Thrust blocks are a specialised form of thrust bearing used in ships, to resist the thrust of the propellor shaft and transmit it to the hull.
The large horseshoe thrust block represents a set of Michell thrust pads, as fitted to the 1,000 ton cargo steamship SS Orchy in 1930. These were removed after seven years' service and 227,000 miles. The ship had a single triple-expansion steam engine of 1,500 ihp and made 13 knots on trial. The effective outside diameter of the pads is just under 24".
The single large gold-coloured pad is a wooden model of one of the pads fitted to HMS Hood. The ship had four screws, each with a single thrust block using twelve of these pads, six used for going forward, six astern. Each pad was made of bronze, but faced with white metal on the shaft side. The rear face was made spherical, to allow the pad to tilt according to Michell's principles for a wedge-shaped lubricant film. Each shaft was 24" in diameter and ran at 210 rpm to transmit 36,000 shp, giving rise to a force of 17 tons on each pad.
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