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1、Adoption of a Stripper Header for a Thai-made Rice Combine HarvesterR. Kalsirisilp; G. SinghAgricultural & Aquatic Systems and Engineering Program, School of Environment, Resources and Development, Asian Institute of Technology,Bangkok, Thailand; e-mail of corresponding author: singhgait.ac.thA Thai
2、-made 108 kW rice combine harvester was modied by replacing the cutter bar system with a stripperheader. The power requirement of the modied machine was measured at no load and during eld operation.The stripper header system consisted of a 3 m wide stripping rotor, a metal hood and an adjustable nos
3、e. Theouter diameter of the stripping rotor was 450 mm. The stripping rotor consisted of eight rubber blades xed onan octagonal drum with each blade having 71 teeth. The work rate and harvesting losses were measured toexamine the eld performance of the modied machine.Results obtained from the test s
4、howed that the power requirement for the whole machine during eldoperation at 1600 min1 was 58 kW. The threshing, traction and stripper header units consumed 11)4, 22)8 and16)9 kW, respectively and the power transmission loss was 6)9 kW. For standing crop, the average eld capacityof the machine was
5、0)66 ha h1 with a corresponding eld e$ciency of 74%. In a lodged crop condition, theaverage eld capacity was found to be 0)3 ha h1 with a corresponding eld e$ciency of 72%. The total grainloss of the machine was 4% of grain yield in the standing crop condition and 5)6% in the lodged crop condition.N
6、o major mechanical or operational problems were observed during eld operations.( 2001 Silsoe Research Institute1. IntroductionIn 1987, the rst Thai-made rice combine harvesterwas developed by adopting some of the design principlesfrom combine harvester models of western countries,modifying some part
7、s to better suit local conditions andincorporating the International Rice Research Institute(IRRI) designed axial-#ow thresher, which is commonlyused in Thailand as a stationary thresher. In 1989, theThai-made rice combine harvesters, became acceptableto farmers and commercial production was started
8、. In1993,performanceevaluationof the Thai-maderice com-bine harvesters, powered by a 108 kW engine and con-sisting of a 3 m wide cutter bar, showed that the eldcapacity of the machine varied from 0)10 to 0)71 ha h1,with an average of 0)40 ha h1. The total grain lossesvaried from 1)30 to 10)8% of gra
9、in yield, with an averageof 4)8%. The major problems were found in the under-carriage unit of the machine, particularly in the sprocketand chain transmission parts (Kalsirisilp & Singh, 1999).E!orts have been made to improve the durability andeld capacity, and reduce harvesting losses of the ma-chin
10、e by replacing the direct drive system with a hydros-tatic drive system and the wooden shoe tracks by metaltracks. In 1998, there were eight rice combine harvestermanufacturersin Thailand together producing about 400units annually and selling them at US$ 40,000 per unit. Itwas estimated that about 3
11、000 locally made rice combineharvesters were being used during 1998 as given inTable 1. In 1999, the average eld capacity of the108 kW, 3 m cutter bar harvester was found to be0)52 ha h1 with a total harvesting loss of 3% of grainyield (Kalsirisilp, 2000).Power requirement evaluations on Thai-made r
12、icecombine harvester revealed that the power consumed bythe threshing unit was approximately 52% of the totaloperating power during eld operations at the feed rateof about 100 kg min1 (Kalsirisilp, 2000). The threshingdrum was frequently blocked, particularly in the lodgedcrop condition. In order to
13、 overcome this problem, ThaiTable 1Number of Thai-made rice combine harvesters in useYearCombine harvester, unit19952800199628001997280019983000Source: Krishnasreni and Thongsawatwong (1998).manufacturers attempted to use engine power as highas possible to improve machine performance withoutincreasi
14、ng the cost signicantly.Stripper harvesting involves stripping the grain fromthe crop without harvesting the straw. In rice harvesting,this methodis advantageousas the amountof straw to behandled by the machine can be reduced signicantly.Consequently, the eld capacity can be increased and thepower r
