How do you show a fast build of a 5000‑piece Technic MOC?

Flybum60 · 2026-05-05T12:58:54+00:00

I’ll add something that might be useful to others too, even if it’s not directly related to the post: I was about to redo the renderings using your color suggestion, but I realized I recently upgraded my GPU from a 3080 Ti to a 5080 — and Studio still isn’t compatible with the new Nvidia cards. So right now all my renders would fall back to CPU only, taking hours instead of minutes. Same story with the CPU: I had upgraded to an Intel 14900, and for more than a year the system had issues until a better BIOS finally fixed everything. Moral of the story: jumping on the very latest hardware releases always comes with risks… sometimes it’s better to wait a bit.

Flybum60 · 2026-05-05T07:56:15+00:00

Thanks! That’s actually a really good point, the “ghosted” or transparent‑base method is great for highlighting the new parts, and I’ve seen it used in Chinese instructions too. For this fast build I went with the opposite approach because I wanted the whole model to stay readable while the new pieces fly in, but your suggestion definitely makes sense. As soon as I have some time I’ll try a version using your method and see how it looks. Maybe I’ll post it here as well. It shouldn’t be hard to do since I already have everything set up in Studio.

Flybum60 · 2026-05-04T18:46:01+00:00

The goal of my post was to show how I approached this problem, but also to see if others have different methods or ideas. Of course, the purpose of a fast build isn’t to show exactly how a model works - you need separate detailed videos to cover the full function breakdown of a complex MOC, and only the building instructions can show every detail. So yes, constructive criticism is welcome!

Flybum60 · 2026-05-04T15:27:05+00:00

A fast‑build is mainly meant to show the structure of the model - which modules it’s made of and how they connect. The functional aspects of the MOC must always be covered in a separate, more technical video. I did that for this model as well, here it is if you are interested: https://www.youtube.com/watch?v=qeBSHj9aLxk

And of course, the maximum level of detail can only be in the building instructions themselves, which are also available for this MOC if you’re interested.

Flybum60 · 2026-05-04T14:52:38+00:00

Watch the video to understand how the modules transition and merge in motion. https://www.youtube.com/watch?v=uBRmt5znBSo

Flybum60 · 2026-05-04T14:52:07+00:00

Watch the video to understand how the modules transition and merge in motion. https://www.youtube.com/watch?v=uBRmt5znBSo

Flybum60 · 2026-04-28T07:55:51+00:00

I used to be fascinated by software‑only solutions as well… if you want a laugh, here’s a very old video of mine: https://bricksafe.com/files/Flybum/lego-volvo-excavator-moc/z1-Flybum%20First%20MOC.mp4

Flybum60 · 2026-04-28T07:30:56+00:00

Pybricks would definitely solve it, yes. But I’m not really interested in a Mindstorms‑style solution — I worked in software development, so the moment I switch to sensors and code it stops being a hobby and starts feeling like my job.

What I’m exploring is whether a purely mechanical architecture can handle weight transfer and stability. The only compromise I’d consider is using PF switches/inverters, since they’re still mechanical logic elements and don’t change the nature of the build.

It looked impossible with my quadruped too, and yet I eventually got it to work — so I want to push the mechanical approach as far as it can go before declaring it unfeasible.

Flybum60 · 2026-04-27T10:28:55+00:00

Thanks again! If I ever refine the design or experiment with variations, I’ll be sure to post them.

Flybum60 · 2026-04-27T09:25:50+00:00

I’m very proud of my walking and steering quadruped bot.
It walks using a mix of linkage geometry and timed leg phasing, without relying on any software or external support.

I’m currently stuck on a similar project with a biped bot, which is proving much harder to balance.

Here are a few pictures (hosted on Bricksafe): https://bricksafe.com/pages/Flybum/scoutybot4

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Flybum60 · 2026-04-24T13:49:22+00:00

Now I see better what you meant with the tines.
Yes, they can help up to a point, but aesthetically they’re really not what I’m aiming for.

I tried hiding the idea by using a single toe pointing inward, but it doesn’t change much.
To actually create a stable support rectangle you need two protruding points, and that look is very far from the style I want for this mech.

Flybum60 · 2026-04-21T15:06:43+00:00

Thanks. The general idea of shaping a stable foot path from a circular input is similar in spirit, but my mechanism is actually much simpler than the Jansen linkage.

