PRINCIPLES OF NAVAL ENGINEERING 



BOILER 



P ADDLES 



ENGINE 



147.2 



Figure 1-2.— The Demologos : the first steam-driven warship. 



out more than forty years before. ° The Princeton 

 had an unusual oscillating, rectangular -piston 

 type of engine (fig. 1-4). The piston rod was con- 

 nected directly to the crankshaft, and the cylinder 

 oscillated in trunnions. This ship was also note- 

 worthy for being the first warship to have all 

 machinery located below the waterline, the first 

 to burn hard coal, and the first to supply extra 

 air for combustion by having blowers discharge 

 to the fireroom. But even the Princeton still 

 had sails. 



Almost twenty steam-driven warships joined 

 the steam Navy between 1854 and 1860. One of 



^In 1802, Colonel John Stevens applied Archimedes ' 

 screw as a means of ship propulsion. The first ship 

 that Stevens tried the screw on was a single-screw 

 ship, which unfortunately ran in circles. The second 

 application— a twin-screw shipwiththe screws revolv- 

 ing in opposite directions— was more successful. John 

 Ericsson, who designed the Princeton , developed the 

 forerunner of the modern screw propeller in 1837. It 

 is interesting to note that the original problem with 

 screw propellers was that they were inefficient at the 

 slow speeds provided by the large, slow engines of the 

 time. This is just the opposite of the present-day 

 problem. Both then and now, the solution is gears: 

 step-up gears, in the old days, and reduction gears, 

 at the present time. 



these was the Merrimac . Another was the 

 Pensacola , which was somewhat ahead of its 

 time in several ways. The Pensacola had the 

 first surface condenser (as opposed to a jet 

 condenser) to be used on a ship of the U.S. 

 Navy, It also had the first pressurized fire- 

 rooms. 



It was not until 1867 that the U.S. Navy 

 obtained a completely steam-driven ship. In the 

 Navy's newly created Bureau of Steam Engi- 

 neering, a brilliant designer, Benjamin Isher- 

 wood, conceived the idea for a fast cruiser. One 

 of Isherwood's ships, the Wampanog, attained 

 the remarkable speed of 17.75 knots during her 

 trial runs, and maintained an average of 16.6 

 knots for a period of 38 hours in rough seas. 



The Wampanog had a displacement of 4215 

 tons, a length of 335 feet, and abeam of 45 feet. 

 The engines consisted of two 100-inch single- 

 expansion cylinders turning one shaft. The engine 

 shaft was geared to the propeller shaft, driving 

 the propeller at slightly more than twice the 

 speed of the engines. Steam was generated by 

 four boilers at a pressure of 35 psi and was 

 superheated by four more boilers. The 

 Wampanog propulsion plant, shown in figure 

 1-5, was a remarkable power plant for its time. 



