How to align three circles at their tangent points

[GarryP]

I’ve shown one method to do this in my attached video (the text below isn’t a step-by-step guide, just notes on the video).

“Enable Snapping” should be ON, “Snap to object bounding boxes” should be ON, and “Include Bounding box mid points” should be ON.

Part A – The first circle

If you are not using Designer, and therefore can’t use the Point Transform Tool, or you just want to do it quickly, then, instead of the instructions in this part, you can simply snap the left ‘side’ of circle B to the right ‘side’ of of circle A and then rotate all the circles to how you want them later.

Draw a line from the centre of circle A to anywhere.

Use the Node Tool to move the end of the line to get the angle you want.

Use the Point Transform Tool to move and rotate circle B.

Use the Point Transform Tool to translate circle B so that it touches circle A.

Part B – The second circle

The width of the first construction circle should be: width of circle A plus width of circle C.

The width of the second construction circle should be: width of circle B plus width of circle C.

If you aren’t using Designer (and can’t use the Point Transform Tool) you can draw a line from the intersection of the two construction circles (to anywhere, the end point doesn’t matter) and then use snapping with the Move Tool to drag circle C into place.

Note: If you don't want circle B to be rotated after this then you can just double-click the rotation handle to reset it.

Important: There may be tiny gaps between the circles but that’s because they aren’t perfect circles, and that’s because of the way the Affinity applications draw circles using bezier curves. I don’t think there’s anything we can do about this.

[NotMyFault]

Great tutorial!

i mentioned the issue with circle radius has up to 0.5% deviation depending on position at the radius, largest deviation typically around 45+n*90 degree. This can become relevant here, and maybe the method can be extended. 
simply start with the cloud bubble tool instead of ellipse tool for a better circle approximation.

 

[v_kyr]

Well, this is probably too much fiddle and complicated for many people. - It would be better to have a user friendly switchable mode that then doesn't overlap shapes when aligning.

 

 

 

 

[ronnyb]

Or a tangent Snap option in the Snap Settings....