For anyone who has ever been to a LEGO convention, the sound of a GBC is pretty hard to miss. It’s not a very pleasant sound—in fact, it’s often quite deafening—and it’s almost always crowded with people admiring the different types of contraptions that slowly transport a crazy amount of LEGO footballs (soccer balls for our American readers) and basketballs around a never-ending loop.

What is a GBC?

GBC in the LEGO community stands for Great Ball Contraption. If you are new to GBCs, it’s a build (aka module) with moving parts that transports balls from one point to another. BrickNerd has a comprehensive article on the history of the GBC.

The beauty of this concept is that if you put a bunch of modules alongside each other, the balls can be transported from module to module. If enough are connected, you get a loop that transports the balls in a seemingly never-ending stream of fascinating feats of engineering. Ok, that may be a romanticized description (that sound is still pretty awful).

Kits and Templates: The Best Starting Place for a GBC

Like a lot of other people, I’ve been fascinated by the many GBC modules that I’ve seen over the years. And like a lot of other AFOLs, I’ve talked to the “GBC people” and said, “Oh, that’s awesome, I’ll build my own module soon,” and then never get around to it. Don’t get me wrong, I’ve made a few attempts over the years (some more horrible than others, to be honest with you), but I didn’t have the patience to build something structurally sound and functional. Instead, I’d jump into trying to make something look cool. That is not an approach I’d recommend.

Suffice it to say, the GBC people in my LUG have politely smiled and encouraged me to give it a go; but I suspect they had pretty much given up on me (understandably so) when I stood there at our most recent event and admired their builds, again saying, “I really should build something myself.”

This time I decided to take a different approach because I really did want to build a working module. I mean, I’ve been building MOCs for about eight years now, it was about time. As I’ve stated previously, I am in no way known for building stable structures. In fact, it’s quite the opposite. That part was a bit of a challenge; if I ever wanted to actually display a GBC module, I knew I had to make it dependable, meaning no flimsy “half-connections-because-it-looks-nice.“

Rather than going the same route as before or trying to invent a dependable function and then realizing I suck and give up, I asked if there was a simple, dependable module that I could use as a starting point. The answer didn’t take long to find: the Brickworld GBC Workshop Kit from 2018. The module itself is fairly simple in its mechanism—it basically pumps balls up a sort of chimney—and it doesn’t use any super exclusive pieces or rare parts.

Functional and reliable, but not that pretty to look at

Combining Beauty and Functionality

After building the Brickworld module, I spent some time simply admiring the mechanism like a little child. After that, it was time to get back to the main reason why I’d always wanted to build a module: to make a pretty-looking GBC. I may be stepping on a few toes here, but hear me out; the level of ingenuity and brilliance of almost all GBC modules I’ve ever seen is unquestionable. But a lot of them do tend to look a bit naked.

There are, of course, a number of exceptions to my previous statement. That Akiyuki fellow might have a thing or two to say about GBCs not being aesthetically pleasing, so my apologies to all who feel offended. The reason I wanted to build a GBC was primarily to see if I could pull off making one that looked more like a traditional MOC. Whether or not I succeeded can be up for debate, but that was at least the goal.

I decided to go with a medieval theme. An aqueduct seemed like something that would fit the overall feel of GBC. There is something about the functionality of that structure that I thought would mesh well with the GBC’s motion, so that’s what I landed on. The build itself is made up of a chimney-like structure on the far left side where balls can be pumped up, and then there are three levels where the balls trickle down.

I went through several different versions of the three levels and adjusted the height a few times. Each level ends with a hole down to the lower level, and there is a curved slope at the bottom to give the balls momentum to travel in the opposite direction. There is also a slight decline on each level to make sure no balls get stuck. It´s not really visible from the side, as the walls cover it up rather nicely.

I will admit it took quite a bit of adjusting to get the right angles, as well as making sure no balls would pop out (which they did quite a bit in the first few iterations). It was a fun thing to tinker with, and my admiration for GBC builders’ patience grew with each ball landing somewhere it wasn’t supposed to.

Having figured out the angles, I began covering up the actual GBC module. I figured a house (aka pump station) would fit fairly well. The top of the roof is open, allowing balls from other modules to land in it. There is a standard for GBCs: make sure you can connect them with other modules when displaying as a group. Although I’m not sure I followed that 100%, I’ve been assured that I can join the GBC guys at our next convention!

To make sure I could use this build as a stand-alone model, I added another section on the back side to create a loop of my own, which can be fairly easily removed to join it with other modules when needed.

Having gotten all the technical aspects under control, I continued focusing on decorating the build. I added some foliage and created a scene to give it that finishing touch I had envisioned when beginning this project.

Getting the Balls Rolling

Here is the finished build in all its glory! Hopefully this will inspire some other “regular” MOC builders out there to finally take the plunge and build a GBC module.

My number one piece of advice for those looking to take the plunge would be not to waste time coming up with a fancy mechanism. Someone else has probably already done it. Instead, piggyback off their brilliant work and try and make something pretty that you feel good looking at. Chances are, some other people will find it cool as well.

Make sure you have a look at the video in case you still have doubts that this thing actually works.

To make up for my previous statement about the visual appearance of many GBCs, I would be remiss if I didn´t include some modules that are truly visually stunning. So please check out these builds highlighted in a previous BrickNerd article about GBC. They include builds from amazing talents like Jason Alleman, Akiyuki, Bert van Beek and Staffan Ihl.

Are there any GBC builds I missed? Leave a comment below!

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