[GBC] Newcomer diving right in custom designs

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Hi everybody.


This is my first post (except the "members' introduction").

Not being sure if it is the correct way/place to start I at last go into posting about my GBC projects, which are all only at WIP stage now.

I already watched and read a lot of GBC resources (events videos, standards, famous modules and builders, balls sourcing hints...), which gave me a few ideas of custom builds, which will be new ideas as well as "remakes".

But my work is currently slowed down by a few difficulties when leaving the dark age (getting used to studless building techniques when designing custom only, missing parts despite a huge initial BrickLink investment), so the results would show up bit by bit only.


So, for more concrete stuff, my most advanced work is on a compact cycloidal drive, of course inspired by Akiyuki's one, but being a fully custom from-scratch and trial-and-error build.

At its current state, only the core mechanism is available and it runs smoothly. However the ball transport (currently built on only one cycloidal "tooth") seems to be the hardest thing to make reliable, and it is not yet the case.

A stiffer chassis (with the input bin and agitator + secondary ball transport mechanism will be required too. I'll build it with bricks mainly (when I'll find an opportunity to pick up my childhood stock).

The core mechanism features an outer ring of 8 teeth, based on an octagon made up of 6L axles and 135° connectors, and a 7-teeth cycloidal disc (and some associated tricks), resulting in approximately 2/3 the size of Akiyuki's original design.


So is my prototype worth a picture right now ?



(a few other modules are planned but I built only draft/mock-ups of the core mechanisms now due to the lack of parts.)


Edited by Thierry-GearsManiac

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23 minutes ago, Thierry-GearsManiac said:

So is my prototype worth a picture right now ?


Welcome to GBC

Yes, a picture says a thousand words.

see forum guidelines on how to post images.

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Here is it :

here is an overview of the core mechanism mounted on a very basic scaffold with a few unfinished test elements :

  • a basic ball ramp (bottom right)
  • the currently tested ball holder (bottom left) + a static structure (right) for pushing its gray 'L'-shaped releasing lever


Below is a partial dismantling of the mechanism :

  • on the left, the "stator" + the rotating eccentric (rotation center = lowest round hole of the 28-teeth gear). The current structure has been built with my currently available parts but will be made slightly simpler as soon as I get the right parts
  • on the right, the "rotor" = the cycloidal disc, revealing two main design tricks (guess them !)


Since this mechanism is smaller, I currently encounter difficulties in reliably loading/releasing balls passively (like on Akiyuki's design, no "active" mechanism for pushing the balls into or out of the holders) : the input ramp has to be placed very precisely, so that the ball gets fully pushed into the loader, and the ramp must not interfere with the holder's cycloidal path. I guess that the current eccentric radius (1 stud) does not give a wide enough move, but since this configuration can work for now, I'll increase the eccentric radius later (because it involves readjusting the whole cycloidal gearing in order to keep it smooth as now !).

The places where balls get loaded and released are also different, because of how they get held (first brainstormed idea I had).


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After no post since more than one month, I'm back now.

I managed to pick up a significant amount of my childhood's LEGO stock, and therefore I've been able to continue to work on this first project and turning it into a complete module and make it enough reliable : I'll rather switch to a dedicated topic for showing it .

Edited by Thierry-GearsManiac
Adding lthe link to the newly created topic.

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