Identifier: buildingrepairin00kirk (find matches)
Title: Building and repairing railways
Year: 1901 (1900s)
Authors: Kirkman, Marshall M. (Marshall Monroe), 1842-1921
Subjects: Railroads Railroads
Publisher: New York and Chicago, The World railway publishing company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
cticable, and not less than 3.5 feet in any case.Compensation is not only provided for the increase in startingfriction over rolling friction, but in addition to permit trainsto acquire speed more rapidly. Train stops near the foot ofa long grade are most limiting in this respect.VIRTUAL GRADES. The motion of a train represents stored energy, derivedfrom the engine or gravitation, and, under appropriate condi-tions, the power of the engine may be in part absorbed inimparting speed to the train, or augmented by the surrenderedmomentum of the train. When rolling and grade resistances exceed the applied force,motion is retarded and energy released in definite proportions,and conversely, when applied force is in excess, motion isaccelerated and energy imparted in like proportions. The moving energy of the train at different speeds is givenin Fig. 2 in terms of Velocity Head, which is the verticalheight, through which the train would be lifted, at each degreeof speed by its momentum alone.
Text Appearing After Image:
Fig. 2. DIAGRAM SHOWING LENGTHS OF VELOCITY GRADES. ;\PrEXDIX H. 570 (1.) Formula for Determining the Average Virtual Grade. 20 ( W J Sv — average virtual grade expressed in per cent.T — mean cylinder tractive power in lbs. for given initial and terminal speed.W — wright of train in tons of 2,000 lbs.; including engine and tender.R — mean train resistance in lbs per ton of train. Note -The maximum virtual grade for a given train-load (W) is found byinserting in above formula tlie train resistance (R)and the cylinder tractivepower (T) for minimum speed (10 miles per hour). Example: In above diagram is shown the length of velocity grades forengine Class D 3 Mogul, pulling a train weighing 1,250 tons (including engineand tender) for an initial speed of 30 miles and a terminal speed of 10 milesper hour. The difference in velocity heads (A M) taken from Table of Velocity Heads-31.96-3.55-28.4 feet. The average virtual grade (Sv) is calculated from formula:1 f T 1 If 11.743 1 Sv R 7

Note About Images