Combine Research Paper

Overview

The following is a research paper related to the Microcombine project.

Paper

THE MINI COMBINE-HARVESTER: RESEARCH RESULTS AND A RELATED AUTOMATION CONCEPT

By Phan Hieu Hien (*), Le Van Ban (**) (*) Center for Agricultural Energy and Machinery Nong Lam University, Thu Duc, Ho Chi Minh City, Vietnam E-mail: phhien@hcm.vnn.vn (**) Faculty of Engineering and Technology Nong Lam University, Thu Duc, Ho Chi Minh City, Vietnam

ABSTRACT

In Viet Nam, rice harvesting is a rising problem due to shortage of manual labor during harvest. Attempts to mechanize this operation using combine harvesters encountered problems with soft soils, frequent breakdowns, and lodged crops. Conventional combine models weighs at least 1.2 tons and such heavy units could not manage soft soils or “seemingly dry” soils in the Mekong Delta.

A Chinese-originated lightweight mini-combine, improved in several components by the Philippine Rice Research Institute, was recently selected by the Nong- Lam University Research Team on Combine, who added and compared different wheel designs for wet soft soils. In 2004, test results in several Provinces in Viet Nam showed the performance of this model at one ha per day capacity, cutting width is 1.2m, and total grain losses is less than 2%. The combine harvesting cost is 1/2 - 2/3 that of the current practice of manual cutting and mechanical threshing. The light weight of the machine (570 kG) proved to be an absolute advantage in soft soils typical of the Mekong Delta rice fields. Very soft soils leading to bogging down could easily be overcome within minutes by seven people. No other combine so far could allow such troubleshooting. Thus, the design was transferred to VINAPPRO, a manufacturer of engine and machinery, which planned to manufacture 20 units for the Spring harvest of 2005.

The resulted advantages pointed to a new automation concept in combine operation: The lightweight combine could be made even lighter in operation. If the pooled operating weight of the combine could be further reduced, then more trafficability and mobility on very soft soils could be realized. This can be simply done by removing about 120 kG of the two operators (driver and bagger) from the combine, and incorporating a device to conctrol the steering of the machine from a short distane. Likewise, an automatic bagging device replacing the manual bagger (who used to sit on the machine) would reduce the total weight. Together, 17% of weight in combine operation could be reduced. Such scenario is not too complicated in terms of automation circuit, and a plan is underway to verify the concept.

INTRODUCTION

Rice harvesting in the Mekong Delta of Viet Nam is still mostly done manually and thus is a rising problem due to shortage of labor during harvest. Over the past 20 years, among efforts to mechanize rice harvesting in this region, combines have been attempted by different government agencies as well as the private sector, but failed to be accepted by farmers.

This paper describes the adaptation work on a mini- combine, including the testing of different versions, design and selection of wheel systems for wet soils, and initial promotional work in Southern Viet Nam; the information draws heavily on an earlier publication (Tran Van Khanh et.al. 2004). The second part of the paper presents a new automation concept in combine operation by eliminating the driver’s weight from the combine operation.

Review of literature: problems with combines

Thailand maybe the only country in South East Asia with some success in adapting the combine. There are about 8000 units of Western-style Thai-made combine (with cutting width 2- 3m) in current use. In other countries including Viet Nam, introduction of such large combines have encountered three major problems:

Soft soils

Most combine weights 1.2 – 2 tons (excluding imported models of 4 – 11 tons). Such heavy machines easily bog down in soft soils. Even during the dry- season harvest, a seemingly dry field with a localized soft spot can stop a heavy combine and make it helpless in areas without access road for the rescue vehicle. This is the main reason that have failed many researchers and engineers in the area. One researcher even concluded that there is no “dry soil” in the Mekong Delta as far as the combine is concerned. Many people now maitain that, for a large combine- harvester to work, the field must be well irrigated and drained, and should be large enough for the machine to easily maneuver. This sounds logical, except that the investment to implement such requirement for combine operation is too big to be drawn from the

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agriculture itself, a condition for a sustainable progress of a developing country. A more feasible option is to develop a light-weight mini-combine that local operators can easily pull out of soft sink spots if a bogged-down situation occurs.

Frequent break-downs

Due to the single-unit fabrication with limited resources, sometimes by village mechanics, combines often fail under operation. Each break-down cost hours or days to repair; one week’s time for repair could result in significant lost income during the harvest season and unreliability discouraged users to adopt such new technology. This problem can be addressed through improved manufacturing and continuous design improvement with due consideration to added costs. A workable initial design, a competent local manufacturer, close monitoring of field operation, and after-sales service support will help realize successful adoption of this new technology.

