# How to Draw This?

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Radii is the plural of radius. Since you have two arcs the term "radii" would apply. Again, you should know this from school.

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So, how do I draw the green arcs shown in post #5?

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Do you want an ogee curve? Look it up.

We will need some curve data.

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Do you want an ogee curve? Look it up.

We will need some curve data.

What's a "ogee curve"?

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Following through on Eldons post #8 using that technique but replace point A with any point you want in the entire modelspace and you can draw curves through point BCD that are continuous.

But this thread is very much a case of "you can lead a horse to water but you can't make him drink"

Basty if you cannot see that drawing a line in your dwg from #3 between A an B and finding where a line drawn perpendicular from the center of that line crosses a ray drawn between the center of your arc and point B then it is time that you seriously start looking for another profession. I'm not being abusive here or cruel or picking on you, this is just the cold hard truth, some people just are not suited to certain jobs. And that is the end of my input on this thread.

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So, how do I draw the green arcs shown in post #5

I know that you have posted this in the Beginners section, but I hope that you have discovered all the Drafting Settings that make life easy.

For example drawing the perpendicular bisector of a line. The old fashioned way is to strike an arc from each end of a line, and then draw a line between the intersecting arcs. But using AutoCAD's drafting Settings with Polar Tracking on, one merely draws from the mid point of the line.

Another example is when you want two lines to extend to meet at a point, use the Fillet command with the radius set to 0.

So back to the matter in hand which is to draw the green arcs. This is a special case where the uppermost point of the arc is tangentially vertical.

Draw the chord B-C. Draw the perpendicular bisector to meet the line B extended at E.

Draw the chord C-D. Draw the perpendicular bisector to meet the line E-C extended at F.

E and F are the centres of the circles, which now you can draw. Trim the circles, tidy up all temporary construction lines and there you have it.

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ReMark gave you the answer in post #13. POLYLINE

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@ReMark

How do I draw an ogee curve and reverse curve?

Can someone please teach me that?

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nail down jello
Hi Remark was watching a show on Foxtel and some smart people added a chemical to water, it still acts like water but provide a violent reaction and it turns solid, they did stuff like run across it no problems, walk slowly and just sank, rode a bicycle across it !. So maybe hammer a nail into jello.

Basty you need to do some homework on curve interaction, google land surveyors formula for curves.

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This is a pline using a repeating arc function within the pline command.

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@ReMark

How do I draw an ogee curve and reverse curve?

Can someone please teach me that?

Have you looked at post #26 by eldon?

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What about if I draw the B-C arc first like post #19?

How do I draw the A-B arc?

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......How do I draw the A-B arc?

Draw the perpendicular bisector between A and B. Draw the line D to B and extend it to the perpendicular bisector at F. F is the centre of the circle.

Edited by eldon
point nomenclature correction

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As noted, there are an infinite number of solutions to this problem but they all as Steven-g noted must have " two arc centres should be on a straight line that passes through the tangent point".

I created a parametric model (see attached file) that lets you dynamically review the solutions. Just drag the free end of the yellow or magenta lines and the arc radii and location will adjust automatically. It should be noted that in order to determine and reference the intersection point of the yellow line and the blue line (the perpendicular bisector) I cheated a bit. There is a small circle (0.01 dia) that is tangent to the two lines. This circle is used as the reference point for the center of the arc. There is a collinear constraint between the yellow and magenta lines

A Screencast of the movement is here: http://autode.sk/2DCVzXR

HowToDrawThis-1.dwg