help with equation in function component - catenary from two points - where is arcsinh function?

I want to calculate these equation in a function component:
sinh^(-1)[h/sqrt(s^2 - h^2)] - L/(2a) but it's not working...
Can someone help me with the correct syntax for the "expression editor" in grasshopper?

PD: "h", "L" and "a" are inputs variables.

I'm trying to do a catenary from two points like in these video: http://www.grasshopper3d.com/video/catenaria-1

The equation it's suppose to be the "A" constant in the catenary equation: y(x) = a cosh(x/a + A) + B
The "B" constant is B = -a cosh A

Replies to This Discussion

Permalink Reply by Arthur Mamou-Mani on December 4, 2009 at 1:28pm

Thanks Pep,
Did you manage to make the catenary work with a function?
I opened your definition and only the parabolic function worked...
Parabolic curves are as efficient structuraly as catenary no?
thanks a lot,
Arthur

Permalink Reply by Arthur Mamou-Mani on December 4, 2009 at 1:30pm

Hi Giulio,
Thanks a lot for thyis script it s really useful.
What are all the checks for in the C# ?
Why did you need to rotate the curve?
Is there a way to do a catenary through a function and not a script?
thanks a lot,
Arthur

Permalink Reply by Benedetta Gargiulo on April 29, 2010 at 4:12am

Ciao Arthur,
How are you?
How is everything?
Hope you and Sanem are doing great :)
I am tryingout how to draw a catenary curve in rhino but I cant find the manual or the gh way...do you know how to make it a function in gh without using the complicated script?
Thanks so much!!!
So much to still dooo and so little lefttttt!!!
Hope to see you soon!
Betty

Permalink Reply by David Rutten on April 29, 2010 at 8:19am

I just moved Giulios excellent solver into the core product.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Pep Tornabell on April 29, 2010 at 1:15pm

very nice David...

Permalink Reply by Brian Osborn on July 12, 2010 at 3:51pm

Is there now a catenary solver built into the core product? Having trouble finding it. I'm running v. 0.6.0057.

Thank you.

Permalink Reply by taz on July 12, 2010 at 4:17pm

Brian, you need 0.7.0030 (from below) but there should be an more stable update coming out soon (this week?).

http://www.grasshopper3d.com/forum/topics/grasshopper-070030-available

Permalink Reply by Arthur Mamou-Mani on May 3, 2011 at 11:06am

Hi David,

I am getting a weird result when applying the catenary solver...

Any idea what could cause this?

Somehow when reducing the size, of the arch, it works...

Many thanks,

Arthur

Attachments:

catenary.3dm, 42 KB
catenary.ghx, 53 KB

Permalink Reply by Bojan Koncarevic on November 30, 2011 at 6:06am

Dear David

I have a problem with the catenary gh component..

It does outcomes in a curve as You have attached the set of curves creating the arched tunnel..

but actually it gives out the simple triangle connection of the 2 base point and height ending point

What i am doing wrong (since i do not have curve (actualy i do but it is not the curved one) ; ) )

I hope i will get the reply asap your schedule can estimate..

I did not upload any file since the question is very simple.

I just simply make 2 points and catch them to the Catenary icon (or line end points)

best

Bojan

Permalink Reply by David Rutten on November 30, 2011 at 7:32am

Are you guys using the latest Grasshopper? Giulio fixed a bug with faulty catenaries. The files Arthur posted work fine on my version.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Giulio Piacentino on November 30, 2011 at 7:44am

Hi Bojan,

yes, if this is not working, could you please upload a file?

Numerical methods to find roots of the catenary equation can run into numerical instabilities (extremely small or large numbers). I've discussed this with structural engineering PhD candidate Riccardo La Magna one day and he came up with a probably more stable approach. This would need further testing though.

I'd need some samples from Grasshopper 0.8.0061 to help reviewing the component code again.

Thanks,

- Giulio
_______________
giulio@mcneel.com

Permalink Reply by Henners on January 25, 2011 at 12:33pm

this is a great definition thankyou, im new to grasshopper and needed to learn a way of creating a catenary curve.

However could anybody help me. I have a pattern from grasshopper which has multiple points, what i need is for the vector between two points to become individual catenary curves but the catenary curve has to be the length of the original distance between the vectors. Therefore the longer the distance, the larger the curve?

Thankyou for any assistance