From: Internationales Maritimes Museum Hamburg The steam engine was one of the main pillars of the Industrial Revolution and changed the world of shipping forever. As such, this invention is one of the principal subjects in our section dedicated to the history of shipbuilding on deck 3 of the museum. The stars of this section are without any doubt the fully functional engine models of Karl-Friedrich Pohlmann. They include a reproduction of the engines of the RMS Titanic, the SS Deutshcland (1900), but also this masterpiece that shows how steam power opened fully new possibilities in shipping.
You are looking to the engine system of an ocean-going and salvage tug, around 1900, in a scale of 1:25. This type of vessel needs an imense amount of power to carry out their duties - and really needs to be able to operate independently from the wind. So, for such a comparably small vessel, an ocean-going tug will always need a comparably large, mighty and complex engine. This is still the fact for modern offshore operating tugs. The model of the stern of this tug shows two three-cylinder expansion engines with main condensers, and air and water feed pumps, as the heart of the propulsion system. Furthermore, two twin expansion engines with two cooling water centrifugal pumps for the main condensers and two single-cylinder expansion engines with two electric power generators as auxiliary engines. The model is completed by a two-cylinder steering gear with alternating steam valve, to control the rudder of the tug.
This parts are known as compound steam engines. In them, he steam is fed in progressively larger and lower pressure cylinders while it loses heat. This way, the engine uses more power from the steam. This engines are usually closed systems, where the steam is cooled into water to be reheated and reused as steam. This is specially relevant for sea operation, because the use of salt water would damage the boiler. The compound steam engine was invented in the early 1780s, but it took approximately a century to develop functioning maritime applications for the multiple compound steam engine. This system will be the highest propulsion technology for ships until the steam turbine and the Diesel engine were developed.
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