I am trying to draw the profile of the tyre of a railway vehicle. In essence it consists of three circles in contact. The size and position of the two smaller circles are fixed. The position of the larger circle (but not the size) needs to be adjusted so that it makes glancing  contact with the two smaller circles. The contact must be such that the excess parts of all three circles can be trimmed away.

I expect there is some easy way of getting the circles to connect at the contact points, but I can't find it! Help please.

Drawing of three circles is attached.

Andrew

Try the "Tangent Point Circle" tool.

Enjoy
Mitch

Thanks Mitch

That works fine for circles making external contact but in my case one of the smaller circles is inside the larger one. I can't figure out how to force it to make the small circle make tangential contact with the larger one from inside. Am I missing something?

Regards

Andrew

Ok, I think I now understand your question. Use the "Three Point Circle" tool + Option key.

Enjoy
Mitch