Lodged crops

Rice lodging is often caused by extreme climatic conditions such as typhoons or floods but this is also related to the works of plant breeders and agronomists. To date, attempts to develop a combine that can harvest severely lodged crops have been unsuccessful. Plant breeders and agronomists need to improve lodging resistance of rice varieties. However, a partially-lodged field area, say a 10%, still means that 90% of the field is still readily available for combine harvesting, especially if the combine is small enough to circumvent around more severely lodged spots that can be managed through manual harvesting.

Thus, a suitable combine for local Viet Namese conditions can be summarized into two basic requirements: light weight and reliability.

MATERIALS AND METHODS

Design adaptation

Different surveys by the NLU Center for Agricultural Energy and Machinery (CAEM) resulted in a considerable database, including hundreds of pictures. In 2003, the Philippine Rice Research Institute (PhilRice) shared a design of a light-weight mini-combine (570 kG), to continue a long tradition of cooperation between NLU and the Institute in the area of Agricultural Engineering. The project has been sponsored by Briggs & Stratton Corporation, a well- known gasoline manufacturer.

The first design of the mini-combine originated in China. In 2003, PhilRice re-designed and improved key functions adding significant improvements to the prototypes, which were then transferred to NLU for testing in Viet Nam. The new design is a typical Western-type combine, with a reel wheel at the top of a reciprocating cutting blades and a feeding crop auger at the back of the cutter to feed a conveyor that brings the cut plants towards an axial-flow thresher. The cleaning of paddy is done beneath the thresher concave by an oscillating screen and a fan, similar to the IRRI axial-flow threshers, before the paddy grain is conveyed upwards for bagging. The combine is powered by a 16-HP B&S gasoline engine (weighing 40 kG), which is commonly used for axial-flow threshers in the Philippines.

In Viet Nam, design adaptation by the NLU included: a) identifying areas for strengthening and optimizing design performance and reliability; and b) comparing different wheel designs for wet soft soils. The NLU believes problems of combine harvesting in Viet Nam are “of the earth, and not of the air”, that is to say, they are more concerned on soil and wheel interactions rather than the working principles and components which are already common knowledge.

a) b)

Figure 1. a) The -mini-combine prototype from PhilRice. b) Mini-combines in DongThap; both units are made by Vinappro.

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After evaluation and further “fine-tuning” of the prototype, the design was transferred to the Viet Nam Agricultural Power Company (VINAPPRO), a leading manufacturer of diesel engines and other machinery who then fabricated two units for local field testing and evaluation.

Testing

The mini-combines (one from PhilRice and two from Vinappro) have been tested in five locations in the Mekong Delta and Eastern Provinces from March to October 2004, including exploratory test, performance tests in semi-wet and wet conditions, durability test.

Seven different traction types and variations were tested for trafficability, namely: 1) rubber tyres, 2)dual rubber tyres, 3)steel cage wheel, 4)original pyramid-shaped lug wheel with 10 lugs/wheel, 5)pyramid-shaped lug wheel with12 lugs/wheel, 6)wider pyramid-shaped lug wheel with 12 lugs/wheel, and 7)retractable lugs mounted to rubber tyre.

Standard test instruments, such as stop watch, tachometer, scales and a penetrometer (ASAE, 1994) to measure the hardness of soil, were used in the tests.

Automation concept

The positive test results prompted to a new automation concept in combine operation: The lightweigt combine could be made even lighter in operation. If the pooled operating weight of the combine could be further reduced, then more trafficability and mobility on very soft soils could be realized. This can be simply done by removing about 120 kG of the two

operators (driver and bagger) from the combine, and incorporating a device to conctrol the steering of the machine from a short distane. Likewise, an automatic bagging device replacing the manual bagger (who used to sit on the machine) would reduce the total weight. Together, 17% of weight in combine operation could be reduced. Thus, work efforts on developing device to realize this automation concept are under way, with some initial results.

RESULTS AND DISCUSSION

Field performance

The field tests were conducted under different soil and crop conditions. The performance and specifications of the combine are summarized in Table

1. Average harvest was one hectare per day. The total losses ranged at 1.0 – 1.4 per cent, and never exceeded 2 per cent. (Table 1) Trafficability

Our tests indicate that, on dry soils, the rubber tyre is most suitable in terms of both traction and vibration of the machine. However, in soft and wet soils, the rubber tyres sank and bogged down the combine. Two types of wheels were found to be suitable:

1) The pyramid-shaped lug wheels could manage soft soils with penetration resistance of more than 0.4 MPa.

2) The retractable lugs mounted to rubber tyre proved to be most useful in soft soil. The rubber tyres provide floatation, while the lugs provide both traction and flotation.

