calculating Radius
« Reply #10 on: July 05, 2009, 07:13:26 PM »
Quote from: Artie on edge on July 05, 2009, 06:59:55 PM
Anybody want the calcs for determining just how many more cc's a rebore will gain? Thats easy too.... let me know if you want it...  ;)
THAT I can do and YES you are a post whore.I should know one when I see one ya know!
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

artie on edge

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Re: Calculating Radius
« Reply #11 on: July 05, 2009, 07:46:59 PM »
 :-\ :'( I can reform.... with help an dcounselling....
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Offline Boostinjdm

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Re: Calculating Radius
« Reply #12 on: July 05, 2009, 10:12:40 PM »
The formula....Who gives a shit.  Cad will figure it for ya. ;D
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This post has been edited due to content.

trojan

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Re: Calculating Radius
« Reply #13 on: July 05, 2009, 10:36:40 PM »
Quote from: Artie on edge on July 05, 2009, 06:56:52 PM
Precisely. In fact I just used your figures and used a piece of cable to check it. It is indeed a 15" Rad. In fact to 'prove' the calc I just measured out your figs on a piece of paper and a piece of cord to check it......

Oh the wit!!!


Fab it's called a Chord.

http://www.ajdesigner.com/phpcircle/circle_segment_chord_c.php (first link off google)
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trojan

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Re: Calculating Radius
« Reply #14 on: July 05, 2009, 10:44:25 PM »
Quote from: Boostinjdm on July 05, 2009, 10:12:40 PM
The formula....Who gives a shit.  Cad will figure it for ya. ;D

On the down side, it'll make you look real stoopid when you can't explain "why it is so"?
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