Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . he same time a clockspring connected within the drum iswound up. On the return stroke themotion of the drum is reversed and thetension of the spring returns the drumto its original position and also keepsthe cord taut. To the outside of the drum a piece ofblank paper of suitable size is attached and held in placeby two clips. Upon this paper the pencil in its motionup and down traces a complete diagram of the pressuresand other interesting events transpiring within the en-gine cylinder during the
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . he same time a clockspring connected within the drum iswound up. On the return stroke themotion of the drum is reversed and thetension of the spring returns the drumto its original position and also keepsthe cord taut. To the outside of the drum a piece ofblank paper of suitable size is attached and held in placeby two clips. Upon this paper the pencil in its motionup and down traces a complete diagram of the pressuresand other interesting events transpiring within the en-gine cylinder during the revolution of the engine. Infact the diagram traced upon the paper is the compoundresult of two concurrent movements. First, that of thepencil caused by the pressure of the steam againstthe indicator piston; second, that of the paper drumcaused by, and coincident with, the motion of theengine piston. The upper end of the indicator cylin-der is always open to the atmosphere, the steam actingonly upon the underside of the small piston, and whenthe cock connecting the cylinders of the engine and. CROSBY INDI-CATOR SPRING. 172 ENGINEERING indicator is closed, both ends of the indicator cylinderare open to atmospheric pressure, and the pencil thenstands at its neutral position. If now the pencil isheld against the paper and the drum rotated either byhand or by connecting it with the cord, a horizontalline will be traced. - This line is called the atmosphericline, meaning the line of atmospheric pressure, and itis a very important factor in the study of the diagram. If the engine is a non-condensing engine the pencilin tracing the diagram will, or at least, should not fallbelow- the atmospheric line at any point, but will onthe return stroke trace a line called the line of backpressure at a distance more or less above the atmos-pheric line and very nearly parallel with it. If theengine is a condensing engine the pencil will dropbelow the atmospheric line while tracing the line ofback
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Keywords: ., bookcentury1900, bookdecade1900, bookpu, booksubjectsteamturbines
