The Trunk Engine

When the Crimean War Broke out in October 1853, the Royal Navy was presented with a major problem. With most of its warships being of large, ocean-going types, how was it going to support the army through the suppression of Russian shore batteries in the shallows of the Black Sea, Sea of Azoff and the Baltic Sea. The problem presented by using shallow draught ships was that the standard marine steam engines of the time stood with their pistons operating vertically. The production of a high powered, high revving engine for a gunboat meant that the top of the cylinder block would stand above the height of the deck, rendering it prone to damage by gunfire. The solution was to build an engine that would lie horizontally, but of such a size that it could be installed, out of reach of shot and shell, below the waterline. Nonetheless, this would still lead to the production of an engine that would be difficult to install in the narrow beam of a gunboat. The answer to the problem came from the marine engineer John Penn. Instead of building an all-enclosing crank case and cylinder head in which the pistons would operate, the pistons would be installed in a ‘trunk’, i.e. a housing from which they would emerge at top and bottom, thereby reducing the height of the engine and saving weight. Ironically, few of the planned gunboats were built, and even fewer saw action.

Raising the Xantho engine.
Credit: WA Museum

An isometric projection of the Xantho wreck.
Credit: John Riley

Conservators from around the world (Those here are from France, Brunei & Canada) joined WA Musuem staff in deconcreting the Xantho engine.
Credit: WA Museum

Volunteer Marine Engineers join WA Museum staff in helping develop the engine exhibit.
Credit: WA Museum