Tobi Wankenobi

Wow. That is purely mechanical, correct? No Electronic/Software Control!? I find shooting mechanisms very challenging. Especially if they have a "automatic" function. I built one for my Fire & Rescue Tank, and making the shooting mechanism working reliably was about the same challenge as building the rest of the vehicle. I think the challenge comes from the fact that there are high speeds, high forces in combination with very limited space. Several sub-mechanisms need to be combined in very small space (accelerating the round, feeding the next one, preventing others from doing the same, preventing the loaded one from rolling away)

What is the most challenging mechanism you have ever built (or even failed to buid)? What mechanism do you think is impossible to build with Lego Technic? I like to start this thread as a collection of challengig mechanisms. You may get inspired to try to realize something which is precieved as "impossible". Or people might post solutions to "impossible" mechansims in this thread.

Thank you!

Congratulations to everyone! I reached exactly the rank I was expecting to reach. Thanks again for organizing this excellent contest!

In my opinion, the voting for the own entry should not be restricted in any way. If you really think your entry is the best, give it 15 points. When you think it is 4th place acording to the rating criterias, place it on rank 4. I like the sportsmanship approach. I kinda felt sad to place mine on the last rank, because I would not have placed it there if it was from a different person. (which is of course arguable, if it really belongs there )

Very nice! I once made a manual-activated transformer, but I can hardly imagine, how this is possible with a motor activated transforming mechanism... And yes, spreading the legs was also challenging in this build.

As we have no insights into the voting process (which I think is a good thing), we could start some guesswork, which entries will make it for the first three places. I have a strong feeling, that the Arctic Explorer Truck and the Arctic Walker will make it for rank 1 and 2 (though not sure, which will be on 1). For the Arctic Explorer Truck features many functions and the innovative gear-box through the crane arm and is built with many details. The Arctic Walker on the other hand has an exceptional walking mechanism and is built very clean. It also has the originality, as something like a walker does not exist in reality (at least to my knowledge). For the third place, it gets difficult to guess, but my guess would be for the Icebreaker. Featuring many function and the cycloidal propulsion system will score it a high ranking. I guess my Arctic Monowheel will not make it to rank 1-3, as the quality, originality and functionality of many entries outplay the monowheels electronic stability control and its originaliy. So this is my guess. Who wants to go next? Anyway, I am curious to see the final results in two weeks.

Thank you! The key element of the self-balancing is the programming code at 5.) The angle of the hub is multiplied with the Proportional Factor (in this case 1.5). As soon as the hub gets out of the horizontal positon, the difference is multiplied with 1.5 and the value is feeded into the motor drive block as power parameter. The more it gets off, the more power the motor gets to steer against and make it go back to horizontal position. The additional coding is used to allow the steering, as well as to have a seperate path with not electronic stability control.

@Jim and @Milan: Thank you for organizing this contest! It is my first time participaing in an Eurobricks Building Contest and I like the whole setup and organization of it. It is exciting to watch how ideas and models develop and to be part of it. Very well done!

A model like the Arctic Monowheel is not only done by assembling bricks and pieces, but also assembling programming-blocks. I like to share the programming of the Arctic Monowheel (explanation below): 1. Mode selector for "Electronic Stability Control" (Enabled/Disabled). The position of the hub in the controls is read out (The hub is connected to the mode select lever, and tilts, when the lever is moved) 2. Path for Operation of the Monowheel with Electronic Stabilty Control Disabled. 3. Block to enable smooth and proportional steering of the two drive motors with one joystick. Joystick Y-Position is used to make one motor turn slower (or even backwards), in relation to the other. I used this part for a tank before, and I could take it over 1:1. 4. Path for Operation of the Monowheel with Electronic Stabilty Control Enabled. 5. Proportional Controller for the stability of the cabin of the Monowheel. 1.5 is the proportional factor which I determined experimentally. Making it too big, makes the Monowheel become unstable, making it too small will not give enough stabilitzation effect 6. Steering block of this path (basically copy and paste from above) 7. Stoplights activation block. (Whenever the joystick speed controll is reduced for more than 3 units, the stoplight is turned on for a certain time) For completeness, the programming showing the most right blocks:

