1 8 0 ° 1 8 0 ° 1 2 0 ° 1 2 0 ° 1 2 0 ° 1 2 3 4 1 2 3 4 1 2 5 6 3 4 3 4 1 2 5 6 Cylinders Crank arm Journal Figure 1-7. Solid types of crankshafts.  many throws it may have, each crankshaft has three main  parts—a journal, crankpin, and crank cheek. Counterweights  and dampers, although not a true part of a crankshaft, are  usually attached to it to reduce engine vibration. The journal is supported by, and rotates in, a main bearing. It  serves as the center of rotation of the crankshaft. It is surface- hardened to reduce wear. The crankpin is the section to which  the connecting rod is attached. It is off-center from the main  journals and is often called the throw. Two crank cheeks  and a crankpin make a throw. When a force is applied to the  crankpin in any direction other than parallel or perpendicular  to and through the center line of the crankshaft, it causes the  crankshaft to rotate. The outer surface is hardened by nitriding  to increase its resistance to wear and to provide the required  bearing surface. The crankpin is usually hollow. This reduces  the total weight of the crankshaft and provides a passage for  the transfer of lubricating oil. On early engines, the hollow  crankpin also served as a chamber for collecting sludge,  carbon deposits, and other foreign material. Centrifugal force  threw these substances to the outside of the chamber and kept  them from reaching the connecting-rod bearing surface. Due  to the use of ashless dispersant oils, newer engines no longer  use sludge chambers. On some engines, a passage is drilled  in the crank cheek to allow oil from the hollow crankshaft to  be sprayed on the cylinder walls. The crank cheek connects  the crankpin to the main journal. In some designs, the cheek  extends beyond the journal and carries a counterweight to  balance the crankshaft. The crank cheek must be of sturdy  construction to obtain the required rigidity between the  crankpin and the journal. In all cases, the type of crankshaft and the number of crankpins  must correspond with the cylinder arrangement of the engine.  The position of the cranks on the crankshaft in relation to the  other cranks of the same shaft is expressed in degrees. The simplest crankshaft is the single-throw or 360° type.  This type is used in a single-row radial engine. It can be  Figure 1-8. A single-throw radial engine crankshaft. 1-9 Crankpin Journal Crank cheek Counterweight Damping weights