Studies on the Power Reduction of Rotary Typed Power Tillers (II)

Abstract

In order to reduce the tilling power required of the rotary type, we carried out some comparative experiments about practical rotary tines, and we obtained from these experiments almost same tendencies of cutting characteristics as the model rotary tines (see the report 1).
The principal results obtained from these experiments are as follows:
(1) It is more advantageous for the power required to make the length of the curved edge of the blade as short as possible.
(2) The greater the width of a blade, the more advantageous for the power required. The cutting width of a blade can enlarge considerably at the paddy field cultivations, but it should be determined according to the relation of the number of the blade and the cutting pitch.
(3) It is important to take the proper value of a back angle (or a free angle) of the tine, and to form the curving part of the tine more smooth.
It is better to make smaller the cutting angle of the horizontal part of the tine so that the straw, the manure and other things may not get coiled round the blade, and it is more advantageous to make the angle of cutting path in the soil—the angle between the first point and the last point of cutting—as small as possible.
If we want to increase the speed of tractors in the rotary cultivation, we must consider the adoption of the other installing methods (two or three blades type) in place of Japanese customary method (one blade type at one point on the rotary shaft).
Therefore, we carried out some comparative experiments to obtain the characteristics of each type.
The principal results from these experiments are as follows:
(1) The position of the max. value of torque process curves of a tine is hardly changed, even when the revolution of the rotary shaft increase remarkably, that is to say, the impact resistances in this experiments don't occur when the blade pierces into the soil.
(2) The peak of the vertical component force curve occurs at earlier period than in the case of torque curve, and the value of the vertical component force becomes negative at the last period. The process curve of the horizontal component force shows the same tendency with the torque.
(3) Fig. 15 shows the relation among the working speed, the revolution of rotary shaft and the power required of each installing method of one blade, two blades and three blades.
Anew, Fig. 16 that was obtained from Fig. 15, shows the relation between the tilling pitch (slice length) and the power required.
From these figures, we can find the proper range of tilling pitch for working speeds of each type. But it seems to be more advantageous to make the number of blade less and the tilling pitch larger, for the simplification of structure, the reduction of weight and the removal of the tilled soil.
(4) Fig, 17 and Fig. 18 show the relation between the work of vertical and horizontal component forces of each type and the revolution of rotary shaft.
From Fig. 17 and Fig. 18, we discussed the piercing characteristics of the rotary type equipments as it is difficult to get the desirable tilling depth. fined according to the relation of the number of the blade and the cutting pitch.