Technical Drawing question?

[Rob]

This'll test who paid attention at school, 'cos I obviously didn't.

 

Take two random size circles, adjacent to each other but not touching. How do you draw another arc that joins both circles touching them tangentially?

 

I used to do this at school and I'm b@##ered if I can remember how to do it now.

 

I am trying to do it AutoCAD right now, but not by using Circle Tan Tan tools, but by the old way.

[Nic]

I'm doing this in my head and can't test it on paper, so it may be complete b*ll*x.

 

Draw an arc from centre point of one circle, so the arc bisects the other circle's centre. Do the same from the other circle's centre point. Where the 2 arcs bisect, these are the centre points for the arc that touches both circles at a tangent.

[Rob]

Nope sorry, that doesn't work. Gah, where's my old teacher when I need him? I got a A in A level TD dontcha know..

[Animal]

Your using AutoCAD, why struggle? Circle TTR. [\yoda]Unlearn what you have learned [\yoda]

[Rob]

It's the principle of the thing. I sat there for two years learning all that, and now I've forgotten most of it.

 

Maths? Calculus, differentiation, complex numbers? It's all gone.

[Burna]

That's why I use Autocad so I can forget how to properly do it

 

Roll on Solidworks and Edgecam so I can forget even more

[Charlotte]

Shame on you.

[Animal]

I feel no shame...

[Charlotte]

The only shame is to have none.

[Ewen]

You have circle A and circle B

You want to draw an arc C thats tangental to circles A and B.

For internal arcs.......

1/ Decide the radius of arc C.

2/ Draw an arc from the centre of circle A, with a radius that is rad of arc C plus rad of circle A..

3/ Draw an arc from the centre of circle B, with a radius that is rad of arc C plus rad of circle B.

For external arcs...

2a/ Draw an arc from the centre of circle A, with a radius that is rad of arc C minus rad of circle A.

3a/ Draw an arc from the centre of circle B, with a radius that is rad of arc C minus rad of circle B.

4/ The intersection of these two arcs is the centre of arc C.

5/ Draw arc C with pre-defined radius and it will be tangential to both circles A and B. The exact tangent point can be found by drawing lines from the centre of arc C, through the centres of circles A and B.

[RobSheffield]

Forget circles, they are so 2005, squares are where its at

[Rob]

That does work, but that's a concave curve, I was think of a convex curve. Like two radii of kerb edges, linked by a curving road.

[Ewen]

That does work, but that's a concave curve, I was think of a convex curve. Like two radii of kerb edges, linked by a curving road.

 

Ive edited my post Rob....same method, just minus instead of plus

[Rob]

He shoots, he scores, he draws an old fashioned telephone handset.

 

Ta muchly.