15、equirement reduced (Tado et al., 1998).Klinner et al. (1987) reported that the power consump-tion of a stripping header for a conventional combineharvester varied between 0)7 and 0)8 kW m1 at no loadcondition and for working conditions the same wasbetween 2)0 and 2)9 kW m1 in barley at a forward spe
16、edof 4 km h1 and between 2)8 and 3)9 kW m1 at6)0 km h1 for wheat. The power requirement of thestripping header in standing rice varied from 1)0 to4)5 kW m1 of harvesting width with a forward speed of7)5 km h1 (Metianu et al., 1991).A self-propelled stripper combine harvester mountedon a track chassi
17、s was developed at Northeast Agricul-tural University in China. The stripper harvester wascomposed of a drum-type thresher for threshing thestanding rice, a pneumatic conveyor system for providingair suction to reduce harvest losses, and a pick-up systemfor harvesting the lodged crop (Jiang et al.,
18、1992).A transverse rotor was used in the design of the SilsoeResearch Institute (SRI) stripper header in which strip-ping of the grain takes place along the length of the rotorarranged transversely to the direction of travel (Tadoet al., 1998). The outer diameter of the rotor was 450 mm.The stripper
19、 rotor was tted with eight rows of #exibleteeth. The stripping elements were made of mouldedpolyurethane that was essentially &V shaped but witha 20 mm diameter circular recess at the base. The rststripper system was evaluated in the eld in the form ofa 3)6 m wide header for attachment to a conventi
20、onalcombine harvester (Metianu et al., 1991). In 1989, a col-laborative project funded by the Overseas DevelopmentAdministration in the UK was set up between TheInternational Rice Research Institute (IRRI) and SRI inorder to evaluate the feasibility of the stripping rotor asthe basis of pedestrian-c
21、ontrolled harvesting machinesuitable for the small rice farms of Asia.The International Rice Research Institute, in collabo-rationwith SRI developeda strippersystem. Thestrippergatherer (SG 800) was built and eld tested during the1992 dry season in the Philippines. This machine hada harvesting width
22、 of 800 mm and was propelled bya 6)7 kW gasoline engine which also drove the strippingrotor. Gathering losses were less than 1% of yield instanding semi-dwarf rice varieties (Douthwaite et al.,1992). Vechasit (1995) found that the unstripped loss ofthe SG 800 was less than 1% in Thailand rice condit
23、ions.A lightweight stripper model (LS 600) was developedby the Philippine Rice Research Institute (Philrice) in1997 to suit the local eld conditions. The total weightwas 190 kg compared to 250 kg of the SG 800 design.The harvestingwidth was 600 mm and it was powered bya 4)56 kW gasoline engine. The
24、eld capacity was0)7 ha day1 with shattering losses of about 2% (Aldas& Bautista, 1998). Trimo (1996) evaluated the perfor-mance of an Indonesian-made rice stripper harvester.The machinewas powered by a 6)3 kW diesel engine. Theaverage eld capacity was 0)08 ha h1 with a harvestingloss of about 2)1%.T
25、he Shelbourne Reynolds stripper header was investi-gated to determine its potential use for grain harvestingin many countries with di!erent conditions. In Italy,research at Milan showed that the minimum header lossin rice harvesting was 0)4% of the yield for Ringo andEuropa varieties. For Panda vari
26、ety, the lowest loss was1)3% of the yield. Panda variety seemed to be sensitive tothe header setting resulting in higher header losses(Hobson & Metianu, 1989). The stripper header tted onaThai-maderice combineharvester had not beenstudiedyet. This study, therefore, was intended to investigateits per
27、formance in eld conditions and the results arepresented in this paper.2. Design and development of stripper headerThelocallymade ricecombineharvestermanufacturedby Kasetpatana Manufacturing Company, Phitsanulokprovince, northern Thailand, was selected for this study,as it was found to be the most po
28、pular model in thecountry. This combine harvester is a self-propelled ma-chine equipped with a cutter bar mechanism havinga cutting width of 3 m and a 108 kW diesel engine as theprime mover (Fig. 1). Power was transmitted by V-beltsfrom the engine shaft to other components of the ma-chine, except fo
29、r traction and header height controlwhichused ahydrostaticpowertransmission system.Thepower from the traction shaft was further extended totwo independent hydraulic pumps (gear type) via doublechain couplings. Two low-speed, high-torque, radial pis-ton motors were selected to drive the sprocket whee
30、l ofFig. 1. Thai-made rice combine harvester equipped with cutterbar mechanismFig. 2. Mechanical transmission system of the stripping rotorTable 2Speci5cations of the Thai-made combine harvester with stripper headerStripping width, mm3000Stripping rotor diameter, mm540Number of stripper rows8Number
31、of teeth per row71Transmission systemHydraulicRange of speed, min1600800Nose adjustment, mm200Power source, kW108 (reconditioned Isuzu diesel engine)Number of operators2Number of unskilled labourers3Forward speed, km h137the machine. The working speed of the machine wasvaried from 3 to 6 km h1 depen
32、ding on the crop andeld conditions. An axial #ow thresher was used asa threshing unit and the mechanism consisted of a peg-tooth cylinder which rotated inside a concave doublesection. The locally made rice combine harvester equip-ped with a cutter bar cut almost the whole rice plantwhereas the strip
33、per header stripped only grains, leavingmost of the straw in the eld.Modications of the rice combine harvester for ttinga stripper header were carried out by removing the pickup reel and cutter bar units of the machine. Three rubberpaddles (5 cm by 50 cm) were fabricated and attached tothe centre of
34、 the front auger which enabled it to conveystripped material easily from both sides of the table augerthrough the centre of the feeder conveyor. The feederconveyor was attached with rectangular rubber pieces(5 cm by 35 cm) along the chain conveyor in order toconvey the stripped material into the thr
35、eshing unit. Thepower from the engine was transmitted to the strippingrotor through a combination of pulleys and V-belts(Fig. 2) or through a combination of hydraulic andmechanical transmission system.2.1. he prototype stripper headerA stripper header was fabricated and mounted ona Thai-made rice co
36、mbine harvester and the performanceof the header was evaluated. The stripper header mainlyconsisted of the stripping rotor, ba%e, hood, nose, frontauger and the hydraulic motor and pump which were usedto drive the stripping rotor. Design parameters of the strip-ping rotor were based on the stripper
37、rotor system de-velopedintheUK bySilsoeResearch Institute. A summaryof the specications of the stripper header is presented inTable 2 and its main components are explained below.The outer diameter of the stripper rotor was 450 mm.Along the direction of rotor axis, a stripper rotor wasinstalled with
38、eight rows of teeth, each row consisting of71 teeth. The rotation of the stripping rotor was in thereverse direction in relation to the ground wheel rotation(Fig. 3). The stripping rotor speed was between 600 and800 min1 resulting in a peripheral speed of 1722)7 ms1. They were essentially &V shaped
39、but with a 20 mmcircular recess at the base (Fig. 4). The height of thestrippingrotor could be adjusted from the operatorsseatusing hydraulic means.Fig. 3. Schematic diagram of the stripping rotorFig. 4. Proxle of stripping elements (all dimensions are in mm)The prototype stripper header was tted wi
40、th localindustrial rubber teeth. This was because the importedpolyurethane was expensive and di$cult to obtain lo-cally. The cost of local rubber teeth was US$ 125 for a setwhereas a set of polyurethane stripper elements for thestripper harvester cost about US$ 1000 and needed to beimported from the
41、 UK. The performance of the localrubber teeth was found to be satisfactory during eldtesting in standing and lodged crop conditions.The ba%e positioned behind the stripping rotorprevented crop re-entry into the rotor. It was made of3 mm thick sheet metal.The metal hood, positioned in front of and ab
42、ove thestripping rotor, de#ected the harvested material into thefront auger. The wall of the hood was made of 3 mmthick sheet metal.The nose determined the position of the crop duringharvesting. The position of the nose could be adjusted bysliding it up or down the hood. The nose was held inposition
43、 by a pair of wing nuts, making adjustment easy.The nose height could be adjusted up to a range of200 mm.The use of readily available materials andtheuncomplicated design enabled the stripper header to bemanufactured locally.3. Testing and evaluation methodology3.1. Power requirementThe instrumentat
44、ion employed for measurementsof power requirement included a torque transducer, adynamic strain amplier, a portable tape recorder andan autonomous data acquisition unit. The torquetransducer was connected to the strain amplier whichperformed the signal conditioning. The conditionedsignal was recorde
45、d using a tape recorder. The speedof the engine shaft was measured with the help of aproximity switch and tachometer indicator. Powerwas supplied from the 12 V battery of the combineharvester.The power demand of the engine shaft was the amountof power required to operate all mechanisms of the riceco
46、mbine harvester, i.e., threshing, traction and headersystems. The power required for the threshing unit in-cluded the power requirement of the threshing cylinder,oscillating screen, auger conveyor and the blower unit.The power requirement of the header unit comprised thepower required for the front
47、auger and the strippingrotor. The power requirement of the whole machine,threshing and header units was calculated using thefollowing formula (Liljedahl et al., 1983):P2nn/60,000(1)where P is the power requirement in kW; n is the speedof shaft in min1; and is the torque transmittedin N m.3.2. Estima
48、tion of ,eld capacityThe e!ective eld capacity was determined by measur-ing all the time elements involved while harvesting. Thetotal time was categorized into productive and non-pro-ductive time. The productive time is the actual time usedfor harvesting the grains while the non-productive timeconsi
49、sted of the turning time, repair and adjustment timeand other time losses. The area covered divided by thetotal time gave the e!ective eld capacity. The elde$ciency was determined by the ratio of productive timeto the total time.Fig. 5. No load power requirement of conventional combine withstripper
50、header:, threshing system (1);, hydraulic system fortraction (2);, stripper header (3);, sum of (1), (2), (3);, engine operating power; a, power loss3.3. Estimation of harvesting lossThe grain losses were determined based on the grainyield recorded during harvesting operation. Shatteringloss refers
51、to the ears and grains fallen on the groundduring harvesting. To determine the shattering loss,framesmade of metal 1 m long by 0)5 m wide were placedbetween the rows of plants before harvesting the eld.After harvesting, all the grains found on the frames arecollected and weighed.Blower and screen lo
52、sses were measured from thestraw discharged by the machine. The discharged strawwas collected for a machine coverage of 3 m. This wasdoneby using anylonnet carriedby two personswalkingbehind the machine. The collected grain was cleaned byhand to separate the grains that were blown over.Unstripped lo
53、ss refers to the rice grain that remainedon standing straw after eld harvesting.Total machine loss refers to the summation of shatter-ing loss, blower and screen losses and unstripped loss.The quality of paddy was determined in terms of percent purity, which was determined by taking three sam-ples o
54、f grain, each weighing 200 g. These samples weretakenat successivetimeintervals dependingonthe sizeofthe eld. Foreign matter was manually sorted andweighed to ascertain per cent purity.3.4. Estimation of fuel consumptionBefore starting the test, the engines fuel tank wascompletely lled. The quantity
55、 of fuel required to ll thetank after harvesting the test eld was measured usinga 1 l graduated cylinder. Thus, the fuel consumed duringthe test was determined.FA(2)where F is the fuel consumption in l ha1; A is the areaharvested in ha; and is the quantity of fuel required toll the tank after harves
56、ting the test eld in l.3.5. Estimation of harvesting costThe cost of harvesting with the stripper header wascalculated by considering the xed and variable costs.The following formula was used for calculating annualcost of the machine. The harvesting cost per hour fordi!erent annual uses was calculat
