Astonishing Science. Spectacular museum.
A pulley block comprises a pulley or sheave turning on a pin inside a shell. Its main use was in the management of the sails of the ship.
The development of the pulley block was fundamental to the workings of a ship as it meant heavier loads could be carried with less power. Increasing the number of pulleys increased the weight that could be moved. On a seventy-four gun ship 922 blocks were used.
The Science Museum’s collection holds many of the machines which were used in the production of blocks at Portsmouth, all of which are highly innovative for their time. The process for making the shell was begun with the cutting of the wood, usually done by a circular saw. The wood was then bored, mortised, shaped and scored to create the shell. The pulley was formed through the rounding saw machine, which simultaneously trimmed a slice of wood and bored a hole through it. The coak, a metal lining in the hole, was then fitted on. Finally the pulley was placed on a lathe to smooth the faces and cut the groove. The iron pin was turned to size in a lathe and polished on a pin-polishing machine. After the parts were manufactured by machine they received some light hand-finishing before the block was assembled by hand.
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