Design of a Dual Operated Cassava Chipper

European Mechanical Science 2017, Vol. 1(3): 104-110 Research Paper EUROPEAN MECHANICAL SCIENCE Design of a Dual Operated Cassava Chipper M. G.Yisa1, A. Fadeyibi2*, K.P. Alabi3 1,2,3 Department of Agricultural and Biological Engineering, Kwara State University Malete, P.M.B. 1530, Ilorin, Nigeria Abstract Size reduction of agricultural products is an essential requirement for their processing and transportation. This research designed and fabricated a manually operated and motorised cassava chipping machine, which is adaptable to the local farmers at the cottage level. The design was carried out by empirically computing the threshold force required for cutting the cassava tubers, with a prior knowledge of the length (350 mm) and thickness (1.5 mm) of the cutting blades as influencing indexes. Also, the capacity of the machine was evaluated using six different cutting forces above and below the cutting threshold force (68.99 N). The results show that the cutting force increased exponentially with the length and diameter of the tuber. Also, less force was required to chip cassava tuber with longer length and shorter diameter probably due to the presence of inner and central crack defects, which is capable of forming easy crack initiation points with the slightest blade effort. The size of the electric motor required was a single phase 1 hp (4500 rpm), which is capable of powering the machine to an approximate capacity of 225 kg/h and comparable to the required human effort. The machine was also found effective in chipping cassava tuber to average size of 30 mm. Key words: Chipper, Performance, Design, Cassava, Cottage 1. INTRODUCTION The processing and storage of cassava tuber (Musa esculanta crantz) are required for the extension of the storage life and transportation of the product. The high amount of moisture contained in the cassava tuber [1-2] might be responsible for its deterioration in just few days after harvest. The size reduction of the product is therefore a way of value addition, which is capable of curtailing or minimising the deterioration and the postharvest loss involved, and this can be achieved either by the manual or mechanised chipping techniques. The manual cassava chipping technique is usually time consuming, wasteful and the uniformity of the chips are difficult to achieve. Besides, the increasing versatility of the cassava tubers as an industrial raw material makes manual chipping inadequate for the future chipping need of the cassava processing industry [3]. The mechanised techniques are an improvement on the manual method since the issues of drudgery and none uniformity of the sizes of chips have, to a large extent, been addressed in their designs. There have been a number of attempts in designing appropriate mechanised techniques and systems of reducing the size of the cassava tubers for the purpose of storage, particularly in minimising the huge cost involved in transporting the products to the end-users [4-5]. For instance, the chipping machine used in Malaysia consists of rotating circular plate, which is about 12 mm thick and 1 m in diameter. The circular plates have fixed steel blades which are corrugated at the cutting edge. The machine produces strips of about 6 mm wide and 3-6 mm thick. The blades can be replaced and may be adjusted to produce strips of the required dimensions. The machine also involves two operators one feeding and the other pedaling [6]. In Thailand, petal chipper usually consists of thin circular plate which has been cut and formed to produce cutting element across the whole surface. Chips up to 0.03 m in diameter can be obtained from the Thai chipper [6]. However, not much work has been done in mechanising the cassava tubers in Nigeria even though the country is the second largest producer of the commodity in the world [5,7]. The few cases sighted have been reported by the International Institute of Tropical Agriculture (IITA, Nigeria), which has worked on cassava mechanisation and its various applications [8-9]. The institute has already developed two cassava chipping machines. The first one was powered by a 3.5hp petrol engine and 0.5hp electric motor. It has a capacity of chipping up to 1.2 t/h and fuel consumption rate of 0.8 l/h together with an operating speed of about 260 rpm. The second one was manually operated with a chipping capacity of about 200 kg/h at an operating speed of 60 rpm. However, one major challenge of the motorised system was that it depends on electricity and petrol for its power operation, and these are not readily available in the rural settings where the crops are *Corresponding authour Email: (A. Fadeyibi) mostly grown. The manual type was produced with wood thus limiting its useful life and the production capacity of the machine was quite low compared to the amount of energy expended during its operation. Additionally, the designed a pedal operated cassava chipping machine, which is made from a bicycle attachment connected to a chipping plate, have been described [10]. The chipping late carried the knives which adapted the machine for both slicing and chipping operations. The machine was operated by two operators with one pedaling and the other feeding the crop through the cute. A motorised cassava chipper was used to chip cassava tubers after washing the tubers with a mechanical washer-peeler. The machine consists essentially of an assembly of knives, which rotates clockwise at 375 rpm and are driving by a 0.75 kW electric motor, are mounted on rotating discs, supporting cylinder rotated in a counter clockwise direction at 95 rpm by direct gearing to the rotating discs, and a hopper holding the peeled tubers. The peeled tubers were cut into slices as they pass through the machine, which has an average output of 225 kg/h [6]. Despite the numerous success stories about the already existing cassava chipping machines, their application especially at the small scale is a huge challenge. Besides, the machines are cumbersome and some required high technology and degree of literacy to operate, thus limiting their overall acceptability by the local farmers. There is therefore the need for an alternative design that can accommodate and address these deficiencies to increase productivity of the product. Information on the design and fabrication of the new machine has not been reported in the open literature. Thus, the objective of this study was to design and fabricate a manually operated and motorised cassava chipping machine for increasing the productivity of the chipping process at the cottage level. 2. MATERIALS AND METHODS 2.1 Materials Selection and Specification The materials used in the fabrication of the cassava chipping machine were sourced locally. Galvanized metal sheet of 1 mm thickness together with 10 x 10 x 200 mm mild steel square rod, 45 mm x 45mm angle bar and 25 mm x 25 mm iron rod were used for the construction of the cassava chipping machine. The fabrication of t (...truncated)