Plate taken from the Illustrated London News (Vol 65/2 p 377). John Penn and Sons of Greenwich were responsible for several innovations in the field of marine engineering including compact oscillating engine. The elder John Penn (d. 1843) begun the factory, and his son John Penn (1805-1878) patented the double-trunk engine in 1845, which was extensively used in screw propulsion thereafter. These engines made 58.4 revs per minute, and indicated 6545 hp, which gave a speed of 14.1 knots. The use of lignum vitae, pioneered in 1858 in asociation with Francis Pettit Smith (1808-1874), enabled the widespread use of the propeller.
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