The camera or iPhone is mounted on a 3-ring Universal Joint / Handle to maintain a steady field of view as you move.
A weight on the bottom of the pendulum provides the torque to maintain the camera in a stable pair of axes (X and Y), but not vertical (Z).
A one-foot long ¼-20 threaded steel rod connects the handle to the pendulum. Four brass pins are used between the rings in the Universal Joint. Rotation of the rings is provided with holes that are slightly oversized for the 3 mm pins in one ring and press fit into the adjacent ring. The press fit prevents loss of the pins.
I considered using printed pins, but a failed pin might allow the camera to be dropped. The brass pins are more than strong enough, have a smooth surface, and low friction coefficient.
The heavier 35 MM camera has a center of gravity forward of the mounting hole. This caused the field of view to point down. I added a second threaded rod to the pendulum to achieve a horizontal field of view. I made a PLA coupling for this connection.
Twenty pins from Amazon cost less than $7. Home Depot provided the threaded rods (under $3 each) and the 10 fender washers (3/8" x 1-½) (cost $.13 each)
Two clips on the rod to hold an iPhone 5 or 12. The ¼-20 rod threads into the bottom of most cameras.
The author marked this model as their own original creation.