2d, To find center line of motion, and amount of offset in rocker-arms.
3d, To find relative positions of crank-pin and eccentrics when at full and half stroke.
4th, To determine the correct length of eccentric-rods.
5th, To find position of saddle-pin.
6th, To find the position of the center of lifting-shaft and length of arms.
Fig. 20.
Problem 1, Figs. 20 and 21.—To find the position of crank when the piston is at full and half stroke.—Let the center of wheel and the axis of the cylinder be in the same straight line as AD, [Fig. 20]. With any point C as a center, and a radius equal to the length of the crank, describe a circle F, ½F, B, ½B; and let us call this the crank-pin circle. The straight line AD intersects the circumference of the circle in the points F and B. The point F will be the center of crank-pin when piston is at full stroke at the forward end of the cylinder, and point B will be the center of crank-pin when the piston is at full stroke at the rear end of the cylinder. With the point F as a center, and with a radius equal to the length of the connecting rod, describe an arc intersecting the line AD in the point F′; with the point B as a center, and with the same radius, describe an arc intersecting the straight line AD in the point B′; and with the point C as a center, and with the same radius, describe an arc intersecting the straight line AD in the point C′. Point F′ will be the center of cross-head pin when the center of crank-pin is at F, and B′ the center of cross-head pin when the crank-pin is at B, and the point C′ will be the position of center of cross-head pin when piston is at half stroke. With point C′ as a center, and a radius equal to the length of the connecting rod, describe an arc passing through the point C, and intersecting the crank-pin circle in the points ½F and ½B: these points will be the position of crank-pin when the piston is at half stroke, or when the center of cross-head pin is at C′.
Fig. 21.