Number of hubs for a dome at 4v.
Top, 4 points: 1
Side, 6 points: 8 + 4
Bottom, 4 points: 8
Bottom, 3 points: 4
I played with how to build hubs for connecting rods of geodesic dome.
The thickness of sheet metal is 0.3 mm to 0.35mm. The diameter of bolt is around 3mm.
I will make sheet metal rods and connect them at the center.
Next dome model will be closer to the perfect Geodesic Dome of Buckminster Fuller without much slack in each joint of rods.