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40 Handaka and Joko Pitoyo Indonesian Journal of Agricul ture 4(1), 2011: 40-45

1)Article in bahasa Indonesia has been published in Jurnal Enjiniring

Pertanian Vol. VI No. 2, 2008, p. 77-84.

ABSTRACT

One of the critical points of the postharvest problems in rice is the

high price of rice harvester machines that meet the standards of

low shrinkage and affordable by the consumers. For this reason, a

commercial lawn mower had been modified into a rice harvester

machine. Modifications that had been made were (1) replacing

the cutter blade with a rotary blade; (2) changing the dynamic

balance of the harvest machine into a mower type; (3) adding a

gu id er and a pr opel le r; and (4 ) ad di ng an oper at or be lt .

Perfo rmanc e tests on 100 m2 with a standard engine for crop

harvest showed that the modified machine had a working capacity

of 18-20 hours/ha, fuel consumption of 15.0 l/ha, work efficiency

of 95%, and weighing of about 10 kg. All the standard components

were available in the market, while the frame of the propeller and

the operator belt could be made domestically. Price of the machine

is in the range of IDR2.5-30 million/unit in 2007. In this respective

capacity and price of the machine, the operational costs were in

the range of IDR75,000-100,000/ha.

[Keywords: Rice harvester, grass cutter, lawn mower]

INTRODUCTION

Food crop harvests in Indonesia are still done using human

power. Despite the outpouring of human labor for the

harvest is still high, this work is very hard to replace with

the engine power because human power is quite abundant,

so harvest labor fees are relatively low. However, in some

areas in Indonesia, such as in South Sulawesi, rice harvest

has been done using the engine power (Koes-Sulistiadji et

al.2005).

Research on rice harvester machine had long been

done, since the introduction of reaper machine in 1978 until

the 1990s. Silsoe (NCAE) has also conducted research on

stripper harvester, which was done in Indonesia together

with GTZ and Bogor Agricultural University (Tado and

Quick 2003). For other food crops, Rojanasaroj et al. (2003)

conducted research on soybean harvester in Thailand

using two wheel tractors. The study reported that the

harvest with a small machinery is getting a lot done.

Lately, China developed a small harvester machine

called a crop harvester, which is like a lawn mower for

cutting grass and other cereal crops such as rice, wheat,

corn, feed grasses, and shrubs, by changing the blade

piece (Boshima 2007). Excellence of the China’s designed

machine is simple, lightweight, inexpensive, easy to

assemble and disassemble, and very easy to operate. From

shape and structure of the frame, crop harvester (Boshima)

is an advanced modification of a standard lawn mower,

with a light engine (2-2.5 hp), high rpm (<4,500) and the

steering and shaft grip (swing arm), and the circular blade

is detachable and removable.

Chattopadhyay and Pandey (1999) reported that the

cutting speed and leaning angle of the rice stems to be cut

affected cutting energy of the cereal cutting machine.

Further information also showed that cutting speed could

increase cutting energy consumption by 10%. However, the

speed of forward motion did not affect the cutting energy.Important parameters to be used in the modification

and conversion of a lawn mower into a rice harvester are

working capacity, working efficiency, and fuel consumption.

Based on these criteria, a reference coefficient for the

harvest machine is a minimum working capacity of 18 hours/

ha, minimum working efficiency of 80%, and maximum fuel

consumption of 0.8 l/hour. Maximum weight of the machine

is 12.5 kg with a maximum engine power of 2.5 HP. Harvest

shrinkage should be less than 2%. Engine uses pure

premium fuel and the fuel flow system is gravity. Besides,

a operator belt is added, which is adapted to the operator

demands. The belt can be obtained from the market with

an attractive design.

With a simple design, a lawn and shrub mower valuable

IDR2 million (2008) can be converted into a cutting machine

for rice, maize, grass, and other cereal crops. These

machines are expected to be easier and faster to replace

the crescent as a mean of harvest. This is particularly

because after more than 25 years, the machine that was

researched and developed by IRRI in early 1980, and

commercially traded by the industrial machinery Kubota,

Yanmar, and some Korean agricultural machinery industries

had no progress in Indonesia.The purpose of the modification of a lawn mower into a

rice harvester machine was to find innovative solutions

MODIFICATION OF A GRASS CUTTER INTO A SMALL RICE HARVESTER1)

Handaka and Joko Pitoyo

Indonesian Center for Agricul tural Engineering Research and Development Situgadung, Legok, Tangerang, PO Box 2, Serpong 15310, Phone: +62 21 5376787, 70936787, Facs.: +62 21 71695497

E-mail : [email protected]

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Modificat ion of a grass cutter into a small rice harvester 41

for simple harvesting machinery that serves to multi-cereal

commodities, lightweight, easy to operate, and has a

relatively large capacity.

