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Found 30 results

  1. I recently published my findings on using a sprung differential as a torque converter. I believe I have proved that a simple combination of a pb&g motor and a differential can amplify the pb&g's spring action down the drivetrain to compensate for a resistance on the wheel assembly. I would like to ask for some help with this. My mechanical engineering knowledge is topped out, and I'd really like to continue exploring this. Let me know if you have any ideas, more formal collaboration would be appreciated also. I'm looking at combining this torque converter with existing gearboxes, and also exploring its response at different speeds.
  2. Today is PI DAY! A very important day for all mathematicians to celebrate. What better way to celebrate than combining it with Lego Technic?! Here I present a PI Day special Lego Technic MOC that produces a gearing ratio of PI to 6 decimal places. This is using two differentials to produce a gearing ratio of 355 to 113. Happy PI Day.
  3. 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.
  4. 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.
  5. 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.
  6. There is one thing which has a great influence on off-roading performance, that is differential. Open diffs will severely cripple off-roading capability of a vehicle, but without a diff, turing radius is going to be awful. Can you really balance the two? I’m showing you two new MOCs regarding this topic: a Land Rover Defender & a monster truck. (There will be two new official LEGO sets which happens to be a Defender and a monster truck, I think this is pure coincidence...) 1. Land Rover Defender I have never tried building a model with no differentials. So maybe I should give it a try to see how it performs. The drivetrain is pretty straight forward: Then I started adding details to it. I was expecting it to be a lightweight model, but when it seems aesthetically acceptable to me, the final weight (1.3kg) is beyond my expectation (around 1kg). Other than that, the actual turing radius is really bad, something I can’t take. So Let’s not talk about performance, just take a look at some details: I have to say this MOC is not too sucessful, so I didn’t bother making a video for it. Even it is fully remote-controlled, to me it is still a display set. 2. Monster Truck So how can we really get maximum performance without losing the benefit of differential while cornering? Most of us know the answer: diff lock. We’ve seen so many great builds with manually or remotely controlled diff locks, and I want to make something different. Then I came up with an idea: Can I design an automatic diff lock, which locks when the vehicle goes in a straight line, and unlocks when it takes a turn? Of course in many cases the vehicle also needs that diff lock to be locked when it takes a turn, but considering it’s a fully automatic action without an extra motor to control the lock, This is an acceptable trade-off. Besides, other factors could somehow compensate for that, like grippy tires, responsive suspensions, etc. I soon realized that this is not going to be a tough job. I only need a simple mechanism that somehow links the diff lock to the steering motor (Servo motor). A video (4K) to show it all: The concept of this MOC came from Monster Jam trucks, that’s why it has roll cage and detachable body. The chassis and axles is no way near a real monster truck, it is built solely for the purpose of demonstrating the auto diff lock. And I think it performs great and seems reliable enough. Hope you like these two MOCs!
  7. Hi. I was working on my car MOC (with a four-speed gearbox designed by Sariel) and had some unfortunate events happen. As stated in the title, the differential is somehow making the gear ratio higher than I need it. The gear moving the diff is moving at the same speed as the power input, but the wheel hub moves one rotation for every 3/4 rotation that I move the input shaft. Is this differential piece supposed to do this? I want the wheels to move at the same speed as the motor at 4th gear, which brings me to my next problem. I hear rapid-fire clicking noises every time my car is in 3rd and 4th gear. This happened to my other MOCs too, but I was able to solve it. Since the car is to be powered by two EV3 large motors, I actually believe there might be a clutch mechanism in the motors such as in the Technic linear actuators that also make a terrible clicking sound when they move all the way up or down. Whatever it is, I'm open to responses and hope the Eurobricks community could provide an explanation and solution about both of these issues. Here's some pictures, the orange and red pieces in the first pic were for testing the rotations. ' Thank you for your time.
