Friction in Journal Bearing:
A journal bearing forms a turning pair as shown in below fig. The fixed outer element of a turning pair is called a bearing and that portion of the inner element which fits in the bearing is called a journal. The journal is slightly less in diameter than the bearing, in order to permit the free movement of the journal in a bearing.
Types of Friction in Journal Bearing:
1. Friction of Pivot Bearing: The rotating shifts are frequently subjected to axial thrust. The bearing surfaces such as pivot bearing is used to take the axial thrust of the rotating shaft. The propeller shafts of ships, the shafts of steam turbines and vertical machine shafts are examples of shafts which carry an axial thrust.
The bearing surfaces placed at the end of a shaft to take the axial thrust are known as pivots. The pivot may have a flat surface or conical surface as shown in fig. When the cone is truncated or trapezoidal pivot as shown in below fig.
2. Friction of Collar Bearing: The collar may have flat bearing surface or conical bearing surface, but the flat surface is most commonly used. There may be a single collar as shown in below fig. Several collars along the length of a shaft as shown below fig.