MATERIALS AND METHODS

Materials

The scope of this activity was engineering to modify a

model or prototype of a lawn mower available in the market

(Table 1). The engineering materials consisted of aluminum

plate, circular blade that is enriched with a layer of carbide,

belt carriers, aluminum pipes, and engines.

Methods

Steps taken were as the following.

1. Performing a design by specifying the design capacity,

among others modified lawn mower with (a) a maximum

weigh of 10 kg; (b) price of about IDR2.5 million,

including an engine with a minimum engine speed of

4,500 rpm; (c) had a circular blade with carbide layer;

(d) competitive harvest cost compared with harvest

cost using manpower, and (e) the most important thing,

had a maximum shrinkage of 2%.

2. Testing for performance evaluation, including capacity,

fuel consumption, ease of operation (handling test),work efficiency, and operational cost estimates. The

tests were conducted at the Laboratory of Equipment

and Agricultural Machinery of the Indonesian Center

for Agricultural Machinery Development, including

functional and verification tests in the field (rice field

and dry land). The tests were conducted according to

the applicable ISO standard and other standards

recognized by the international community on the

planning of agricultural mechanization (FAO 1997).

3. Financial analysis to estimate the fixed cost using the

assumption of capacity, investment, and cost variables,

such as wages, fuel prices, cost of repairs, and mainte-

nance.

The field test was conducted at the Klirong Village,

Kebumen District, Kebumen, Central Java in June 2007. In

this test, the trial plots were set up using the local

measurements (ubinan), which then converted to an area

of 100 m2 per plot. The trial was performed using a test

standard using a reapper, in accordance with the existing

ISO (BBPMP 2005). The machine testing followed the

concept of a single test with 12 plots as replicates.

Observations were made on capacity, working speed, fuel

consumption, and work efficiency (Anonymous 2007).

RESULTS AND DISCUSSION

Design and Development of Rice Harvester

Machine of Mower Type

Design of cutting blades

Design of the cutting blade is shown in Figure 1. Blade

type was circular with the number of cutting eye 42 pieces.

Blade material was carbide tip with blade size of 4 mm

length, 3 mm width, and 2 mm height. Rotation speed was

3,000-4,000 rpm. Blade diameter was 255 mm. Cutting speed

could be measured using the formula as follows:

2πn 2π3000υ=ωr ω= —— ω= ——— rad/second

50 60υ = π.100,0.1275 m/second

= 40.05 m/second

Circular type cutting blades are available in the market.

This type of blade would experience wear and tear on the

cutter eye or the carbide tip, as shown in Figure 2.

At the time of cutting rice plants, which were in parallel

hills and regular space, a unique propeller or impulse was

needed so that three or even more than four rice hills could

be cut and neatly arranged in a single stack. The boost

was resulted from movement of the cutting blade with the

Table 1. Specification of a straight type of lawn mower

Parameter Remark

Type Carry (back)

Model Grass cutter

Power motor 2 steps/2 HP/6000 rpm

Weight 9 kg (including engine)

Fuel Mixed premium/premiun

Harvested commodity Rice, maize

Source: Brush_Cutter_Grass_Trimmer_Grass_Cutter_CG415

2008. Internet web Figure 1. Design of cutting blade

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42 Handaka and Joko Pitoyo

knife hook, and a propeller to push the rice hills that has

been cut so that the rice hills will not fall or collapse per hillthat cause the rice straw runoff. The booster speed should

not be too high or too low. If the speed is too high, it

causes the rice hills fall down or bent but not cut off

because the rice hills have not been all cut off by the edge

of the blade, but it has been driven by the machine.

Meanwhile, if the speed is too low or slow, the rice hills

that have been cut beforehand would collapse and cannot

be collected with the next rice hills. Based on experiences,

the value of propeller speed to cut four rice hills with a 25

cm plant spacing or equivalent to a 100 cm working width

of propeller impulse started from the beginning at the right part until the left ranged from 0.7 to 1 second (1-1.4 m/

second).

