Restricting the max and min length of a spring

Replies to This Discussion

Permalink Reply by Chris Tron on July 9, 2012 at 4:48pm

I'm thinking my original post was a little vague... I'll explain a little further.

I am building a truss system where each member of the truss will be a linear actuator. I will be using grasshopper, kanagroo and firefly. I ideally would like to manually adjust a node on the rhino model, and feed the data from the changes of lengths of the line into firefly. Firefly will then direct the arduino to move each linear actuator accordingly.

I have my model, and most of the grasshopper sketch (minus the firefly part). Now I need to figure out how to restrict the length of each of the lines of the truss since a linear actuator can only extend so far.

I hope I am clear..

Here is my simple rhino model and my current grasshopper sketch:

Attachments:

• variable truss.3dm, 833 KB
• variable truss.gh, 5 KB

Permalink Reply by Daniel Piker on July 9, 2012 at 5:27pm

Hi Chris,

The way I would recommend to do this would be to actually use 2 springs for each member, one with a regular stiffness, and the other with a very high stiffness, and its LowerCutoff and RestLength both set to the max length you want to limit the spring to.

Permalink Reply by Chris Tron on July 9, 2012 at 7:19pm

Hi Daniel,

 

Thanks for the reply!

 

I tried out your suggestion (or I think i have tried it out) and it still does not seem to work. I'm sure that I am missing something; I've just started learning the program....

 

This is what I have got:

and I want to grab each point of the truss with my cursor and move it, like this:

thanks for all the help!

Permalink Reply by Chris Tron on July 10, 2012 at 10:15am

Hi Daniel,

 

I have now got it working. Thanks again.