Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

f 221 OF ENGINEERING FORMULÆ. Tractive Power of Locomotives. D = Diameter of cylinder in inches. P = Mean pressure of steam in cylinders in lbs. per square inch. L — Length of stroke in inches. W = Diameter of driving wheel in inches. T - Tractive force on rails in lbs. rp .. D2 P L w ‘ Effective Pressure of Steam on Piston, With Different Rates of Expansion.—Boiler pres- sure being assumed as 100 lbs. per square inch. Effective pressure. Steam cut off at f of stroke = 90 = 80 = 69 /«= 50 . = 40 7 Rule to find the Load which an Engine WILL TAKE ON A GIVEN INCLINE. G tt Resistance due to gravity on the steepest gradient in lbs. per ton (see “Resist- ance of Trains”). R — Resistance due to assumed velocity of train in lbs. per ton. T = Tractive; power of engine in lbs. as found above. W - Weight of engine »nd tender in tons. L — Load the engine can take in tons, including the weight of the waggons, but not that of engine and tender. T L = —- W. i