Dynamic balance of rice harvester of mower

type

The main consideration in designing length of sleeve or

rod was safety and comfort to the operator when swinging

the harvester in a half circle movement.

Sleeve length, L = 150 cm

W1L1 = W2L2

Given W1 = 6 kg, L1 = 25 cm, and L2 = 125 cm, hence the

maximum W2 added was 1.2 kg.

Various types of lawn mowers are available in the

market, but most of them are the carried type. Engine or

power motor is back-carried (strapped onto the operator’s

back) and power is then channeled to the cutting blade

through a flexible shaft (axis) into a rigid shaft in an

aluminum pipe, which is also held by the operator’s hands

to move the cutting blade as shown in Figure 4.

The other type of lawn mower is the construction of the drive motor to the tip of the cutting blade connected

directly using a straight shaft (axis). This type of lawn

mower is rarely found in Indonesia (Figure 5). Modifications

made from back-carried type of lawn mower was to change

the construction into a straight form, which is to add a

straight pipe at the end of the drive motor to the aluminum

pipe, so that the shape and construction resembles a

straight type lawn mower.

Design of cutting guider and driver

The cutting process at the time of harvesting using a cir-

cular blade type is expected to cut materials collected and

arranged neatly as if using a reapper harvester machine.

To meet this purpose, a guider or a cutting driver is

designed in such a way to meet one hill width of thickness

plus the distance of a clump of a left and right loose distance

(space) so as to separate the cut and not cut plant hills.

Figure 2. Commercial cutting blade with carbide lining at the

blade tip

Figure 3. Dynamic balance of rice harvester of mower type

t t

s

t

t

t

s

s

s t

W2 W1

L1L2

L

Engine

ConnectionGuider & propeller

Cutting blade

Figure 4. Back-carried type of lawn mower

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Driver of plant hills was designed curved or concave so as

to collect the cut hills with a driver that is arranged

accordingly with plant height in the plant row, as illustrated

in Figure 6.

Performance test results for the rice harvester

The performance test for the rice harvester machine was

conducted at an average speed of 9.07-10.95 m/minute.

With a theoretical work width of 75-100 cm (3-4 lines), a

theoretical work capacity of 18.54-26.3 hours/ha was

obtained. The fuel consumption of the machine was in the

range of 0.60-0.86 l/ha.

Table 2 shows that performance of the machine on rice

varied on its capacity, speed, and work efficiency, which

was caused by the conditions of rice field. Under a dry ricefield, a high cutting efficiency (99%) was obtained, whereas

under a wet rice field condition in Kebumen, its cutting

efficiency was only 82-85% (BBPMP 2007).

The field test results for a lawn mower that has been

modified into a maize harvesting machine showed that the

working capacity of the harvest was not significantly

different from the land preparation machinery or from three-

row capacity of a reapper (18-19 hours/ha), with working

of efficiency >95% and fuel consumption of 0.8-0.9 l/hour.

In this modification, a larger belt with a more ergonomic

construction was added, so operators did not feel weary

(tired) despite working more than 0.5 hours continuously.

This was in contrast to the original machine design, which

used a smaller belt, hence it was less comfortable to wear.

Estimated Cost of the Machine

Based on the price of the lawn mower in the market, before

the modification, price was around IDR2-2.5 million/unit,

depending on the engine used (2 HP, 6,000 rpm). After the

additions and changes of driver/booster, steering handle,

carrying belt, and other accessories, it was estimated that

the price of the new prototype of multi-commodity

harvesting machine worth IDR3-3.5 million/unit. With this

price assumption, an estimate of operating cost of the

machine is shown in Table 3. Based on data in the table,the operating cost of the harvester machine per hectare

was about IDR246,000. If the expected yield of maize grains

Figure 5. Straight type lawn mower

Figure 7. The main assembly of the lawn mower (rice

harvester)

Figure 6. Guider and propeller parts of rice harvester

Table 2. Test results of rice harvester machine in rice field

Kebumen, Central Java

Parameter testedLocation

1 2

Working speed (m/min.) 9.51 10.95

Width of work (cm) 80.00 90.00

Working capacity (hour/ha) 26.30 19.60

Working efficiency (%) 82.38 86.28

Fuel consumption (l/hour) 0.60 0.59

Source: BBPMP (2007)

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44 Handaka and Joko Pitoyo

is 5 t/ha, the harvesting cost per kg was approximately

IDR50/kg. For rice, an additional cost was needed for

collecting and threshing the rice grains, which may reach

IDR100/kg.