Table 1. Mini- combine performance and specifications (Tran Van Khanh et.al. 2004)

Working width: 1.2 m maxmum Working speed: 1.5 – 2.1 km/hr Idle travel speed: 2.0 – 5.0 km/hr Working time utilization efficiency: 70 – 80 % Field capacity: 1 ha /day (0.9 – 1.3) Cutting height: Adjustable 0.1 – 0.4 m Combined losses (shattering, unthreshed and separating): < 2.0 % Power requirement: 16-HP B&S gasoline engine Fuel consumption: 15 Liter/ ha Labor requirement: 5: one driver, one bagger, and three haulers of grain bags to levees. Traction: Semi-dry soil: Soft, wet soil: Rubber tyres 6.00 x 12 Pyramid-shaped lug wheel, or Retractable lugs + rubber tyre Overall dimensions (L x W x H): 3.5 m * 1.5 m * 1.5m Net weight: 570 kg

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On soft soils, the light weight of the combine proved to be an absolute advantage. If the machine was about to sink, the bag laborer in the rear seat could dismount temporarily to reduce machine weight, thus allowing the mini-combine to pass through soft spots while maintaining operation. This suggests that any additional weight (i.e. from alternative heavy diesel engines) would pose major problems on soft soils and also re-confirms why one-ton-plus combines could not work so far.

During the test on extreme soft soils leading to occasional bogging down, the problem was overcome within minutes by eight people, who simply pulled back the combine out of the troubled spot.

Reliability

The mini-combine have been operated on 12 hectares to date. Breakdowns and troubles occurred, such as shear of cotter pin of the steering wheel, failure of the rear U-fork..., but these were considered minor and were right away fixed in the field or by small village mechanics.

Cost comparison to current harvesting methods

Although the actual unit cost from the production line is not yet available, the estimated sale price is 41.000.000 VND (H” US$2600). Based on test data and assumptions usually made for cost calculations, the harvesting cost for 1 hectare using this combine is 361 000 VND or about US$23, of which 35% are for depreciation-interest-repair, 34% are for gasoline, and 31% are for labor. How is this cost compared to current harvesting methods ?

The most practiced harvesting method in the Mekong Delta of Viet Nam is manual havesting + mechanical threshing. Depending on the province, rice yield, and cropping season, the total cost in 2003 of existing methods ranged from 700 000 to 900 000 VND per hectare, with 60% representing harvesting costs and 40% for threshing costs.

Thus a total cost of 361 000 VND/ha with the mini-combine represents a cost reduction of 48 to 60 percent, compared to current practices. This is significant, considering that this saving is equivalent to about 15% of the profit from a typical hectare of rice.

Moreover, labor cost decreases appreciably with use of the combine. The current harvesting and threshing system normally requires dozens of laborers and 150 man-hours per hectare, which is now reduced to five people and 40 man-hours per hectare with the combine.

In summary, Test results showed both the technical and economic feasibility of the mini-combine under Vietnamese conditions. The outstanding advantage of this combine lies in its light weight, which enables the trafficability in typical soft soils of the Mekong Delta.

A CONCEPT IN COMBINE AUTOMATION

The above resulted advantages pointed to a new automation concept in combine operation: The lightweigt combine could be made even lighter in operation. If the pooled operating weight of the combine could be further reduced, then more trafficability and mobility on very soft soils could be realized. The idea stemmed from our observations in the field tests. In some very soft soils wherein the combine was about to bog down, the bagger-laboror jumped out of his seat and walked along, then the trafficability improved, and the combine surpass the obstacled soft soil. In worse situation, the driver had to jump down too and steer the combine walking alongside until better, harder soil was present.

The implication is that even 120 kG of the two operators, or even about 60 kG of the bagger is accountable for the trafficability of the combine. Thus, if we remove these operators’ weight from the combine, and incorporate a device to conctrol the steering of the machine from a short distane, then the combine mobility would be improved. Likewise, an automatic bagging device replacing the manual bagger would reduce the total weight. Together, 17% of weight in combine operation could be reduced. Such scenario is not too complicated in terms of automation circuit. The following schematic diagram and description serve to illustrate the concept.

Control objectives

The objectives to control the combine operation are as follow:

-Control of the reel height

-Control of the cutter bar height

-Control of the engine speed

-Control of the forward speed (high or low)

-Control of the turning (left or right)

-Control of the stopping (open or close)

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A plan is underway to verify the concept and operation.

