Lego GBC WIP Catapult was originally designed by Tom Atkinson, that has gained notoriety as a perpetual Work-In-Progress, so I decided to reverse engineer it from YouTube videos.
Night Lighting
The module is has my custom Lego UV/Led lights, with the UV shining on the balls and the Lego light passing through a trans-blue brick to color the module.

Videos of the Original
This module has featured in a lot of videos over the years.
BrickWorld Chicago 2014, the module can be seen at 6:58
BrickFair Virginia 2014, the module can be seen at 11:16.
BrickWorld Fort Wayne 2016, the module can be seen at 11:09.
These are the videos I used to reverse engineer the original.
BrickFair Alabama 2016, the module can be seen at 9:40.
BrickFair Virginia 2017, the module can be seen at 16:26.
BrickWorld Indy 2017, the module can be seen at 8:04.
Videos
Videos of this module in operation.
Modules
Builds and revisions to this module.
Original

Pieces | Cost | Time |
---|---|---|
600+ | $$ | N/A |
Around 2016 Tom said he would re-build the module, this is when it gained notoriety and started to feature more in videos.
Revision 1

Pieces | Cost | Time |
---|---|---|
600+ each | $$ | 1 Month |
- Reverse engineered from YouTube videos.
- Ended up being 90% similar as a few areas I needed to guess.
Revision 2

Pieces | Cost | Time |
---|---|---|
600+ each | $$ | 1 Week |
Tweaks to improve the original.
- Redesign gearbox to reduce complexity.
- changed shooter arm design to stop a jam between the chute and the arm.