load exceeding the predetermined load as a result of the fatigue condition in the embodiment being described it was determined empirically that when the predetermined load was established is at least 130 percent or more of a maximum normal running load the arm 28 remained rigid enough to handle the normal wiping yet flexible enough to bend during fatigue conditions thus when the predetermined load exceeds about 130 percent of the maximum normal running load for the flexible arm 28 the wiper system 10 was able to operate with maximum efficiency while protecting the components of the system 10 in the embodiment described the predetermined load is defined as follows p link a maximum normal running load for a comparably sized steel or rigid link which does not flex equ4 e is the flexural modulus mpa and i is a moment of inertia in mm 4 if the cross sectional shape of member 28 is rounded on its edges as shown in fig8 b then the formula for the area moment of inertia i is calculated using the following equation equ5 where w h and r are width height and fillet radius respectively of the cross section of member 28.