. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . these varying points of pistontravel and consequent variation insteam pressure, a diagram may be read-ily made showing the actual work per-formed by the steam in a graphic man-ner, as is done by an instrument knownas the indicator, which describes withan attached movable pencil a curvedline forming a rectangular hyperbole. Railway men are well aware thatwhen a locomotive is required to exertits full power for a short time, as whenstarting a heavy train, or in moving upan incline, ste
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . these varying points of pistontravel and consequent variation insteam pressure, a diagram may be read-ily made showing the actual work per-formed by the steam in a graphic man-ner, as is done by an instrument knownas the indicator, which describes withan attached movable pencil a curvedline forming a rectangular hyperbole. Railway men are well aware thatwhen a locomotive is required to exertits full power for a short time, as whenstarting a heavy train, or in moving upan incline, steam is admitted to the cylinder at the fullest pressure throughalmost the entire length of the pistonstroke. There is considerable loss ofsteam during these periods, as thesteam is released while at a compara-tively high pressure and is consequent-ly wasted with a corresponding wasteof fuel. The careful engineer, recog-nizing the seriousness of such loss,shortens the period of admission ofsteam as soon as practicable. This isa matter that can be learned from ex-perience, but it is easily understood. KkllJGK .STANDS ON END LIKE ATOWER. that the momentum acquired after atrain has been in motion a short dis-tance, or the fact that the summit ofan incline has been reached rendersthe continued motion of the train moreeasy of accomplishment, and conse-quenlty requires less steam to keep thepiston in motion. It must also be noted that in themovement of the piston, wliile tliesteam pressure is acting on one side ofit, the other side is open to the atmos-phere, and is consequently subject atall times to an atmospheric pressureof nearly 15 lbs. per sq. in. In all practice there is an additionalback pressure varying according to the amount of pressure in the releasedsteam, but which, under any condition,is always several pounds in ofthe atmospheric pressure. This is dueto incompleteness of exhaust in high-pressure engines, and which is almostcompletely overcome in the
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