TechnicBrickPower

Here I present methods for designing N:P Lego Technic Gear ratios where N and P are prime using two differentials. Several differential topologies are presented and one cross connected topology is mathematically analysed and the relationship equation between the input and output derived. Using this equation and the computer solutions for the 1:N gear ratio designs, an example is worked through to create a 313 to 421 gear ratio. This gear ratio design is much more efficient than simply connecting an N:1 and 1:P design in series.

Hi Ludo & Piterx, thanks for the feedback and glad you liked it. It's not easy making videos lol. I have posted a follow up video about designing a 1:N gear ratio for N=prime, and give all solutions for N < 1000.

Hi there, I have made a 73:1 design for you using the optimal solution found by the computer search. It's not that elegant but should work (I haven't built and tested it sorry lol). Let me know if it works!

In this video I present optimal computer generated solutions for designing 1:N (N=prime) ratios using a single Lego Technic differential. Insights and ideas are shown for implementing the 1:N designs in practice using Lego Technic liftarms with an example 421:1 gear ratio device. All the possible solutions for N less than 1000 are shown and can be used in your own Lego Technic MOC designs if you are needing to create a particular gear ratio.

Hi Samuel, Thanks glad you got something out of it. Of course the truly clever guy was the engineer Onésiphore Pecqueur from 1827. The differential is one of the most versatile gear configurations while still being relatively simple..

.Hey 1980SomethingSpaceGuy. Glad you liked it. I am working on part 2 where I look into some computer generated optimized solutions for 1:P (p=prime) ratios using 1 differential gear. Have some interesting preliminary results already.

Hi I have been learning about gear ratio designs for a while. I have been working on understanding the differential gear mechanism. It's fascinating once you start analysing and understanding how much you can do with this amazing device. In this video I briefly talk about why and when it was invented and then go over the mathematical relationship between the axles to allow easier designs of desired gear ratios. I illustrate a design of a 17:1 gear ratio and show a list of other potential design options for creating any of the prime numbers up to 53. Of course you can probably create any prime number but will explore that in a later video.

Thanks again Doug. I have ordered that one also - looks like a great book with many ideas and examples. Sometimes it's easier to start with someone else's solution and modify that from there.

Hi Doug, Thanks for that reply. A few people have recommended Isogawa's book so I have now ordered it from Amazon! Look forward to learning from it. Thanks again, Rob

Hi Everyone. I spent some enjoyable time creating an MOC gearing mechanism that produces an exact 7:1 gear ratio and can be modified to create a 13:1 ratio. It's not that practical but shows how I converted an idea into a working model - it's never guaranteed that what you think will work actually works in practice. I think I have inadvertently created a variation of a differential gearing.

Yes you're right it's out by 1/625 from 7, i.e. 6.9984 = 7 - 1/625. I found this by running a search algorithm and it can find ratios to a high precision, but these need 1000's of gears - so not practical! For example 5 ^ 571 / (3 ^ 571 x 2 ^ 418) = 6.99999683.

Hi Just an update...someone on reddit posted that you can create an exact 7:1 using a differential with 1:5, and 1:9 input to create a 1:7.

Hi Everyone, I have made a video about creating a 7:1 gear ratio mechanism using just 2:1, 3:1 and 5:1 gears. No 28 teeth gears used. Youtube subscriptions appreciated! Kind Regards and keep building, Rob

Here's a good 1:4 or 4:1 I created (between black and brown axles). Strong and smooth. Can attach directly to a liftarm. Hope you find it useful.

Hi Guys thanks that's good to know. I never knew there were any 7 multiple gears out there. Interesting that one has recently been introduced. Will put in a bricklink order now and get some. Will still try to create a 7 to 1 without using one of those. Otherwise I will try an 11 to 1.

Hi Everyone, Just made a video about a problem I had to solve: Trying to create a 2 to 1 gear ratio for a MOC project I was working on. These are just some of my solutions - I'd be interested in hearing about other people's solutions to this problem. I found one elegant solution that I show near the end of the video that surprised me to discover. Obviously I won't be the first to find this - but it's nice to re-invent things by yourself! Let me know what you think. My next project is to create a 7 to 1 gear ratio LOL. Comments invited! Rob New Zealand.

Hi JopieK Thanks for pointing that out. I wasn't that confident when I said it because it didn't make much sense to have a capacitor in series LOL. Appreciate your feedback and I will get it right next time. Regards Rob

Hi Everyone! This is a video made about modifying a technic battery box to use a 9v supply. Hope you like it. Subscribe to my channel if you like this kind of content.

In this video from a while ago I demonstrate the torque calculation of a Lego Technic MOC crane axle in order to work out the maximum torque before axle failure (i.e. twisting itself to bits). This would apply to any high torque technic mode (axle failure torque). https://youtu.be/OydlrN3sdKI Hope you like this video. Any comments or feedback appreciated. Kind Regards and keep building, Rob

Thanks Sadap and vectormatic. Glad you both enjoyed this measurment. It's nice to receive some good feedback on my hobby videos. Yes the results are interesting and am looking doing some more tests with other gear combinations like you suggest. The heavier weights do increase the friction dramatically and I need to design the support around the axles better so they don't bend as much. Am away on a 4 week holiday at the moment so won't be until next year!

Thanks for the welcome. Yeah definitely awesome forums.

Did you end up finding out Thanks for the information in the link - you have a lot of very interesting set of graphs there. Thanks for taking the time to make all those measurements - I think I will be referring to them often in the future :)

Hi All, For those that like measuring and calculating things...like me...here's a video I made on measuring the efficiency of a Lego Technic MOC crane. Would appreciate any comments or feedback - it's a lot of work (but fun work of course) making a video so I do hope some people out there enjoy this kind of thing. Am always trying to improve my videos - am a newbie at it lol. If you have any video ideas around this theme let me know (unless you're making one yourself already). Even better would be if you could subscribe to my channel - that will encourage me to make more videos! It's hard to get content out there. Please share with your friends if you think they might enjoy it too. Take care, and keep building... Rob PS Don't forget to subscribe!

Thanks for that answer! I cranked it up to 10v the other day, lucky I didn't go any higher, lol. It did start behaving funny even at that voltage - the current suddenly dropped to almost 0. What about the motor itself without an IR receiver?

Hey everyone... received a few messages about putting on a disclaimer...so here it is: BE CAREFUL - I can't be held responsible if you destroy your battery box. If you are not confident doing this mod then don't do it - that said it is pretty straight forward...lol. Also don't plug it into the mains! 9V DC only. Also there are other solutions to this problem. I don't know how high a voltage you can put on there before you blow stuff up. Maybe someone else can share their experience? Anyway good luck and have fun.