57、ed and the break-evenarea for the machine was determined (Hunt, 1995).ACFC#Rm#HF#O#a#o(3)where ACis the annual machine cost in Baht; FCisthe total annual xed cost in Baht; Rmis the annualrepair and maintenance cost in Baht; H is the annualuse in h; F is the fuel cost in Baht h1; O is the lubri-cant
58、cost in Baht h1; ais the cost of labour forbagging in Baht h1; and ois the operator cost inBaht h1.4. Results and discussion4.1. Power requirement under no load conditionThe average no load power requirement of themachine increased gradually as the engine speed wasincreased from 1200 to 1600 min1 (F
59、ig. 5). The powerrequirement of the machine at a design speed of1600 min1 was 42)9 kW at the engine shaft. The thresh-ing unit consumed 9)0 kW (21% of total no load power).The stripper header and hydraulic system for tractionconsumed 15)5 kW (36% of total no load power) each.The power transmission l
60、oss was calculated to be 2)9 kW(7% of total no load power). The power consumed by theheader unit increased as the engine speed was increasedbecause of the increase in windage energy. The strippingrotor also functioned as a blower and therefore more airwas displaced per unit time at higher velocity w
61、hen therotational speed of the stripping rotor was increased.Due to higher air movement inside the metal hood, moreturbulence was created in the air stream which againincreased resistance against the stripping rotor move-ment. As a combined e!ect of these two factors, the noload power requirement of
62、 the stripper header increasedwith the engine speed. It was also observed that the noload power requirement of the hydraulic system fortraction unit rapidly increased as the engine speed wasincreased from 1500 to 1600 min1.Table 3Crop and soil conditions of the 5elds during machine testsParameterFie
63、ld no.1234Crop conditionRice varietySuphan-60Suphan-60Suphan-60Suphan-60Average plant height, mm9501000980890No. of days over ripe, day#4#4#3#2Grain moisture content, % w.b.22181920Straw moisture content, %w.b.72746268Average crop inclination, deg151035Average yield, t ha16)06)03)84)8Soil conditionS
64、oil typeClayClayClayClaySoil moisture content, %w.b.30283126Machine conditionForward speed, km h155)45)56)0Rotor speed, min1600600600600Rotor height above ground, mm130130130130Harvesting width, m2)82)82)62)8Table 4Average power requirement of conventional combine harvester with stripper header duri
65、ng 5eld operation in Phetchaburi provinceComponentsPower requirement, kW1600 min11700 min1Test 1Test 2Test 3Test 4Engine57)757)658)961)9Threshing11)6 (20%)*11)8 (20%)10)9 (18%)12)1 (20%)Header17)0 (29%)17)0 (30%)16)6 (28%)18)1 (29%)Traction22)8 (40%)22)8 (40%)22)8 (39%)23)5 (38%)Transmission loss6)3
66、 (11%)6)0 (10%)8)6 (15%)8)2 (13%)*Figures in parentheses represent percentage of total operating power.4.2. Power requirement during ,eld operationFields seeded by broadcasting &Suphan-60 varietyof rice with a grain yield of about 5 t ha1 wereused in the tests. Engine speeds of 15001700 rpm, whichwe
67、re recommended by thecombinemanufacturer,were used during eld operation. The crop conditionsand soil properties in the test eld are shown inTable 3.The average power requirement for the whole machineduring eld operation at 1600 rpm was 58 kW. Thethreshing, traction and stripper header units consumed
68、11)4, 22)8 and 16)9 kW, respectively and the power trans-mission loss was about 6)9 kW (12% of total operatingpower). The average power requirement for the wholemachineduring eld operation at 1700 rpm was 61)9 kW.The threshing, traction and stripper header units con-sumed 12)1, 23)5 and 18)1 kW, res
69、pectively (Table 4). Thepower transmission loss was about 8)2 kW (13% of totaloperating power). During eld operation, the power con-sumed by the traction unit was found to be the highest,whereas the power requirement of the threshing unit wasfound to be the lowest. The machine, with stripperheader,
70、was operated on level land and the soil moisturecontent during eld operation varied from 26 to 31% wetbasis (w.b). The high power consumption of the tractionunit was due to heavy weight of the machine and lowe$ciencyof the hydrostatictransmissionsystem. The lowpower requirement of the threshing unit
71、 was due to thefact that the straw intake of the stripperheader was muchless than that of a conventional combine with cutter barheader.The mechanical losses at no load condition and duringeld operation constituted a high proportion of totalTable 5Comparison of average power requirement of convention
72、al combine harvester with stripper header under no load and during 5eldoperationComponentsPower requirement, kWNo loadField harvestingEngine42)959Threshing9)0 (21%)*11)6 (20%)Header15)5 (36%)17)2 (29%)Traction15)5 (36%)23)0 (39%)Power transmission loss2)9 (7%)7)2 (12%)*Figures in parentheses represe
73、nt percentage of total operating power.Fig. 6. Conventional combine harvester with stripper header inoperationpower required. This indicated that attention should begiven to both design and assembly of the combine. Com-parison of the average power requirement of the machineand its main components un
74、der no load condition andduring eld harvesting is given in Table 5.4.3. Field performance4.3.1. General observation on the machine operationThe machine required three labourers to collect thegrain output into sacks. As soon as a sack became full, itwas removed, placed on the ground and replaced with
75、 anempty one. The combine with stripper header in opera-tion is shown in Fig. 6. The machine could be operatedeasily since only a few adjustments were needed duringeld operation. The operator had to control the height ofthe stripping rotor to suit the crop condition. The noseheight of the machine wa
76、s adjusted prior to conductingthe experiment.4.3.2. Field capacityFor a standing crop, the e!ective eld capacity was0)66 ha h1 and the corresponding eld e$ciency wasfound to be 74% (Table 6). However, the e!ective eldcapacity of the stripper header was 0)3 ha h1 in thelodged crop condition and the c
77、orresponding eld e$-ciencywas found to be 72%. The averageeldcapacityofthe machine in the standing crop condition was greaterthan that in the lodged crop condition due to higherworking speed during eld operation. It was observedthat the increase in grain throughput at higher forwardspeed of the stri
78、pper header caused overloading at thefront auger. It is proposed that the chain conveyor bereplacedwiththe doubleauger conveyor to eliminatethisproblem and increase its capacity. The eld capacity ofthe conventional combine rice harvester equipped witha 108 kW engine and a 3 m cutter bar in the stand
79、ingcrop was 0)52 ha h1. This shows that the eld perfor-mance of the stripper header combine harvester washigher than that of the original cutter bar combine har-vester.This was due to highworking speed of the strippercombine during eld operation. The average workingspeed of the stripper combine in t
80、he standing crop was5)5 kmh1 compared to 3)4 kmh1 for the cutter barcombine harvester.4.3.3. Harvesting lossThetotal grain loss of the machinein the standingcropconditionwasabout 4%of grain yield. For a lodgedcropthe total grain loss was 5)6%. The unstripped loss of themachine varied from 0)2 to 2)4
81、% with an average of1)5%. The machine was found to be very e$cient instripping the grains from the crops. Blower and screenlosses varied from 0)2 to 0)3% with an average of 0)22%.These losses were found to be the lowest during eldoperations. As only the grains were stripped at the strip-per header,
82、the straw discharged from the threshingcylinder at the rear of the machine was very low resultingTable 6Field performance of 108 kW, 3 m wide combine harvester with stripper headerParameterField no.123456No. of days over ripe, day#4#4#3#2#10#10Grain moisture content, %w.b.221819201618Average crop in
83、clination angle, deg151035LodgedLodgedAverage plant height, mm9501000980890840980Soil moisture content, %w.b.302831262929Cone index, kPa410441400462420420Straw moisture content, %w.b.727462685865Fuel consumption, l ha1161615)815)81817Forward speed, km h15)05)45)56)02)52)5Average grain yield, t ha166
84、3)85)25)03)4Area harvested, ha0)20)180)130)360)160)48Field size (widthlength), m405040453438527032506080Unstripped loss, %1)61)62)22)40)70)2Shattering loss, %2)01)831)831)634)635)3Blower and screen loss, %0)30)330)180)160)160)18Total grain loss, %3)93)764)214)195)495)68Field capacity, ha h10)750)720
