Design and mechanics of belay devices and rope brakes

Belay devices and rope brakes are an integral part of climbing equipment, required for personal protection such as injury prevention or life saving purposes. In spite of mushrooming design improvement the malfunctioning of brakes is reported repeatedly, caused by handling mistakes or un-optimised design. This review article provides a detailed discussion of the evolution and the design of rope brakes and introduces a new design classification. Design varieties are examined and addressed in detail. Subsequently, the mechanics of rope brakes are reviewed and the differences between dynamic and static belaying are compared as to static and kinetic friction as well as belt and linear friction. In this critical review of modelling and testing of rope brakes, we discuss misconceptions as well as improvements. The issues covered in this review article aim to highlight the problems and challenges which the design of rope brakes and belay devices is facing in the quest for developing an optimised brake which never fails and which is ready to use without training. The shortcomings of modelling and testing of rope brakes are mainly due to neglecting kinetic friction, which disadvantageously affects design optimisation but also opens design opportunities.