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tangent arc (non-sketch)

Genius
Genius
I need to draw an arc tangent to both a spline and a straight line, with: 
 
  • the arc-start coincident with the spline start
  • the position of the arc-end on the straight line varying with the radius set by an expression
 
I know it is an easy job in sketch, but can't get it done outside sketch.
 
Thanks for your advice!
 
ScreenClip [3].png
8 REPLIES

Re: tangent arc (non-sketch)

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

If your arc passes through the spline end point and is tangent to both the spline and line, that will lock down the radius value. Holding the line and spline constant, you won't be able to specify an arbitrary radius value and satisfy all the other constraints simultaneously.

Re: tangent arc (non-sketch)

Siemens Phenom Siemens Phenom
Siemens Phenom

@surfactant:

 

You did not mention why a Sketch is not acceptable. Putting stuff like this is a Sketch is much preferred over building up a "stick model" of 3D curves, especially if you want to do associative updates downstream.

 

It's not impossilble the other way, but you have to take care yourself to keep everything assocative, while use of Sketch pretty much will handle that work for you.

 

So having "warned", the command you probably want to use in the non-sketch case for your example is "Circular Blend Curve".:

 

Pat

Re: tangent arc (non-sketch)

Genius
Genius

Hi @cowski1 You're right. Sorry for the mistake. Thanks!

 

Hi @PatMcManus Rejecting sketch sometimes is more of psychological reason Smiley Happy A sketch looks bulky and sometimes loss of constraints seems to be a big trouble. You are right and it should be much preferred for certain cases. And thanks for your reference to "Circular Blend Curve"!

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Re: tangent arc (non-sketch)

Phenom
Phenom
@surfactant

You wouldn't be able to utilize the expression, but also take a look at Fillet under Basic Curves dialog - the resulting arc can be edited fairly simply for these "quick & dirty" scenarios outside of Sketcher which are completely planar. You will also have some control over the trimming options of the adjacent curves as well.
-Tim

Re: tangent arc (non-sketch)

Genius
Genius

Hi @TimF

 

I was told that Basic Curves is non-associative, and therefore never tried to learn the set of tools. In my mind the tools are to be retired. Maybe I was wrong and should spend some time to have a look. Thanks!

Re: tangent arc (non-sketch)

Genius
Genius

Hi @PatMcManus

 

Please refer to my previous thread regarding the usability of Sketch. In that thread, I showed that minor editing of conics/splines in sketch may disrupt their associativeness, leading to a disaster for the whole model.

 

Since that thread I began to avoid the use of sketch, especially conics/splines in sketch, although I know sketch is a very flexible and powerful tool.

 

I'm wondering whether there are some golden rules regarding the use of conics/splines in sketch without harming associativeness.

 

Hope to have your suggestions. Thanks!

Re: tangent arc (non-sketch)

Phenom
Phenom
@surfactant,

While that's true concerning the associativity, the lengths, radii, diameters, etc. of lines and arcs can be edited quite easily using the Edit Curve tools. I certainly wouldn't ignore them and I seriously doubt they're going anywhere anytime soon, but given some of the strange decisions I've seen made in the past couple of years, I wouldn't be surprised.
-Tim

Re: tangent arc (non-sketch)

Genius
Genius

Hi @TimF

 

If you think Bacis Curves has it use, there must be some advantages in it. I would try it later. Thanks for sharing!