TechnicBrickPower

Here I present an 8 speed gearbox that does the seemingly impossible - creating eight speeds using just two levers/selectors. Normally two selectors are used to create a 4 speed gearbox - however this design allows for 1 of 8 different speeds to be selected - thanks for the idea @SNIPE

Hi thanks for the feedback - I generally don't design with a size in mind - it's more the concept I am trying to demonstrate. For a particular application you may be able to redesign it to be smaller - there are a few gaps in the current design.

Here I present a smoothly switching 2 speed automatic gearbox. The gearbox uses the "differential jam" phenomena to prevent reverse torque transmission during the gear switch over point, when the driving gearing can be momentarily disengaged. The gearbox automatically switches down by a ratio of 2/3 when the load on the output is sufficiently high by using a differential to detect the loading and to drive an orange rotary catch. This is a smooth transition due to the reverse path being only one directional. https://youtu.be/h7j50GRm6Vc

Hi Everyone, I have created a video - aimed more at beginners but maybe interesting for experienced lego technic fans too about meshing any two lego gears on a regular grid (i.e. whole number spacing, no halves etc.). This technique allows you connect any two gears A and B on the grid and create the gear ratio A/B. Also has a cool intro animation if you like those. Sorry bit of a long video...

Hi all, a couple of weeks ago I presented some experimental results of comparing the relative friction of 4 different motion transfer methods - 16 teeth gears, 40 teeth gears, a perpendicular axle, and a chain. I have now published the build instructions for anyone wanted to run their own experiments. Please post any results if you do. https://rebrickable.com/mocs/MOC-50089/TechnicBrickPower/relative-friction-measurement

Great idea - I like it!!!

Here's a smaller way of doing it. Video https://www.flickr.com/video_download.gne?id=50229833833

No I haven't tried it in a vehicle - not all automatic gearboxes have to go in vehicles LOL ;) You can set the change over torque point by increasing the rubber band strength. In this demo I had 2 bands - but could increase that to 3 or 4 etc. Also you can gear down after the automatic transmission to the wheels so you see less torque at the transmission point. But yes I will try it in a vehicle sometime!

This is a compact 2 speed automatic gearbox design. Instead of using a differential to react to torque on the output it uses the force on the gear teeth to push a liftarm to automatically change the gearing ratio to the 2nd speed once the torque threshold has been exceeded. The automatic gearbox will switch back down to the first speed once the torque on the output is reduced by using two rubber bands to pull back the liftarm. The first speed is simply a 1 to one ratio and the second speed is a 0.6 ratio. The design can be easily modified to change the the second gear speed to other ratios such as 0.36 or 0.2.

Yes I agree - a load comparison would be most important as most models are run under at least some loading. Maybe I will look at that sometime. I don't have anything to measure noise with. They are all loud!

The relative friction of four different solutions for transferring motion from one axle to a far away axle are compared. The friction load differences are compared using a differential to measure the speed difference of the load on two medium motors. The four motion transfer solutions that are compared are a series of nine 16 teeth gears, three 40 teeth gears, a chain, and bevel gears driving a perpendicular axle.

Hi All, Have just published the build instructions for my recent automatically reversing gearbox on rebrickable: https://rebrickable.com/mocs/MOC-49276/TechnicBrickPower/auto-reversing-gearbox Here's the video about it:

Hi Doug72. I am sure it can be - at least one differential can be eliminated by replacing it with a different reversing mechanism. Also I think there may be other torque conversion options instead of a differential so then they'll be both gone and the mechanism will be a lot smaller.

Hi Everyone, This gearbox has been designed to automatically reverse if there is a high load on the output. The gearbox works by using a differential to react to the torque on the output and it drives a two state switch to select the reverse or forward direction in the gearbox.

Hi all, the instructions for an MOC automatic gearbox that I made a while ago are now available on Rebrickable. https://rebrickable.com/mocs/MOC-48521/TechnicBrickPower/3-speed-automatic-gearbox youtube video on how it works: :

Hi Ludo. Thanks so much for your detailed answer on the mathematics of the torques and forces involved - that is one area I'd like to study more. Also very interesting link you sent about the differential that won't go backwards - I have discovered the same in some cases and found it quite frustration - I don't fully understand what is behind this problem!

Hi @arieben, thank you and am really happy you found my content on differentials useful - it's good to hear when someone can use it for their own projects. I find it very satisfying to use math to discover solutions you'd never find by just trial and error. Will do my best ;)

Thanks guys - great feedback - I thought no one would be interested when I posted this. Hope to do more in the future.

Hi All, Just made a video that presents an analysis of a two degrees of freedom differential gearing system that I have been basing some previous designs on. I use this to explain why the "Slow reverse Car" mechanism did not work as expected. Only for maths fans - don't watch otherwise ;)

Hi Erik, Thanks - yeah I did mean that ;). The Golden ratio - yes that would be a good challenge! Appreciate your positive feedback - and yes used to use LaTex in my uni days - old habits are hard to break. You're the first person to notice lol.

Hi All, I have made some build instructions for my Pi day MOC gearing mechanism that I made a while back. It implements a gearing ratio of 1 to 3.1415926 using two differentials. Here's the video about it: and the instructions on rebrickable: https://rebrickable.com/mocs/MOC-48047/TechnicBrickPower/pi-day-gearing-ratio-mechanism

Yeah it is a bit of fun. Just trying to do something different ;) I was actually surprised how well it worked. Hey Gray Gear - yeah you probably won't miss the other 1017 speeds - I didn't lol I guess you won't be interested in a 100,000 speed gearbox then? What if it had reverse?

A 1023 speed gearbox has been built into a large remote controlled car chassis. The car can be steered and driven via remote control using two channels. The gears can be manually changed using ten selectors that drive ten differentials. This allows for one of 1023 different speeds to be selected to set the car's forward and reverse speeds. The car drives well on carpet as well as a smooth surface. It uses 4 large 10cm diameter wheels and a medium sized motor for the steering mechanism. The main drive is from a large power functions motor. The gearbox functions are explained in detail.

Hi All, This is my first attempt at a car chassis. It is remote controlled with forward and reverse and remote controlled steering. What is different about this design is that it implements a special gearing mechanism that allows the car to drive forward at a normal speed, and 1/5 the speed in reverse. It uses a special configuration of differentials and a pair of ratchet gears to achieve this - however I did discover a flaw in the design after I built it.

Hi @Pas_de_nice Thanks for that calculation of power loss - that will help me with future designs. I will try to estimate these numbers and see what % of power is actually lost - will be interesting to see what that is.