. A manual of marine engineering: comprising the design, construction, and working of marine machinery. ines; consequently, when the engine is on the centre,the upper end of the adjustable link, H, and its block, J, may be movedthrough the whole range of the quadrant, I, from right to left, or vice versd,without moving the slide valve. This arrangement reduces to a minimum the wear of the die block inthe quadrant, for, when it is once set in position for working, there is littleor no motion. 40 626 MANUAL OF MARINE ENGINEERING. APPENDIX B. Cotterells Method of Constructing Inertia Curves, An a
. A manual of marine engineering: comprising the design, construction, and working of marine machinery. ines; consequently, when the engine is on the centre,the upper end of the adjustable link, H, and its block, J, may be movedthrough the whole range of the quadrant, I, from right to left, or vice versd,without moving the slide valve. This arrangement reduces to a minimum the wear of the die block inthe quadrant, for, when it is once set in position for working, there is littleor no motion. 40 626 MANUAL OF MARINE ENGINEERING. APPENDIX B. Cotterells Method of Constructing Inertia Curves, An acceleration curve may be constructed by graphical differentiationof the velocity curve, a method which it may be worth while to illustratein detail. Divide the crank pin circle into a number of equal parts, and, supposingthe connecting-iods drawn, let them cut the vertical through 0 in thepoints r, 2, 3, in fig. e. Also find and mark off the correspondingpositions of the piston, 1, 2, 3, &c. Now, since the lengths 01, 0 2,0 3, ifec, represent the velocities of the piston and reciprocating parts. Fig. e. when in positions 1, 2, 3, &c., the difference between any two con-secutive lengths, for example, 1, 2, will represent the change of velocitythat has taken place in the corresponding movement of the piston, 1, we suppose the crank pin to revolve uniformly and divide the circle intoequal parts, equal times will be occupied in the motions from point topoint, and, thei-efore, equal times in the motions between consecutivepositions, 1, 2, 3, 4, &c., of the piston. Accordingly, the differences,0 r, r2, 23, (fee, will represent the force required to change the velocityof the reciprocating parts; and if we set them up as ordinates between thecorresponding positions of the piston we shall obtain the curve expressingthe effect of inertia. The ordinate should be erected from the position ofthe piston when the crank-pin is at the middle of the intervals, 1, 2, 3, &c. It will be seen t
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