Threshing Machines(TM)

Prepared by

Er.Uttam Raj Timilsina(MSc.Engineering,IITRoorkee)Professor of Agricultural Engineering,AFUuttamrajtimilsina@gmail.com, 9841684994

ForBatch 2069/2070,BSc.Ag,4th semester(071/7/16-071/10/15)

Course Code:AEN-301,Farm Power and achinery(1+1

Threshing Machines(TM)

• Threshing methods and their mechanization

• Types of threshers,their working principle and constructional details

• Factors affecting thresher performance

• Maize sheller and its construction details

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• Threshing :- It is the seperation/removal of grains from harvested crop by striking action, beating action,treading or rubbing action.It is accomplished either by treading the grain under the feet of man or hooves of animals,on striking the grains with stick or beating or impacting it on hard and rough surface.

• Method of threshing:- Hand beating with capacity of 17-20 kg/hour Treading or rubbing with bullock with the capacity of

140 kg/hour Pedal Thresher with the capacity of 40- 45kg/hrMulticrop thresher with the threshing capacity of 300-

500 kg/hr

Hand beating

Hand beating

Animal hoobing

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• Mechanization of threshing methods:-The threshing operation of cereals crops has been mechanized in developed countries in comparison to threshing operation of pulse crops.oilseed crops.Threshing of wheat crop has been totally mechanized in comparison to other cereal crops like rice.Threshing of rice/paddy crop is still carried out manually and to a small extent by treading the crops under tractor tyresin under developing countries.Now a days mechanization or modernization of threshing operation is carried out in combine harvester where harvesting, threshing ,winnowing,cleaning the threshed crops is done in a single operation by a single unit of machine called combine harvester.

TM• The combine harvester is a latest development in mechanization or

modernization of harvesting, threshing and cleaning operation of grain crops.Various action research /experimental research or doable research were done to develop thresher machines for threshing operation of cereals crops in different regions of the world and with the successful result of those research now we got the present thresher.The research which is a never ending process is continue in different parts of world to modernize the present threshers to fulfill the demand and requirement of future days .Even these days not only for thresher but for the modernization of present combine harvester, research and development is continue for future ,specially to minimize in size and shape as well as to maximize working capacity,efficiency and better performance of machines depending upon the source of power available ,use of electronic and computer devices to fulfill the demand of modernized working performance .

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• Threshers:-Threshers are the machine to perform the works required for threshing mechanism or threshing process which separates the grains from the stalks. A general purpose thresher capable of threshing a variety of crops is operated by 5 hp -8 hp electric motor or engine with the threshing capacity of about 200 kg/hr or 1600 kg /day of 8 working hours at a rotary speed of 550-850 rpm.Thresher mostly consists of different units to perform different actions/ mechanisms like threshing, seperatingand,cleaning

Types of thresher based on threshing unit:-- Spike tooth or pigs type thresher -Rasp bar types type thresher,

-Angle bar types,-wire loop types .

Pig or spike tooth cylinder

Rasp bar threshing cylinder/drum

Wire loop

Rasp bar type

Spike tooth type

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Types of thresher based on source of power available-Manually operated like pedal thresher-Engine operated thresher or tractor operated thresher with power range of 5-40 hp and capacity range of 200-500 kg/hr

-Self propelled engine type as combines harvester Types of thresher based on crop

-Wheat thresher-Rice thresher- straw hold on type or throw in type-Corn sheller-Multi crop thresher-Other crops or special crops thresher

Hold on type thresher

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Parts of thresher

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Threshing process/mechanism-A feeder schute is located in front of threshing drum.Most thresher consists of rasp-bar type cylinder with rasp bar of 6-8 in number,half of these have right hand ribbing and half left hand ribbing and are fixed alternatively. It also consists of angle bar type cylinder as well as spike tooth-type cylinder and concaves. The grain is rubbed or beated to seperate from the stalk without cutting the stalks and damaging the grains between spike tooth or rasp bar or angle bar type cylinder and perforated concave type basket

Threshing drum

Threshing process

Separating process/ Mechanism:-The main separation of the grain from the straw is through the concaves.The loose grains mixed with straw as it leaves the cylinder are separated by oscillating straw rack.These racks may consist either of one piece or of several sections which alternately move with a slight elliptical action to pitch the straw rewarded with each movement

Cleaning process/mechanism:-The function of cleaning unit is to remove chaff or other foreign matters from the grain.This is done by passing uncleaned grains over a series of oscillating sieves and screens through which a current of air is forced/blowed by a fan/blower.Different types of sieves and screens are available for different kinds of crops.Partially unthreshed heads of grain termed tailings drops into thr auger which deliver the tailings to an elevator which in turn conveys the materials upward to the threshing drum for re-threshing action.

Cleaning process

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• Parts of multi crop thresher and their function:- Feeding schute-it perform the feeding action of crop

materials called feeder Threshing cylinder/drum –it is generally 1.4-1.5 m long

and 55-65 cm in diameter and perform the threshing action ,fitted with cylinder pegs,beaters of rasp bar type or angle bar type or spike tooth type or wire loop type threshing devices

Concave type perforated bucket- It seperate the grain and straw,bhusa/chaff

Blower -It blow or supply air for cleaning as well as forcing chaff/straw out of the machine

Thresher

Perforated concave

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Top sieve- it perform the action of sieving

Oscillating sieves –It perform the action of sieving as well as separating straw and grain

Straw/chaff discharge outlet- It discharge chaff out of machine

Grain hopper-It allow the cleaned and collected grains to collect in bags/containers

Transport wheel-It support and allow the whole machine to move forward and backward

Rice thresher

Pedal thresher

Working condition

Non safety operation

Threshing yard

Rice thresher

thresher

Multi crop thresher

• Maize sheller- it is a machine which separate the grain(kernels) from maize cobs. It consist of peg-studded cylinder of diameter 20 cm rotating in side a cylindrical screen.The shelled corn drops through the holes in the screen for cleaning process.Simple type and small handy corn sheller is also available with rotating type tooth disc.

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• Types of corn sheller

• Spring sheller-It has a plate under spring pressure to hold the ears against a rotating disc which loosens and separate the kernels(grains) from the cobs.The grain pass downwards through the cleaning unit and the cobs are rejected by conveyer

• Cylinder type-These are the bigger and larger in capacity engine or tractor operated as 10-35 hp with the cylinder speed of 600-1000 rpm

Multi crop thresher

• Factor affecting thresher performance-

Plant or crop factor-types of crops,moisturecontent of grains,variety of crops ,drying of crops etc.

Machine or mechanical factor-types or models of machines,manufacturing quality,operating quality of machine ,care and maintenance of macnines, handelling of crops,threshers etc.

Miscellaneous factors-Safety factors for grains injury etc