  8. Hi All! Often a "reader", now a "poster", i´ve got a problem i cant fully wrap my head around. I try to keep a steering axle straight while going through a pivoting point or turntable. The axle should rotate with the pivot (eg in the picture below the yellow bricks should always align with the grey liftarms even if the liftarms are at 90 degrees of each other) but i want to rotate it manually on one side, with the rotation + offset of the pivot on the other side. Like the axle itself would have been twisted. The furthest ive got with this is pictured below and works as long there is no friction on the left output. I want both sides to rotate at the same time, but if you rotate the pivot/turntable then it should add just an offset "within" the axle. I dont know if this is actually possible or how to split the axle in two, add the pivot rotation to one part and then add both rotation together.
  9. (Sorry for mistakes (I'm not from Britain / America)) I was thinking about LSD (Limited Slip Differential) in lego. Because all I saw yet were just differentials with locking mechanism that engages after few turns of axle. And only thing it was limitting was main function of differential. So I came out with this solution - I know it isn't great, but it is very simple and compact (actually you add one rubber band inside differential (under spider gear)). What that does ? - When axles want to spin at different speeds (while cornering) more power is required (so you lose some speed if you don't have powferful motor) but, if one wheel lose traction the other one gets more power (compared to open differential) and you can also set how much additional friction you wat (by adding different number of rubber bands inside). Here is one picture of it : I just want to know what do you think about it, and if there is possibility to create a real LSD in lego.
  10. Hello, I've been building with lego technic for a couple of years, but found myself never having the right pieces for my builds. I recently bought a second-hand lego set with some nice wheels (8386). So I could finally start building some bigger and cooler cars. I started with my first supercar this week and am having trouble with the rear axle. I am using the method you see in this picture ( with 2 separate axles. The problem is that I want to use a differential, but can't figure out how that would work with this. Does anyone have a solution for this, or does anyone have a different, stable (compact) method for this? Any rear axle that has suspension is welcome. I would appreciate it to see more ideas from you. One more thing to keep in mind is that I only have the type of universal joints you see in the picture ( I don't have any other. Thanks in advance ;)
  11. I said before in my previous post that I had some problems with my GX EV3 4x4 chassis that I needed to fix. Once again, it's more gear grinding/clicking, but this time it's only in the front and rear differential gears. The grinding occurs whenever the chassis tries to drive into a wall or when it tries to drive in different conditions (because as an SUV it should drive smoothly in dirt or uneven terrain). What also annoys me is that when I push the car, instead of letting the motors move, the differentials make clicking noises that, like I said before, sound like a machine gun. I really need help so I can stop the differentials from clicking so when the car tries to drive into the walls, the motors won't still move while the differentials click, and so the car can be a lot more versatile on uneven terrain (such as what I used for testing, blankets) without the differentials causing a problem when the car moves. Here's some pictures of the bottom of the chassis.
  12. shuoshuoliuliu

    6x6 truck VS

    just made a truck similar with Mr. Madoca's new moc work same function on differencial lock and 2 speed gearbox,but 6x6 -Weight: g -2 XL motors for propulsion,1 XL for 1st axle,1XL for 2nd、3rd axle -2 Servo motor for steering,1st & 3rd axle -M motor for 2 speed gearbox -M motor for locking rear differential,1st axle - 2nd、3rd axle -Portal axles for 1st、3rd axle in order to make a powerful crawler, I need different rotating speed of front and rear axle. For the reliability, I not use the weak center differential. I design 2 seperate XL motors for 1st axle and 2nd+3rd axle. But I add a lock, to lock the 2 XL motors together when necessary. That means there are 2x 2speed gearbox + 1 lock. And to make sure the enough power, I add 2 battery boxs.
  13. TechnicRCRacer

    Locking Differential?

    Hi, I am seeing more and more locking differentials on MOCs, but I do not see how they are useful. Does anyone know why?
  14. Hello everyone, I have many old sets which are using this differential and as you can see, you can easily create differential lock using part But I was wondering - is there any official set which actually uses this parts combination?
