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-Brian

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I googled "circle arc radius chord" and found: http://www.1728.com/circsect.htm

This has a built-in calculator for various circle calculations... You select which of the "Knowns" you have and it calculates the "Unknowns".

Unfortunately, it did not have a selection for the Knowns of Arc and Radius... but it did have Arc and Chord

So, I selected that and entered 5-ft for the Arc (the length of the rail and then tried 4-ft for the Chord (the distance between the ends when it is bent into an arc) and the displayed Radius was way below 12-ft. So I tried 4.9-ft and it was still low, so I tried 4.95 and that was still too low, so I tried 4.95-ft and that was too low, so I tried 4.975 and that was over 12-ft Radius, so I backed off a bit and kept at this "try one and see what happened" narrowing down the answer until I got to 4.96391-ft and the answer came out to "12" for the radius.

So, converting 4.96391 to Feet and Inches, I get 4-ft, 11.56692 inches... or about 4' 11.57".

EDIT: note, I was doing 12-ft RADIUS, not DIAMETER, so you can try 6-ft RADIUS if that is what you meant.

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Google to the rescue... kind'a.

I googled "circle arc radius chord" and found: http://www.1728.com/circsect.htm

This has a built-in calculator for various circle calculations... You select which of the "Knowns" you have and it calculates the "Unknowns".

Unfortunately, it did not have a selection for the Knowns of Arc and Radius... but it did have Arc and Chord

So, I selected that and entered 5-ft for the Arc (the length of the rail and then tried 4-ft for the Chord (the distance between the ends when it is bent into an arc) and the displayed Radius was way below 12-ft. So I tried 4.9-ft and it was still low, so I tried 4.95 and that was still too low, so I tried 4.95-ft and that was too low, so I tried 4.975 and that was over 12-ft Radius, so I backed off a bit and kept at this "try one and see what happened" narrowing down the answer until I got to 4.96391-ft and the answer came out to "12" for the radius.

So, converting 4.96391 to Feet and Inches, I get 4-ft, 11.56692 inches... or about 4' 11.57".

EDIT: note, I was doing 12-ft RADIUS, not DIAMETER, so you can try 6-ft RADIUS if that is what you meant.

Semper...Semper...

Once again you kill me with this quick google stuff... and this based on other threads. I love it.

NOTE: you are using the two research venues in concert with each other yes? AND then using the appropriate thread to communicate and point people in the right direction..

My response to this thread: tape measure and common logic.

KISS theory

gg

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When I was building my garden layout, I took a pencil and a long piece of string and drew some curves of 7', 8', 9' and 10' radius on my work table top. I also drew them on some cardboard and cut them out as 'templates', or 'track alignment gauges, as mentioned above. Works for 12' curves too (radius OR diameter.)

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For the GR&G railway, I will measure and stake the center of the circle be whatever diameter, attach 2 point string to obtain a straight vertical on the circumference peg and then drag it along, making the curve and marking it out with a string of flour.

With the flour line in place I am now ready to set up my ladder.

gg

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Stan

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