Combine Harvester Systems and Components

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Questions and Answers

Which of the following is NOT a machine parameter that affects combine performance?

  • Cutter bar speed and its adjustment
  • Speed of threshing cylinder
  • Time of harvest (correct)
  • Machine vibration

What does header loss primarily indicate?

  • Loss of grains due to over harvesting
  • Loss of grains during moist conditions
  • Loss due to machine vibrations
  • Loss of grains before they reach the platform (correct)

Which factor can contribute to cylinder loss?

  • Improper time of harvest
  • Field size and shape
  • Amount of unthreshed grain from straw walker (correct)
  • Crop density

Which option reflects a technical specification related to operational efficiency of combines?

<p>Height of cut (B)</p> Signup and view all the answers

What is a primary cause of rack and shoe loss?

<p>Excessive afflux from straw walker and sieve (D)</p> Signup and view all the answers

Which of the following is a field parameter that affects combine performance?

<p>Size and shape of the field (C)</p> Signup and view all the answers

What can be a disadvantage of using a combine harvester?

<p>High costs of machine maintenance (C)</p> Signup and view all the answers

What is the impact of crop moisture content on combine harvesting?

<p>It influences grain loss due to shattering (D)</p> Signup and view all the answers

What is an important factor in determining total seed yield when using a combine harvester?

<p>Cutter bar loss (B)</p> Signup and view all the answers

Which operational parameter is NOT relevant to the performance of a combine harvester?

<p>Angle of inclination of the field (D)</p> Signup and view all the answers

What does the reel index represent in the context of harvesting?

<p>Proportion of operational speed to forward speed (D)</p> Signup and view all the answers

Calculating the total grain loss in a combine harvester involves which of the following?

<p>Total seed harvested minus net grain collected (A)</p> Signup and view all the answers

What does the variable $q_g$ represent in the formula for the capacity of a combine harvester?

<p>Yield of grain per hectare (B)</p> Signup and view all the answers

Which of the following represents an advantage of using a combine harvester?

<p>Reduces the labor cost significantly (D)</p> Signup and view all the answers

In the context of operational efficiency of a combine harvester, which parameter is critical?

<p>Peripheral speed of the reel (D)</p> Signup and view all the answers

Which type of loss is associated with the unthreshed seeds in a combine harvester?

<p>Unthreshed over shoe loss (B)</p> Signup and view all the answers

What does a high cutter bar loss signify when harvesting a crop?

<p>Inefficient harvesting leading to potential losses (C)</p> Signup and view all the answers

What is the purpose of adjusting the cylinder-concave clearance in a combine harvester?

<p>To enhance grain separation and minimize losses (A)</p> Signup and view all the answers

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?

<p>1:0.37:0.8 (C)</p> Signup and view all the answers

For medium combines (2.1 m < 𝑙ℎ < 3 m), what is the limit for the ratio of length to diameter to width?

<p>1:0.36:1 (D)</p> Signup and view all the answers

What does the variable 𝑞𝑐 represent in the design of a combine harvester?

<p>Conveyer output, kg/sec (B)</p> Signup and view all the answers

How is the capacity of a horizontal feed auger (𝐶𝑎) calculated?

<p>Using the formula $\frac{\pi D_0^2 - d_i^2}{4} P n$ (D)</p> Signup and view all the answers

What power factor should be used when the required power is between 1 and 2 kW?

<p>1.25 (D)</p> Signup and view all the answers

What factor is NOT included in the calculation of the conveyer output (𝑞𝑐)?

<p>Total weight of the crop (kg) (C)</p> Signup and view all the answers

Which of the following statements about the threshing mechanism is correct?

<p>The number of revolutions (n) is calculated based on linear speed and diameter. (C), The feed rate can be determined using the formula $0.25 * R_b * n * l_d * k$. (D)</p> Signup and view all the answers

In terms of operational efficiency, what is the main benefit of having a high bulk density of crop material on the conveyer?

<p>Enhances the factor of filling (ε) in the conveyer. (C)</p> Signup and view all the answers

Flashcards

Paddy Harvesting Loss

Loss of paddy grains during harvesting, affected by machine and crop factors.

Machine Parameters

Features of the harvesting machine, like speed and clearance, influencing grain loss.

Crop Parameters

Characteristics of the crop, such as moisture and density, affecting grain loss.

Cutter Bar Loss

Grain loss that occurs from the cutter bar area of the combine harvester.

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Reel Index

The ratio of reel's peripheral speed to the forward speed of the combine harvester. (Peripheral speed / Forward Sp. )

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Combine Losses (percentage)

The fraction of total seed yield lost throughout the combine harvesting process.

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Seed Yield (kg/ha)

The total amount of grains harvested per hectare of land.

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Combine Harvester Capacity

The rate at which a combine harvester collects grains.

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Header Length (lh)

The length of the header of the combine harvester.

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Grain Loss Calculation

Identifying the source, and measuring grain loss during harvesting, and calculating the final quantity produced after losses from various areas.

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Tailing

Unthreshed ear heads too heavy to be blown out of the machine, and large enough to pass through the sieve opening.

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Combine Performance Factors (Machine)

Factors related to the combine harvester's machinery, including reel speed/position, cutter bar speed/adjustment, threshing cylinder speed, straw rack/sieve/blower speed, and machine vibration.

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Combine Performance Factors (Crop)

Factors about the crop itself affecting the combine's performance, like moisture content/condition, harvest time, density, and variety.

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Combine Performance Factors (Operating)

Factors related to how the machine is operated, like forward speed, height of cut, and direction of cut (relative to plant orientation).

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Combine Performance Factors (Field)

Factors about the field affecting the combine's performance, like size/shape, soil moisture content during harvest.

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Header/Cutter Bar Loss

Grain loss from the header or cutter bar due to grains being dropped, missed, or shattered by the reel or cutter bar.

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Cylinder Loss

Grain loss in the threshing cylinder, often seen in the straw walker and cleaning sieve.

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Rack and Shoe Loss

Grain loss resulting from the straw and chaff afflux, collected from the straw walker and sieve.

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Combine Dimensions

Relationship between header length (lh), header width (ld), and cylinder sweep (cs) for small, medium, and large combine harvesters.

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Conveyer Output (qc)

The amount of crop material a conveyer transports per second, in kilograms.

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Feed Auger Capacity (Ca)

The volume of material a horizontal feed auger moves per minute (in cubic meters.

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Feed Auger Power (Wh)

The power required for horizontal movement of material by the feed auger.

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Threshing Speed (n)

The rotational speed of the threshing cylinder.

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Threshing Feed Rate (q)

The amount of material fed to the threshing mechanism per unit of time.

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Conveyer Power (Wl)

Power required to lift material vertically.

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Auger Fill Factor

A factor or percentage that represents how efficiently the feed auger fills, affects the calculation of the capacity in tons per hour.

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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.
  • Feeder Conveyor: Transports crop to threshing unit.
    • Sprockets are fixed on two shafts.
    • Serrations on mild steel slats prevent crop from rolling back.
  • 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.
  • 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.
  • 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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