# 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:N gearing ratio?

31 Oct 2021

So you need to make a 1:N gearing ratio for your project where N is some whole number like 21, 40, or even 100?  In general this can be easy or difficult depending on your number N. One general solution is to create a gear chain using n gearing ratios of 1:M0, 1:M1, 1:M2,... ,1:Mn. such that M0 x M1 x ... x Mn = N then the overall gear chain ratio will be 1:N. So that means you need to break down your number N into a number of factors that can be created by a pair of Lego gears. For example if N is 36 then you can write

36 = 3 x 3 x 2 x 2

So then you create a 1:36 gear ratio by creating a gear chain of simpler gears using 1:3, 1:3, 1:2 and 1:2. Now of course since the order of multiplication doesn't matter you can put these in any order, e.g. you could also use 1:2, 1:3, 1:3 and 1:2. So below is an example solution for a 1:36 gearing ratio using the first order shown.

Here the gearing ratio between the brown input axle and yellow output axle is 1:36.

Now due to the limited number of gears available in Lego Technic, it is only possible to create the gearings ratios of 1:2, 1:3, 1:5 and 1:7 directly using just two gears (i.e. without differentials) so that means your number N must be a product of one or more of the numbers 2, 3, 5 and 7 for this method shown here to work. For example below are the possible 1:N gearing ratios up to N <= 50 using this method:

 N Factors 2 2 3 3 4 2 x 2 5 5 6 2 x 3 7 7 8 2 x 2 x 2 x 2 9 3 x 3 10 2 x 5 12 2 x 3 x 3 14 2 x 7 15 3 x 5 16 2 x 2 x 2 x 2 18 2 x 3 x 3 20 2 x 2 x 5 21 3 x 7 24 2 x 2 x 2 x 3 25 5 x 5 27 3 x 3 x 3 28 2 x 2 x 7 30 2 x 3 x 5 32 2 x 2 x 2 x 2 x 2 35 5 x 7 36 2 x 2 x 3 x 3 40 2 x 2 x 2 x 5 42 2 x 3 x 7 45 3 x 3 x 5 48 2 x 2 x 2 x 2 x 3 49 7 x 7 50 2 x 5 x 5

Now of course you are not limited to just 1:M gearing ratios in the product, especially since 1:7 can only be made with an 8 tooth gear driving a 56 tooth turntable and so it is more convenient to use a 20 to 28 which gives 4:7 and you then need to cancel out the 4 by placing it in the denominator.

In summary, to create your 1:N gearing ratio, just look up your number in the table above and use the required factors (you will have to work them out for yourself for N > 50) in a gear chain.

Now what if you need to create a gearing ratio of 1:N where N cannot be created as a product of 2, 3 ,5 and 7 (e.g. 13, 17, 71 or other  primes)? The answer is to use a differential! (see the section of differentials for more details when that becomes available...).

# More to explore

## Lego Technic PU 2 Speed Automatic Gearbox

8 Jul 2022

This video presents a lego technic two speed automatic gearbox using two motors and the Powered Up (PU) lego technic control system. Each motor uses a pivoting gear to either connect to it's gear to the left when rotating in the forward direction or to the gear to the right when reversing. Th...read more

## 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

## 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.

## Lego Technic Gearing Ratio Calculator Tool

16 Jul 2021

Here I present my new Lego Technic Gearing Ratio Calculator tool. This tool allows you to upload your Lego Technic .ldr (Lego Draw) file and it will simulate the gearing system and visualize it as well as showing the gearing ratios relative to the input component.

The tool can be accessed...read more

## How to mesh any two Lego gears on a regular grid!

22 Aug 2020

In this video I analyze all of the eight regular lego technic gears and demonstrate how any two of them can be meshed on a lego grid.

A sum of radii chart is used to determine the possible diagonal meshing combinations. These are then combined with "intermediate" or "idler&...read more

## How to measure a Lego Technic Crane's Efficiency. The results surprised me!

27 Nov 2019

Here I demonstrate how to measure the efficiency of a Lego Technic MOC crane using basic physics. Efficiency is the ratio of the useful energy output (the potential energy put added to the weight) the to the input energy (power source power). The efficiency curve is interesting and does not look ...read more