Images 6 and 7 show a detail of the Wheatstone pendulum, in different states of motion.
Image 6:
The top side of the image shows the shape of the springs when the Wheatstone pendulum is not in motion. Both springs are equally stretched, and they are aligned. The bottom side of the image illustrates the outward displacement of the pendulum bob when the platform is rotating. The inner spring is more extended than in the rest state, the outside spring is less extended than in the rest state, and thus the springs provide the required centripetal force to make the pendulum bob circumnavigate the central axis of rotation.
Image 7:
The top side of the image shows the shape of the springs when the Wheatstone pendulum is vibrating, but not rotating around the central axis. Both springs are equally stretched, and at the equilibrium point they are aligned. The bottom side of the image shows that when the pendulum bob is vibrating while the platform is rotating the midpoint of the vibration is the outward displaced point of the pendulum bob.