MTech

The term ‘Pokkali’ used in the common parlor refers to a salt tolerant
traditional rice cultivar grown in the coastal saline soils of Kerala, India. The
Pokkali field is a unique eco-system prevailing in the coastal tract of Kerala with
rich bio diversity and amazing capacity to produce organic rice and shrimp
alternatively. Rice is grown during non-saline period and the farmers carry out
shrimp culture during the saline phase with both having unique symbiotic
benefits. Pokkali areas lie in Trissur, Ernakulum and Alappuzha districts covering
a total area of 8500 ha. It spreads over 34 Krishibhavans of these three districts. In
the saline, water-logged Pokkali farm lands, rice and shrimps are farmed
alternatively. The conventional method of harvesting of Pokkali paddy crop by
using sickles. The various farming operations in Pokkali paddy cultivation, the
harvesting is done by women labourers by walking on the swampy and marshy
inundated paddy fields at waist-deep water, which is laborious, tedious and
cumbersome.
Though a number of paddy combine harvesters are commercially available,
none cannot be used in such marshy water logged areas for harvesting paddy.
Hence, a power operated floating harvester with provisions for harvesting and
conveying the ear heads (panicles) of submerged paddy was developed at
KCAET, Tavanur. The overall size of the harvester is 9.6 x 2.2x 2.2 m with a total
weight of about 3 tonnes. Due to the over size and weight, the manoeuvrability
become a great problem for transportation and operation in small paddy lands. It
necessitated designing a scale down proto type of the harvester to operate in all
Pokkali areas for easy transportation and good manoeuvrability.
The major functions of a Pokkali paddy harvester are floating in
water/moving in puddled soil, cutting and conveying of the panicles. The design
analysis of the harvester is sequentially carried out for the floating barge,
harvesting unit and hydraulic system. Hydraulic drive system consisted of a
hydraulic pump, pressure gauge, valves, filters, etc. to guide and control the
system. The capacity of the hydraulic tank was 150 litres and double acting
hydraulic pump has 61.0 l min-1. Harvesting unit of the Pokkali paddy harvester
consists of a reel, cutter bar and conveyor. Reel delivers the stalks to the cutting
mechanism, the cutter bar cuts crop and conveys through front conveyor and
transferred to in the central conveyor. Width of the cutter bar was 2.1 m with
serrated blade to avoid spilling of the stalks. The vertical centre of gravity of the
harvester was designed as 0.854m and longitudinal centre of gravity as 4.58 m. It
was found out that the design of the existing KAU Pokkali paddy harvester was
perfect considering the buoyancy and stability aspects.
The overall size of the newly designed scale down prototype is 6.2 x 1.7 x
1.7 m with a total weight of about 1700 kg. A scale down prototype of the
harvester is designed in such a way that to suit for fragmented Pokkali areas. The
vertical centre of gravity of the scale down prototype is 0.58 m, longitudinal
centre of gravity is 2.67 m and transverse centre of gravity is zero. As the
transverse centre of gravity is zero, scale down Pokkali paddy harvester is stable
to float and longitudinal centre of gravity lies near to the centre and adjacent to the
front and rear side of the harvester, it become a well-balanced machine.