# TOOLS

## 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!

# How do you make a 1:7 gearing ratio?

8 Sep 2021

To make a 1:7 gearing you would need to have two gears where the one being driven has 7 times the number of teeth relative to the driving gear. The only lego technic combination that has this ratio is an 8 tooth gear driving a 56 tooth turntable, however a turntable is not that suited to a gearing system as it has no center. The next option is to create a gear train that produces an overall 1:7 gearing ratio. There are many ways of doing this and the general technique is to create a ratio with a 7 as the denominator and then to cancel out the numerator with a matching reciprocal gearing ratio. For example 2 / 7 could be followed by 1 / 2 to make 2 / 7 x 1 / 2 = 1 / 7. Similarly 3 / 7 could be followed by 1 / 3 to make 3 / 7 x 1 / 3 = 1 / 7. There are more combinations that follow this pattern.

The first option is shown below. Here a 2 / 7 is created by driving a 28 tooth gear with an 8 tooth gear and then the 1 / 2 is created in the gear train with a 12 tooth driving a 24 tooth gear to create an overall 1:7 gearing ratio between the yellow and brown axles.

This is quite a compact solution and gives a close axle spacing between the axles (2 lego units).

If you need a greater distance between the axles you could use the 3 / 7 x 1 / 3 technique. Here 3 / 7 is made by driving a 28 tooth gear with a 12 tooth gear - now these can't be connected directly on a whole number regular grid so an intermediate 20 tooth gear is used to connect them. Finally the 1:7 gearing ratio is created by adding a 1 / 3 gearing ratio at the beginning of the gear train (an 8 tooth driving a 24 tooth gear) to give the overall solution below:

Here the overall gearing ratio between the yellow and dark blueish axle is 1:7 and has a spacing of 7 lego units. The topology of the gears can be changed to create many more possible lay outs.

# More to explore

## Lego Technic Gearing Ratio Tool Update

4 Sep 2021

This video presents updates to the Technic Brick Power Lego Technic Gearing Ratio Calculator tool specifically on underconstrained differential systems. These are systems in which the differentials are not fully constrained and therefore have 1 or more degrees of freedom within them.

## New Flat 12/20 Gear Friction

23 Apr 2022

The Lego Technic set 42140 App-Controlled Transformation Vehicle introduces two new gears - a flat version of the 12 tooth bevel gear and a flat version of the 20 tooth bevel gear. These gears are designed to have less friction.

In this video I measure the difference in gearing efficiency...read more

## Measuring Gearbox Efficiency

6 Nov 2021

This video describes a method for measuring the efficiency of a gearbox using the Lego Technic Powered Up hub. Gearbox efficiency is defined as the ratio of the output power to the input power and here I show how to measure each of these values to allow you to calculate the overall efficiency.read more