Tieán (Forward) Reõ phaûi (Turn right) Reõ traùi (Turn left) luøi (Reverse) Thaáp (Low) Cao (High) Toác ñoä ñoäng cô (Engine speed ) Phanh (Brake) Ñoùng (Close) (Gear box) Soá (1) (2) (4) (3) Reel Air Cylinder Cutter bar Air cylinder Figure 2. Block schematic diagram of remote control for mini combine harvester

Selected method for control system

A total of 10 actuators would be needed. Three different methods were evaluated: by high pressure air, by servo-motors, and by hydraulic system. Considering the cost, ease of installation and operation, and reliability, the air pressure system was selected. The control is by the remote cable, with the operator walking along or at a distance with the combine; the power source is a DC 12 volt system. The drawback is a compressor is needed, and the advantages are ease of control, component parts are easily available.

The block schematic diagram of remote control for mini-combine is shown in Figure 2.

CONCLUSION

A newly designed mini-combine has been successfully adapted in Viet Nam. Data for its technical and economic performance seems to be favorable for local acceptance of this new technology. The outstanding feature of this combine is its very light weight, which enables its mobility on soft soils and difficult access roads, a fact rarely achieved by other hevier combines. A campaign is underway to commercialize this mini-combine in Viet Nam for the

winter-spring harvest of 2005. The first batch of 20 combines will be launched to farmer-users at this time.

Continuing in the direction of making the combine as light as possible to keep the maximum mobility, a new design concept in combine automation has been put forward with the aim of removing the operators’ weight during operation of the combine. Different scenarios with different alternative setup are planned to be evaluated to verify the concept.

ACKNOWLEDGEMENT

The support for the design, testing, and promotion in various ways from Briggs&Stratton Inc (Wisconsin), and from VINAPPRO Company (Dong- Nai) is gratefully acknowledged. PhilRice is acknowledged for sharing the initial design of the mini- combine.

REFERENCES

ASAE. 1995. ASAE Standards 1994. American Society of Agricultural Engineers, St. Joseph, Michigan, U.S.A.

BARDAIE M.Z. 1980. Economic farm size for rice combine harvester in Malaysia. Agricultural Mechanization in Asia, Autumn 1980 pp.49- 52.

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BAUTISTA, E.U. and A. SCHMIDLEY. 2004. PhilRice- B&S Collaboration: Building partnerships across Asia. Paper presented at the Philippine Rice R&D Conference, PhilRice, Maligaya, Munoz, Nueva Ecija. 114-16 April

BENSON E.R., J.F. REID, Q. ZHANG. 2003. Machine vision-based guidance system for an agricultural small grain harvester. Transactions ASAE Vol.46 (4) 12551264.

PHAN HIEU HIEN. 1991. Development of the axial- flow thresher in Southern Vietnam. Agricultural Mechanization in Asia J. Vol.22 No.4 pp.42-46.

SUZUKI M. 1980. Performance of rice combine harvesters as evaluated by the national test in Japan. Japan Agricultural Research Quarterly Vol.14 No.1 pp.20-23.

TRAN VAN KHANH, PHAN H. HIEN, E. BAUTISTA,

A. SCHMIDLEY, K.LEE, MAI D. BAN. 2004. Testing and promotion of a rice mini-combine in Viet Nam. Proceedings of the Mekong Rice Conference, organized in HoChiMinh City, Viet Nam, 15- 17 October 2004. Journal of Agricultural Sciences and Technology, No 4/2004 Nong Lam University

Development of rice combines in Viet Nam

Phan Hieu Hien, Tran Van Khanh# # , Graeme R. Quick ***

E-mail: phhien@hcm.vnn.vn 

This is not a peer-reviewed article. Electronic-only Proceedings of the International Conference on Crop Harvesting and Processing, 11-14 February 2007 (Louisville, Kentucky USA) Publication Date, 11 February 2007. ASABE Publication Number 701P0307e

ABSTRACT

Rice combine development in Viet Nam, especially in the Mekong Delta in the South, has been a slow process. Mechanized farm equipment is accepted only if it matches local agricultural conditions technically and economically. Earlier attempts at bringing in or developing combines by Central research institutes, Provincial factories, and farmer-mechanics were unsuccessful at actual scale operation. Three main problems were encountered over the past 20 years:

(1) Machines working in soft paddy fields bog down, especially heavy Western-style combines. (2) Reliability at lowest cost is critical; delays caused by machine breakdowns result in significant lost income during the harvest, and unreliability discourages users from adopting new technology. (3) Harvesting severely lodged rice crops is challenging, not so much as an engineering problem as it is a matter of plant breeding and varietal selection to improve lodging resistance. Nevertheless there has been intensive development in the past 5 years by as many as 15 small- scale Vietnamese manufacturers. One mini-combine manufacturers has lately sold 90 units to private farmers across the country. In 2006 a combine contest was organized by the Vietnamese National Testing Agency. Three designs were given “accredited recognition awards”, meaning recognition for future promotion through the governmental Extension system. The recent development of mini-combines follows.

