Abstract: A set oil ring to be assembled into a piston ring groove is made up of a spacer ring and a pair of side rail rings to be placed on both sides thereof. In assembling one of the side rail rings into a first groove portion which is on an upper side of the spacer ring in the piston ring groove, a guide member, which can be moved up and down for fitting the rings onto a piston, is moved to a first fitting position which is substantially the same level as the groove wall surface of the first groove portion. A restricting member is disposed oppositely in front of the guide member while leaving a clearance facing the first groove portion. One of the side rail rings is pushed out of the front end of the guide member in a condition in which split end portions of the spacer ring are restricted by the restricting member so as not to overlap.

Abstract: A piston ring is assembled into a groove of a piston by pushing the piston ring out of a front end of a guide member. The piston ring is mounted on an outside of the guide member which has a diameter larger than an outside diameter of the piston. The pushing is carried out while maintaining a clearance which allows for the piston ring to undulate. This clearance is formed between a front end of the guide member and a plane including a groove surface which lies away from the front end of the guide member.

Abstract: A steering control system for a moving vehicle causes the vehicle to travel along a predetermined traveling course in a region in which a predetermined working operation, such as grass cutting or the like, is to be performed by the vehicle as it moves along the traveling course. An obstacle sensor is mounted on the vehicle, and when the sensor detects presence of an obstacle on the predetermined traveling course, the steering control system operates to cause the vehicle to leave the predetermined traveling course and to detour around the obstacle while maintaining a substantially constant distance between the obstacle and the moving vehicle.