John Penn and Sons supplied Warrior's trunk engines after establishing a strong position in naval machinery. In 1844, the firm doubled HMS Black Eagle's power with oscillating engines without increasing their weight or occupied space. Trunk engines then drove screw propellers in Encounter and Arrogant, followed by a Penn installation in Agamemnon. By John Penn's death in 1878, his engines had been fitted in about 230 ships. Work with Francis Pettit Smith on stern bearings helped screw ships undertake ocean voyages without wearing their stern glands. Penn also worked on superheated steam for marine engines.
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John Penn and the rise of screw propulsion
John Penn's machinery combined more power in limited space with improvements that made screw propulsion practical for ocean voyages.