THE FIRST WILLISON coupling improvements delivered the ‘Restraint Coupling’ in 1994, which is now in widespread use on 4-tonne and 6-tonne wagons throughout the Australian sugar industry. The improved Willison cane wagon coupling and the various components that make up the coupling commenced development in 2005. The improved Willison coupling has been redesigned to address loads from longer trains, improve reliability, increase life and reduce maintenance. These improvements were realised through: simplifying the design; selecting appropriate materials for long life; tightening manufacturing tolerances, with machining of critical areas and adopting more reproducible casting techniques. The ‘Restraint Coupling’ was designed for a tractive load of 374 kN whereas the improved Willison coupling has been designed for a load of 510 kN. The improved coupling has been developed with two variations in lateral restraint: ‘LS5’: five degrees either side of centreline for the 4-tonne and 6-tonne wagon application; and ‘LS10’: 10 degrees either side of centreline for the longer wheel base wagon applications such as the 10, 11 and 15-tonne wagons. The improved coupling was designed for investment casting as this manufacturing process results in enhanced dimensional accuracy and smoother surface finish while also removing pattern joins and draft angles from the exterior surfaces. Initial trials of the LS5 were conducted at Invicta Mill starting in 2009. With the automation of Proserpine Mill’s feeding station in 2014, there was a need to expedite the introduction of the LS10 coupling. Sufficient confidence was gained to manufacture and trial 68 couplings in the Proserpine, Herbert and Burdekin districts. These 68 trial couplings remain in operation and a recent in-service inspection has confirmed that they are performing to expectations.