Er. Uttam Raj Timilsina(MSc.Engineering,IIT Roorkee) Professor of Agricultural Engineering,Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal uttamrajtimilsina@gmail.com *All Right Reserved** Uploaded and Shared by AgriYouthNepal

1. Threshing Machines(TM)
Prepared by
Er.Uttam Raj Timilsina(MSc.Engineering,IIT
Roorkee)
Professor of Agricultural Engineering,AFU
uttamrajtimilsina@gmail.com, 9841684994
For
Batch 2069/2070,BSc.Ag,4th semester(071/7/16-
071/10/15)
Course Code:AEN-301,Farm Power and
achinery(1+1

2. 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

3. TM
• 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/hr
 Multicrop thresher with the threshing capacity of 300-
500 kg/hr

4. Hand beating

5. Hand beating

6. Animal hoobing

7. TM
• 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 tyres
in 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.

8. 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 .

9. TM
• 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, seperating
and,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 .

10. Pig or spike tooth cylinder

11. Rasp bar threshing cylinder/drum

12. Wire loop

14. Rasp bar type

15. Spike tooth type

16. TM
 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

17. Hold on type thresher

18. TM

19. Parts of thresher

22. TM
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

26. Threshing drum

27. Threshing process

28. 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

29. 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.

30. Cleaning process

31. TM
• 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

32. Thresher

33. Perforated concave

35. TM
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

36. Rice thresher

37. Pedal thresher

38. Working condition

39. Non safety operation

40. Threshing yard

41. Rice thresher

42. thresher

44. Multi crop thresher

45. • 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.

46. TM
• 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

48. Multi crop thresher

49. • Factor affecting thresher performance-
Plant or crop factor-types of crops,moisture
content 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