arc length? SOS

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macitect
Posts: 618
Joined: Tue Jul 06, 2004 10:52 pm
Location: California

arc length? SOS

Post by macitect »

Is there a way to specify the length of an arc?

peatle
Posts: 160
Joined: Fri Nov 10, 2006 4:39 pm
Location: Vancouver

Re: arc length? SOS

Post by peatle »

I'd like to know this too !!!

All I've done before is :
From the known radius, calculate the included angle of the segment of a circle that will contain the required length of arc. Then draw that segment of the circle using the calculated angle.

Peter

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alexwhite
Posts: 266
Joined: Tue May 04, 2004 4:45 pm
Location: Indianapolis USA
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Re: arc length? SOS

Post by alexwhite »

Its late here... could you rework the classic circumference formula?
fat guy in a little coat

peatle
Posts: 160
Joined: Fri Nov 10, 2006 4:39 pm
Location: Vancouver

Re: arc length? SOS

Post by peatle »

Circumference of a circle = πd or ( 3.14159 x the diameter)

So if you want to find the included angle of the segment req'd to draw an arc of a certain length then this angle is found by :
•Calculate the total circumference of the circle from the known diameter (d) ( or 2x radius )

•Divide the result by the known arc length req'd

•Divide the result into 360º

e.g to draw an arc that is req'd to be 7.5" long with a radius of 5" ( 10" diam )
• circumf = 10" (d) x 3.14159 .............................= 31.4159

• 31.14159 divided by the req'd arc length of 7.5".......= 4.18879

• 360º divided by 4.18879 ..................................= 85.943669º ( angle of segment )

So .... start to draw the arc of 5" radius, set 'A' to 4.18879 and complete the arc of 7.5" length.

Peter

peatle
Posts: 160
Joined: Fri Nov 10, 2006 4:39 pm
Location: Vancouver

Re: arc length? SOS

Post by peatle »

Oops ! Sorry ......... Set 'A' to 85.943669º ( not 4.18879 )

Peter

macitect
Posts: 618
Joined: Tue Jul 06, 2004 10:52 pm
Location: California

Re: arc length? SOS

Post by macitect »

peatle wrote:Circumference of a circle = πd or ( 3.14159 x the diameter)

So if you want to find the included angle of the segment req'd to draw an arc of a certain length then this angle is found by :
•Calculate the total circumference of the circle from the known diameter (d) ( or 2x radius )

•Divide the result by the known arc length req'd

•Divide the result into 360º

e.g to draw an arc that is req'd to be 7.5" long with a radius of 5" ( 10" diam )
• circumf = 10" (d) x 3.14159 .............................= 31.4159

• 31.14159 divided by the req'd arc length of 7.5".......= 4.18879

• 360º divided by 4.18879 ..................................= 85.943669º ( angle of segment )

So .... start to draw the arc of 5" radius, set 'A' to 4.18879 and complete the arc of 7.5" length.

Peter
I love geometry, I really do, but when I am DRAFTING, I would rather just be able to specify my desired length - either during the operation or in the Object Info palette... ;-)

peatle
Posts: 160
Joined: Fri Nov 10, 2006 4:39 pm
Location: Vancouver

Re: arc length? SOS

Post by peatle »

Me too ........ !

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