There are four moving components at each pier. The tire rolls on two support rollers, and the shell moves circumferentially relative to the tire ID. Any relative misalignment of these interactive components results in mechanical instability.
Consider the rolling motion of the tire on a support roller. If the tire axis is parallel to the roller axis, both components roll in the same direction. If the tire axis is not parallel to the roller axis, the tire will roll in a direction slightly different than the roller. The two components are rolling in different directions, and have a common interface. The result is instability via a horizontal motion component, causing the roller to move axially in one direction, and the kiln in the opposite direction.
The roller will move axially until the thrust mechanism inside one of the bearings stops the lateral motion. If the degree of roller misalignment is high, the pressure on this thrust mechanism (either a bearing end cap or a thrust collar) becomes high and increased bearing temperature results. The reaction to the axial motion of the support roller is kiln movement in the opposite direction. This axial movement of the kiln is resisted by a thrust roller, which may become overloaded and either fail or overheat.
The difference in the direction of the tire motion and the direction of the support roller motion results in friction and erosion at the point of contact between the tire and the roller. Consequently, the wear of both components is accelerated, and frequent resurfacing becomes necessary.
The difficulties encountered because of the rolling motion of the shell inside the tire ID, commonly referred to as tire creep, are more difficult to envision. If the plane of the tire is perpendicular to the rotating axis of the kiln, the motion of the shell and the motion of the tire are in the same direction and the system is stable. If the plane of the tire is tilted relative to the kiln axis, the tire will roll in a slightly different direction than the shell. The relative hor
