How to Create and Animate a Mechanical Watch Balance Spring (Spiral) in Cinema 4D?

[attempt-reflection]

Hi everyone,

I'm trying to create a mechanical watch balance spring (also called a hairspring) in Cinema 4D. It's the flat spiral spring you find in the movement of mechanical watches — it expands and contracts rhythmically as part of the oscillator.

I’m looking for a way to model and animate it in a controllable way — ideally with parameters that allow me to control the number of coils, spacing, and possibly animate the compression/expansion over time (simulating the heartbeat of the watch).

So far, I’ve tried using the Helix spline, but it doesn't give me the tight, flat spiral shape I need. I also thought about drawing a custom spline manually, but that’s hard to control and animate.

Has anyone built something similar? Is there a procedural way to build this type of spring, maybe with Xpresso or deformers? Any tips on animating the contraction and expansion realistically would be much appreciated!

https://www.youtube.com/watch?v=MpCknwUFxdI

Thanks in advance

Mirko

[Dr. Sassi]

Hi Mirko,

I would always go with real references. Not that your link was questionable.
https://youtu.be/rL0_vOw6eCc?si=mbJlNXoD71bJh-87&t=662

Here is the simplest way I would do it:
CV4_2025_drs_25_ANbs_01.c4d

The keyframes are based on Spline interpolation to get a Sine Curve-like "swing" into it. as it slows down at each "extreme" point. You might adjust it.

The keys need to be closer to each other to make it faster.

All the best

[attempt-reflection]

Hi Dr. Sassi,

Thank you for the example – very helpful! I'll need to check with my CAD files to see if the shape of the spring could be a match. or how I can tweak it

All the best,

Mirko

[Dr. Sassi]

You're very welcome, Mirko,

If I had known the diameter needed, I would have set up the example accordingly.

The size can be changed. Just place all parts under a Null, then use the Coordinates of that Parent Null and set the scale.

Example
CV4_2025_drs_25_ANbs_02.c4d

All the best

[attempt-reflection]

Hi,
Thanks,

Please find attached the CAD part that I have to animate,

cadpart.c4d

All the Best, Mirko

[Dr. Sassi]

Hi Mirko,

The CAD part was mostly needed for the size, however, I used a simple and hopefully useful method to get it animated. The key to getting such a complex animate shape to move in the needed way is based on the falloff of the Sphere Field. This might be the way to go if the little imperfections are not in the way.

CV4_2025_drs_25_ANbs_11.c4d

Besides, I have included a Spline animated version, this time just with Keyframes and the Timeline Editor> Function> Track After> Repeat After
To get this working the first key of a F-Curve needs to be selected (Active)

I combined three Spline into one since the provided shape is not doable with the Helix alone.

My best wishes for your project

[attempt-reflection]

Hi Dr. Sassi,

Wow! Thank you so much, that was really helpful. I was also trying with the twist deformer, but the imperfections in the mesh need to be fixed. Maybe if I remesh the spring in quads and use a spline deformer? I'll give it a try!

Thanks a lot for your help.

All the best,

Mirko

[Dr. Sassi]

Hi Mirko,

A Field is needed to make that work with the Twist, as the strongest changes will typically differ between the Outside and Inside. Hence the shifts in geometry. As mentioned, Imperfections (Process-based, not based on the model you shared.)

Here is a model that used only one side of the CAD model (Remeshed), allowing us to deform it much cleaner. Then Thicken is used to bring the "Volume" of the spring back. The different dimensions are done with a Vertex Map.

CV4_2025_drs_25_ANbs_21.c4d

Cheers

[attempt-reflection]

Just perfect !

[Dr. Sassi]

Thank you very much, Mirko.

My best wishes for your project