general, the torque ratio increased when the ground speed and PTO
rotational speed increased. The greater ground speed and PTO
rotational speed were during the rotary tillage, the greater loads on
the PTO input shaft were. The torque ratios of the PTO input shaft
were greater than those ofthe transmission input shaft as shown in
Fig. 5. The range of the maximum torque ratio of the PTO input
shaft was 0.8–2.5 and the greatest torque ratio was found also at
L3P1, like for the transmission input shaft. The greater PTO
rotational speed was, the greater load on the PTO input shaft was.
Fig. 6 shows evaluation of the severeness by the gear setting
during the rotary tillage. The severeness for each gear setting was
represented by ratio of the damage sum to the smallest damage
sum among the speed combinations. Fig. 6(a) shows the severeness
for the transmission input shaft. The smallest severeness was
obtained at the lowest speed combination when the transmission
was geared to L1 and the PTO gear was set to P1. The severeness
increased when the combined speed increased, and the increasing
amounts were greater when the ground speed increased. The
severeness increased by 573–746% when the ground speed
increased by 201% as the transmission gear was shifted from L1
to L3 at the same PTO rotational speed. At constant ground speeds,
the severeness increased by 187 to 340% when the PTO rotational
speed increased by 185% as the PTO gear was shifted from P1 to P3.
There was no statistical difference when the average load