Flexible coupling reduces noise and vibration

'Sea Shepherd', Aberdeen Harbour Board's pilot launch vessel is powered by twin Scania engines, developing 265kW at 1,880 rpm, driving close coupled twin disc MG gearboxes that have a 2.45:1 reduction ratio, PTO clutch and hydraulic pump. The gearboxes on the vessel were not originally designed for flexible couplings, the oil pump was positioned very close to the output flange. The flange is 7.25" in diameter and only a 7.5" diameter coupling will fit without fouling the oil pump. A four-inch spacer would have been required to clear the pump and a manually clutched PTO and hydraulic pump requires an even longer spacer of 500mm. A spacer of this length plus Centa's Centaflex AGM coupling would have been too long for the installation and would have upset the flexible mounting arrangement, so Centa developed a special, composite universal joint integrated with a Centaflex series 'A' cardan shaft, to solve the problem. And, to achieve the required noise and vibration insulation levels, a flexible element providing a long articulation length enabled significant engine movement to reduce noise and vibration without the need for additional spacers. DP Pointers * The flexible coupling is a combination of a composite universal joint and Centa's Centaflex series 'A' cardan shaft * The coupling solved a common marine gearbox location problem of the oil pump being too close to the gearbox output flange * Centa's solution required no additional spacers