Design and Working Performance of Sugar Cane Stubble Shaver Powered by Four Wheel Tractor

Abstract

Cutting of sugar cane stubbles is an important activity in ratoon sugar cane production system. Stubble shaver powered by four wheel tractor, has been used in several sugar plantation in Indonesia. However, there were some problems encountered the application such as high power consumption; excessive blade tip wear; and low cutting quality of the stalks. The objectives of this research were: 1) to design a stubble shaver powered by PTO of four wheel tractor and 2) to analyze the influences of blade tip design, forward speed, rotation speed and tilt angle of the rotary cutting unit on cutting power and cutting quality. A sugar cane stubble shaver consisting of a rotary cutting unit with 8 blades rotated by tractor PTO, was designed and constructed. The prototype was tested to measure its working performance. The test was conducted using two types of blade tip design, on two levels of working speed (0.3 and 0.5 m s-1), two levels of rotational speed (500 and 850 rpm), and two levels of blade tilt angle (45o and 60o). The test result showed that the blade tip design with increased tip radius provided a lower working torque than the conventional blade tip design with constant tip radius. The lowest working torque was provided by operating condition of working speed of 0.5 m s-1, blade rotating speed of 850 rpm and tilt angle of 60o. The average working torque on that condition was 22.46 Nm. However, 0.3 m s-1 working speed, at 850 rpm rotating speed and 45o tilt angle provided a better stubble cutting quality than the other working condition.

Pengeprasan merupakan salah satu kegiatan penting dalam budidaya tanaman tebu ratoon. Pengeprasan tebu dilakukan dapat menghemat biaya bibit, biaya pengolahan tanah dan penanaman ulang untuk menghasilkan tanaman baru. Umumnya pengeprasan hanya dilakukan sampai ratoon ketiga, bahkan sering kali dibongkar setelah ratoon pertama jika produktivitasnya menurun. Pengeprasan cara manual dengan cangkul membutuhkan biaya yang besar, waktu yang lama dan rendahnya kualitas keprasan. Di sisi lain alat kepras stubble shaver yang digunakan beberapa pabrik gula di Indonesia memiliki beberapa kelemahan antara lain mata pisau yang cepat tumpul sehingga hasil potongan tunggul banyak yang pecah dan menyebabkan produktivitasnya menjadi rendah. Salah satu untuk meningkatkan produktivitas tebu keprasan adalah mendesain suatu prototipe alat kepras tunggul tebu tipe rotari menggunakan pisau berputar yang mampu bekerja pada kedalaman tanah 5-10 cm dengan tenaga PTO traktor roda empat. Tujuan penelitian untuk : 1) mendesain dan membuat prototipe mesin kepras tunggul tebu tipe rotari (menggunakan pisau berputar) yang mampu bekerja pada kedalaman tanah 5-10 cm yang ditarik traktor roda 4 dengan tenaga putar poros PTO, 2) menganalisis pengaruh bentuk mata pisau, kecepatan maju mesin, kecepatan putaran pisau, dan sudut kemiringan mata pisau terhadap kualitas hasil pemotongan dan tenaga putarnya.