Studies on the Development of a Lotus-roots Harvester by Water Jet (III)

The Property and Strength of Lotus-roots

Abstract

In the process of the development of a lotus-roots harvester by water jet, the distribution, the property and the strength of lotus-roots were revealed. The results were summarized as follows.
1. The growing depth of lotus-roots at harvest time varied with the variety, the method of culture, the condition of soil and others. But in this study internodes distributed in the depth of 15-40cm and terminal buds in 10-40cm. The growing depth of winter lotus-roots distributed in wider range than that of summer lotus-roots. Therefore, in order to harvest lotus-roots perfectly, it was necessary that soil was digged and was liquidized by water jet to the depth of 40cm.
2. The specific gravity of internode, intercellular spaces of which were filled with water, was 1.0-1.2 and that of node was 0.85-0.98. Therefore, lotus-roots would not float in the water if intercellular spaces of internode were filled with water. If intercellular spaces of internode were filled with air, lotus-roots would float in the water. The specific gravity of primary lateral shoot (class M, S, 2S) or secondary lateral shoot (class 2S) was smaller than that of main shoot (class L), and that of lotus-roots was smaller in the back part. But when lotus-roots were floated by water jet, the terminal bud and the first part of internode floated at first by the influence of nodal root in the third node and its following nodes.
3. A straight relation was found between the specific gravity of internode filled its intercellular spaces with air and the space ratio (=intercellular space volume/intercellular space volume+flesh volume), and the specific gravity decreased in proportion as the space ratio increased. The space ratio of main shoot was smaller than that of primary or secondary lateral shoot and the space ratio of the first part of internode was 20-30% and that of the last part of internode was 40-50%.
4. When compression stress was applied to the internode, the strain increased gradually and the first destruction occured. The compression strength meaned the stress to occur the first destruction. The compression strength of internode was 7-20kg/cm². The compression strength of the upper side of internode was smaller than that of the lower side. It was the smallest in the upper side of the first part of internode. But the compression strength of internode was generally large and bad influence by water jet or travelling machine was not found.
5. The maximum bending moment of main shoot was 15-22kg-cm, and that of primary or secondry lateral shoot was 4-8kg-cm. The maximum bending moment of the second node was the largest. The bending strength of node was 3.8-7.8kg/cm².
6. The broken loss of lotus-roots often occured by smaller energy than the energy of water jet to dig and liquidize soil. Therefore, in order to prevent the broken loss, it was necessary to decrease the number of hitting lotus-roots by jet as much as possible.