The myth of the motte and bailey castle in Scotland
An assessment of medieval earthwork fortifications in Scotland and their relationship to traditional Anglo-Norman motte and bailey castles, and earlier Scottish sites....
The first practical hydraulically operated machine wasthe hydraulic press, invented by Joseph Bramah in 1796.Bramah’s press embodied the principle originally demonstrated by Pascal in 1647, where-in fluid pressure created by applying a force to a small area plunger in aclosed cylinder can be used to act on a larger area plunger to produce a correspondingly larger force if the fluid spaces in the two plunger cylinders are connectedby a pipe. In Bramah’s machine the larger plunger or ram operated the moving platen of the press.Bramah went on to conceive other ideas for transmitting and using hydraulic power, most notably as documented in his ‘omnibus’ patent specification of 1812, howeverthese ideas were not taken up in his lifetime (McNeil1968).
It was not until 1840 that William Armstrong –later knighted for his pivotal work in improving armaments – developed his ideas for a hydraulically operated crane based on the hydraulic jigger. The hydraulic jigger comprised a ram in a closed cylinder arranged with multiple pulley sheaves at each end so as to multiply movement of the free end of a chain or rope wound around the sheaves when a pressurised fluid, normally water, was admitted into the cylinder. (The hydraulic jigger operated in the reverse manner to the conventional block and tackle).A 5 ton (5t) hydraulically operated crane based on Armstrong’s design was installed on a Newcastle-on-Tyne wharf in 1846 (Armstrong 1858).
Its success led to similar hydraulic cranes being installed for wharves and railway yards in other places in the UK. Figure 1 shows a diagram from Armstrong’s 1858 paper of an early hydraulic crane with hydraulic jiggers used for both the hoisting and slewing motions. The source of the pressurised fluid for these early hydraulic cranes wasthe town’s water supply. Water pressures of up to 90 psi(600 kPa) could be obtained in this way to act on the ram within the individual hydraulic jiggers, with control by way of lever operated three-way valves.
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