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About Flybum

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Technic
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42100 Liebherr
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Quick update: I added a short clip showing the key gear‑switch moment of the backhoe’s mechanics. This should help clarify how the whole transition works.
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CENTAURO II -1:13 Scale MOC
Flybum replied to Flybum's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
No, it’s the same MOC — I just never showed the interior before, so I made a video focused on that. -
CENTAURO II -1:13 Scale MOC
Flybum replied to Flybum's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
This is a short cinematic overview of the internal mechanics of my Centauro II MOC. The model follows the real vehicle’s internal architecture very closely, including the H‑shaped transmission, suspension layout and crew stations. Only the sequential gearbox is simplified compared to the actual machine. -
Thanks! Bricklink Studio works wonders. I just hope they update it for the new NVidia architecture, right now the 5080 can't be used for rendering. Thanks! I’m glad you appreciate the focus on functional realism. For me it’s an essential part of what Technic should represent.
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You are perfectly right about the electric motors. Since we don’t have hydraulic motors in Technic, we inevitably have to use electric ones, and if you want to split the power between the two tracks you always end up needing two of them, whatever layout you choose. I chose the double‑differential solution because it felt closer to the idea of a single power source, placed in the upper structure, whose output is then distributed to two users. But I don’t pretend that this matches the real machine’s layout one‑to‑one. And I knew it wasn’t the simplest option. In fact, the whole concept originally came as a sort of reaction to the solution used in the LEGO Liebherr, which many people criticized as being too simplified for a model of that size.
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Thanks! Glad you like the model. Yes, I bought the bucket from set 42215 as soon as it became available and tested it. In the end I found that the older bucket was closer to the shape and proportions of the real machine, so I kept that one. About the drive: from a pure power‑distribution point of view you’re absolutely right — with one motor per track you get the full torque of both motors when driving straight, while with a single motor the power is split between the two tracks. However, I tried to stay as close as possible to the real engineering of an excavator. In real machines you never have two separate motors directly driving the tracks (like in the LEGO Liebherr). The engine is always in the upper structure, and the tracks are powered through independent hydraulic circuits, not through two dedicated motors. I could have mounted two motors in the upper structure and routed the drive through the coaxial shafts of the slewing axis directly to the tracks, but in the end I preferred the single‑motor solution plus a second motor for steering, because this reproduces more closely how the real machine works. Besides, the linear speed of the real Volvo model is really low, so you have plenty of power even with a single XL motor. So yes — two motors would give more straight‑line power, but for this model I prioritized mechanical realism over maximum performance.
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This MOC of mine has already been built by many people. Since the working layout is not easy to imagine just by looking at the outside, I decided to create a full INSIDE‑style breakdown of the mechanics. Our graphic tools are continuously improving and allow us to produce fantastic internal visualizations. Here is the video: https://youtu.be/pxropYx-Y7w
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Thanks! I tested several front‑wheel options, but these matched the real vehicle best. And, since the front and rear wheels have different diameters, you need a vertical offset to keep the chassis perfectly level. With this combination, the required offset is exactly 1.5 studs, so achieving it with a half‑stud addition is straightforward. The front axle also has to pivot longitudinally, so keeping the geometry simple really helps.
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Almost! The general idea is right, but the internal setup works a bit differently. There are 6 motors in total: 3 large motors are the “main” ones. In Front Mode they drive the 3 front functions (boom lift, boom tilt, drive). In Rear Mode the same 3 motors control the 3 rear functions (boom lift, dipper lift, bucket tilt). So each main motor has one front function and one rear function, selected by the gearbox. Then there are 3 medium motors: 1 medium motor is dedicated to switching the mode. It performs a three-step automatic sequence using two clutch gears: – it switches the motor selectors – it rotates the driver’s seat – it raises or lowers the stabilizers. 1 medium motor is dedicated to steering. 1 medium motor is dedicated to rotating the rear boom. You can see the transmission chain for the mode‑switching sequence in the video I linked above at points 5 and 6. And if you want to see how this translates into actual controller commands, here’s a short video that shows it in action. Black levers=main functions. Blue lever: forward: front mode/backward: rear mode. Yellow levers: dedicated functions. https://bricksafe.com/files/Flybum/full-rc-backhoe-loader/Test%20Commands.mp4
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From the outside, the mechanics of this backhoe are not easy to understand, so I prepared a transparent rendering that shows the full internal layout. Each of the six motors has its own color‑coded transmission chain, making it easier to follow how the power is routed inside the model. If you’re interested, this video shows the complete internal structure and how all 10 functions correspond to the six motors: Link to my previous post:
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Flybum started following CENTAURO II -1:13 Scale MOC
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Thanks! I watched your video now, very nice work. What’s funny is that I only discovered that other similar builds existed after finishing mine. Maybe it’s just me, but sometimes the web hides exactly the things you’re looking for, even when you search deeply. I guess the same will happen with my MOC: people who would be interested will probably find it years later. For this project my only goal was to keep the machine compact while still having every function remotely controlled. I avoided pneumatics because, even if they’re easier to implement, they usually give slower and less reactive movements. And yes, while designing it I realized how challenging a backhoe really is. Probably one of the hardest machines I’ve ever tried to fit inside a Technic model.
- 9 replies
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- backhoe
- backhoe loader
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Thanks! Yes, it turned out surprisingly responsive and quite playable. I also recorded a small test video to show how the control layout behaves - it ended up being really fun to make. The model reacts very much like the real machine, and just like the real one it needs a bit of training before you get smooth control. The clip shows a few fails at the beginning, but also how quickly you can learn to operate it. The link is available on my Rebrickable page for anyone interested.
- 9 replies
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- backhoe
- backhoe loader
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(and 3 more)
Tagged with: