Technical analysis and performance test of chopper machines for composting rice straw

Nutrients diminishing become one of the low productivity of rice. Treatment of straw burned and the ashes as fertilizer remove nutrients contained therein. Composted rice straw so that the soil nutrient enhanced by the provision of rice straw compost continuously. Rice straw compost necessary optimal cutting rice straw with a length of 5 cm to 10 cm to accelerate the composting process. Paddy straw chopper is able to produce the chopped length, but the lack of data and the technical feasibility test engine performance so that the necessary research. The experiment was conducted in March-May 2016 in Bumiwangi Village, Ciparay, Bandung West Java and Agriculture Equipment dan Machine Laboratory Faculty of Agriculture Industrial Technology University of Padjadjaran. The method used descriptive analysis, namely making measurements, observations, calculations, and analyses so that the data obtained eligibility machine. Results of analysis techniques, namely the need for locomotion 1.83 HP, unit transmission with 4 belts, shaft diameter 23 mm, the diameter of the pin cylinder enumerator 7.58 and pin diameter motor of 7.40 mm, the size of the spi (9 × 9 × 27) mm, bearing life 6,740.64 h, the deflection order of 1.3 × 10−3 mm and the weld strength 44,660 N and 57,417.07 N meets the technical feasibility than the number of belts. The results of the performance test, the density 128.78 kg/m3, the theoretical capacity 336.20 kg/h, the actual capacity of 304.680 kg/h, the enumeration efficiency of 90.62%, the fuel consumption of 3.19 liters/h, the theoretical power consumption 41.91 HP, enumeration yield 88.302%, the percentage of chopped chunks of 46%, the noise 97.5 dB and vibration of 21.6 mm/s as a whole meets the performance specifications except the cut length, noise and vibration


Introduction
Ciparay is the one of subdistrict in the area south of Bandung regency. The district is located in the major subdistrict in Bandung, namely subdistrict Majalaya and subdistrict Baleendah. Ciparay subdistrict has extensive rice fields, thus become one of the centers of the rice seed industry in Bandung.
Ciparay subdistrict consists of 14 villages and each village has farmers groups combined, especially the Bumiwangi Village has farmers groups comprising 10 farmers groups. Each group of farmers cultivates 30 hectares of rice fields. Each one-hectare rice paddy yields of 6 tons/ha in the rainy season and 5 tons/ha in the dry season. Straw generated each harvest of 1.4 fold of harvest. In the rainy season earned 8.4 tons/ha of straw and dry season 7 tons/ha of straw. The straw potential is not utilized optimally by farmers. Straw is usually burned and the rest of the combustion propagated in paddy fields as fertilizer. In fact, burning of straw resulting emission of carbon dioxide (CO2), energy waste, dead soil organisms and nutrients in the hay on fire so it does not greatly affect the soil organisms and nutrients in the hay on fire so it does not greatly affect the soil when sown as a fertilizer [1].
Farmers also add chemical fertilizers to reduce nutrients in the soil due to chemical elements in chemical fertilizer accumulated in the soil. Less of nutrients are obstructed from crop production and decreasing fertility soil. Composting increases crop productivity and soil fertility of physical, chemical, and biological [2].
One of the compost that can be used farmers is rice straw compost. The rice straw contained some useful nutrients for plants, among others, nitrogen (N) and potassium (K). Compost is organic fertilizer from weathering plant materials or organic waste to the decomposition process and stabilization of organic material by microorganisms under controlled conditions [2].
Composting can be accelerated by addition microorganisms decompose (e.g. Trichoderma harzianum) and reduce the size of compost material, for example using rice straw chopper machine. Size finer must be better because it helps the decomposition, flow of air and accelerates the Trichoderma harzianum growth on the surface of the substrate [2].
Long pieces of rice straw for decomposition is 5-10 cm [1]. Rice straw chopper machines can produce these sizes. Laboratory Equipment and Agricultural Machinery Faculty of Agriculture Industrial Technology, Padjadjaran University has developed a chopper machine to chops rice straw. The chopper machine has been applied in the Bumiwangi Village, Ciparay Subdistrict, Bandung Regency. However, the engine performance and technical specifications are not yet.
Therefore, research is needed regarding the analysis techniques and test the performance of the engine to determine the feasibility of the machine and its ability to produce standard chopper rice straw. Rice straw chopped be used decomposition the composting process.

Methodology
In this study technical analysis and performance test of chopper machine used raw material rice straw from the Bumiwangi Village, Ciparay Subdistrict, Bandung Regency as much as 80 kg for preliminary research and composting in the Bumiwangi Village and 52.48 kg for research in the Laboratory of Metal, Wood and Rattan Faculty of Agriculture Industrial Technology, University of Padjadjaran. Additional materials used be water as much as 24 L and 80 g activator based calculation composting needs.
The tools used in this study, the scales electric meter, stopwatch, tachometer, sound-level meter, vibration meter and a ruler to technical analysis and testing engine performance, while the tool used for composting, i.e, measuring cups, buckets, stir bar, shoe boot, tarpaulins, and rope.
The method used in this research is descriptive analysis method, measurement, observation and calculation of the chopper rice straw and then analysis the data to obtain the data feasibility machine by comparing data calculation results with actual size in addition to analyzing the performance of a chopper straw and comparing the result with quality standards and performance test for chopper.
The stage of the research is divided into two, engineering analysis performed the driving power requirements, analysis of transmission unit, analysis of shaft, analysis of pin, analysis of spi, analysis of bearing, analysis of power and analysis of framework presented in figure 1.  Figure 1. Flow chart technical analysis.

Dimensional measurement of rice straw counting machines
Measure the dimensions of the components of rice straw chopper includes hopper, counter space, the cylinder counter, a component unit of the transmission, the frame and the overall rice straw chopper, then make a technical drawing rice straw chopper using AutoCad software.

Technical analysis and data processing
Engineering analysis performed by measuring a specific component in the straw chopper and the chopper cylinder rotating speed or rotary speed of the motor is required in the calculation parameter analysis techniques.
1. The need for locomotion requires the measurement of the diameter, length and mass, and diameter of the cylindrical counter; diameter and length of counter space. The calculations were performed, among others, tangential force and torque moment so that the theoretical power value obtained during enumeration. 2. Analysis of the shaft requires measurement of the actual diameter and length axis enumerators.
It was calculated torque moment, deflection torsion, theoretical diameter shaft and the countershaft rotational speed-critical. 3. Analysis of the pin requires measurement of the radius of the cylinder chopper pulley and drive motor as well as the actual diameter of the pin. The calculations were performed, among others, the moment of torque, tangential force and diameter of the pin. The calculations were performed, among others, the moment of torque, tangential force, spi shear stress, shear stress allowable, width and length spi. 5. Analysis of bearings needs to measure the pulleys and cylinder enumerators. The calculations were performed, among others, radial loads and bearing life. 6. Analysis of the strength of the framework requires a sustained load measurement framework and dimensions of the frame. The calculations were performed, among others, the moment of inertia, deflection order, permit deflection, and critical load. 7. Analysis of the weld strength requires measurement of the thickness and length of the field of welding. It was calculated weld strength of actual and theoretical.

Benchmarking results against actual data analysis techniques
The results of the analysis of rice straw chopper technique compared with actual data dimensions rice straw chopper and the standard size used farm machinery in order to know the feasibility of construction and durability of rice straw chopper machine during operation. Stages second study, the performance test conducted, among others, the measurement of water content, density rice straw, the theoretical capacity, capacity actual, efficiency of chopping, fuel consumption, power requirements theoretically, the efficiency of specific chopping, the level of noise and vibration levels are presented in figure 2.

Moisture and density measurement rice straw
Measurements were performed before and after the enumeration, rice straw samples taken later testing using water content based on Standard Nasional Indonesia [3] samples were tested in laboratory testing services, Industrial Technology Faculty of Agriculture, University of Padjadjaran. Density measurements made with rice straw to make a tank measuring 1 m × 0.3 m × 0.3 m without cover. Rice straw is inserted into the tank to the brim, then weighed and counted rice straw to five times the density measurement to obtain the average density rice straw [4].

Preparation of rice straw counting machines, measuring and rice straw
Components of rice straw chopper checking so hopefully not interfere with the operation of the machine, in addition to the need for diesel fuel and tarps to accommodate chopped rice straw needs to be prepared. Rice straw chopper expected in decent condition, especially the checking part of the enumeration area. Measuring instruments used for the performance test conducted checking battery and calibration before used. Rice straw to be chopped divided to five repetitions and weight.

Measurement performance test counting machines rice straw
a. Cylinder rotary speed counter and drive motor is measured using a measuring instrument by directing a laser tachometer photo of a tachometer to the counter shaft and the motor that has been marked with black tape. Measurements were made when the machine is turned on without the inclusion of rice straw and rice straw chopping time. b. The noise level of the rice straw chopper was measured using a measuring instrument with a direct microphone sound level meter sound level meters from the position of observer 2 m tall ears to the sound source based International Organization for Standards [5]. Measurements were made when the machine is turned on without the inclusion of rice straw and rice straw chopping time. c. Vibration levels of rice straw chopper using a vibration meter was measured by putting parts of the accelerator meter to the center point of the vibration, the hopper, counter space and order. Measurements were made when the machine is turned on without the inclusion of rice straw and rice straw chopping time. d. Weighing rice straw chopped engine results using electric scales.
c. The theoretical capacity is calculated using equation [6]: d. Actual capacity is calculated using equation [5]: e. Counting efficiency is calculated using the equation: f. Fuel consumption was measured when the machine is turned on in a state without the inclusion of rice straw and time of chopping, calculated using the equation: g. Power consumption can be calculated by using the theoretical fuel consumption data are converted into units of power using the equation: P ap = FC × NK (7) h. The specific energy engine chopping calculated using equation [7]: i. The yield of chopped engine results calculated using equation [7]: j. The percentage of a sample taken from the chopped shredded and sorted by 5-10 cm long chopped then calculated using equation [5]: k. The noise level can be used to determine the length of working hours for working operator, calculated using the equation: l. Obtained from the vibration level measurements are averaged and analyzed the level of safety of the operators work.

Benchmarking performance against standards test results
Results from testing of rice straw chopper performance compared to the International Organisation for Standard (ISO 7580-2010) for the quality and test thrasher fertilizer materials [5], SNI 16-7063-2004 for threshold values for noise [8] and ISO 2372 guidelines for the amount of engine vibration [9], so unknown rice straw chopper performance during operation and provides a solution to address performance deficiencies as well as the level of safety for operators working.
The stages of decomposition of rice straw is presented in figure 3.  Figure 3. Flowchart composting.

Composting rice straw
a. Chopping rice straw by using straw chopper machine. So that got chopped straw with a length of 5-10 cm. b. Setting up a bucket and water to dissolve the activator according to the dosage required (800 g activator + 24 L water for 80 kg of rice rapids). c. Setting up a tarp as a decomposition of rice straw and cover. Size tarp used according to the number of rice straw to be composted d. Incorporating straw layer by layer into the mold compost. e. Sprinkle evenly over the surface activator straw. Each layer stacks with an activator watered sufficiently. f. Tamp each layer haystack. g. To repeat the stages 4-6 until the rice straw exhausted. h. Closing the pile of rice straw using plastic and tied with a rope. i. Fermentation/incubation for one month.

Analysis techniques
Paddy straw chopper is a method of feeding a machine with a throw-in, that is done by removing feed rice straw into the space enumeration. This machine has overall dimensions of 1918.76 mm × 793 mm × 1128.09 mm and using the motor with power 8 HP and a maximum rotational speed 2600 rpm.

a. Power Requirement
The driving force theoretically required of 1.83 HP and actual force with 8 HP shown in table 1.      [10]. The average of the rotational speed of five measurements at 1,185 rpm when no load of hay and 1,108 rpm when there is a load of hay. Based on the technical parameters comparison of theoretical and actual axle are presented in table 3.  In table 3, the diameter of the shaft used feasible and safe to use because it has a larger size than the theoretical diameter. The critical rotating speed of calculation of 5,019 rpm, according to [10] rotational speed must be less than 80% critical rotational speed, which amounted to 4,015 rpm. Three technical parameters of the shaft in table 3 are eligible for the safety and feasibility of the rice straw chopper machine.

d. Analysis of pin
In rice straw chopper, pin cylinder chopper used on pulleys and drive motor. The position of the pin on the cylinder pulleys enumerator seen in figure 6, while the pin diameter size comparison of theoretical and actual is shown in table 4.   In table 4, the theoretical diameter of the pin is smaller than the actual diameter so that when the rice straw chopper operated, pin capable of locking pulley from being shifted or have damaged.

e. Analysis of spi
Spi used rice straw thrasher is spi is a rectangular cross-sectional shape and are prismatic and tapered head for easy retraction. Spi position on the machine invaders rice straw is in the cylinder axis enumerator, which can be seen in figure 7. Based on the calculations, resulting in spi theoretical dimensions shown in table 5.  According to Sularso and Suga (1997) width and length spi have standardized, so if there is a load caused by a large force should be solved by adjusting the length of spi [10]. However, spi that are too long cannot withstand the pressure evenly on the surface. Besides the dimensions spi, spi shear stress must be smaller than the allowable voltage so spi undamaged and able to withstand the cylinder enumerator during enumeration.

f. Analysis of bearings
Rice straw chopper sustained load is an axial load of pulleys, belt tension cylinder and the counter of 258.62 kg. The load is supported by the bearing type P 208 (figure 8) with a nominal capacity of 2,380 kg specific dynamic [10]. Based on calculations, the theoretical bearings life values obtained are presented in table 6.  According to Sularso and Suga (1997), the nominal bearings life must be greater than the nominal life permitted for agricultural machinery, in the amount of 2,000 to 4,000 hours [10]. Thus, bearings used hay thrasher feasible and safe to use.

g. Analysis strength of the framework
The machine frame using iron U with a size of 44 mm × 79 mm × 44 mm and 7 mm thick. Frame straw chopper can be seen in figure 9. Frame counter space bears the weight of the cylinder counter, bearings, pulleys and shafts of 574.47 N and order hopper bear the weight of 102.96976 N. Imposition cause horizontal and vertical deflection on the frame, Calculation deflection caused and allowable deflection can be seen in table 7.   The results of the calculations in table 7 show that the framework is able to bear the weight and experienced a smaller deflection of the deflection critical. Thus, it can be concluded that the framework of rice straw chopper has a strong foundation to withstand the engine components on it during enumeration, besides the ergonomic dimensional framework allows an operator in the introduction of rice straw.

h. Analysis strength of joint
Type of weld joints that are used are welding angle (filled) that can withstand the pressure, pull, shear, torsion and bending (figure 10a), but it is also used intersection welding (butt) that can withstand the pressure and pull (figure 10b). Welding treatment is applied aims to connect the metal framework relating to the composition. Weld strength is taken into account in order to withstand the load of the engine components, the weld strength calculation results are presented in table 8.   Large density shows rice straw requires a large storage space. The greater the density, it is expected that large-capacity machines. Density also is used as a baseline in the design and mechanism of action of agricultural machinery.

b. Water content
Treatment of rice straw into compost is withering for ± one day to obtain the optimum moisture content approaching 60%. Based on the measurement of water content with the test method SNI 01-2891-1992, the water content of rice straw before chopped of 67.54% and 69.74% after chopped. The measurement results exceeded the optimal standard for composting material, due to experiencing respiratory straw hay resulted in increased water content. Therefore, the environmental condition testing, hay storage and testing time should be considered to obtain the optimum moisture content. However, rice straw can still be used as composting material.

e. Efficiency of chopping
Rice straw chopper based on calculations have chopped high efficiency due to comparison with a theoretical capacity of the actual capacity of 90.62%. Chopped efficiency of this engine has been qualified minimum efficiency of the engine, is by 80%.

f. Fuel consumption
Measurement of engine fuel in the motor is done manually, so we get the result of calculation of 2.52 liters/hour when there is no income and amounted to 3.19 liters/hour when the income of rice straw. SNI 7580-2010 based on the classification of motor fuels are included in Class B and corresponds with the recommended requirements for engine fuel consumption, which is between 2-3 liters/hour.

g. Theoretical power consumption
The theoretical power consumption of rice straw chopper without income amounted to 33.10 HP straw and rice straw with revenues amounting to 41.91 HP. If the available power of 8 HP motor fuel compared with the theoretical power motor fuel obtained thermal efficiency of 19.09% and 24.17%.