The force for rotating the reflector is given by a weight of ~50kg which is applied to the axis of rotation. The weight is pulled up manually when the reflector is rotated into its morning position. Now the weight wants to fall down – with the effect of rotating the reflector into its evening position very fast. In order to keep the focus in a fixed position the rotational movement of the reflector has to be slowed down ® the weight has to fall with the same speed the sun travels across the sky. A mechanical clockwork can be used as a breaking system. The pendulum will give way to the fall of the weight at intervals (period of the pendulum) that allow the reflector to rotate simultaneously with the sun.