The Artizan . dle-Boats,viz.: One for river steamers and vessels intended for smooth waters. Here c = 625. Another coefficient is used for steamers intended to encounter gales andheavy seas. Here c = 575. There are likewise two coefficients for Crankshafts used in Screw-Boatsviz.:— One for larger engines, c = another for smaller ones, c = 515. Example.—The diameter of cylinder 92in., stroke 4ft., pressure onpiston 201bs. steam + 131bs. vacuum ; what is the diameter of crankshaft ? 92 inches diameter = 66476 square inches in x 33 x 2 x 2* = 877,480 (*the last 2 = No. of engi
The Artizan . dle-Boats,viz.: One for river steamers and vessels intended for smooth waters. Here c = 625. Another coefficient is used for steamers intended to encounter gales andheavy seas. Here c = 575. There are likewise two coefficients for Crankshafts used in Screw-Boatsviz.:— One for larger engines, c = another for smaller ones, c = 515. Example.—The diameter of cylinder 92in., stroke 4ft., pressure onpiston 201bs. steam + 131bs. vacuum ; what is the diameter of crankshaft ? 92 inches diameter = 66476 square inches in x 33 x 2 x 2* = 877,480 (*the last 2 = No. of engines) 9574 X/ 877,480 = 95-74525 = 18-236 inches, say 18j inches. Ceanks. r In calculating a crank we must first find the size of the crankshaft andcrankpin, and then consider the crank itself entirely as a single beam (I)(see page;i32); from this we will find the breadth and depth of the crankitself. Make the area of a section of the large eye on one side of the shaftequal to £ part of the crushing This will be better understood by referring to an example. Sup-nosing we have 93,2911bs. on piston, crankshaft 12in, and length of crank 2ft. 3in. Making the length of the crankpin 1-25 x diameter, weget the diameter of pin = lOin. Now considering the web of crank as asingle beam, and using 10 as the factor of safety, we get (S) = 100,and using the formula for beams, we get the constant (b d2) = 2099. Fixing 5 = 8; 2099 -h 8 = 2623. V 262-3 = 16-2. This is the depth of the web at the crankshaft centre. We have nowto fix the sizes of the metal of the large eye of crank, and in doing so wemust find, how many square inches the area ought to contain to resistthe crushing force upon it. Setting W = weight on piston in pounds per square = length of the crank in inches,r = half diameter of crankshaft in inches,and 4500 lbs. = J part of the crushing force upon wrought iron. Then, WR r x 4500 Rule.—Multiply the weight in pounds per square inch on piston by thelength
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