Master-and-Articulated Rod Assembly articulated rods are assembled and then installed on the  crankpin; the crankshaft sections are then joined together. In  engines that use the one-piece type of crankshaft, the big end  of the master rod is split, as is the master rod bearing. The  main part of the master rod is installed on the crankpin; then  the bearing cap is set in place and bolted to the master rod. The centers of the knuckle pins do not coincide with the  center of the crankpin. Thus, while the crankpin center  describes a true circle for each revolution of the crankshaft,  the centers of the knuckle pins describe an elliptical path.  [Figure 1-12]  The elliptical paths are symmetrical about a  center line through the master rod cylinder. It can be seen that  the major diameters of the ellipses are not the same. Thus,  the link rods have varying degrees of angularity relative to  the center of the crank throw. The master-and-articulated rod assembly is commonly  used in radial engines. In a radial engine, the piston in one  cylinder in each row is connected to the crankshaft by a  master rod. All other pistons in the row are connected to  the master rod by articulated rods. In an 18-cylinder engine,  which has two rows of cylinders, there are two master rods  and 16 articulated rods. The articulated rods are constructed  of forged steel alloy in either the I- or H-shape, denoting the  cross-sectional shape. Bronze bushings are pressed into the  bores in each end of the articulated rod to provide knuckle- pin and piston-pin bearings. The master rod serves as the connecting link between the  piston pin and the crankpin. The crankpin end, or the big end,  contains the crankpin or master rod bearing. Flanges around  the big end provide for the attachment of the articulated rods.  The articulated rods are attached to the master rod by knuckle  pins, which are pressed into holes in the master rod flanges  during assembly. A plain bearing, usually called a piston-pin  bushing, is installed in the piston end of the master rod to  receive the piston pin. When a crankshaft of the split-spline or split-clamp type is  employed, a one-piece master rod is used. The master and  Because of the varying angularity of the link rods and the  elliptical motion of the knuckle pins, all pistons do not move  an equal amount in each cylinder for a given number of degrees  of crank throw movement. This variation in piston position  between cylinders can have considerable effect on engine  operation. To minimize the effect of these factors on valve and  ignition timing, the knuckle pin holes in the master rod flange  are not equidistant from the center of the crankpin, thereby  offsetting to an extent the effect of the link rod angularity. Figure 1-11. Connecting rod assemblies. 1-11 Fork-and-blade rod Solid-type master rod Split-type master rod Plain rod Blade rod Fork rod Shank Cap Connecting rod bolts Crimp or pinch Bearing shells lined with bearing material Piston pin end Bronze bushing Articulating rod Knuckle pin lock plate Knuckle pin