85、)560)620)270)3Field capacity, t h14)504)322)133)601)351)02Field e$ciency, %727371786974Purity of grain, %859293908486Cracked grain, %1)51)71)71)51)61)4Note: Rice variety: SP-60 (Suphan-60), soil type: clay, losses: given as % of grain yield.Fig. 7. Break-even area for combine harvester with stripper
86、header:, manual harvesting;, stripper header combineharvester; b, break-even areain low blower and screen losses. The shattering loss wasfound to be highest in the lodged crop condition. Thiswas mainly due to low working speed during eldoperation as well as low grain yield. The nding is inconformity
87、 with Jiang et al. (1992) who reported thatthe front-end losses on the stripper header remainedaproblem,especiallyinlodgedcropconditions.Likewise, Tado et al. (1998) also reported that the strip-per did not perform well in thin, low yielding andimmature crops. The reduction of losses under certaincr
88、op conditions is, therefore, an area which needs furtherresearch.4.3.4. Quality of grainThe quality of grain in terms of per cent purity andper cent crack was observed from the collected samplesof output of the stripper header and the results obtainedare presented in Table 6. The percentage of grain
89、 purityvaried from 84 to 93% with an average of 88%. Thecrack grain varied from 1)4 to 1)7% with an average of1)6%.4.3.5. Fuel consumptionThe fuel consumption in standing crop condition wasabout 16 lha1. For lodged crop condition, the fuelconsumption was 18 l ha1.4.3.6. Costs of harvestingBased on t
90、he average eld capacity of the stripperheaderof 0)66 ha h1and assumingannualuseof 660 ha,the total cost of harvesting was calculated as Baht1583 ha1. The cost of using the stripper header is givenin Table 7. The break-evenanalysiswas done consideringthe actual cost of operation of the machine and th
91、eprevailing cost of manual harvesting as Baht 3860 ha1.The break-even area for the stripper header was found tobe 68hayr1 or 103 h yr1 (Fig. 7).Table 7Cost analysis for the 108 kW, 3 m combine harvester with stripper headerParticularAmountCombine harvester cost, Baht800,000Header cost, Baht50,000Ann
92、ual use, h1000Assumed useful life of the header, yr5Salvage value of header, Baht5000Salvage value of combine harvester, Baht80,000Annual ,xed costs for combine harvesterDepreciation (8 yr, useful life), Baht yr190,000Interest (16%), Baht yr170,400Fixed cost for harvester160,000Annual ,xed costs for
93、 headerDepreciation (5 yr, useful life), Baht yr19000Interest (16%), Baht yr14400Fixed cost for header, Baht yr113,400Total annual 5xed cost for machine, Baht yr21173,800ariable costs per hourFuel cost of stripper harvester at 11 l h1 and 14 Baht l1, Baht h1154Lubricant cost (at 30% of fuel cost), B
94、aht h146Labour costTwo operators, Baht h1140Three unskilled labourers, Baht h175Repair and maintenance (header), Baht h18Repair and maintenance (harvester), Baht h1200Total variable cost, Baht h21623Total machine cost, Baht21797Average eld capacity of the machine, ha h10)66Variable cost of operation
95、, Baht ha1944Operational cost of the machine, Baht ha11208Average cost of labour for clearing the headlands (15 man-h ha1 at 25 Baht/man-h), Baht ha1375Total cost of the machine operation and manual 5eldwork, Baht ha211583Note: Exchange rate 1 US$40 Baht.Table 8Proposed changes in the design of a co
96、mbine harvester equipped with stripper headerItemPresent designProposed designThreshing cylinderTypeAxial #owConventionalDiameter, mm600300Harvesting width, m3)03)04)0Dimensions of track81024708102800(widthlength), mmType of trackWooden or metalMetal cleat trackFeeder conveyorChain conveyorDouble au
97、ger conveyor5. Proposed modi5cationsReplacing the axial #ow thresher with a conventionalconcave thresher of a smaller size and removing theoscillating screen would reduce both the weight and thepower requirement of the machine. This would allowthe elevator into the thresher to be placed at the centr
98、e ofthe machine rather than o!-set as it is now. This wouldalso reduce blocking of the auger. Omitting the screenwould simplify the construction and reduce the vibrationof the machine. This would result in higher e$ciencyin grain harvesting. As a large amount of grains wasstripped and conveyed to th
