The Turgo cup used in the testing above was purchased from a supplier, as mentioned in Section 3. Section 2 modelled this cup in 2D using the inlet and exit angles measured from this cup, and the impact angle calculated from the geometry of the cup. As discussed in [26], the three-dimensional shape of the cup can have a signifi- cant effect on the efficiency of the system. Another DOE study is undertaken on the design of the cup, changing the height, breadth and depth of the cup by ±25% of each original dimension to find if there is an improved version of the cup for a 30 mm jet. To assess the different cup designs, each cup is mounted in a static rig that can measure the force in the plane of the turbine disc through a high resolution load cell. A 30 mm jet of water is fired at the cup and the force at different simulated speeds is measured to form a pseudo torque and power against rotational speed curve. Nine dif- ferent cups designs are assessed for a fixed jet inclination angle of 20, and compared with the purchased cup performance. From this testing, an improved design for the Turgo turbine cup geometry has been identified. The new cup, shown in Fig. 17 (white) compar- ison to the purchased cup (black), is bigger in all dimensions and has been manufactured as part of a complete turbine disc with an integral mounting hub using rapid prototyping technology. The cup is designed into a turbine with the same pitch circle diameter as the original. This new turbine is tested in the rig with a 30 mm jet, inclination angle of 20, head at 3.5 m and aiming point in the centre of the cup. The comparison between the com- mercially available cup and the new rapid prototyped design for the turbine disc can be seen in the efficiency graph in Fig. 18, the maximum efficiency of the redesigned Turgo cups shows an approximately 10% improvement at maximum power speeds over the purchased Turgo cups. Therefore, the reduction in turbine effi- ciency due to increased jet diameter has been, in part, avoided.