  15. While playing around with the small turntable, I realised it can also be used to make a strong open differential, as follows (the red part of the differential need not be present, depending on usage): Top view : Side View : (lxf) I'll be using this as the center differential for my "Yet Another Supercar (Gen II)" . Another good place to use this is in mechanisms that uses those inner gears of a differential heavily - e.g. automatic transmissions that rely on a differential to detect overwhelming torque.
  16. After a little tinkering, I managed to create this self-locking differential. It locks when the car goes straight and unlocks when turning: A set of 12t gears are connected to the steering rack. When the rack is in the middle (and the car going straight), the two halfshafts are coupled together, locking the differential. When the rack moves to the left or right to steer the car, the 12t gears disengage with the 20t gears and let the differential act like an open diff: The main downsides I see with this setup are that the differential may stay locked during wide turns with small rack movement and the width of the axle is increased. A standard independent suspension with a differential and 68.8x36 ZR wheels (the combination I usually use) is 25 studs wide; with this feature it increases to 27.
  17. Four wheel drive on Lego Technic cars with small wheels is hard to realize, as they become relatively too wide (which is ugly) and the ground clearance is also compromised. The problem then is: how to get the same grip back with only rear wheel drive? Then you need to push something 'extra' in the back of your already crammed, small nice-looking vehicle... This concept is an approach to keep this 'something extra' as small as possible while giving awesome and unexpected grip to the car. (At least, I was astonished by what it achieved!) Instead of typing a lot, I've put it all into a video with the theory of how it all works at the back of the video to let the 7 billion minus 1000 viewers that are not interested into more advanced Technic stuff experience how it works in practice on a 2 cm (that is: inchy) thick ice floor. As for the car, it is built from Power Functions spares as all my L-motors (which have quickly become the main workhorse for every Technic builder) are ehm... in use. That is why you find me using a geared up XL motor, which gave me memories of the good old times when the poor knob wheel parts splattered around. Sharp images of the car and mechanism explanation can be found on: http://www.brickshel...ry.cgi?f=564319. On MocPages (beware, there is a piece of code there that simply destroys anything such as image resolution on .png files...) http://www.moc-pages.../moc.php/428881 Video: I finally have found PovRay so (with many thanks to all those who make that software) I can present a high-quality render:
  18. When I read the chapter describing custom differential in Sariel's book, trying to follow instructions to build it . Unfortunately, I only had "two" Knob wheels. Then I came up with a idea that is there possible to replace Knob wheels with double bevel g20t ? That means I have to build a different frame for three double bevel g20t which the 5X7 studless frame can not house. After trial and error of building process , I managed to build a frame that can enclose three double bevel g20t and connected it to a turntable . This differential is going to take more space than Sariel's when actually put to use. Here is a short video demonstration of this differential . A link to BS
  19. This is a fully automatic clock that was finished end of 2014. So, why do I call it "fully automatic"? - The clockwork runs as a normal mechanical clock with a pendulum and counterweight. - There is a motor that winds the clock every hour. - The speed of the clock is adjusted once a day using the Mindstorms unit. The speed is adjusted by changing the length of the pendulum. In total, the clock runs for itself without any assistance, and it shows the right time, even if it is build using only LEGO bricks. (Apart from the string to the counterweight) There have been many challenges in this design. My main focus, except the obvious goal to make everything to work, was to make this as compact as possible. The whole clockwork fits inside 14x14x14 studs. I did a short video to show the "action": The two sensors are used for: 1. Stop when the counterweight is fully winded 2. Give feedback from the minute hand rotation back to the Mindstorms unit. The counterweight is made out of 12 train/boat weights and is about 0.68kg. Winding is done through a differential to avoid interruptions during the winding. There are two medium motors inside the clockwork for the winding and adjustment. The Mindstorms unit is hidden in the base behind a hatch: WIP pictures Specially designed differential gear to reduce the friction between the counterweight and clockwork as much as possible. The winding motor rotates the large turntable gear: Clockwork prototype, without any automation: Very first prototype of the escapement:
