# Translate change of length to force in hanging chain problem

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1. Feb 22, 2016

### cm85

I'm trying to write a simple script in blender python in order to show load deflection in cloth simulation. My question is: Is it possible to translate the change of length (distance between two nodes), into a force? (newton between those nodes)?

In addition you will find a minimal example. The chain is created with blender-cloth. Let's assume that each node is dragged down by gravity with 100 Newton. This are 900 Newton overall, right? How would the distribution of force look like? (I'm no structural engineer) There is a correlation between movement and force, even if we would assume same link-strength for everything, isn't it? I'm interested in normal-force only. I could also work with the velocity of links also.

#### Attached Files:

• ###### chain.png
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79.9 KB
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42
2. Feb 22, 2016

### A.T.

Acceleration and force.

What's normal force here? The vertical tension force components must balance gravity in the static case.

3. Feb 23, 2016

### cm85

Maybe i have made a wrong approach from the beginning on. Here is another way from scratch based on various processing-sketechs. It's a simple particle simulation which is adding a value to the z-coordinate of each particle aswell as the velocity of the next neighbors. It is based on a pseudo-code i have found and a lot of trial and error. I don't know if this is correct or not.

The import section is this one:

v_1 = self.next_1.vertex.co - self.vertex.co
v_1 = v_1 * strength

v_2 = self.next_2.vertex.co - self.vertex.co
v_2 = v_2 * strength

self.vertex.co = self.vertex.co + v_1 + v_2

How could i sum up the forces in order to get the force of each link?

#### Attached Files:

• ###### chain.blend.zip
File size:
75.5 KB
Views:
42
Last edited: Feb 23, 2016