Combine harvester

Er. Uttam Raj Timilsina(MSc.Engineering,IIT Roorkee)
Professor of Agricultural Engineering,Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal
[email protected]
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1. Combine Harvester(CH) Prepared by Er.Uttam Raj Timilsina ( MSc.Engineering,IIT Roorkee ) Professor of Agricultural Engineering,AFU [email protected] , 9841684994 For Batch 2069/2070,BSc.Ag,4 th semester(071/7/16-071/10/15) Course Code:AEN-301,Farm Power and achinery (1+1

2. Components and Working Principle Combine Harvesters :-These are the machines used for harvesting,threshing,cleaning the grains from straw in a single operation. These can be pulled and operated by tractor as well as self propelled combine machines are available .The suitable working speed of combine harvester is o.8-8km/hr for rice and 2-6 km/hr for wheat with the reel speed of 1.25-1.5 times greater than working speed. The cutting width or capacity of tractor drawn combine varies as 1.25-2.5 meter in smaller combine and 3-6 meter in bigger combine with the power requirement of 10 hp/meter of cutting width.The self propelled combines are the latest model with the power of 60-150 hp and cutting width of 2-7 meter.The combine harvester consists of cutting or harvesting unit,threshing unit,seperating unit,cleaning unit ,grain handling /storage unit,and straw handling unit.The power requirement per meter of cutting width in self propelled combine is about 15 hp/meter.

3. CH Function of combine harvester- Feeding the standing crops to the cutter bar with the help of reel Cutting the crop(harvesting) Feeding the crop to threshing unit Threshing the crop Separating the husk from grains Cleaning the grains Conveying and storing the grains

4. CH Requirement of a perfect Combine Harvester-: There should be less broken of grains No grains losses on the ground at the cutter bar end No grain losses at the back end of the harvesting unit No unthrashed grain Proper threshing of grains without any injury It should give clean grains Machine should be capable of operation on crop even with higher moisture content Machine should be capable of working on various crops Ease of operation More output with safety measures Easy to maintain Less consumption of spares and fuels

5. CH Type of combine harvester(CH) Pull type or tractor mounted/drawn CH- These are of two size smaller and bigger with the cutting width(capacity) of 1.25-2.5 meter and 3-6 meter with the power requirement of about 10 hp/meter of cutting width Pull type or tractor drawn with auxiliary engine CH :-These are the machines ground speed is covered tractor and working power is covered by auxiliary engine Self propelled combine harvester(CH ):-These are the latest model with the power of 60-150 Hp and cutting width of 1.5-2 meter(smaller) and 2-7 meter(bigger).The power requirement per meter cutting width is about 15 Hp/ meter.The suitable working speed in field is 2-6 km/hr and in road is 4-20 km/hr.

6. Tractor mounted CH

7. Tractor mounted CH

8. Self propelled CH

9. Self propelled CH

10. Self propelled

11. Self propelled CH

12. Rice CH

13. Rice CH

14. Main parts of Combine Harvester(CH) Reel Cutter bar with automatic cutting height adjuster( censer type) Auger Elavator to threshing cylinder Stone trap Threshing cylinder with front beater Rear beater Perforated friction deviced concave Main grain pan of oscillating type Oscillating sieves more than one Air blower with fan Grain elevator to tank Unloading auger Grain tank Straw walker Grain loss monitor Pan under walker

15. Cutting,threshing,cleaning mechanism of a combine harvester:- The standing crop is guided to the cutter bar by the help of reel and dividers. The reel diameter is 1-1.5 m.The clearance between cutter bar and bottom of reel is 12.5-25cm and adjustable. The cutter bar with serrated knives to cut the crop is placed 7.5-90 cm above the ground level and adjustable.The crop is cut by the action of cutter knives and the cut crop is accumulated by auger and send to thresher cylinder through elevator .Threshing takes places between threshing drum and concave at a speed of 2000-7000 rpm. .The threshing clearance between drum and concave at front is 19-13mm and at rear is 9-6mm as at the ratio of 2.5:1.After threshing the threshed materials like straw or chaff pass on to the shakers type straw walker while mixture of grains and chaff pass to the series of shaker sieves where wind blower blows the chaff out of the machine and cleaned grains are collected to the returned pan and is send to grains tank by the help of grain auger and elevator.Pieces of unthreshed heads are subjected to pass to the main threshing drum for re-threshing or some small re-thresher devices .The losses crop ,grains and all the problems of machine parts is monitored by grain loss monitor.