Tangent Tangent raduis

[Rag742]

I am trying to connect two Circle with another curve that is tangent to these two circle at a radius of 3. When I use the Tan-Tan rad command the new circle connects both the circle but with a concave line. How do i connect them so i get a convex line (i.e 180 degree).

[ReMark]

One must always be careful where they are making their picks otherwise the circle that is created comes in opposite of what was expected. Try again.

 

AutoCAD is not very specific when it asks....

 

Specify point on object for first tangent of circle:

Specify point on object for second tangent of circle:

 

I tried a little experiment and found, or at least it seems so, that its the second point that you pick that appears to be the determinant. I could pick anywhere on the first circle and it didn't seem to matter as long as my point on the second circle fell within the quadrant where I expected the third circle to be tangent. Interesting.

[JD Mather]

I would also pick in a counter-clockwise sequence (maybe supersition on my part, but that is how CAD draws circles, I think).

So imagine tracing out your TTR circle on a sheet of paper with a pencil.

What would be the first logical tangent point and moving in CCW direction the second logical tangent point?

That is the order and approximate location (predicted tangent locations) that I would create the TTR.

That is what I have always taught my students and it has always seemed to work.

 

Post example file if you find one that seems to not follow my rule of thumb.

[BIGAL]

For the circle - crircle add arc solution there is actually 4 mathmatical solutions. There are some lisps around. The method used by some other software was very simple pick arc/circle pick arc/circle enter rad pick approx cen pt all done a visual arc appears before you hit enter.

 

[Rag742]

Thank you. That worked.