I was fascinated by these Nautilus Gears, and I decided to change the bar in order to avoid having anything covering the top of the gears, sort of "spoiling" the spiral effect you get when they turn fast.
I made a bar on the underneath of the gears, and just two caps clipping to the shafts to hold the gears in place.
I printed mine in black PLA, 0.2mm layer height on my Arduino Materia 101.
The "Nautilus_Gear.stl" file is the original one by MishaT.
Print (no support needed):
2x "Base_Cap.stl" (Print with hole facing upwards!)
Slide the gears on the shafts, paying attention to their initial position (which should be the one depicted in the photos I uploaded), then push the caps the whole way down on each shaft. They should fit snugly and keep the gears in position though allowing them to turn freely.