Keywords: Combine, Rice Harvesting, Mechanization

INTRODUCTION

Viet Nam is an agricultural country with 82 millions (M) inhabitants in 2005, of which 61 M are in rural households. Rice is the most important crop, cultivated on 80 % of the total farm area, and rice accounts for 85 % of the country’s food grain output. In 2003 , Viet Nam produced 35 M ton of paddy on 4.2 M ha of rice land. This total production was four times more than that of 1976. Viet Nam is the world’s third largest rice exporter. For the past 10 years, the export of rice has been 3 – 4 M tonnes a year.

The Mekong Delta in Southern Viet Nam , with 2.7 M ha of rice land, is producing about 50 % of Viet Nam total rice output. With only 17 % of the total population, this region has accounted for more than 90 % of Vietnamese rice export in the past decade. Average farm size is about 1

Paper for presentation at the International Conference on Crop Harvesting and Processing, February 11-14 2007, Louisville, Kentucky.

1. # Lecturers, Nong-Lam University (formerly: University of Agriculture and Forestry), HoChi-

Minh City, Viet Nam,

• • • Consulting Engineer (Queensland, Australia) and Former Head, IRRI Agricultural

Engineering, Philippines.

� ha per household, although in some newly-reclaimed districts, 3 - 10 ha per household is not uncommon.

Rice harvesting in the Mekong Delta of Viet Nam is still mostly done manually, but threshing was completely mechanized. Over the past 20 years, effort to introduce rice harvest equipment in this region have been attempted by different government agencies as well as the private sector, from central research institutes to skilled village mechanics. Different alternatives have been tried, i.e. the reaper or the combine, but these either failed or were only half-way solutions to the problem.

This paper describes the slow process of combine development in the Mekong Delta, identifies affecting factors and related problems. Details of the work on a mini-combine, including wheel systems for wet soils, and promotion to the industry for manufacturing are presented.

CURRENT STATUS OF RICE HARVESTING AND PROBLEMS

In the Mekong Delta of Viet Nam, as in various parts of South-East Asia, rice harvesting is mechanized to varying degrees beyond traditional manual methods. Three types of mechanized harvesting are:

1) Manual harvesting + mechanical threshing. More than 95% of rice is threshed mechanically by the axial-flow thresher (Phan H. Hien 1991). However, due to lack of technically suitable and economically viable methods of mechanically cutting rice plants, local people continue to harvest rice manually with a sickle.

Figure 1: (a) Rice reaper, made by Long-An Mechanical Factory in 1985…

(b) … and one from 3 major reaper manufacturers remaining in 2004; (c) A combine made by a farmer-mechanics in Dong-Thap Province; (d) An imported combine under test in 1998. 2

� 2) Mechanical reaper + mechanical threshing. The Chinese windrower reaper was introduced to South-East Asia through the International Rice Research Institute (IRRI) way back in the 1980’s. The IRRI-designed reaper was introduced to Viet Nam in 1984 by the University of Agriculture and Forestry (now renamed Nong-Lam University NLU). Commercialization of the reaper (Figure 1a) peaked in around 1988 with about 15 manufacturers but there remain only three manufacturers producing 100-200 units per year each in the year 2000. (Figure 1b) Reaper adoption did not expand rapidly because it was only a partial solution. Manual gathering of the cut windrows still cost about 2/3 of the traditional hand cutting-gathering. Besides, the long-length cut of the plants is less suited to mechanical threshing, unlike manually harvested crops.

3) Combine. (See Next Section)

COMBINE DEVELOPMENT

Unlike Thailand, the only country in South-East Asia with some success in adapting the combine (with about 8000 units of Western-style Thai-made units in use), the introduction of such large combines have encountered three major problems in Viet Nam:

(1) Soft soils. Most local combine weights 1.2– 2 tonnes while imported models weigh 4– 11 tonnes. Such heavy machines easily bog down in soft soils. Even during the dry-season harvest, a seemingly dry field with a localized soft spot can render a heavy combine helpless in areas which may not have access roads for a rescue vehicle (Fig.1c and 1d). This is the main reason that has failed many researchers and engineers; one researcher has even concluded that there is no “dry soil” in the Mekong Delta as far as the combine is concerned. Many people now maintain that, for a large combine-harvester to work, the field must be well irrigated and drained, and should be large enough for the machine to easily maneuver. This sounds logical, except that the investment to implement such requirement for combine operation is too big to be drawn from the agriculture itself, a condition for a sustainable progress of a developing country. (2) Frequent break-downs. Quality is often lacking in one-off manufacture by village mechanics, and such combines breakdown. Each break-down cost hours or days to repair; a week’s repair time means significant lost income during the harvest season. Unreliability discouraged users from adopting new technologies. Thus, reliability at lowest cost is critical. The frequent breakdown of combines can be addressed through improved manufacturing and continuous design improvement with due consideration to added costs. A workable initial design, competent local manufacturer, close monitoring of field operation, and after-sales service support are all essential for the realization of a new technology. (3) Lodged crops. Rice lodging is often caused by extreme climatic conditions such as typhoons or floods and attempts to develop a combine that can harvest severely lodged crops have been unsuccessful. Plant breeders and agronomists need to improve lodging resistance of rice varieties. However, a partially-lodged field area, say 10 % lodged, means that 90 % of the field is still available for combine harvesting, particularly if the combine is small enough to circumvent severely lodged spots that can be manually harvested. These are the three reasons why combine development in the Mekong Delta of Vietnam has been slow over the past 20 years. Things are changing however in the last 5 years.

