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Title:DISCHARGE OF SHIP OVER WATER GAP : 1. Marine Cableway 2. Modified Union Purchase [Main Title]
Film Number:ADM 990
Other titles:INVASION EQUIPMENT TRIALS [Allocated Series Title]
Summary: Gravity-assisted tackle for transferring cargo from ship to shore over a water gap.
Description: I. "Discharge by Marine Cableway". Two lines are run between quayside and ship's crane - a supporting line which runs over main jib-head sheaves, and a working cable which runs over subsidiary sheaves and is rove through both the travelling runner, set upon the supporting cable, and a pulling line which is attached to the base of the runner and is led over purchase blocks suspended from the jibs. Cargo is swung up from the ship's hold on a platform sling, suspended from a shackle run through a becket on the jawed moving block. The cargo is lifted by the working cable, until the block connects with the travelling runner set upon the main supporting cable, and the pulling line is then used to bring runner and cargo across the water gap. The runner block bears the legend "COXE(TPN) Torridge House/ Westward Ho/ Bideford N. Devon/ GWR Bideford".
II. "Discharge by Modified Union Purchase". A supporting line is run from the central sheave of a quayside crane to the head block of a ship's derrick. The runner upon this line supports a common block through which is rove the working cable from a subsidiary sheave on the crane, and a retaining line rove through a purchase block on the boom of the derrick. Cargo is swung up on the working cable and the runner let go - the crane must take in cable during the run of the set if the cargo sling is to be kept stable.