Field hockey sticks are interesting hand-held sports equipment, due to their duality in preferred stick behaviour. The stick is used for striking, where a high power is desired; but also for stopping, where good control is required. This report aims to identify the properties that influence stick performance and to design a field hockey stick with adaptable properties to improve stick performance; where performance is defined as the ability of the stick to develop a high velocity when hitting a ball, and to provide proper control when stopping the ball.
The stiffness, damping and mass of the stick are properties influencing the stick behaviour; these properties are present locally, at the impact location, as well as over the full length as deflective properties due to the moment originating from the ball impact.
The deflective stiffness and damping properties are identified by applying a disturbance force on the stick tip and measuring the displacement; this shows a range of stick stiffness from 1.4 to 3.0 kN/m and a stick damping from 0.5 to 2.7 Ns/m. Measurements are performed analysing the influence of stiffness, damping, mass and effective mass; this is done by a setup where a stick falls down towards a ball and the ball distance is measured. Additionally, a mathematical model is developed for the analysis of these stick properties. This consists of a collision model, including the coefficient of restitution reflecting the stiffness and damping properties. It can be concluded that the effective stick mass is most influential and the desired properties are opposite for striking and stopping.
A design of a mechanism that fits inside the stick is proposed, this mechanism reacts to the angular acceleration of the stick, and thereby changes its properties between striking and stopping a ball. It adapts the effective mass of the stick, by two weights moving towards the head of the stick when striking a ball. By this increase in effective stick mass, an increase of 7% (compared to the original effective mass) of the ball velocity after hitting the ball is expected.