Based on the cost analysis, this simple harvester

machine can be used as an alternative tool when there is a

shortage of harvest labor. If it is used in rice production

areas with a high cropping intensity (more than twice a

year), this machine will likely be readily accepted by farmers

due to time lines problem. However, thing still needed to

be taken into account is the engine durability.

CONCLUSION

Modification of a lawn mower into a harvester machine

has been done by the Indonesian Center for Agricultural

Machinery Development. This machine was designed for

the demands for a simple harvesting machine that cost

less than IDR5 million/unit, and inspired by the innovation

of small harvest machines that have been widely traded by

China. The modifications were done by replacing cutting

blade on the lawn mower with rotary blades (circular blade),

adding a guider and a driving force to drive the cutting (to

lay down), put the engine in a straight line with the blade,

and adding an operator belt carrier for easy operation.

The harvester machine of this modification had a power

of 2 HP/6,000 rpm, with pure premium fuel or mixed gasoline.

Its working capacity was 19 hours/ha, with an efficiency

of over 90% depending on field conditions as well as,

operator’s ability and skills. It had a working width ranging

from 75 to 100 cm, depending on farmers’ cropping patterns,

with fuel consumption of less than 1 l/hour. In principle,

this machine can be used for cutting and windrowing stemsof rice, maize, grass, and other cereals.

With the price of lawn mower of around IDR2-2.5 million/

unit, and additional costs to completeness of the harvester

machines, estimated total price of the new machine would

reach IDR3-3.5 million/unit. At this price level, the

operational cost was IDR245,000/ha or estimated at IDR100-

50/kg, including the additional costs for transport,

collection, and milling. With these assumptions, the

machines will be an alternative harvester to replace the

current harvest technique.

REFERENCES

Anonymous. 2007. Farm Mechanization Planning. http://www.

Fmech_20 htm/Farm Mechanization Planning.

BBPMP (Balai Besar Pengembangan Mekanisasi Pertanian). 2005.

Standar Prosedur Pengujian Mesin Pemanen Reapper. BBPMP,

Serpong.

BBPMP (Balai Besar Pengembangan Mekanisasi Pertanian). 2007.

Laporan Hasil Pengujian Mesin Pemanen Multicrop Boshima.

BBBPMP, Serpong.

Boshima, Co. Ltd. 2007. Boshima Harvester and Grass Cutter. A

hand out. Shenshen, China.

Brush_Cutter_Grass_Trimmer_Grass_Cutter_CG415.2008.

Internet web.

Table 3. Main components of operational cost for a maize

harvester machine

Component and assumption Unit Value

Capacity hour/ha 19.00

Early investment IDR 3,500.000

Economic age year 3.00

Bank rate %/year 18.00

Fixed cost IDR/hour 1,745.63

Fixed cost IDR/hour 11,195.00

Total operational cost IDR/hour 12,940.63

Total cost/ha IDR 245,871.88Total cost/kg

(maize yield 5 t/ha) IDR/kg 49.17-50.00

Figure 8. Testing the harvester machine in the laboratory of

the Indonesian Center for Agricultural Engineering

Research and Development (top), and in the field

(below)

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Chattopadhyay, P.S. and K.P. Pandey. 1999. Effect of knife and

operational parameters on energy requirement in flail forage

harvesting. J. Agric. Engin. Res. 73(1): 3-12(10).

FAO (Food and Agriculture Organization). 1997. Concept, Selection,

Testing and Evaluation of Farm Machinery. FAO Bulletin. No.

Document, FAO, Rome.Koes-Sulistiadji, A. Hendriadi, Harjono, dan J. Pitoyo. 2005. Penguji-

an Mesin Panen Stripper Harvester tipe Chandoe. Balai Besar

Pengembangan Mekanisasi Pertanian, Serpong.

Rojanasaroj, C.R., C. Sirisomboon, R. Nochai, W. Tangjaroendai.

2003. Small soybean harvester: Implementing a two wheel

tractor. Proc. Int. Conf. on Crop Harvesting and Processing,

ASABE, St Joseph, Michigan, 9-11 February 2003.

Tado, C.J.M. and G.R. Quick. 2003. Development of pedestrian

rice harvester. Proc. Int. Conf. on Crop Harvesting andProcessing, ASABE, St. Joseph, Michigan, 9-11 February 2003.

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