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I am looking to model a rotational spring, e.g. a balance wheel of a mechanical clock. The [rigid body constraint/generic spring] only allow for translational springs. How could I do this?

Zorbas
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  • are you looking to simulate, or just model that spring? – David Feb 27 '16 at 23:53
  • I am looking to simulate this. Just any object would behave like a rotational oscillator. To model the spiral spring geometry is the next step, but this should be easy to do. – Zorbas Feb 27 '16 at 23:59

2 Answers2

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This can be done using...

Shape Keys + Curve Modifier + Skin Modifier

Enable the Add Curves: Extra Objects add-on.

Enabling the Add Curve: Extra Objects add-on

Add > Curve > Spiral

Adjust the spiral as you like. I recommend a high step count for a nice looking SubSurf.

Add Spring - Operator Panel settings

Convert to Mesh (AltC)

Add > Curve > Circle

To your spiral object, add the following modifiers:

Curve - Set the object to be your BezierCircle

Skin - Smooth Shading

SubSurf - 3 Subdivision levels

Rotational spring - modifier settings

Create two Shape Keys - a Basis one where the spring is fully squished, and a second one where the spring is scaled up on Z, fully sprung... [ahem].

Rotational spring - shape keys

You can then animate the Shape Key slider to make the spring extend.

Rotational spring extending

Community
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Mentalist
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  • Nice work, but a rotational spring doesn't work like that. See https://en.wikipedia.org/wiki/Balance_wheel#/media/File:Pocket_Watch_Balance_Wheel.jpg – Xtremity Mar 30 '16 at 11:16
  • @Xtremity Ha! ...crap. Well thanks for pointing it out. I'll give this some thought and post again if I solve it. Not that OP even seems to be following anymore, but in case others come searching. This is why reference photos are a good thing. – Mentalist Mar 30 '16 at 14:24
  • Oh, I didnt know how I can add a reference foto. I thought the term 'rotational spring' and balance wheel for a mechanical clock is reference enough. The problems still stands though. – Zorbas Apr 11 '16 at 22:12
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I did this to model a roll of thick plastic - My way was to create a spiral in adobe illustrator , add a stroke to it, expand the stroke so it becomes one solid spiral shape and then exported it as an SVG file.

I then imported the SVG into blender and extruded it along a single axis.

pezzatron
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  • This is not a good solution either since a spiral spring changes diameter while its rotated. – Zorbas May 04 '16 at 23:27