LECTURE-10-HARVESTING-AND-THRESHING.pptx

Machinery module

1. HARVESTING AND THRESHING MACHINERY

2. Identity various harvesting and threshing machinery; Operate and evaluate the performance of harvesting and threshing machinery. OBJECTIVES:

3. HARVESTING It is the operation of cutting, picking, plucking, digging or a combination of these operations in removing the crop from under the ground to separate the plant’s useful parts.

4. THRESHING I t is the process of detaching grains from the straw. Additionally, it may include cleaning the grains.

5. SYSTEM OF HARVESTING AND THRESHING

6. HARVESTING 1. Traditional System Hand tools like sickle, yatab , and lingkao are used to cut the standing crop. The sickle is the most popular tool for manual harvesting of rice. Manual harvesting needs about 80-160 man-hours for a hectare of field. 2. Conventional System

7. Harvesting is done using mechanical reapers, reaper-binders and reaper windrowers. Harvesters may be categorized into manually operated and power harvesters. Manually-operated harvesters requires about 50 man-hours per hectare Power harvesters requires 5 man-hours. About 3% to 6% field losses HARVESTING 3. Mechanical System

8. HARVESTING 4. Combine Harvester single machine called combine performs harvesting and threshing while on the go Using a combine harvester may reduce field losses to about 1.5% to 6%, requiring only about 3-21 man-hours per hectare of field

9. HARVESTING 5. Stripping This method is also called in-field threshing or simply stripping and is performed by a machine called stripper The panicle is made to pass between two bars of “V” configuration to separate the grain from the straw. Most strippers are equipped with tanks to temporarily store the harvested grains, or contain mechanisms to transfer the grains into sacks Reduce field losses to about 2% to 6%

10. THRESHING 1. Traditional System Traditional threshing involves the use of non-mechanical power sources to separate the grains from the straw. Hampasan is a popular device for farmers who used it by striking the panicles to wooden slats. Foot threshing and animal treading are old techniques employed for threshing grains Traditional threshing requires 140-220 man-hours per hectare of field. High field losses ranging from 5% to 16%

11. Done using mechanical threshers Mechanical threshers reduces the labor requirement to about 100 man-hours-pedal threshers while 12 man-hours per hectare for power threshers Cleaning grains by winnowing or manually operated winnowers Power threshers with built-in blowers and oscillating screens Reduces the field losses to about 3% to 10% THRESHING 2. Conventional System 3. Mechanical System

12. THRESHING 4. Combine Harvester single machine called combine performs harvesting and threshing while on the go Using a combine harvester may reduce field losses to about 1.5% to 6%, requiring only about 3-21 man-hours per hectare of field

13. THRESHING 5. Stripping This method is also called in-field threshing or simply stripping and is performed by a machine called stripper The panicle is made to pass between two bars of “V” configuration to separate the grain from the straw. Most strippers are equipped with tanks to temporarily store the harvested grains, or contain mechanisms to transfer the grains into sacks Reduce field losses to about 2% to 6%

14. FACTORS AFFECTING CHOICE OF SYSTEM: Kind of crop Timeliness of operation Topography Farm size Type of culture (row or broadcasted, upland or lowland) Availability and cost of labor Availability of capital

15. FACTORS AFFECTING CHOICE OF SYSTEM A major factor affecting choice of system is timeliness of operation because it affects field losses, time available for the next crop and grain quality If the crop is harvested too early, it will have a large percentage of imperfectly formed kernels. The field should be drained 1 – 1.5 weeks before harvesting to harden the soil

16. CUTTING MECHANISMS FOR HARVESTERS Slicing/tearing action – employed in hand tools

17. CUTTING MECHANISMS FOR HARVESTERS 2. High velocity, single-element, impact action – use of sharp or dull edged blades moving at high velocity of 2,000 fpm to 9,000 fpm

18. CUTTING MECHANISMS FOR HARVESTERS 3. Two-element, scissor type action – shearing action between the moving and stationary blades

19. THRESHING MACHINERY Rubbing action – grains are detached from their panicles because of a rubbing action as in treading by man, animal and vehicle. Output of man treading is 14 kg/ hr 2. Impact action – grains are accelerated faster than their panicles and are detached as in hampasan and mechanical threshers. Output of hampasan is 34 kg/ hr Output of mechanical threshers vary with size of machine and power source. 3. Stripping action – grains are detached from their panicles when the straw is pulled through a “V” configuration or a comb-like device is passed through the panicles.

20. MECHANICAL THRESHERS Mechanical Threshers Mechanical threshers are machines that separate the grains from the panicles. This function is achieved by employing impact action. In addition to this primary function, modern threshers also perform the following tasks: Feed the un-threshed grain to the threshing cylinder in an even stream, free from heavy, solid bunches (Feeding Unit) Separate the straw from the grain and chaff, and separate the chaff and dirt from the grain (Cleaning Unit) Deliver the straw through the stacker to the stack and deliver the grain through the grain elevator, weigher or stacker to wagon or bin (Stacking and Storage Unit)

21. Variability of threshers come from : 1. Power source – manual as in pedal thresher or power thresher as in engine-driven thresher (Figure 8 and 9)

22. Variability of threshers come from: 2. Type of feeding: a. Hold-on feeding – Straws do not pass through the threshing section (Figure 10). Low power requirement Lightweight construction Examples: Pedal thresher and Japanese combine

23. Variability of threshers come from: 2. Type of feeding: b. Throw-in feeding – Straws pass through the threshing section (Figure 11). High power requirement Heavyweight construction Examples: Axial-flow thresher and US combine

24. Variability of threshers come from: 3. Direction of threshing materials (Figure 12): a. Tangential-flow – Materials are feed between the revolving cylinder and stationary concave and go straight out of the thresher tangentially. About 60% of the grains pass through the concave and the rest are separated in subsequent operations. b. Axial-flow – Materials are fed between the revolving cylinder and stationary concave on one end, go around the cylinder several times axially and discharge at the other end. About 90% of the grains are separated from the straw at the cylinder.

25. Variability of threshers come from: 4. Types of cylinder teeth (Figure 13): Wire-loop Peg-tooth Rasp-bar

26. Sample problem 1: A 5-m self-propelled combine makes an average stop of 4 minutes everytime its 2-ton grain tank is to be unloaded. The yield of the 20-ha field is 40 tons. The operating speed is 4.8 kph. The time for turning on the headland at the ends of the 500-m field is 15 seconds. Find: a. theoretical field capacity b. actual field capacity c. Field efficiency