Gearing Ratio Calculator

Check out the Beta version my Lego Technic Gearing Ratio Calculator Tool:

This tool allows you to upload your Lego Technic project .ldr file and analyse the gearing ratios between any two connected gears or axles. Currently supports most gears, axles, worm gears, some differentials, cv joints and universal joints. See the video tutorial on how to use it. It is a work in progress and I would love to hear your feedback on it. Click here to try it out.

Note: As of 25 Septemeber 2021 the tool supports CV joints, linear speed via the radius of the component and improves on the frame rate for higher numbers of parts in a model).

Technic Elbow Art

This is a tool to create "Lego Technic Elbow Art" - a series of intertwined elbow pieces as a single sequence. Choose your dimensions and search parameters and search for new dense solutions and set a record! 

Download your Elbow Art as an .ldr file and build it yourself. Click here to try it out!

Gearing Ratio Calculator Tool Help

26 Feb 2022

This tool has been designed to simulate and analyse the gearing components of your Lego Technic model. It will calculate the gearing ratios between all connected components and visually show the gears of the model in action. It is best used from a laptop or desktop computer running the Firefox or Chrome browser.

You can access the Gearing Ratio Calculator Tool here.

To get started you need to load your model's .ldr (Lego Draw) file into the tool. Depending on how you created your model, you should be able to export it as an .ldr file from the program you have used to edit it. For example Bricklink Studio allows you export to the .ldr format from the File menu.

1. Load your LDR file

Just click the file "Browse" button near the top left of the screen.

Once you have selected your file it will be loaded into the tool and displayed on screen. Note: Only gearing parts are loaded, e.g. axles, gears, differentials, connectors etc. - supporting parts are not shown.

You can rotate the view of your model using the mouse. Hold down the right mouse button and move the mouse to rotate the model. Hold down the left mouse and move the mouse to pan. Use the scroll wheel to zoom in and out.

2. Connect a motor

To connect a motor to your model simply click one of the 3 motor gears (16 tooth gear). I will start flashing and the mouse cursor will change to a target symbol. Now move the mouse and click on the part you wish to drive with the motor. Once you have selected a part it will start rotating and flash green (meaning it is the driven part). All of the connected gears will start rotating with the correct gearing ratios and speeds relative to the driven part.

3. View parts of interest

Once you have connected a motor to your model and the gears are turning you can mouse over any part to see the relative speed and gearing ratio of that part compared to the part being driven. You can change the speed of the motor with the slider. You can connect more than one motor if your model allows. The following information is shown:

Item Explanation
Rot. Speed Speed of rotation in RPM (revolutions per minute)
Lin. Speed The linear speed of the component if it acted like a wheel. So for example this would measure the speed of a car if the part is a wheel
Ratio (F) The gearing ratio relative to the driven part as a fraction
Ratio (D) The gearing ratio relative to the driven part as a decimal


Driving Rings

If you have driving rings in your model you can switch them by selecting the driving ring (click on it) and then pressing the SWITCH button that appears at the bottom left.

Gear Jam

If you connect more than one motor to your model that are in conflict or are driving a worm gear in the wrong direction then the affected parts will flash red. See the example picture below.

Underconstrained Gears

If you have a gear model with more than one degree of freedom (i.e. due to a differential) then the affected gears will flash orange. That means the gear speeds/ratios cannot be fully resolved. You can resolve these gears by adding another motor. The speeds and ratios displayed will then be in terms of the two motor speeds combined.

Supported Parts

Not all Lego Technic gearing parts are supported. The tool only supports rotational movement (i.e. not steering racks, linear movement etc). The following types parts are currently supported:

axles, flat gears, bevel gears, crown gears, worm gears, universal joins, turntables, driving rings, clutch gears, cv joins, knobbed wheels, differentials, axle connectors, chains, sprocket wheels, tracks, fans.

Unsupported Parts

The following parts are currently unsupported as well as any linear movement, or secondary rotation movement (e.g. pieces attached to pin holes of gears etc).

Most wheels, rotary catches, steering racks, engine shafts and pistons.

More to explore

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