Penurunan draft dan energi pembajakan pada model subsoiler getar dengan menggunakan metode Self-Excited Vibration

Abstract

Soil compaction potentially inhibits plant growth and reduces crop productivity. To loosen the compact soil, however high draft force and energy consumption are needed. The cause of which is due to soil cohesion, adhesion and friction between soil and tillage tool. It’s well known that vibratory-tillage could reduce that soil cohesion, adhesion and friction between soil and tillage tools so that the draft force and energy consumption required is reduced. In this research, soil tillage by self-excited vibration (SEV) method has been conducted. The objective of this research was to obtain vibratory-system of self-excited vibration vibratory-tillage (SEVVT) so that the vibration of the tillage tool will reduce draft force and energy consumption during tillage operation. The research was divided into three steps, i.e.: analytical study, equipment design and experiment study. In the analytical study, the vibration of SEVVT was simulated as a vibration with single degree of freedom system (SDOF) and two degrees of freedom system (TDOF). The vibration of tillage tool was exerted by natural excitation of the varying cutting force. The elasticity of the elastic spring or the inertia of the tillage tool was optimized such that the tillage tool vibrates violently around its resonant frequency. Draft force reductions about 22-47 % were observed. In the second step, the equipment was designed methodologically using VDI2221, with focus on the conceptual design. The embodiment design was then conducted to exemplify that the conceptual design was simple, easy to understand, and economically realizable. In the last step, soil tillage was conducted in a soil bin with the dimension of 1.2 m long, 0.3 m wide and 0.4 m depth. Clay loam soil was conditioned in soil bin into two layer namely hardpan and top soil. The tillage tool was connected to a fixed structure using a new model of semi-elliptical spring. The tillage speeds used were 0.158, 0.212 and 0.265 m/s. Five treatments were tested, i.e.: Non vibratory-system (NST), SDOF with rear spring orientation (RST), SDOF with front spring orientation (FST), TDOF system (TST) and low energy vibratory-system (VST). In the RST orientation, the draft force raised the elevation of the tillage tool tip, and the draft force caused the tillage tool tip elevation decrease in the FST orientation. Compared to NST, the average draft force in the FST orientation showed an increase of up to 46-96 %, whereas a draft force reduction were found in the RST and in the TST treatment. In the VST treatment, a small unbalance mass of 0.24 and 0.35 kg was rotated 530 and 1150 rpm respectively and causing tillage tool vibrate with low amplitude. Compared to NST, draft force reduction about 7.3-38.3 % and energy reduction about 4.8- 14.4% were found.

Indonesia merupakan negara agraris dan mempunyai lahan pertanian yang sangat luas. Sebagai gambaran luas lahan pertanian di Indoneia sekitar 76.4 juta hektar yang meliputi lahan basah sekitar 8.4 juta hektar dan lahan kering sekitar 68 juta hektar. Adalah wajar bilamana sektor pertanian dijadikan sebagai faktor utama bagi ketahanan nasional. Adanya lahan pertanian yang dilalui oleh alat-alat berat, mesin-mesin pertanian, manusia dan binatang serta adanya konsolidasi pada tanah berakibat terbentuknya lapisan kedap di dalam tanah. Lapisan tanah padat dengan tahanan penetrasi tanah di atas 2 MPa. atau mempunyai densitas tanah di atas 1.8 g/cm3 sulit ditembus oleh akar tanaman, menghambat penetrasi air dan nutrisi serta menghambat sirkulasi udara di dalam tanah. Hal ini dapat menghambat pertumbuhan tanaman serta menurunkan produktivitas hasil tanaman. Untuk membongkar lapisan padat demikian diperlukan draft pembajakan dan konsumsi energi yang besar. Besarnya draft pembajakan ini digunakan untuk mengatasi gesekan antara tanah dengan permukaan tillage tool, mengatasi gesekan antar tanah, mengatasi percepatan tanah bongkaran di depan tillage tool serta karena adanya kelengketan antara tanah dengan tillage tool. Telah terbukti bahwa dengan penggetaran batang bajak, maka kohesi tanah, adhesi antara tanah dengan pisau bajak serta gesekan antara tanah dengan pisau bajak akan menurun sehingga draft pembajakan dan konsumsi energinya akan turun pula. Dalam penilitian ini upaya menurunkan draft pembajakan dan konsumsi energi dilakukan dengan penggetaran batang bajak dengan menggunakan metode self-excited vibration (SEV). Penelitian dilakukan dalam tiga tahap yang meliputi studi analitis, perancangan peralatan dan eksperimen. Untuk eksperimen dibagi menjadi eksperimen membajak tanah tanpa getar, eksperimen membajak tanah dengan penggetaran SEV dan eksperimen membajak dengan penggetaran berenergi rendah pada bajak getar SEV.