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� 1980- 1999

Between 1980 and 1999, several combines were developed by Central research institutes, Provincial factories, and even farmer-mechanics. Attention was focused in 1997 when the Vietnamese Ministry of Agriculture organized a combine contest in Can-Tho Province, the heart of the Mekong Delta. Seven models participated, several locally made combine that were heavier than 2 tonnes, and one 5-tonne European combine. All bogged down in soft soils, except for a second-hand Japanese head-fed combine that weighed around 1 tonne. All bogged down in soft soils, except one second-hand Japanese head-fed combine weighing around 1 ton. About ten of these “light weight” combines were later sold by some trading companies. But these secondhand units quickly broke down in the first harvest season; spare parts were not available as they had been no longer fabricated in Japan; so these combines were junked. Among “best” locally made combines, the manufacturer was able to sell a few units; but again after one harvest season, buyers returned the machine to the manufacturer because of frequent breakdowns; each time requiring a severak critical days for repair. A one-week downtime meant that half of the peak harvest season was missed in the area. That meant significant lost harvest income as rice quality deteriorates when not harvested at the optimal time (Quick, 2003).

2000- Present

Since 2000, the Vietnamese economy has demonstrated rapid growth, and as a consequence harvest labor has become a serious problem. Rural people prefer higher-paying jobs at construction sites or other industrial jobs. This has motiovated researchers and manufacturers to renew efforts at promoting combines, this time with experience learnt from the earlier efforts. From 2000, about 15 small-scale combine manufacturers have tried their products. A combine contest was organized in 2006 by the Vietnamese National Testing Agency (Fig. 2). Eight local models and one Chinese imported model presented. Unlike the previous contest, these machines had been used by the manufacturers for harvesting their own rice or else extensively tested. Some manufacturers had sold up to a dozen units before entering the contest. From the contest, three designs were given “accredited recognition awards”, meaning recognition and future promotion through the governmental Extension system. Two winners were the local Chin- Nghia 1500-kg combine, and a 2300-kg Chinese imported combine. The third was a 600-kg “mini-combine” with several distinctive features, which are described in the following Section.

Figure 2: Combines at the contest in Can-Tho Province, 2006.

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� THE MINI-COMBINE

Design

The NLU Center for Agricultural Energy and Machinery (CAEM) was established in 2001 and began research to improve rice harvesting methods and conditions in Viet Nam. Different surveys resulted in a database, including hundreds of pictures. In 2003, the Philippine Rice Research Institute (PhilRice) shared a design of a light-weight 600 kg mini-combine, to continue a long tradition of cooperation between NLU and the Institute in the area of Agricultural Engineering. The mini-combine project was sponsored by Briggs & Stratton Corporation, a U.S leading gasoline manufacturer.

The initial design came from China. In 2003, PhilRice re-designed and improved key functions adding significant improvements to the prototypes, which were then transferred to NLU for testing in Viet Nam. This is based on a tricycle undercarriage, and uses a Western-style combine open front gathering head (Fig. 2a), to feed a conveyor that brings the cut plants towards an axial-flow thresher. The cleaning of paddy is done beneath the thresher concave by an oscillating screen and a fan, similar to the IRRI axial-flow threshers (Quick, 1998), before the paddy grain is conveyed upwards for bagging (Bautista &Schmidley 2004). The combine is powered by a 16-HP B&S gasoline engine that weighs 40 kg.

In Viet Nam, design adaptation by the NLU included: a) identifying areas for strengthening and optimizing design performance and reliability; and b) comparing different traction wheel designs for wet soft soils. The NLU believes problems of combine harvesting in Viet Nam are “of the earth, and not of the air”, that is to say, they are more concerned about soil and wheel interactions rather than the working principles and components which are already common knowledge.

