A great ball contraption (GBC) is a machine built of Lego®, consisting of discrete modules, each of which pass balls from a defined input to a defined output, and arranged such that the output of one module feeds the input of the next.
The idea was first publicly proposed by Steve Hassenplug on a LUGNET forum on October 7, 2004.
The first public collaboration was at Brickfest in 2005.
The first GBC in Australia appeared in Melbourne, at Brickvention in 2013, when Rasika Amarasiri built a small layout of contraption modules for display. Later that same year, Canberra builder Owen Dive displayed a small, non-modular ball contraption at BrickExpo. In 2014 both Rasika and Owen displayed contraptions at Brickvention, but sadly, the two displays were not able to be joined together.
The first Australian group-built GBC layout was displayed in later in 2014, when Brisbane builders Alan Burchill and Damien Kee collaborated to display a modest 2-module layout at BrisBricks 2014. Rasika and Owen both returned for Brickvention 2015, accompanied by several other builders, and created a larger collaborative build which Owen coordinated.
Great Ball contraption displays have steadily increased in size and popularity, and have been displayed at more Lego® conventions and displays around Australia.
Collaborative GBC take a lot of planning and coordinating - especially when there might be a hundred or more individual modules, built by many different builders. When planning large event displays, it is common practice to have a spreadsheet list of the modules builders are working on, what their status is and whether they will be ready (or GBC-Standard compliant) to participate in the collaborative display.
Several of these modules are "old faithfuls" and are displayed at several events, either in different cities, or the same venue in two or more consecutive years. Rather than having to "start from scratch", Cadder devised and wrote the Australian Great Ball Contraption Database site as not only a means of keeping track of the hundreds of modules that have been built and displayed at Australian Lego® conventions, but also one which serves as an historic record of displays gone by.
In 2018, Rasika built a small website intended to give a semi-live feed with current informations on all the modules at Brickvention 2018. The intention is that the AusGBC.org site would also serve a similar purpose for future events all around the country.