These camera mounts are designed to move and track the rocket. The theory used to track the rockets is explained in detail on the Pivot Mount Design page. There are three different pivot mounts that are nearly identical. These all contain a GoPro that records at normal 30fps speed, the Sony camera shooting at 120 fps, and also a Nikon camera to take still images. The forth pivot mount is the Pitch Arm Mount and contains only a Sony camera.
The Construction of most of the Pitch Mounts is nearly identical. Since there are several cameras for each mount, the only practical way to build it was to put all the cameras into a box. In order to keep the weight down a custom box was made from plastic. Keeping the weight low reduces the torque necessary to pitch the cameras at the desired rate.
One important factor in construction is to pivot the cameras around the center of gravity. Since the Nikon far out weighed the smaller action cameras, it was the most critical. The cameras were placed in the enclosure and the center of gravity for the entire structure was determined. Pivoting around the center of gravity also reduces the require torque the motor needed.
To determine where the center of gravity is located, the completed enclosure with cameras installed was hung between two pins from one corner. Using a lightweight string and weight as a plumb bob, a mark was made on the opposite corner. Repeating this process from another corner, the intersection of the two line determines the center of gravity.
The Pitching Arm Mount is different in that it only has the Sony camera. This is necessary due to the very rapid pitching rate the camera requires since it is so close to the rocket during lift off.