topic Re: How to create a 2 point arc only knowing the center x-axis of the arc in AutoCAD Forum

How to create a 2 point arc only knowing the center x-axis of the arc

Anonymous — Mon, 18 Nov 2019 17:11:58 GMT

I am trying to reverse engineer a design and end up needing to fill in the blanks. Now i am in dilemma where in i have to create a round corner between two points. i know that the center of the circle is anywhere in same x axis as the bottom line, the two end points of the line is at the end of the circle. I tried using the arc and circle alternate modes but i could not achieve the desired result without having to guess a value. Also fillet would just continue the line and connect them

here is a sample picture of what it should look like :

Is there a command or a cookie cutter way to do this ? thank you for your help

Re: How to create a 2 point arc only knowing the center x-axis of the arc

RobDraw — Mon, 18 Nov 2019 17:16:54 GMT

Draw a line from the endpoint of the upper line that is perpendicular to it. (There are several ways to do this.) The resulting intersection is the center of the arc. The length of the line is the radius.

Re: How to create a 2 point arc only knowing the center x-axis of the arc

Anonymous — Mon, 18 Nov 2019 17:44:38 GMT

thanks for your reply, upon doing what you said the bottom line passes the edge of the circle (by using circle). and using arcs it would not fit a tiny bit higher on the upper line

Re: How to create a 2 point arc only knowing the center x-axis of the arc

RobDraw — Mon, 18 Nov 2019 17:52:24 GMT

@Anonymous wrote:
thanks for your reply, upon doing what you said the bottom line passes the edge of the circle (by using circle). and using arcs it would not fit a tiny bit higher on the upper line

I really don't have enough information to answer that. I was assuming that the endpoint of the upper line is where it is supposed to be and that the arc needs to be tangential to that line. Trimming the lower line would finish the solution that I gave. If the endpoints in question are exact and the arc needs to be tangential to the upper line, then there is no geometric solution.

Are the endpoints in their exact locations or can either one be adjusted?

Does the arc need to be tangential to the upper line?

Re: How to create a 2 point arc only knowing the center x-axis of the arc

Anonymous — Mon, 18 Nov 2019 18:02:49 GMT

After doing some testing on my own, it would seem that my assumption of the x axis wrong, what if the x-axis is not on the same x-axis as the bottom line ( it can be anywhere now) how would i make the arc fit that still keeps position of the endpoints the same?

Re: How to create a 2 point arc only knowing the center x-axis of the arc

Kent1Cooper — Mon, 18 Nov 2019 18:15:15 GMT

@Anonymous wrote:

.... how would i make the arc fit that still keeps position of the endpoints the same?

If you want the arc a tangential continuation of the upper line and ending at the right end of the lower line, you can use PolylineContinue.lsp with its PLC command, available >here<. Call the command, and pick the upper line [whether it's a Line or a Polyline] anywhere nearer to the tangent-point end than to the other end. Enter the Arc option in the resulting Pline command. It will go into a tangential continuation from there -- pick on the end of the lower line, and make sure you end the Pline command with Enter or space, not with ESCape. The Arc will be an arc segment in a Polyline together with the upper line [which you can Explode to separate them if you prefer], or will be joined to it if it's already a Polyline.

Re: How to create a 2 point arc only knowing the center x-axis of the arc

RobDraw — Mon, 18 Nov 2019 18:23:08 GMT

I would use the Start, End, Direction arc command. Pick the endpoint of the upper line as the start, the endpoint of the lower line as the end, and the intersection of the two lines as the direction.

Again, you really haven't enough information for a single solution. With what you have given so far, there are multiple solutions.

Re: How to create a 2 point arc only knowing the center x-axis of the arc

Anonymous — Mon, 18 Nov 2019 18:31:07 GMT

i appreciate the answer , but i rather not use a plc.

Re: How to create a 2 point arc only knowing the center x-axis of the arc

Anonymous — Mon, 18 Nov 2019 18:33:21 GMT

Sir that it ! no comprises here

@RobDraw wrote:
I would use the Start, End, Direction arc command. Pick the endpoint of the upper line as the start, the endpoint of the lower line as the end, and the intersection of the two lines as the direction.

used both end points and the center is on the x axis of the bottom line 🙂

Thank you very much

Re: How to create a 2 point arc only knowing the center x-axis of the arc

RobDraw — Mon, 18 Nov 2019 18:39:07 GMT

@Anonymous wrote:
used both end points and the center is on the x axis of the bottom line 🙂

Then my first suggestion should have worked if done properly.