It has never been easier to build a complete Great Ball Contraption (GBC) loop yourself! The GBC 49 Geneva Drive features a 4 step rotating mechanism which brings GBC Balls from one side to the other. The GBC can be used as a self contained loop or participate in a GBC layout. Using a more accessible LEGO Set and focusing on one single mechanism this GBC is by far one of the best GBCs to get started.
This GBC is entirely built using only parts from the LEGO Rescue Hovercraft and can be referred to as Alternate Build of the 42120. This GBC makes sure you master the GBC building techniques and tricks so that you eventually also can build your own GBCs. By default the whole machine is powered by hand but it can easily be upgraded with any LEGO motor (more information in the building instructions).
Automation at its best!
As the name GBC 49 Geneva Drive already implies, the main core mechanisms is the Geneva Mechanism. On every full rotation on the main drive shaft, the output of the Geneva Mechanism rotates a perfect 90 degrees. This output rotation is linked to a 4 arm carousel which can hold 4 GBC Balls, 1 ball on every arm. Another clever mechanical linkage system, which is linked to the same main drive shaft, lifts a GBC Ball up to fill each arm on the carousel on every full rotation. 5 beams work perfectly in sync to get the exact angle and ball track required for the loader arm to reach its position. At the same time a GBC Ball is automatically released at the top. In this way a beautiful ballet of mechanical linkages follow each other with a pitch perfect synchronization. A feast for the eye! A small mechanism connected to the drive train makes sure you can only operate the GBC in one direction. This mechanism also prevent the lift arm to fall down suddenly when the lift arm is in the air.
Once the GBC Balls are lifted they can spin in the optional GBC Funnel Turbo Spin (Left version) and roll down back to the input of the GBC via the return path. While building you will learn about gearing, linkages, mechanisms, synchronization, sturdy construction and so much more.
Be default the GBC is powered by hand but you can motorize it. However due to the lack of different sized gears in the LEGO set we were unable to slow down the mechanisms. For that reason, if you want to connect a LEGO Technic motor you have to use other gears to slow the GBC down or power the LEGO Technic motor with a lower voltage. In the building instructions we provide several solutions.
Fun Fact
It took some time to build the Geneva mechanism in a way that it is reliable and sturdy. On top of that we also find it very important that the mechanism is clearly visible once the build is completed and in operation. This made us rebuild the complete mechanisms and construction multiple times, just to get the aesthetics perfect. We think this really paid off in the end :)
History Time
The name, Geneva drive, is derived from the devices earliest application in mechanical watches, which were popularized in Geneva (city in France), being the classical origin of watchmaking industry. The mechanism is frequently used in mechanical watches, since it can be made small and is able to withstand substantial mechanical stress. These 2 advantages makes the mechanism great for uses in LEGO Technic and in particularly in Great Ball Contraptions where we push LEGO to its limits every day.
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- LEGO 42120 set
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- GBC 49 Geneva Drive – 42120 Alternate Build
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- GBC 49 – 42120 Alternate Build
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- GBC 49 – 42120 Alternate Build
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- GBC 49 – 42120 Alternate Build
Building Instructions Preview
Preview
Try before you buy. We completely understand. See the building instructions previews on the left or try one of our free building instructions.
Upgrade your GBC 49 Geneva Drive
In the building instructions is explained how to easily upgrade the GBC 49 Geneva Drive with various parts.
GBC Funnels
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Power & Automate
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N.O. –
I am sending this because my son wanted to show his Geneva Drive. He built. played, disassembled and rebuilt Geneva Drive for some times since August. Children played GBC #49 Geneva Drive and #52 Flight Fair this holiday. Those GBCs made our holiday much more fun.
Thank you for all those products and services, and we wish you all a Happy New Year.
https://www.youtube.com/watch?v=jNWcArWUUGs
mysteaka –
I bought this instructions for my son’s 7th birthday gift, as he requested.
He is not a big fan of LEGO but really likes GBC videos. He made a few small GBC modules by watching examples from GBC promo videos before, but it was the first time for him to build a GBC module by following building instructions.
With some short breaks, my son took about 8 hours to build the module himself. For him, this was neither too difficult nor too easy, neither too large nor small, but there were a few exciting challenges and lots of fun to build and play.
The instructions were clear and detailed. Timing mechanisms, geneva mechanism, and arms of the caroucel might be more challenging, but they were actually not, because of the detailed “Fine Tuning” section.
On the other hand, the geneva mechanism snagged every round because a large bevel gear connected to a weapon barrel (#6 on Page 18) and a small bevel gear under the ratchet mechanism (#13 on Page 24) didn’t mesh properly. To solve it, axles/axle-pegs connecting a weapon barrel and shell 3x1x2 technic beams needed to be adjusted by a little poking and prodding, about 0.5 mm or so (Page 19). It was tricky because what he needed to adjust was not the bevel gears themselves but other parts. When my son solved it, he was really excited, looks super happy and proud.
The LEGO Technic 42120 set is a retired product in our country, but I was fortunately able to purchase the 42120 set. Like other PV-Production’s instructions, it was really awesome that all the parts came from a single existing LEGO set and we did not have to gather parts up from here and there.
Only if the instruction was printable. It seems that books/prints are still easier for this age group of children to follow instructions.
It feels like more than just STEAM learning. It was a big hit and still is. My son wants more PV-Productions’ building instructions, and I’d definitely buy.
James Quinnell –
This is such a fun little GBC with and very impressive mechanism. Definitely build this one!