Document Type : Research Article
Authors
Department of Biosystems Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Abstract
Introduction
One of the most important parts of agricultural operations is tillage, which accounts for about 60% of the total energy consumed. Therefore, reducing tillage energy demand by lowering the number of passes through the development of cost-effective machinery is highly essential in modern farming. One of the main implements that helps farmers achieve this is the disc harrow. As the most important secondary tillage tool, the disc harrow improves soil structure, breaks up clods, and increases the penetration of water and air into the soil. However, its optimal performance is influenced by parameters such as disc diameter, disc edge type (toothed or plain), disc gang angle, and tractor forward speed. Soil bins, as controlled environments for testing tillage tools, serve as an ideal alternative to agricultural lands. They allow accurate simulation of field conditions while minimizing the effects of climate change and variable soil properties.
Materials and Methods
The present study was conducted with the aim of designing, constructing, and evaluating a disc harrow carrier chassis in the controlled environment of a laboratory soil bin. First, the design phase was carried out using SolidWorks 2020 software, followed by an analysis of the design performance under maximum load using the von Mises method. The next step was the construction of the design. After construction, the evaluation phase was performed by examining the effects of four independent input variables: forward speed (6.43 and 13.15 m min⁻¹), soil moisture content (2.37 and 13.25 percent on a wet basis), disc edge type (plain or toothed), and disc gang angle (0, 15, and 30 degrees), on the dependent output variable, draft force. Each test was replicated three times, resulting in a total of 72 tests.
Results and Discussion
The results showed that the engineered chassis exhibited sufficient strength during the initial evaluation tests, with all components performing well. The findings indicated that increasing forward speed and disc gang angle led to higher draft force, while higher soil moisture levels reduced draft force. Under low moisture conditions, plain discs generated greater draft force; however, this trend reversed as moisture increased. The highest draft requirement (3.588 N) was observed for plain discs at 2.37% moisture, while the lowest (1.724 N) occurred at 13.25% moisture. At a forward speed of 6.43 m min⁻¹, plain and toothed discs required equal draft, but at 13.15 m min⁻¹, the toothed discs required substantially more draft.
Conclusion
The experiments showed that there was no significant difference in draft force between disc gang angles of 0 and 15 degrees. However, increasing the angle from 15 to 30 degrees caused a significant rise in draft force. This indicates that the initial increase in gang angle has a smaller effect, but beyond 15 degrees the impact becomes more pronounced. Therefore, selecting an appropriate disc gang angle can help reduce fuel consumption and improve the productivity of agricultural machinery. Both increasing disc gang angle and forward speed raise draft force because soil resistance to disc movement increases. At higher speeds, the disc must exert more force to cut and move the soil, leading to higher energy consumption and greater equipment wear. Conversely, at lower speeds, draft force decreases, but tillage efficiency may be reduced and plowing uniformity may be affected.
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