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Questions and Answers
Which of the following is NOT a machine parameter that affects combine performance?
Which of the following is NOT a machine parameter that affects combine performance?
What does header loss primarily indicate?
What does header loss primarily indicate?
Which factor can contribute to cylinder loss?
Which factor can contribute to cylinder loss?
Which option reflects a technical specification related to operational efficiency of combines?
Which option reflects a technical specification related to operational efficiency of combines?
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What is a primary cause of rack and shoe loss?
What is a primary cause of rack and shoe loss?
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Which of the following is a field parameter that affects combine performance?
Which of the following is a field parameter that affects combine performance?
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What can be a disadvantage of using a combine harvester?
What can be a disadvantage of using a combine harvester?
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What is the impact of crop moisture content on combine harvesting?
What is the impact of crop moisture content on combine harvesting?
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What is an important factor in determining total seed yield when using a combine harvester?
What is an important factor in determining total seed yield when using a combine harvester?
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Which operational parameter is NOT relevant to the performance of a combine harvester?
Which operational parameter is NOT relevant to the performance of a combine harvester?
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What does the reel index represent in the context of harvesting?
What does the reel index represent in the context of harvesting?
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Calculating the total grain loss in a combine harvester involves which of the following?
Calculating the total grain loss in a combine harvester involves which of the following?
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What does the variable $q_g$ represent in the formula for the capacity of a combine harvester?
What does the variable $q_g$ represent in the formula for the capacity of a combine harvester?
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Which of the following represents an advantage of using a combine harvester?
Which of the following represents an advantage of using a combine harvester?
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In the context of operational efficiency of a combine harvester, which parameter is critical?
In the context of operational efficiency of a combine harvester, which parameter is critical?
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Which type of loss is associated with the unthreshed seeds in a combine harvester?
Which type of loss is associated with the unthreshed seeds in a combine harvester?
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What does a high cutter bar loss signify when harvesting a crop?
What does a high cutter bar loss signify when harvesting a crop?
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What is the purpose of adjusting the cylinder-concave clearance in a combine harvester?
What is the purpose of adjusting the cylinder-concave clearance in a combine harvester?
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What is the ratio of length to diameter to width for small combines with a longitudinal height (𝑙ℎ) less than or equal to 2.1 m?
What is the ratio of length to diameter to width for small combines with a longitudinal height (𝑙ℎ) less than or equal to 2.1 m?
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For medium combines (2.1 m < 𝑙ℎ < 3 m), what is the limit for the ratio of length to diameter to width?
For medium combines (2.1 m < 𝑙ℎ < 3 m), what is the limit for the ratio of length to diameter to width?
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What does the variable 𝑞𝑐 represent in the design of a combine harvester?
What does the variable 𝑞𝑐 represent in the design of a combine harvester?
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How is the capacity of a horizontal feed auger (𝐶𝑎) calculated?
How is the capacity of a horizontal feed auger (𝐶𝑎) calculated?
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What power factor should be used when the required power is between 1 and 2 kW?
What power factor should be used when the required power is between 1 and 2 kW?
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What factor is NOT included in the calculation of the conveyer output (𝑞𝑐)?
What factor is NOT included in the calculation of the conveyer output (𝑞𝑐)?
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Which of the following statements about the threshing mechanism is correct?
Which of the following statements about the threshing mechanism is correct?
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In terms of operational efficiency, what is the main benefit of having a high bulk density of crop material on the conveyer?
In terms of operational efficiency, what is the main benefit of having a high bulk density of crop material on the conveyer?
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Study Notes
Combine Harvester Systems
- Combines all operations: cutting, feeding, threshing, cleaning, and discharging grain.
- Straw is typically discharged behind the combine in a windrow.
- Various types exist: mini combines, small rice combines, and large combines.
- Tractor-drawn and self-propelled types are available.
Combine Harvester Components
-
Reel: Holds and guides crop to the cutter bar.
- Diameter ranges from 1-1.5 meters.
- Hydraulic attachments adjust height and clearance.
