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circular curve fitting

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swah2000

Civil/Environmental
Joined
Jun 28, 2019
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Location
HK
As the coordinates of two tangent points are fixed by some constraints. I would like to fit a circular curves to joint them together. If begin radius say is 80m. How can I find the second radius which shown in attached file ?
 
 https://files.engineering.com/getfile.aspx?folder=9d747308-2902-48b1-8689-1f520d7db8f9&file=circularcurve.png
You don't seem to have fully defined all your constraints; is it supposed to be smooth curve? To what degree?

What was the rationale for picking 80?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
One method would be to use the Sine Rule and Cosine Rule:

CaptureTRIANGLE_ihqivw.png


Solving, as follows:

capture_triangle2_jvgafh.png
 
Doing it graphically in CAD is easier using the AutoCAD 'ARC' command with 'Continue' arc.

Knowing the end point of first arc (R1 = 80000), and knowing the PT (tangent point of the end of the second arc) 'ARC Continue' will continue a tangent arc from the PCC (compound curve point) to the PT, then use 'dimension' to obtain the drawn radius.

I also get R2 = 41772 using CAD.
 
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