Arctic Monowheel Imagine the huge flat arctic snow-fields. Not every way is difficult to manage and needs a tracked vehicle. Some missions just require a transport to go fast. The Arctic Monowheel is the vehicle of choice, when tracked vehicles are too slow and weather conditions do not allow to fly. Functions The Arctic Monowheel features: Remote control with proportional steering and speed control Working Stoplights Electronic Stabiliy Control. The Arctic Monowheel is driven by two XL motors, one for the left wheel, one for the right wheel. Both motors as well as the stoplights are controlled by a PU Technic hub. As monowheels only have one axis, an electronic stability control system was programmed. It basically features a P-controller (Proportional Controller), who is programmed to get the passenger cabin of the monowheel horizontally. Therefore, the motors actively worke agains wiggling of the monowheel. This is possible, because the technic hub has a build-in gyro sensor, which can easily be read out and serves as input for the controller. When accelerating the monowheel, there is no direct speed command sent to the motors, but instead, the P-controller is given a different input value. (e.g. to controll the cabin to -10° tillted position) This then makes to monowheel to move forward. Because of this additional stability control, it was not possible to use a Buwizz, as they dont offer programming capabilities. Last picture: Monowheel with equipped snow-spikes...

Finished building, porgramming, video shooting. The Arctic Monowheel features remote control with proportional steering and speed control, working stoplights as well as an electronic stabiliy control. The electronic stability control is especially important, as monowheels tend to seesaw as easily can be seen in the video. The Arctic Monowheel is driven by two XL motors, one for the left wheel, one for the right wheel. Both motors as well as the stoplights are controlled by a PU Technic hub. As monowheels only have one axis, an electronic stability control system was programmed. It basically features a P-controller (Proportional Controller), who is programmed to get the passenger cabin of the monowheel horizontally. Therefore, the motors actively worke agains wiggling of the monowheel. This is possible, because the technic hub has a build-in gyro sensor, which can easily be read out and serves as input for the controller. When accelerating the monowheel, there is no direct speed command sent to the motors, but instead, the P-controller is given a different input value. (e.g. to controll the cabin to -10° tillted position) This then makes to monowheel to move forward. Because of this additional stability control, it was not possible to use a Buwizz, as they dont offer programming capabilities. To control the Arctic Monowheel, I used my Universal Vehicle Controls, becuase I like to have haptic feedback, and it just feels better. See how it moves:

Deadline approches, so its time to finish up things... Video will follow soon. Arctic Monowheel: The fastest Arctic Transport if you cannot fly. :-)

I had to change the small 12-tooth gears to larger ones, because the motor was not able to provide enough speed to compensate the wobbling movements... (I could have geared-up before, but I want the motor-wheel connection as short as possible and with as little play as possible.) I also implemented a P-Controller with the PoweredUp App. Works fine, but I can imagine, that even smoother movement can be achieved. Has everyone implemented a PID-controller with PoweredUp App?

Imagine the huge flat arctic snow-fields. Not every way is difficult to manage and needs a tracked vehicle. Some missions just require a transport to go fast. The Arctic Monowheel is the vehicle of choice, when tracked vehicles are too slow and weather conditions do not allow to fly. „Riding a Monowheel is a very unique feeling. You get the impression, that you’re half flying, and half sailing. But with an incredibly speed and always in control of the direction.“ Robert, Monowheel Pilot The idea to build a mono wheel, started growing at that moment where my son saw one in a „future-book“ and told me, that this is not possible… :-) AND YES, it is not actually a monowheel, as there are two wheels. But looking at it from the side it looks pretty much like it. The vehicle faces the same challenges for balancing in driving direction, as a real monowheel, but is of course more stable in the other direction. The challenges for building the final versions are: - Implement a decent controlling algorithm to keep the mono wheel stable while driving. - Build it with even weight distribution - Make it look nice and clean (my biggest challenge :-) First Prototype. Two XL Motors driving the Monowheel (one for each side).