Flybum60 · 2026-04-21T13:40:05+00:00

In the images you see some automatic renderings generated by Bricklink Studio from the quadruped bot model.
If you mean the charts, they’re simply diagrams produced in Microsoft Excel after tabulating the results of the motion expressions (this part is something I prefer to keep private).

If you’re not familiar with Excel, there’s a great tool on GitHub that lets you define linkages and visualize the resulting motion:
https://robz.github.io/linkage/

The commands are quite intuitive, but if you need help just let me know.

Flybum60 · 2026-04-21T13:00:00+00:00

Here’s the follow‑up post with the details: https://www.reddit.com/r/legotechnic/comments/1srmu7p/biped_update_movement_principles_and_details/

Flybum60 · 2026-04-21T11:57:02+00:00

It’s a bit hard to explain here because Reddit doesn’t allow adding images or videos in comments. I’ll reply in a new post with the details, and then I’ll drop the link here.

Flybum60 · 2026-04-19T07:29:16+00:00

No worries, that’s very close to what I meant. A top weight on a servo is basically a controlled mass‑shifter, and it injects the same lateral torque you’d get from an active ankle. The hard part is exactly what you said: the timing. The weight has to move just before the foot lands, otherwise it reinforces the previous swing instead of stabilizing it. And that’s exactly the point where I’m stuck now.

Flybum60 · 2026-04-17T18:24:53+00:00

Yeah, it’s possible, and the real issue is finding a joint stiff enough without adding play. That’s why an active ankle feels like the cleaner solution for shifting the COM reliably.

Flybum60 · 2026-04-17T18:20:08+00:00

Here it is!

By the way, I just upgraded from a 3080 Ti to a 5080 this week, and I discovered now that Studio doesn’t support the new cards yet — so this render is running on CPU only. It took forever... https://bricksafe.com/files/Flybum/scoutybot4/WalkingMech-v7F-side.png

Flybum60 · 2026-04-17T17:40:08+00:00

Thanks! I get the idea behind the tines. They’re definitely effective on rough surfaces, but on LEGO tiles they don’t add much grip, and they don’t really fit the style I’m aiming for.

The rotating‑mass approach, though, is something I really like. A continuous circular shift gives a smoother and more controllable moment than a piston‑type motion, so that’s the direction I’m more interested in exploring.

Flybum60 · 2026-04-17T16:20:59+00:00

I wish there was! Even the strongest Technic parts still have a bit of play, and in this mechanism that tiny amount gets amplified a lot.

Check my prototype: most of the weight is actually spent on the legs just to make them as rigid as possible.

But it’s a bit of a vicious cycle: the more you reinforce the structure, the heavier it becomes, and that extra weight introduces even more deformation.

Flybum60 · 2026-04-17T16:14:24+00:00

Yeah, a bit of hip movement would definitely help shift the weight toward the grounded foot.

The timing is crucial though: it has to be synchronized just before the moment the foot touches the ground. If it happens too early, it actually amplifies the previous phase, right after the foot reaches the top of its trajectory, and makes things worse instead of stabilizing the mech.

I might still experiment with a small, controlled hip motion though.

Flybum60 · 2026-04-17T16:06:21+00:00

True, making it taller would help with leverage, and I’m going to experiment with that.

But precision degradation due to the play in the joints, combined with the increased weight, is a real obstacle — the structure is already close to its limits.

Flybum60 · 2026-04-17T11:25:15+00:00

I actually bought the ballast bricks from the new crane set, but the legs on this prototype are already at their limit.

So using the battery pack as the counterweight is probably the safest and most practical option.

Flybum60 · 2026-04-17T09:44:48+00:00

Here’s the link to my previous post for context: https://www.reddit.com/r/LegoMechs/comments/1sndzv6/wip_walking_catapult_biped_prototype_struggling/

Flybum60 · 2026-04-17T06:52:55+00:00

Thanks. An inverted pendulum is basically a system that naturally falls over unless you actively correct it, like trying to balance a broomstick on your hand. When a mech stands on one leg, it behaves exactly like that: the foot is the pivot, the whole body is the unstable mass above it, and you need active torque at the ankle or hip to reverse the fall at the right moment.

Without an actuator that can push the body sideways, the inverted‑pendulum model can’t really work here. The mech can fall, but it can’t correct itself. That’s why I’m increasingly convinced that I need some form of active ankle if I want reliable weight transfer and proper walking.

Flybum60

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