After evaluation and further “fine-tuning” of the prototype, the design was transferred to the Viet Nam Agricultural Power Company (VINAPPRO), a leading manufacturer of diesel engines and other machinery, who then fabricated two units for local field testing and evaluation, before deciding to go on with mass production.

Testing

In 2004, the mini-combines were tested in different provinces, first for exploring the working capabilities of the PhilRice unit (Fig.3a), then for measuring the performance of the Vinappro units in wet conditions (Fig.3b), and for durability evaluation

Seven different traction types and variants were tested for trafficability (Figures 4), namely: 1)rubber tyres, 2)dual rubber tyres, 3)steel cage wheels, 4)original pyramid-shaped lug wheels with 10 lugs/wheel, 5)pyramid-shaped lug wheels with12 lugs/wheel, 6)wider pyramid-shaped lug wheels with 12 lugs/wheel, and 7)retractable lugs mounted next to rubber tyre.

Standard test instruments and a penetrometer (ASAE 1994) to measure the hardness of soil, were used in the tests.

Results

The performance and specifications of the combine are summarized in Table 1 (Tran V. Khanh et.al 2004); the field tests were conducted under different soil and crop conditions. Average

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� harvest was one hectare per day. The total losses ranged at 1.0 – 1.4 per cent, and never exceeded 2 per cent.

(a) (b) Figure 3: a) The 600-kg mini-combine prototype from PhilRice (Tran V. Khanh et.al 2004). b) Mini-combines in DongThap; both units are made in Viet Nam by Vinappro. Table 1: Mini- combine performance and specifications

Working width : 1.2 m maximum Working speed : 1.5 – 2.1 km/hr Idle travel speed : 2.0 – 5.0 km/hr Working time utilization efficiency : 70 – 80 % Field capacity : 1 ha /day (0.9 – 1.3) Cutting height : Adjustable 0.1 – 0.4 m Combined losses (shattering, unthreshed and separating) : < 2.0 % Power requirement : 16-HP B&S gasoline engine Fuel consumption : 15 Liter/ ha Labor requirement : 5: one driver, one bagger, and three haulers of grain bags to levees. Traction: Semi-dry soil : Soft, wet soil : Rubber tyres 6.00 x 12 Pyramid-shaped lug wheel, or Retractable lugs + rubber tyre Overall dimensions (L x W x H) : 3.5 m * 1.5 m * 1.5m Net weight: 600 kg

Trafficability Tests, among the 7 types of wheels:

The tests indicated that, on dry soils, the rubber tyres were most suitable in terms of both traction and vibration of the machine. However, in soft and wet soils, the pyramid-shaped lug wheels (Fig. 3a) could manage soft soils with penetration resistance of more than 0.4 MPa. The retractable lugs mounted to rubber tyres proved to be the most useful in soft soil. Rubber tyres provided floatation, while the lugs provided both traction and flotation (Fig.3b).

On soft soils, the light weight of the combine proved to be an critical advantage. If the machine was about to sink, the bag laborer in the rear seat could jump off temporarily to reduce machine load, to allow the mini-combine to pass through soft spots while maintaining operation. In extremely soft conditions where there was occasional bogging down, the problem was overcome

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� within minutes by seven people, who simply lifted and pulled the combine out of the trouble spot (Fig. 3f). No other combines could be managed that way!

As for reliability, the mini-combine was operated on 15 hectares, before transferring the design to industrial production. During the tests, breakdowns and troubles occurred, such as shear of cotter pin of the steering wheel, failure of the rear U-fork..., but these were considered minor and were immediately fixed in the field or by small village mechanics. Nevertheless, this indicates more attention is needed during local manufacturing.

Figure 4: (a) The pyramid-shaped lug wheel; (b) Retractable lugs mounted adjacent to rubber tyre;

(c) Dual tyre blocked with clay; (d) The cage wheel; (e) The combine is easily lifted for changing wheels; (f) Bogged-down combine on soft soil was simply pulled out by 7 people. (Tran V. Khanh et.al 2004). 7

� Mini-combine commercialization

The VINAPPRO Company produced a total of 90 units between 2005-2006. Apart from a few units that went to state agencies for extension, the majority of these combines were bought by private farmer-contractors with their own money. Four users placed repeat orders, each for a second unit after the first unit had harvested some hundreds of hectares. All these are positive indicators that the mini-combine is following the well-known mechanization pattern in the Mekong Delta, where the machine is owned by the service provider. A small farmer owning only 1 ha buys an 80-HP tractor, plows his field for one day or less, and next plows for 100 other farmers on a contract basis. In the same way, the contractors harvest, thresh and dry paddy.

Cost calculations

In 2006, the sale price of a mini-combine from the production line was US$ 2900 ###. Other data and assumptions are listed in Table 2 for estimating the cost of machine use.