  20. This is a large short-course style stadium truck built with Lego Mindstorms Ev3. It features independent rear suspension and a front live axle with steering. One Medium Motor controls the steering, and one Large Motor drives the rear wheels. It also uses the InfraRed Sensor for Remote Control. The reasons I used only one motor in this model are: 1. I was attempting to reduce weight, 2. The chassis of the truck is even studs wide, not odd; not allowing a very easy placement of two motors, 3. This vehicle was built as a test vehicle for the new 4-stud wide differential I got a while back but never used until now. The drawbacks of this truck are: 1. One motor does not exert nearly enough power, 2. The old-type differential makes it impossible to not use more gears in order to transfer the power, 3. All the gears used decreases efficiency massively, 4. The rear independent suspension worsens performance, 5. A 3:5 gear ratio was used (a 1:3 would have been better), 6. The truck is very large, bulky, and heavier than most other robots that I have built. I extremely apologize for the audio/video sync issues, I have no idea why the video turned out that way. Music: [] Extra pictures coming soon! []
  21. This is a fully functional, remote controlled subtractor drive with independent turn and drive function which are separately powered. It is up on LEGO Ideas - support it if you like it, there you will find some more high-resolution photos :) This is a fully functional, remote controlled subtractor drive with independent turn and drive function which are separately powered. It features: - robust design with custom-made differentials that can handle larger forces - transparent, "airy" and parsimonious design - "invisible" electricity, all integrated into the mainframe - front and back lights with light switch integrated into the mainframe - quadruple L-motor power (two linearly coupled blocks of two motors each) - front shield - triple speed freely hanging piston motor - self-stabilizing and self-balancing design - can be mounted with any superstructure, e.g. cranes, hoists, levers Constructed to an 11/15 measure, fully compliant with the rules of LEGO. Only official LEGO parts are used and no parts are modified or altered. Weight: about 4 lbs, dimensions ca. 30 x 25 x 30 cm The chassis can be used as a basis for basically any vehicle that has to traverse difficult terrain, e.g. building machines, bulldozers, search & rescue vehicles, etc. It is designed to provide a multipurpose solution for a variety of tasks. If fitted with different superstructures on top, countless models can be constructed.
  22. I do want to start this topic off by saying I understand what a differential is, how it works and why it is necessary for standard 2wd setup. What I am curious about is the function of a differential when placed in a drive train between two or more driven axles or 4x4 setup. Is a center differential necessary? Are there performance increases or decreases? What type of results have you had when running PF on a setup with and without a center differential?
  23. Hi All I've been working on an rc van using a Raspberry Pi as the control and have decided to incorporate a technic motor for drive and would like to ask for some help and advice. I want to build a simple gearbox/drive in a compact design, but wasn't sure what gearing/design to use? I have forward and reverse control through the Pi/Scratch and it maybe easier to keep it as simple and reliable as pissible, any help/advice appreciated. You can see my project here http://raspivan.weeb.../rasppivan.html
  24. Hey guys, I'm new here and would like to present you the WIP of my lawn and garden tractor. At the moment, it features RWD, a turning blade and a V2-Engine. Both are connected to the RWD, which has a differential. The seat is variable, it moves in one stud steps. The front wheels are steered by the small steering wheel. Things I'm having on my to do list at the moment: - I'll have to optimize the partcount to give the lawn and garden tractor a nice body (194 parts at the moment). - Building the model in real life (this will happen next weekend). And I have a picture of the actual virtual model for you, which shows the drivetrain and the frame. In the model above I made the wrong picture, so you can't see the steering. My second picture shows you my virtual model with body parts. I'll use silver and black or red and black. I'll see which plates I have at home and use them in one of the two colour combinations. The basket isn't ready, when playing with the lawn garden tractor the player can remove it. Another small update: I changed the body design, because the first version of the body was too "fat".