99、e threshing unit, the chainconveyor should be replaced with a double augerconveyor to increase its capacity (Table 8).6. Conclusions and recommendations(1) The power requirement of the machine at an enginespeed of 1600 min1 was 58 kW during eld opera-tion. The power consumed by the thresher, headera
100、nd hydraulic system for traction units during eldoperation was 11)4, 16)9 and 22)8 kW, respectively oftotal operating power. The power transmission losswas 6)9 kW (12% of total operating power).(2) For standing crop condition, the e!ective eldcapacity was 0)66 ha h1 and the corresponding elde$ciency
101、 was about 74%. The e!ective eld capacityof the machine was 0)3 ha h1 in the lodged cropcondition and the corresponding eld e$ciency was72%. The harvesting loss of the machine was 4% ofgrain yield in the standing crop condition and 5)6%in the lodged crop condition. The average percentageof grain pur
102、ity was 88% and the average percentageof crack grain was 1)6%. The break-even area for thecombine harvester with stripper header was found tobe 70 ha yr1.(3) The fuel consumption in standing crop condition was16 and 18 l ha1 in the lodged crop condition.(4) The rubber teeth used as the stripping ele
103、ments werefound to be a good substitute for the original poly-urethane teeth. The rubber teeth were easy to manufac-ture locally and were cheaper than the original teeth.(5) The knowledge and technology used for fabricationof the stripper header was simple. All the materialsused were available in th
104、e local market. However,some modications of the cutter bar harvester wereneeded to mount the stripper header on it. The modi-cation of the conventional combine harvester intothe stripper header should be considered by the com-bine manufacturers.ReferencesAldas R E; Bautista E U (1998). Developments
105、in stripperharvesting in the Philippines. Proceedings of the Interna-tionalAgriculturalEngineeringConference,Vol.1,pp 167178. Bangkok, ThailandDouthwaite B; Tado C J M; Quick G R; Singh G (1992). Fieldperformance of the stripper gatherer rice harvester. Proceed-ings of the International Agricultural
106、 Engineering Confer-ence, Vol. 1, pp 335346. Bangkok, ThailandHobson R N; Metianu A A (1989). Preliminary trials witha 1)5 m wide stripper harvesting rig in Italian rice. DivisionNote DN 1519, AFRC Institute of Engineering Research,SilsoeHunt D (1995). Farm Power and Machinery Management (9thEdn). I
107、owa State University Press, Ames, IA, USAJiang Yi-Yuan; Du Cheng-Hai; Xu Jia-Mei (1992). Study on theperformance of stripping rotor with air suction. Proceedingsof the International Conference on Agricultural Engineering,Vol. 1, pp 176179. Beijing, ChinaKalsirisilp R; Singh G (1999). Performance eva
108、luation ofa Thai-made rice combine harvester. Agricultural Mechaniz-ation in Asia, Africa and Latin America (AMA), 30(4), 6369KalsirisilpR (2000). Evaluation and improvementof Thai-maderice combine harvester DEng Dissertation, Asian Institute ofTechnology, Bangkok, ThailandKlinner W E; Neale M A; Ar
109、nold R E (1987). A new strippingheader for combine harvesters. Agricultural Engineer, 42(1),914Krishnasreni S; Thongsawatwong P (1998). Utilization of com-bine harvester in Thailand. Proceeding of the InternationalAgricultural Engineering Conference, Vol. 1, pp 265275.Bangkok, ThailandLiljedahl J B;
110、 Carleton W M; Smith D W (1983). Tractors andTheir PowerUnits (3rd Edn). John Wiley& Sons, New York,USAMetianu A A; Hale O D; Hobson R N (1991). Review of grainharvesting research and development at Silsoe. Proceedingsof the International Agricultural Mechanization Conference,Vol. 4, pp 124148. Beij
111、ing, ChinaTado C J M; Wacker P; Kutzbach D; Suministrado D C (1998).Development of stripper harvester: a review. Journal of Agri-cultural Engineering Research, 71(1), 103112Trimo (1996).Testing and evaluationof a rice stripper harvestermanufactured in Indonesia. MEng Thesis No. 96-5, AsianInstitute of Technology (unpubl.), ThailandVechasit A (1995). The introduction of small-farm stripperharvester system in Thailand. Agricultural EngineeringDivision (AED), Department of Agriculture, Bangkok,Thailand
