Lofting - Getting one section to follow a sketch (Help)

[thomas-buchan]

Hello 

I am designing a duct for my car i am building, i have been teaching myself how to use the loft feature by watching videos and reading but one thing i'm having trouble with is getting a section of the loft to follow a sketch (Not center line).

Using the Direction function has got me 90% there but the long section needs to be changed so it doesn't tapper off into a point.

If you look at the model and picture, i'd like the back long section (From the middle point) to follow the curve drawn in the Z plane and i'm not sure how to do this. 

Any help is appreciated (all open tolerances if you have to change anything as this is just a prototype and a chance to learn)

Thanks 

[TheCADWhisperer]

Sketch1 is missing many Tangent Constraints and also missing dimensions.

I would model using obvious symmetry about the Origin.

Sketch2 location is not defined?

Sketch4 is not connected to Sketch 1 and 2?

(I would probably create Sketch4 geometry before all other sketch geometry.

[g-andresen]

Hi,

First, sketch 4, which is intended as a guide rail, must be placed in front of the loft in the timeline and positioned (sketch plane) so that the curve can be connected to the two profiles.

günther

[TheCADWhisperer]

I hesitate to mention this - but I might use a Spline for the one closed profile, but most users attempt to use wayyy too many points in their spline.

[g-andresen · Accepted solution]

Hi,

Here is a construction with a mirrored loft for the base profile.

Watch the screencast and follow the development in the timeline.

günther

[thomas-buchan]

Thank you for taking the time to make a video, seeing it really helps, it taught me some other unrelated handy things as well. 

[thomas-buchan]

Any tips for the error "Rail is not smooth"

It's a Tangant arc going into another tangents arc so i wouldn't of thought that wouldn't of been a problem with the both being curves. 

[laughingcreek]

Not enough info to go on. can you attach a file?  The rail not smooth error shows up for other errors also, so it's not always clear.

FYI-once you add a rail, direction condition on a profile no longer has any influence.   I would consider that a bug.  conversation I had with AD a while back seemed to indicate that AD thinks that's the way it should function.  If you need a tangent condition along that profile, you'll have to pull a helper surface off it and use the edge of the surface

[thomas-buchan]

Hi, Thank you for getting back to me

I've attached the new model and i will just use "connected" instead of direction when using rails as suggested from now on. 

[g-andresen]

Hi,

The problem is caused less by the rails than by the quality of sketch 1.
I had already recommended using a spline in an earlier screencast. But it also works with tangential conditions and partial replacement of curves by splines.
Have a look at the screencast and the file.

günther