My series of educational mechanical demonstrations

This model is one of the examples of educational mechanical devices on my 80mm x 80mm baseboard.
You can find all the models of this series in this collection =>[Example of mechanical devices]

 

The current model

This is an educational model of a helical gear system, a type of variable-speed gear system.

 

Introduction

This is a variable gear ratio gear system, whose reference curve is not a circle, but a logarithmic spiral. The key design principle is that the radial distance from the pivot to the curve increases linearly with the arc length, and then suddenly resets to the initial value. Under this constraint, the reference curve takes the form of a logarithmic spiral - crucially, this geometric shape allows two identical gears to mesh with each other. Due to its logarithmic spiral shape, the helical gear is also known as a nautilus gear.

 

When the gear rotates, except for the discontinuous moment of the helix reset, the gear transmission ratio changes monotonically.

 

The tooth profile is generated using the same method as for standard involute gears: the reference curve is rolled against an imaginary gear-shaped cutting tool

 

Related models

 

Shell

This model is compatible withMy first setIt is compatible with the shell included in the package.

Print

• Use a name called???-printable.stlPrint the model。
  named???-assembled.stlThe model is only used to demonstrate its assembly method.
   
• UseA fully dried PETGIn order to achieve better dimensional accuracy.
• UseA layer height of 0.1 mm or 0.08 mmto obtain a smoother surface.
• Use a slower printing speed for the overhanging parts.
• ChooseThe "random" position of the suture lineTo achieve a smoother rotation.
  The randomly distributed sutures should easily wear out after being used for a while. Print

Polishing and filing

Please note that in this model, the rotation of the bearing base is intentionally designed to be not very smooth.

Sometimes, the gears may exhibit a drawing effect and/or a claw effect, resulting in an overly tight fit with the shaft

If there is a rough surface on the shaft due to drawing, please use a small piece of sandpaper to polish off the rough parts.

If you think the gear can't rotate smoothly due to the elephant foot effect, please use a fine round file to slightly enlarge the hole.

If there are no such problems, the parts should rotate very smoothly with minimal friction.

 

Assemble

Use a clamping ring to fix the gear to the shaft.

 

Update

• 2026-04-26 v7
  • Increase the depth of the "Scroll" character on the base plate from 0.1 mm to 0.4 mm. Thank youuser_828642752Report this problem.

Other examples

You might also be interested in the models in my examples of educational mechanical devices.

You can find them in this collection:
https://makerworld.com/collections/15048577-my-educational-mechanism-models

 

Wish you a pleasant printing experience!

Acknowledgments

I was able to get in touch with Gear because ofK. SuzukiIt's wonderfulArticleAndYouTube videoMany of the institutions showcased in this series originated from him.Websitethe introduction on it. He also made it himselfAn excellent gear model. Without his inspiration, this series would not exist.

I'm fromHaguruma-No-Hanashi WebsiteI've learned a lot of technical details about gear tooth design. I'm very grateful for that.

 

License

• The 3D model is based onCreative Commons Attribution 4.0 InternationalPermission.
• However, the text and images on this page are copyrighted.