Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

542 Molesworth’s pocket-book Watek-pbessube Engines. For Pressure per square inch at different Heads, see Tables of pressure of water. POWER OF PRESSURE ENGINES. Q = Quantity of water in cube ft. per minute. h = Head of water in feet. P = Effective horse-power. P = -00151 QA. Wrought-iron pipes are frequently used foi high-pressure turbines. D = Internal diameter of pipe in inches. P = Pressure of water in atmospheres. DP Thickness of metal in inches = ——- 4-0-2. oUv 33 feet from the top = 1 atmosphere nearly. Thickness of metal in cylinder — P d • 0025 + 1 where d '= diameter of cylinder, in inches. Diameter of supply-pipe for water-pressure engines = diameter of cylinder x ‘41 for single- cylinder engines. = diameter of cylinder x '68 for double- cylinder engines. Stroke of engine, about 4 j diam. of cylinder. Velocity of piston, 60 feet per minute. Velocity of water in supply-pipe should no* exceed 400 feet per minute