Rotation and pull

i have canterary curves hanging from the top plane of a box. there is a center rod that has a line, from the rod to the midpoint of each canterary. i need to be able to rotate the center rod, wrapping the line around it, and pulling the midponts of the canteraries inward towards the rod. this is for an architectural installation.

thanks

Replies to This Discussion

Permalink Reply by Danny Boyes on February 15, 2011 at 3:17pm

Is the idea that as you rotate the rod of given diameter you are shortening the lines by PI

can you post something. Sketch, Image, 3dm or ghx to work with?

Permalink Reply by Danny Boyes on February 16, 2011 at 4:36pm

I've given a bit more thought to this and if you're after simple representation then the cosine rule gets you the angle to alter the direction of Gravity for the Catenary. However, its very basic and doesn't take into account the tangent for the line leaving the rod/drum. It also doesn't alter the catenary in any other plane i.e. sideways.. If your after more physics than this then Kangaroo is probably more akin to this. But for what its worth see attached file.

Attachments:

catenaryDrum.ghx, 403 KB

Permalink Reply by Alyssa Sullivan on February 22, 2011 at 3:48pm

i cannot open the attached file. what components and parameters did you use in what order?

Permalink Reply by Chris Tietjen on February 22, 2011 at 10:28pm

Here's a link to a screencast. http://www.screencast.com/t/JewtaWoo

Are you actually trying to create a rotating rod in GH that draws the midline in?

Chris

Attachments:

DoubleCats.ghx, 214 KB

Permalink Reply by Chris Tietjen on February 23, 2011 at 2:26pm

Getting closer I hope.

Chris

Attachments:

DoubleCats.ghx, 277 KB

Permalink Reply by Alyssa Sullivan on February 23, 2011 at 4:00pm

watch this video, its the analog model me and my partner made. it shows at the very end how we need the curves to come to the center point. the turning rod is not important to represent in grasshopper, just the action, which is more of a linear movement than a radial one. thanks!

-alyssa

Attachments:

02-16-11 curves.mov, 29.8 MB

Permalink Reply by Chris Tietjen on February 23, 2011 at 5:32pm

Very interesting. Do you have any drawing that shows the layout of the catenaries?

Chris

Permalink Reply by Alyssa Sullivan on February 23, 2011 at 6:23pm

here is a dimetric view, elevation, and plan. thanks for helping :)

-alyssa

Attachments:

sheet 1b copy.pdf, 30 KB
sheet 2b copy.pdf, 14 KB

Permalink Reply by Chris Tietjen on February 23, 2011 at 9:09pm

This is a brute force definition of what I understand from your video and drawings. From the information given I can't tell what the coordinated motion between the points might be. Also I don't understand where the winding lines are coming from. Are they from the four inner midline points(4 points), the four inner midline points and the four inner mitre points (8 points) or somewhere else?

Chris

Attachments:

HangingCats.3dm, 51 KB
HangingCats.ghx, 1.6 MB

Permalink Reply by Chris Tietjen on February 23, 2011 at 9:25pm

Looking at the video again I can see I still haven't got the geometry right. Do you happen to have a photo of your analog solution that is high resolution? That would probably supply the remaining details.

Chris

Permalink Reply by Alyssa Sullivan on February 23, 2011 at 9:33pm

the midpoints of the catenaries are directly pulled to the center point of the entire model in plan view, and the height corresponds to the height of the midpoint of the curve. all i need to do is change the gravity, like in the image at the top from danny boyes. i just was unable to open his file and see the parameters used.

Attachments: