Thickness of key = width of key multiplied by 42. Diameter of boss for crank-pin diameter of crank-pin multiplied by 2.25. Depth of boss for crank-pin = diameter of crank-pin multiplied by 15. Crank-pin to be shrunk in and riveted at back. Thickness of web of crank = diameter of crank-pin, and a strong rib in centre should connect the two bosses. Crank, Wrought-Iron.-Diameter of boss for crank-shaft = diameter of shaft multiplied by 175. Depth of boss diameter of shaft multiplied by '87. = Diameter of boss for crank-pin = diameter of crank-pin multiplied by 2. by 24. diameter of cylinder multiplied. Length of crank-pin diameter of crank pin multiplied by 15. Eccentric. Throw of eccentric when it works the valve direct = travel of the slide-valve. the Width of recess for eccentric-strap diameter of cylinder multiplied by 18. inch to inch according to size. inch to inch according to Depth of recess in eccentric, from size. Diameter of boss of eccentric = diameter of shafts multiplied by 1·6. Depth of boss of eccentric diameter of shafts multiplied by 7. Eccentric-Strap.-Thickness to its width multiplied by 67 for cast iron. = For brass multiply the width by 53. When the strap is iron lined with brass, the brass lining should be of the thickness of strap in thickness. Eccentric-Rod.-Diameter at slide-valve spindle-end = diameter of slide-valve spindle. Diameter at eccentric strap end = diameter of slide valve spindle multiplied by 13. = Feed-Pump. Diameter diameter of cylinder when stroke of piston; and diameter of cylinder when stroke of piston. Wrought Iron Cross Head, Fig. 2, for 4-slide bars. Diameter of recessed part of boss A = diameter of piston-rod multiplied by 175. Length of recessed part of boss A = diameter of piston-rod multiplied by 1.2. Diameter of collar at end of boss B = diameter of piston-rod multiplied by 2. Width of collar at end of boss B = diameter of piston-rod multiplied by 42. Thickness of fork at the boss C = diameter of piston-rod multiplied by 6. Thickness of fork below the boss D = diameter of piston-rod multiplied by 42. Diameter of the boss of the fork C = diameter of cross-head pin multiplied by 2. Diameter of cross-head pin E = diameter of crank-pin multiplied by 75. Width of fork F = diameter of cross-head pin multiplied by 1.2. Length of cotter-hole in boss diameter of piston-rod multiplied by 8. *75. of an inch per foot. diameter of piston-rod for wrought-iron slidebars; and diameter of piston-rod multiplied by 14 when the slide bars are cast-iron. = Thickness of slideblock= diameter of slideblock-pin multiplied by 18. Length of sliding surface width of sliding surface multiplied by 3 or 4. Wrought-Iron Crosshead, Fig. 3.-For 2 slidebars, viz. one above and one below the crosshead, the slide-blocks being adjustable by locknuts on the slideblock-pin. Width of slide surface of slideblock= diameter of piston rod multiplied by 2. Length of sliding surface of slideblock= width of sliding surface multiplied by 4. centre of the crosshead-pin = From centre of the slideblock From centre of the slideblock-pin to the diameter of crosshead-pin multiplied by 2.5. pin to the outside of the collar on the end of the boss of crosshead = diameter of crosshead-pin multiplied by 2'5. The proportions of the fork and crosshead pin may be found by the same rules as the other crosshead given above. Slide Bars, 4 in number, viz. 2 on each side of crosshead. Slide bars, width = to diameter of piston-rod when wrought-iron; and when cast-iron, width to diameter of piston-rod multiplied by 14. Thickness to width multiplied by 6 for wrought-iron, and by 4 for cast-iron when made with a rib in the centre. Depth of rib = width of bar multiplied by 7. Diameter of bolts for slide-bar = width of slide-bar multiplied by 4. Connecting-rod with strap-end like Fig. 4. Thickness of strap at the end = diameter of bearing multiplied by 33. 