Abstract
Forces around the tractor seat are in the state of the dynamic balance even while operator handles any maneuvering parts. The operating motion on the tractor was discussed basing on this situation.
The results show that the magnitude of the force on the seat which is the vector sum of the force on backrest and the vertical force on seat surface, exists at about 80% of operator's weight. By depressing a foot pedal, the force on backrest increases and the vertical force on the seat decreases; the resultant force on the seat remains almost equal to the magnitude in the static working posture. The pedal force was almost equal to the difference of vectors between the force on seat by depressed pedal and that in the static working posture.
