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Modern warships are required to perform a variety of tasks while being affordable to purchase and operate. The most valuable surface vessels for navies are aircraft carriers. The movement of equipment onboard of these vessels is crucial to their role. | ||||||||||
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MacTaggart Scott & Co. of Edinburgh, Scotland designs and installs elevators for the world’s navies. The company also supplies elevators employed for handling personnel and food cargo and heavy lift with load capacities up to 500 tonnes. According to the company, the differentiators that have enabled it to win contracts against fierce international competition are its innovative designs of high performance and reliability with low through-life cost at an affordable price. This has been achieved by using low risk design concepts, proven components embracing Commercial-Off-The-Shelf (COTS) principles and an intimate appreciation of the operating environment and the requirement. Aircraft elevators typically come in two distinct configurations, wire-driven four-point lift or chain-driven cantilevered designs. MacTaggart Scott has designed, manufactured and installed both of these configurations but experience has demonstrated that the chain-driven cantilevered design to be superior in all respects. This is because the wire-driven, four-post lift configuration was found to be restrictive on the surrounding ship design due to the large jigger assemblies, turning sheaves and spaces required to manage the wires. In addition, through the life of the vessels, the wires were prone to stretch and unpredictable fatigue resulting in extensive maintenance requirements. Drawing upon experience, MacTaggart Scott designed and developed the marketleading hydraulically powered chain-driven cantilevered elevator that is simple and elegant, easy to operate, require low maintenance and have minimum restrictions on ship design. The selection of modern engineered chains to provide lift allowed the use of synchronised rotary hydraulic motors to provide the motive power.
The MacTaggart Scott/Rexnord system is currently being applied to the new Royal Navy future carrier (CVF) programme and will be employed for the two 70 tonne SWL deck-edge aircraft elevators being fitted to these aircraft carriers. The aircraft elevators compete in size with those fitted aboard the gigantic American aircraft carriers, but will exceed their lifting capacity and have lower maintenance demands. | ||||||||||
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A compact, reliable synchronised hydraulic motor unit was selected for the MacTaggart Scott aircraft elevator. This solution has reduced the installation footprint and provided a reliable, low maintenance motive power source. The drive unit uses two independent MacTaggart Scott 100 series hydraulic motors with integral fail-safe mechanical brakes, interconnected via a synchronising shaft. Chain drive sprockets fitted directly to the motor main shaft provide the drive to the chains. Compact, reliable and multiple redundancy, all in keeping with the design philosophy. The Rexnord chains selected for platform lifting fit with the design philosophy. Both duplex and triplex chains have been successfully fitted to MacTaggart Scott aircraft elevators for over 40 years on multiple installations. The Royal Navy fleet support vessel RFA Argus has two aircraft elevators installed which have operated safely for over 19 years. The Rexnord chains fitted to this installation have been continually monitored by MacTaggart Scott and show no evidence of deterioration. The longevity of the chains is ensured through the quality of chain supplied. Their simple maintenance requirements ensure the limited ship maintenance staff available can undertake all necessary maintenance tasks, resulting in through-life cost of the
elevator equipment being kept to an absolute minimum. A single Rexnord chain can safely support and operate the MacTaggart Scott aircraft elevator, so the two fitted in typical elevator installations provide a level of safety and redundancy unmatched by wire-drive alternatives.
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