Abstract
Although the design theory on the rotary blades arrangement has been studied for many years, the most design of the C-shaped blades arrangement is still based on a designer's experience. This might be caused because the necessary conditions for the blade arrangement are not clarified and simplified, and the design process is not well established. Therefore, the authors studied the design theory on the C-shaped blades arrangement theoretically and empirically. The results are as follows:
1) It should be considered for the design of the rotary blades arrangement to keep static and dynamic balance of the rotary axle, to minimize the forced vibrations of the rotary axle disturbed by the tillage resistance, to make the soil slices as uniformly as possible, to level the tilled soil and to make the production of the rotary axle easy.
2) The consideration of the horizontal and vertical components of the tillage resistance on a rotary blade can be omitted by regarding that the curves of the components are similar to a curve of a torque on a blade.
3) It is estimated that the fluctuation of the unbalance moments Mx(θ), My(θ) which are around the axes in the forward and upward direction, is approximately as same as the distribution of the dynamic unbalance moment in the circumferential direction. This means that if the dynamic balance is well maintained, there is no need to consider Mx(θ) and My(θ).
4) The disign process of the rotary blade arrangement was described using the design flow-chart. The performances of the rotary axles which were designed based on the process were mostly satisfactory.
5) The estimation of the torque curve of a rotary axle is an important process for rotary blades arrangement. The estimation method is fundamentally based on a model torque curve of a blade, which is determined experimentally as a quadrilateral in Fig. 6. The characterizing factors of the model are determined by Equation (24). All the torque curves, which are drawn with the phase differences of the peaks equivalent to those of their blade holders, summed up to a overall torque curve. The estimated torque curves showed good approximation to the measured ones from the practical view point.