Table 2: Data and assumptions for estimating the cost of machine use (Tran V. Khanh et.al 2004).

Purchase price : US$ 2900 (˜ 46 000 000 VND) Life : 3000 hours / 6 years (#1) Interest rate : 10 % / year Working capacity : 1.0 ha /day Fuel consumption (gasoline) : 15 Liter /ha Fuel price US$ 0.63 / liter Lubricants and filters… (as % fuel cost): 15 % fuel Labor: Driver: (Number) * Daily wage: (1) * US$ 2.2 Bagger &Hauling laborer: (Number) * Daily wage: (4) * US$ 1.6 Total Repair & M. cost ( as % Purchase price): 40 %

Note: (#1) 3000-hr life ˜ 6 yrs * 3 crop seasons/ year * 17 days/ season * 10 hrs/ day.

Based on the above data, cost of using the mini-combine is calculated and summarized in Table 3 and Figure 5.

1. 1. 1. For the convenience of overseas readers, all monetary numbers in Vietnamese Dong

are converted to US$, with the conversion rate in 2006: 1 US$ ˜ 16 000 VND

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Table 3: Cost of use for the mini-combine 

Cost US$ /ha Depreciation 5.3 Interest 1.6 Gasoline 11.8 Labor 7.2 Repair 2.1 Total US$ per hectare 27.6 ˜ 28

Cost of use, Mini-combine

Deprecia

Repair

tion

19% Labor Interest 26% 6%

41%

Gasoline 8% Figure 5: Distribution of utilization cost ( Total = US$ 27.6 )

Comparing Costs with current harvesting methods

The most common harvesting method in the Mekong Delta of Viet Nam is manual harvesting + mechanical threshing. Depending on the province, rice yield, and cropping season (dry or wet harvest), the total cost in 2004 of existing methods ranged from US$ 45 to 60 per hectare, with about 60% representing cutting and gathering costs and 40% for threshing costs.

Thus the total cost of US$ 28 /ha for the mini-combine represents a substantial cost reduction of 38 to 53 percent, compared to current practices. This is significant, considering that this saving alone is the equivalent of 15% of the profit from a typical hectare of rice.

Moreover, the labor requirement is appreciably reduced by the combine. The current harvesting and threshing system normally requires dozens of laborers and up to 150 man-hours per hectare, against five people and 40 man-hours per hectare with the combine.

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� CONCLUSIONS

Rice combine development in the Mekong Delta of Viet Nam over the past 20 years has been a slow process, following the introduction of axial threshers and reapers. Three problems affect the combine adoption: (a) soft soils; (b) machine reliability, and (c) lodged rice crops. Early attempts in the 1980’s and 1990’s by different agencies and the private sector were unsuccessful at actual scale operation. Since 2000’s severe labor shortage for rice harvesting has prompted intensive development by several small-scale combine manufacturers. Three combine brands gained the “accredited recognition awards” during a combine contest in 2006; these 3 companies have commercialized their combines. Particularly, the Vinappro Company has sold 90 mini-combines. This 600-kg combine was adapted from an initial design from China, with modifications of the cleaning system by PhilRice. Durability testing and improvement of the wheels for soft soils were made by NLU in Viet Nam before transferring the design to industry. The combine represents a good step forward in Viet Nam.

Acknowledgements

The authors wish to thank Dr. Wesley Buchele for his encouragement to submit this paper for ASBAE 2007 International Conference on Crop Harvesting and Processing.

REFERENCES

ASAE. 1995. ASAE Standards 1994. American Society of Agricultural Engineers, St. Joseph, Michigan, U.S.A.

BAUTISTA, E.U., A. SCHMIDLEY. 2004. PhilRice-B&S Collaboration: Building partnerships across Asia. Paper presented at the Philippine Rice R&D Conference, PhilRice, Nueva Ecija., April 2004.

PHAN HIEU HIEN. 1991. Development of the axial-flow thresher in Southern Vietnam. Agricultural Mechanization in Asia J. Vol.22 No4 pp.42-46.

QUICK, G.R. 1998. Global assessment of power threshers for rice. Agricultural Mechanization in Asia J. Vol.29 No3 pp.47-54.

QUICK, G.R. 2003. Rice Harvesting. Chapter pp 491-542, in: Rice. The Monograph, by Wiley & Sons, New York.

TRAN VAN KHANH, P.H. HIEN, E. BAUTISTA, A. SCHMIDLEY, K. LEE, M.D. BAN. Testing and promotion of a rice mini-combine in Viet Nam. Proceedings of the Mekong Rice Conference, HoChiMinh City, Viet Nam, 15- 17 October 2004.

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