- Types include bat type (good for standing crops) and pick-up/tyne type (suitable for lodged crops).
-
Platform Auger: Collects crop from entire length and brings it to center.
- Prongs push crop to the conveyor chain.
- Vertical height adjustment maintains 20 mm clearance.
- Diameter ranges from 40-60 centimeters.
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Feeder Conveyor: Transports crop to threshing unit.
- Sprockets are fixed on two shafts.
- Serrations on mild steel slats prevent crop from rolling back.
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Threshing Unit: Removes grains from heads/pods.
- Works via impact force from rotating cylinder.
- Rubbing action occurs between crop layers.
- Types include raspbar (wheat) and spike tooth (rice).
- Factors affecting effectiveness include peripheral speed of cylinder, concave-cylinder clearance, number of rasp bars/spike teeth, crop type, moisture content, and feed rate.
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Straw Walker: Separates grains from chaff.
- Grains drop onto oscillating pans.
- Long straw is ejected from the machine.
- Number of walkers ranges from 4-7, in a cascade arrangement.
- Length ranges to 4m with speed of 190-200 rpm.
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Grain Cleaning Unit: Separates and cleans grain from straw.
- Returns unthreshed heads to the threshing unit.
- Removes chaff, dust, and short straw.
- Consists of 2-3 oscillating sieves and a blower with 4-6 blades.
- Heavy unthreshed heads are blown out.
- Large enough pieces pass through sieves and openings.
Combine Harvester Advantages and Disadvantages
- Advantages:*
- Reduced labor needs
- Scheduled operations, less affected by adverse weather
- Time-saving harvest
- Allows for timely seedbed preparation for the next crop
- Disadvantages:*
- High initial investment cost
- Difficult to use in small or irregularly shaped fields
- Loss of straw
- High operational and repair costs
Factors Affecting Combine Performance
- Machine Parameters:*
- Reel speed and position
- Cutter bar speed and adjustment
- Threshing cylinder speed
- Straw rack, sieve, and blower speed
- Machine vibration
- Crop Parameters:*
- Moisture content
- Crop condition (e.g., lodging)
- Crop variety
- Crop density
- Operating Parameters:*
- Forward speed of the combine
- Height of cut
- Direction of cut (relative to plant orientation)
- Field Parameters:*
- Field size and shape
- Soil moisture during harvest
Sources of Grain Loss
- Header/Cutter Bar Loss:*
- Determined on parts protected from the combine's airflow.
- Includes manually collected fallen grain and complete/incomplete heads.
- Includes grain shattered by the reel (speed and over maturity), and improper machine adjustment.
- Grain Shatter from Cutter Bar:*
- Excessive vibration can lead to grain shatter.
- Grain can fall before reaching the platform.
- Grain can be missed by the cutter bar due to registration or height issues.
- Cylinder Loss:*
- Measures grain collected from the straw walker and cleaning sieve after harvest.
- Grain collected from a 1 m² area after harvest, minus the grain collected from the area beforehand, divided by the area before harvest.
- Rack and shoe loss:*
- Collects the straw and chaff separately using cloth sheets behind the machine.
- Operation starts 5 meters ahead and ends 5 meters behind.
- Pre-harvest loss:*
- Minimized by selecting three random sample areas.
- Collected from the area with a 1-meter length, and machine width.
- Manually collected fallen grain and complete/incomplete heads.
- Factors affecting grain loss:*
- Threshing cylinder speed
- Cylinder-concave clearance
- Forward speed
- Reel index
- Reel position
- Height of cutter bar
- Blower speed
- Cleaning sieve opening
- Crop moisture content
- Lodging
- Crop variety
- Crop density
Combine Harvester Design and Capacity
- Detailed calculations for header length, threshing mechanism design, power requirements, straw-walker length, and cleaning sieves are provided. Individual components are described in detail as to their functionality and dimensions.
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Description
This quiz covers the essential systems and components of combine harvesters. You'll learn about the different operations involved in harvesting and the specific functions of components like the reel, platform auger, and feeder conveyor. Ideal for anyone interested in agricultural machinery.
