Development and fabrication and testing of Rice seed dresser1Nasirembe W. W., 2Win Kore, 3Kimani, J.

1Kenya Agricultural Research Institute, P.O.Box 100,

Molo, 1Kenya Agricultural Research Institute, Kibos, P.O.Box

1490 Kisumu, 1Kenya Agricultural Research Institute, Mwea

Tebere P.O.Box 298, Kerugoya,.

Corresponding author: nasirembew@yahoo.com, +254 733 812 953

Abstract

To increase efficiency in agricultural production among small

scale farmers, mechanization was found to be the main driving

tool. When all the mechanization aspects were ranked through a

survey, seed processing and harvesting were found to be the most

crucial areas of need hence the decision to fabricate the small

grains seed dresser machine. Two prototypes, one electrically and

another gasoline operated seed dressers (KARI Seed Dresser) were

fabricated and tested for efficiencies. They are still undergoing

testing at KARI Njoro, KARI Mwea, KARI Kibos and farmers fields.

Results have shown that the dresser of 50kg capacity can

uniformly dress small grains in 40 seconds, employs only two

people, self offloading, and low maintenance. The electrically

powered seed dresser loading was found to be 35Kg and the

gasoline one was 50Kg. The difference was due to the prime mover

capacities which were 2Hp and 5.5Hp respectively. Uniformity of

seed pesticide coverage was found to have a variability of 0.998.

Comparing the machine cost, its price was $574 as compared to

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$6711 for imported ones. Aggressive agricultural mechanization

can create job opportunities, speed up agricultural development

and improve overall output in food production through availing

quality seed for farmers in the region.

Key Words; small grain, seed coverage coefficient, seed

dresser.

Introduction

To increase efficiency in agricultural production among small

scale farmers, mechanization was found to be the main driving

tool (Rice Baseline Report, 2012). Mechanization in agriculture

has been practiced by isolated farmers since the advent of

agriculture in an unstructured manner (NAMS 1992). Almost all

agricultural activities can be mechanized at different levels and

magnitudes along the production value chain (FAO, 2008). Critical

areas of mechanization include; seedbed preparation, sowing, pest

control, harvesting and post harvest handling (Sikh, 2000). When

all the mechanization aspects were ranked through a study,

harvesting and seed processing were found to be the most crucial

areas of need (Rice Baseline Report, 2012) hence the decision to

fabricate and test a small scale seed dresser machine. Another

survey was carried out to take an inventory of available machines

in use and determine their appropriateness (Nasirembe et al

2012). Attention has therefore turned to mechanization of seed

dressing to reduce losses following the dwindling labour force as

the youth opt to undertake white collar jobs, increase in demand

for food and the high cost of imported machinery and increase

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efficiency. Import seed dressers are not appropriate to local

conditions and may become unnecessarily expensive when the

imported tools and equipments breakdown due to either lack of

spares or obsolescence. While the rest of the developing world

has moved from traditional agricultural production methods during

the last 50 years, EAAPP countries have remained a sole importer

of agricultural machinery. The objective of the study was

therefore to innovatively design, fabricate and test a seed

dresser for small grains in order to contribute to the food

productivity in the EAAPP countries and beyond. A design concept

was developed from which working sketches were drawn leading to a

bill of quantities. Materials were acquired from local hardware

outlets, cut and shaped from local machine shops for assembly.

Prototypes of a electrically and gasoline operated small grain

seed dresser (KARI Seed Dresser) have been fabricated and tested

for efficiencies and are under observation at KARI Njoro, Mwea,

Kibos and Framers’ farm. The machines main features are

portability, easily and locally assembled, affordability, timely

usage, requiring basic skills to operate, local serviceability

and gender friendliness. The dressing efficiency was found to be

over 95% and the lowest was 85% in offloading. The seed dresser

coated 35Kg of seed with insecticide in 30 seconds with an

efficiency of over 95%. Aggressive mechanization can improve the

overall output in food production.

Objectives

The broad objective was to innovatively design, fabricate and

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test a portable seed dressing machine.

Specific objectives:

To design a small-scale wheat thresher

To fabricate and test the performance of the prototype

To manufacture and continually improve the equipment as deemed

necessary

Materials and Methods

Understanding the crop

physiology at maturity and forces

involved while detaching the grain

from the ear formed the basis of

original design while creating

room for improvement processes.

Sketches of the prototype and

working diagrams were drawn from

which a bill of quantities was

derived. The materials were acquired and using the working

drawings, materials were cut and machined to desired shapes. The

cut and shaped parts were assembled and prototype tested.

Limiting factors were; drum size, Prime mover rating, cost of the

assembly. Data was collected on; Power requirements, drum speed,

coating uniformity, time to acquire desired coating, offloading

time, labour requirement and rate of output. There are other

issues that could be captured such as gender inclusiveness of the

design, aesthetics, environmental safeguard and consumer

acceptability. Some of the data is continually being collected.

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Figure 1 Schematic fabrication flowchart

Two models, gasoline and motor powered dressers were tested.

To determine capacity, rice grains were weighed in batches of 5

kg. The drum door was slid open and loaded and switched on with

an additional 5Kg batch at a time in each model until the machine

was unable to rotate the loaded drum in each case Fig. 2. This

was done without adding the liquid insecticide; it was rotated by

switching on the engine/ motor. In each case when the drum could

not rotate, offloading in steps of 1Kg was done until the

respective drums cold just rotate. Overhanging load was the

calculated as follows;

To calculate overhung load, gear drive manufacturers use the

formula:

Overhung Load = 126,000 x HP x FC x LF x P.D. x RPM

where:

HP = Horsepower

FC = Load connection factor

Lf = Load location factor

P.D. = Pitch diameter of the sprocket, sheave or

gear

RPM = Revolutions per minute of the shaft

The load connection factor, or FC, describes the type of

sheave, sprocket, or pinion mounted on the shaft. A flat-belt has

relatively high tension in order to transmit the load by

friction. A V-belt has moderate tension in order to seat the V-

belt and to transmit the load by friction. A timing-belt has some

tension and a chain has very little tension since the load is

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transmitted by the teeth. A pinion or gear has a separating force

related to the pressure angle of the tooth form.

Therefore, each connection is given a different factor to

account for this additional load.

Flat-belt = 2.50, Pinion or gear = 1.25, V-belt = 1.50.

Timing-belt = 1.30, Sprocket = 1.00

So 30% of load was removed to acquire factor 1.00 in V-belt as in

sprocket.

The operating load capacity was calculated from;

Load factor for V-belt = 1.3

Determined load capacity= 70Kg

Load (gasoline) less overhanging load =70-(0.30×70) Kg

=49 Kg recommend 50Kg

Load (Electric) =45-(0.30×45) Kg

=31.5 Kg recommend 30Kg

0 10 20 30 40 50 60 70 800

20

40

60

f(x) = − 0.02393939394 x² + 0.23303030303 x + 46.6333333333f(x) = − 0.01192307692 x² + 0.20192307692 x + 49.1098901099

Gasoline (rpm)Polynomial (Gasoline (rpm))Electric(rpm)Polynomial (Electric(rpm))

Kg

RPM

Figure 2 Selecting capacity for specific dresser

Uniformity of pesticide coverage

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To determine the uniformity of seed treatment on the electric

seed dresser, two series of tests were carried out. In the first

series, 30Kg of samples of rice were treated with 700ml of water

containing 1% wt/vol. brilliant sulphaflavine dye. Individual

seeds were washed in 10ml. of distilled water and the washings

were then analysed with a fluorometer to determine relative

amounts of dye picked up by each seed.

In the second series five 30Kg samples of the seed were

treated with a mixture of 350ml of Vitrax RS flowable (Uniroyal

limited) seed dressing and 350ml of dye solution. Ten seeds from

each sample were washed individually in 5ml aliquots of distilled

water and the washings were analysed as before. The procedure was

repeated for the gasoline powered dresser. The coefficient of

variation was calculated for the individual seeds within each

sample. The method was adopted from (Ford, 1986)

Table 1. Special features for the seed dresser

Characteristic Gasoline Electric

Drum size 0.21m-3 0.21m-3

Prime mover rating,

Hp

5.5Hp 2Hp

Mean drum speed, rpm 41 37Coating uniformity

coefficient

0.98 0.96

Time to acquire

desired coating, sec

40 30

7

Offloading time,

minutes

3 5

Rate of output,

Kg/hr

545.5 490.9

Labour requirement,

md

2 2

Cost of the

assembly, $

568 524

Results and Discussion

The two models carrying capacity rating were determined as

30Kg for the electric dresser and 50 Kg for the gasoline one. The

amounts of chemical used per kilogram were the same in each case

according to their manufacturers’ recommendation. The

coefficients of dye on individual seeds compare favourably in the

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Figure 4 Electric seed dresser at afield day

Figure 3 Gasoline seed dresser in afarmers grain store

two types of seed dressers, for which coefficients of variation

approaching 100%. The difference between the two coefficients of

variation in this study is likely due to the effects of the

difference in prime mover capacity which led to a differential in

ability to take overhanging load. Though increased motor horse

power will lead to increased cost of production and power

requirement, the ability to take overhanging load may disappear.

Time for attaining those respective coefficients was found to be

30 and 40 seconds for electric and gasoline dressers

respectively.

Conclusion

Output of the two models was found to be 515Kg/hr and 720Kg/hr

for electric and gasoline driven dressers respectively. The

treatment method outlined above provides relatively uniform

application of liquid seed dressings to batch quantities of seeds

with less man-day requirement.

Recommendations

Work should be undertaken to standardize pesticide application

into the drum. Operators should be trained before using the

machine. More work is required to establish energy requirement

and germination trends of seed treated by the dresser.

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