A is to be made according to proportions given on page 135. Bolts to be made according to the same table. NOTE. The bolts for cylinder heads are to be calculated from the formula given for cylinder head bolts in connection with Fig. 1. In this cylinder the stuffing box, S, is a separate piece that is to be bolted to the cylinder head. Crank Shafts. For high speed automatic short stroke engines, the following formula corresponds with good practice: d = .44 D + ", where d is the diameter of shaft and D = the diameter of cylinders. For the Corliss type, in which the stroke is equal to or greater than twice the diameter, d.34 D+21", when D is equal to or greater than 16 inches. When D is less than 16 inches, d = D. The Piston. A form of piston that is much used is shown in the following figure. It consists simply of a hollow circular disc of cast iron. The packing rings 8, 8 are made of cast iron, and are split and sprung into place. Their elasticity causes them to press against the cylinder walls and thus prevent the leakage of steam. The following proportions will give dimensions suitable for this piston: D= diameter of cylinder in inches. a.2 D + 1.5". b = diameter of piston rod. e = .75 c. r = .5 c. c.18 2D-.1875". Number of ribs = .08 (D1 +34). The figure shows a strap end connecting rod. The straps c1 and c are fastened to the ends of the rods by means of the gibs a, and a, and the cotters b1 and b1. The cotters are held in place by the set screws 8, and 82. Small steel blocks shown between the ends of the set screws and the cotters, are used to prevent injury of the cotter by the set screws. The rod, cotters, gibs and straps may be made of either wrought iron or steel. The crank pin brasses are shown babbitted, and wrist pin brasses without babbitt. The brasses are adjusted by means of the cotters, which draw the straps farther on to the rod when they are driven in. The dimensions for the rod are given by the following proportions: 1 = .375 b. m = 1.35 d for wrist pins up q= 1.125 d for wrist pins up to 3.5" in diameter, and to 3.5" in diameter, and q = 4", constant, for pins The taper of the cotter is 34" per foot. Proportions for the crank pin end. D = diameter of cylinder in inches. Eccentric and Strap. The figure shows an eccentric sheave and strap, both made of cast iron. The eccentric sheave is cast solid, and must, there fore, be slipped over the end of the shaft. The eccentric rod is held in a boss on the strap by means of a cotter. For eccentrics used with valve stems 1⁄2" in diameter or less the holes for bolts, j, are not to be cored. A = boss for oil cup. The proportions are as follows: d = diameter of shaft. a=d+2q+2 h. b = 2 D.125". C = 1.5 D. e = .75 D. .75 D. |