Stop-Work Relativity Unwinding
The animations below show the mainspring unwinding to run the watch. There are three different perspectives. The most useful perspective is that relative to the arbor wheel.
These animations are very similar to the winding animations; they differ because the rotation is reversed and because the opposite sides of the barrel wheel slots are used.
Unwinding Relative to God; this is the normal, external view of the watch.
During unwinding the barrel rotates anti-clockwise to run the watch and again the barrel wheel limits the number of turns. Because the arbor does not rotate, this is also the view from the arbor wheel and its pin always faces in the same direction.
Unwinding Relative to the Barrel.
During unwinding the arbor wheel appears to rotate clockwise. Looking at unwinding relative to God above, the barrel and the barrel wheel rotate. If you imagine, at each step of that animation, you can rotate the barrel to keep the barrel wheel in the same place, then you have to rotate the barrel anti-clockwise and, at the same time, the arbor wheel must be rotated clockwise.
Unwinding Relative to the Barrel Wheel:
The barrel now appears to rotate clockwise intermittently. Considering the winding relative to the barrel above, the barrel wheel stays in the same relative place, but it rotates. As we want this wheel to be stationary, we have to rotate the barrel and arbor wheel around the center of the barrel wheel to keep its orientation the same.