Ultimate Toroidal Propeller Generator

The Ultimate Toroidal Propeller Generator is an open source project that provides a way to generate STL files of toroidal drone propellers.

✨ Features

Multi-blade	Configurable propeller rotation: CW or CCW	Attack angle	Customizable hub
Design propellers with the exact number of blades you need	Specify rotation based on your specific application needs	Define the required blade attack angle in a clear and simple way	Design and customize the hub according to your specific needs

💪 Getting started

The Ultimate Toroidal Propeller Generator is meant to be used by anyone and it's not neccessary to code, BUT you have to touch some values that are in the code. Don't worry, it's easy and very strightforward. Let's start!

⬇️ Download stuff

Fist of all you have to download several things:

1. This repository by downloading it or by cloning it (we assume that if you use this method you know how to do it). Then unzip the files.
2. OpenSCAD: the sofware we need to render and create our STL files.

🔨 Creating our first propeller

Let's start by opening the file example.scad with OpenSCAD.

You will see some code but we only are interested in the parameters inside the toroidal definition. Let's change some of them:

This defines a propeller:

$fn = 100;  // global tessellation (higher = smoother preview/export)

toroidal_propeller(
    // -------------------------
    // Blade count + rotation
    // -------------------------
    blades = 2,                                                // number of blades (copied/rotated around Z)
    rotation = "CW",                                           // "CCW" (default) or "CW" (mirrored in YZ plane)

    // -------------------------
    // Hub geometry
    // -------------------------
    hub_height = 6,                                            // hub height
    hub_d = 16,                                                // hub outer diameter
    hub_screw_d = 5.5,                                         // center screw hole diameter
    hub_notch_height = 0,                                      // optional notch height (0 = disabled)
    hub_notch_d = 0,                                           // optional notch diameter (0 = disabled)

    // -------------------------
    // Path / blade geometry
    // -------------------------
    blade_length = 40,                                         // blade span/length used by the toroidal path
    blade_offset = 2,                                          // Z offset between leading/trailing halves
    leading_blade_width = 25,                             // leading half width (percent of blade_length)
    trailing_blade_width = 20,                            // trailing half width (percent of blade_length)
    leading_blade_xoffset = 50,                           // leading half X offset (percent of blade_length)
    trailing_blade_xoffset = 80,                          // trailing half X offset (percent of blade_length)

    // -------------------------
    // Airfoil profiles (keyframes along the path)
    // -------------------------
    profiles = ["2412","2412",["ellipse", 0.5],"2412","8412"], // NACA 4-digit or ["ellipse", scale]
    profile_pcts = [0,35,50,87,100],                           // keyframe positions along the path (0..100)
    chords = [8,3,2.5,3,4],                                    // chord length at each keyframe (same order as profiles)
    chord_pivot_pcts = [50,25,100,50,65],                      // pivot along chord: 0=LE, 50=mid, 100=TE
    attack_angles = [15,40,-90,0,10],                          // attack angle (deg) at each keyframe

    // -------------------------
    // Render only part of the path
    // -------------------------
    path_portion = 1.0                                         // 1.0 = full path, 0.5 = half path, etc.
);

Parameters

Global

• $fn: Defines the global number of facets used to approximate curves. Higher values produce smoother results but slower previews/exports.

Blade count + rotation

• blades: Number of blades replicated around the Z axis.
• rotation: Sets propeller handedness. Use "CCW" (default) or "CW" (mirrored across the YZ plane).

Hub geometry

• hub_height: Hub (holder) height.
• hub_d: Hub outer diameter.
• hub_screw_d: Center hole diameter (motor shaft / screw).
• hub_notch_height: Optional notch/support hole height. Set to 0 to disable.
• hub_notch_d: Optional notch/support hole diameter. Set to 0 to disable.

Path / blade geometry

• blade_length: Blade span/length used by the toroidal path (controls overall size).
• blade_offset: Z offset between leading and trailing halves of the blade.
• leading_blade_width: Controls the Y coordinate of point B (leading half), as a percentage of blade_length.
• trailing_blade_width: Controls the Y coordinate of point C (trailing half), as a percentage of blade_length.
• leading_blade_xoffset: Controls the X coordinate of point B (leading half), as a percentage of blade_length.
• trailing_blade_xoffset: Controls the X coordinate of point C (trailing half), as a percentage of blade_length.

Toroidal Blade Path (Catmull–Rom)

The toroidal blade path is defined by a Catmull–Rom spline passing through five control points in the XY plane:

A → B → M → C → D

The X axis is the blade-length direction and the Y axis controls the lateral opening of the toroid.

Control Points

All points are defined in 3D, but the path shape is governed by their XY projection.

r = hub_d · cos(30°) / 2 leadX = blade_length · leading_blade_xoffset / 100 leadW = blade_length · leading_blade_width / 100

• A — Hub entry
• B — Leading edge control
• M — Midpoint
• C — Trailing edge control
• D — Hub exit

A = ( r·cos(60°), r·sin(60°), hub_height/2 + blade_offset/2 )
B = ( leadX, +leadW, hub_height/2 )
M = ( blade_length, 0, hub_height/2 )
C = ( trailX, -trailW, hub_height/2 )
D = ( r·cos(60°), -r·sin(60°), hub_height/2 - blade_offset/2 )

Airfoil profiles (keyframes along the path)

• profiles: Airfoil profile at each keyframe. Accepts NACA 4-digit strings (e.g. "2412") or ellipse definitions like ["ellipse", scale].
• profile_pcts: Keyframe positions along the path (0..100). Must match the order and length of profiles.
• chords: Chord length at each keyframe. Same order as profiles.
• chord_pivot_pcts: Pivot position along the chord: 0 = leading edge, 50 = middle, 100 = trailing edge.
• attack_angles: Attack angle in degrees at each keyframe. Same order as profiles.

Render control

• path_portion: Portion of the toroidal path to render (1.0 = full path, 0.5 = half path, etc).

That's all! Render it with this values with OpenSCAD and you will get something similar to this:

Now it's your turn. Play with the parameters and try adding more blades, different lengths, attack angles, etc. Let's make something awesome!

Contributing

🚸 If you are new contributing we recommend you to start by playing with the core design file toroidal_propeller.scad.

📝 When you see something you want to add, modify or refactor first of all, you should create a new issue providing as much information as you can. We will appreciate if you can write as an user story (e.g. AS [a user persona], I WANT [to perform this action] SO THAT [I can accomplish this goal].)

🔀 Then you should create a fork of the project, clone it to your local, create a new local branch and you will be ready to start making changes. You'll need a recent version of OpenSCAD.

🚀 When you finish making changes go to pull requests and create a new one selecting your fork as source. More info on GitHub Docs: creating a pull request from a fork. Please add as much information as you can explaining what have you done, strategies you followed, which issue resolves, etc.

💬 Your PR will be commented, reviewed and, we hope, 🎉approved and merged into main branch🎉.

If you want to contribute but you feel lost with all this process please fell free to contact to any of the mantainers, they will help you a lot.