25. Fig. 4. Thickness of strap at the side diameter of bearing = multiplied by 24. Thickness of strap at cotter-hole diameter of bearing multiplied by 4. Width of strap = length of bearing multiplied by 7. Length of strap beyond cotter-hole = diameter of bearing multiplied by 54. Distance from end of brass bush to edge of cotter = diameter of bearing multiplied by 54. Thickness of brass bush at the end = diameter of bearing multiplied by Thickness of brass bush at the side = thickness of brass bush at the end multiplied by 75. Width of gib and cotter at the centre = the diameter of the bearing. Thickness of gib and cotter diameter of bearing multiplied by 22. Taper of cotter, inch per foot. Depth and width of the clip of the gib, each = the thickness of the gib. Diameter of the connecting-rod at the small end = the diameter of piston rod. Diameter of connecting-rod at the large end = the diameter of piston-rod multiplied by 125. Diameter of connecting-rod at the centre = the diameter of large end plus of an inch per foot of length of rod. Length of connecting-rod twice the length of stroke. Connecting-rod with cap-end like Fig. 5. Cap Bolts. The sectional area of each bolt to equal one-half the sectional area of the piston-rod. Thickness of cap diameter of bearing multiplied by 5. = Width of cap and rod-end length of bearing multiplied by 7. Engine-bed when made Box-pattern, like the section of bed, Fig. 6. = Thickness of metal thickness of metal of the cylinder multiplied by 7. Depth of bed diameter of cylinder multiplied by 5 to 6. Weight of Foundation for an Engine.-In stone or brick = one ton per nominal horse-power. Horizontal High-pressure Condensing Engines.-The object of the condenser is to remove the pressure of the atmosphere which opposes the advance of the piston in the cylinder, so that all the work performed by the steam may be brought to bear effectually upon the piston, but there is always a back pressure of about 2 lbs. per square inch in the cylinder due to imperfect vacuum. In this class of engine, the condenser, with airpump and hot-well combined in one casting, is usually fixed on the bed behind the cylinder, the piston-rod of which is continued through the back. cylinder-cover to work the air-pump. Diameter of single-acting air-pump diameter of cylinder multiplied. by 6. Diameter of double-acting air-pump = diameter of cylinder multiplied by 3. Width of air-pump piston Diameter of air-pump rod diameter of air-pump multiplied by 3. diameter of air-pump multiplied Area of delivery and suction-valves by 7. = Capacity of condensor the capacity of the air-pump. Diameter of injection-pipe diameter of cylinder divided by 8. Diameter of cold-water pump = diameter of cylinder multiplied by 3, when its stroke equals the stroke of engine. Diameter of feed-pump = diameter of cylinder divided by 10 when its stroke equals one-half the stroke of the engine. Quantity of injection-water required per nominal horse-power in cubic feet per minute, equal temperature of the steam in degrees Fahr. multiplied by 00304; approximately 5 gallons are required per nominal horse-power per minute. ENGINE GOVERNORS. The Action of a Governor is controlled by two forces, viz., centrifugal force, or the tendency of the revolving balls to fly away from the spindle or vertical axis, and centripetal force, or the tendency of the balls to hang in a vertical line from the centre of the pin suspending the arm, due to the force of gravity. To find the centrifugal force of a governor in terms of the weight of the balls. Multiply the square of the number of revolutions per minute by the radius of the circle described by the centres of the balls in inches, and divide the product by the constant number 35,226. To find the centripetal force of a governor in terms of the weight of the balls. Divide the horizontal distance of the balls from the centre of the suspending pin, by the vertical height of the same centres. Ordinary Governors, Fig. 7.-The centre of the suspension of the B Fig. 8. Fig. 7. arms should invariably be placed in the centre of the spindle, unless it be placed beyond it, as in Fig. 8; because it is essential for a governor to work with the least possible variation in speed, and the placing of the point of suspension away from the centre of the spindle causes considerable variation in velocity. The variation in velocity increases as the distance is in |