DIMENSIONS OF THE CROSSHEAD. 255 By this mode of procedure a table of proportions adapted to the ordinary pressures will be made available for determining the proportions suitable for all pressures, as we have only to fix upon an assumed cylinder which shall have as much more area as the intended pressure has an excess of pressure over 25 lbs. per square inch, and the proportions proper for this assumed cylinder will be those proper for the real cylinder with the pressure intended. In this way the strengths fixed for marine engines may also be made applicable to locomotives and to high and low pressure engines of every kind. In the following rules, therefore, it will be understood the strengths and other proportions are those proper to an assumed pressure on the piston, including steam and vacuum, of 25 lbs. per square inch, and the computations are for side lever engines, but for the most part are applicable to all kinds of engines. CROSSHEAD. TO FIND THE PROPER THICKNESS OF THE WEB OF THE CROSSHEAD AT THE MIDDLE. RULE.-Multiply the diameter of the cylinder in inches by 072. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches × 072 2.880 inches, which is the proper thickness of the web of the crosshead at the middle in this engine. Example 2.-Let 64 inches be the diameter of cylinder. Then 64 inches x 0724.608 inches, which is the proper thickness of the web of the crosshead at the middle in this engine. TO FIND THE PROPER THICKNESS OF THE WEB OF THE CROSSHEAD AT THE JOURNAL. RULE.-Multiply the diameter of the cylinder in inches by 061. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x⚫0612.440 inches, which is the proper thickness of the web of the crosshead at the journal in this en gine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x '061 3.904 inches, which is the proper thickness of the web of the crosshead at the journal in this engine. TO FIND THE PROPER DEPTH OF THE WEB OF THE CROSSHEAD AT THE MIDDLE. RULE.-Multiply the diameter of the cylinder in inches by ·268 Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 268 10.720 inches, which is the proper depth of the web of the crosshead at the middle in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 26817.152 inches, which is the proper depth of the web of the crosshead at the middle in this engine. TO FIND THE PROPER DEPTH OF THE WEB OF THE CROSSHEAD AT JOURNALS. RULE.-Multiply the diameter of the cylinder in inches by 101. Example 1.-Let 40 inches be the diameter of cylinder. Then 40 inches x 101 4.040 inches, which is the proper depth of the web of the crosshead at journals in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x *101 = = 6·464 inches, which is the proper depth of the web of the crosshead at journals in this engine. TO FIND THE PROPER DIAMETER OF THE JOURNALS OF THE CROSS HEAD. RULE.-Multiply the diameter of the cylinder in inches by ·086. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 0863440 inches, which is the proper ameter of the journals of the crosshead in this engine. Example 2.-Let 64 inches be the diameter of cylinder. DIMENSIONS OF THE CROSSHEAD. 257 Then 64 inches x 086 5.504 inches, which is the proper diameter of the journal of crosshead in this engine. TO FIND THE PROPER LENGTH OF THE JOURNALS OF THE CROSSHEAD. The length of the journals of the crossheads should be equal to about 14 times their diameter, but on the whole it appears to be advisable to make the journals of the crosshead as long as they can be conveniently got. TO FIND THE PROPER THICKNESS OF THE EYE OF THE CROSSHEAD. RULE.-Multiply the diameter of the cylinder in inches by '041. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x .041 1.640 inches, which is the proper thickness of the eye of the crosshead in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 041 = 2.624 inches, which is the proper thickness of the eye of the crosshead in this engine. TO FIND THE PROPER DEPTH OF THE EYE OF THE CROSSHEAD. RULE.-Multiply the diameter of the cylinder in inches by ·286. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 286 11.440 inches, which is the proper depth of the eye of the crosshead in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 286 = 18.304 inches, which is the proper depth of the eye of the crosshead in this engine. TO FIND THE PROPER DEPTH OF GIBS AND CUTTER PASSING THROUGH THE CROSSHEAD. ROTE.-Multiply the diameter of the cylinder in inches by ·105, Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 105 = 4·200 inches, which is the proper depth of the gibs and cutter passing through the crosshead in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 105: = 6-720 inches, which is the proper depth of the gibs and cutter passing through the crosshead in this engine. TO FIND THE PROPER THICKNESS OF THE GIBS AND CUTTER PASSING THROUGH THE CROSSHEAD. RULE.-Multiply the diameter of the cylinder in inches by ‘021. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 021840 inches, which is the proper thickness of the gibs and cutter passing through the crosshead in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x .021 = = 1.344 inches, which is the proper thickness of the gibs and cutter passing through the crosshead in this engine. SIDE RODS. TO FIND THE PROPER DIAMETER OF THE CYLINDER SIDE RODS AT THE ENDS. RULE.-Multiply the diameter of the cylinder in inches by '065. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 0652.600 inches, which is the proper diameter of cylinder side rods at ends in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 0654.160 inches, which is the proper diameter of the cylinder side rods at ends in this engine. The diameter of the side rods at the middle should be about DIMENSIONS OF THE SIDE RODS. 259 one-fourth more than the diameter at the ends. Thus a side rod 5 inches diameter at the ends will be 6 inches diameter at the iniddle. The area of the horizontal section of iron through the middle of eye of side rod is usually about one-half greater than the sectional area of the side rod at ends. TO FIND THE PROPER BREADTH OF THE BUTT OF THE SIDE ROD IN INCHES. RULE.-Multiply the diameter of the cylinder in inches by '077. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 077: = 3.080 inches, which is the proper breadth of butt of side rod in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 0774.928 inches, which is the proper breadth of butt in this engine. TO FIND THE PROPER THICKNESS OF THE BUTT OF THE SIDE RODS. RULE.-Multiply the diameter of the cylinder in inches by ·061. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 061: = 2.440 inches, which is the proper thickness of the butt of the side rod in this engine. Example 2.-Let 64 inches be the diameter of the cylinder. Then 64 inches x 0613.904 inches, which is the proper thickness of the butt of the side rod in this engine. TO FIND THE PROPER MEAN THICKNESS OF THE STRAP OF THE SIDE ROD AT THE CUTTER. RULE.-Multiply the diameter of the cylinder in inches by 032. Example 1.-Let 40 inches be the diameter of the cylinder. Then 40 inches x 032 = 1.280 inches, which is the proper mean thickness of the strap of side rod at the cutter in this engine. |