Chapter 1-THE DEVELOPMENT OF NAVAL SHIPS 



WORKING BEAM 



CHAIN 



CHAIN 



WATER INJECTION VALVE 

 STEAM ADMISSION VALVE 



DRAIN LINE- 



PUMP ROD 



AUTOMATIC VALVE 

 GEAR 



INJECTION 

 WATER PUMP 



Figure 1-1.— The Newcomen engine. 



^t^T'jipw*^-: 



"VERTICAL 



LIFT 

 PUMP 



147.1 



After the steam has forced the piston to its 

 top position, the steam valve is shut and a jet of 

 cold water enters the cylinder, condensing the 

 steam and creating a partial vacuum. Atmos- 

 pheric pressure then causes the down stroke 

 (work stroke) of the piston. 



As the piston comes down, the working beam 

 is pulled down on the cylinder side. As the beam 

 rises on the pump side, the pump rod also rises 

 and water is lifted upward. As soon as the pres- 

 sure in the cylinder equals atmospheric pres- 

 sure, an escape valve in the bottom of the cylin- 

 der opens and the condensate is discharged 

 through a drain line into a sump. 



The use of automatic valve gear to control 

 the admission of steam and the admission of 

 cold water made the Newcomen engine the first 

 self-acting mechanism since the invention of the 

 clock. In the earliest versions of the Newcomen 



engine, it is most likely that the admission of 

 steam and cold water was controlled by the 

 manual operation of taps rather than by auto- 

 matic gear. The origin of the automatic gear 

 is a matter of some dispute. One story has it 

 that a young boy named Humphrey Potter, who 

 was hired to turn the taps, invented the valve 

 gear so that he could go fishing while the engine 

 tended itself. This story, although persistent, 

 is considered "absurd" by some serious his- 

 torians of the steam engine,^ 



James Watt, although often given credit for 

 inventing the steam engine, did not even begin 

 working on steam engines until some 50 years 



^See, for example, Eugene S. Ferguson, "The Origins 

 of the Steam Engine," Scientific American . January 

 1964, pp. 98-107. 



