How to create a coil spring (helix) in SketchUp

Updated: April 22, 2022

Recently, I started doing a while bunch of new models in SketchUp, and I always try to only use my own components, never anything from the 3D warehouse. This means extra work, but also more satisfaction when you succeed. But then, I did face one big challenge. How to make a helix, a three-dimensional spiral, that most elusive of shapes.

In essence, most of 3D design is just figuring the intricate intersect of planes in three dimensions. Sounds trivial, but sometimes, you end up scratching your head, not quite sure what to do. I decided to check a number of online tutorials, and while they do accomplish the task, I found them impossible to reproduce. The actual steps needed in SketchUp baffled me more than the concept of how a helix should look like. Well, eventually, with great satisfaction, I worked it out. It's not the prettiest or most efficient method, but it's dead simple. Let me show you.

Teaser

Step by step

So I got meself thinking. If you look at the constant-radius helix from above, it looks like a circle. Well, there's the clue right there. Then, in SketchUp, when you draw a circle, it's actually a polygon. Perhaps it has a lot of sides, but it is still not a perfect mathematical circle. It's a collection of short lines, connected end to end, with a very low incidence angle between them. Another clue right there.

This is the sequence of steps to make the helix then. First draw a circle. Then, extrude it a little to create a coin-like shape. Save it as a component.

Coin component

Now, start stacking these components one on top of the other, like, indeed, a stack of coins. You need as many "coins" as there are sides in your circle-like polygon.

Coins stacked

Next, we need to draw our helix. This is how you do it. Select any which face of the bottommost coin, and place a line starting in one bottom corner, and then draw the line diagonally to the top corner opposite. Again, if you look at our coin components, from a side view, they look like a row of rectangles placed next to each other. Thus, our very first step is a diagonal line across one of these rectangles.

Line outside the coins

Continue drawing the line going up and around the coin stack, diagonally. Your progress is one up, one to the side. Each line end is the beginning of the next line. Each line is drawn on a separate face of the polygon. Your sequence always progress by one face sideways and one coin height up. This is a bit tedious, but it is in fact how you would make a helix manually.

Complete line

Once you complete a full circle, delete the coin components, you will now be left with a helix shape.

Coins deleted

Now, make the helix shape into a component, and stack as many of them as you like on top of each other. For example, if you want to have a coil spring with 10 turns/twists, then stack up 10 of our helix components. Once you're done, grab them, and explode them. This will turn the entire shape into one continuous helix line.

Line component

Adjust the turn ratio of your helix.

Coil, stacked

Explode the line

The next step is to create a circle outline (which will serve as the helix shape profile) at the beginning of the helix line, either bottom or top. You can change the axis orientation of the circle using the Arrow keys. Finally, use the Follow tool to draw the helix. You can choose a polygon or a rectangle instead, but typically, helices have a round profile, but then again, it's entirely up to you.

Helix, complete

Helix, colored

And there you go. You now have your helix. You can change its "depth", by making it taller or shorter. You can go for whatever twist/progress ratio you want or need. Add some color, and Bob's your uncle.

Optionally, you can also have straight lines at the beginning or end of the helix line, as often, coil springs have short straight tails. But this is also a matter of taste. Either way, we have accomplished our task with relish and flair.

Conclusion

There you go. Now you have a recipe for how to make a helix. You can spice things up. Have a helix that has different turn ratios. Make the helix with a growing or diminishing radius, like say a nautilus shell. Once you know the basics, the rest is easy. You just need to stack different coins on top of one another. From this point on, it's up to your patience and fun, and you can save these components for future reuse.

As I mentioned, this is a rather inefficient way of doing it. I'm sure the professionals have quicker, more script-like methods to get things done. In lieu of that, my laborious trick will get you sorted, should you, like I did, struggle with some of the more wizardly ways of helixing about. I hope you find this useful. Take care, and have fun with your models.

Cheers.

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