A header reel is the rotating front assembly on many combine harvester headers that helps move standing crop into the cutting and feeding system. It is especially important in grain crops such as wheat, barley, oats, and canola, where stalks must be guided smoothly toward the cutter bar. A well adjusted reel improves crop flow, reduces shatter loss, and helps the combine maintain a steady harvest rate.
Understanding how the reel works connects machine design with plant mechanics and field efficiency.
The reel uses rotating bats or fingers to contact the crop near the upper portion of the stalk and sweep it backward toward the cutter bar. After cutting, the crop is carried into the auger or feed conveyor, which moves it toward the threshing system. Reel speed, height, and fore-aft position must match crop height, crop density, and ground speed.
Poor adjustment can push crop forward, knock grain loose, or leave uncut material behind.
Key Facts
- Reel speed ratio = reel tip speed / ground speed, and a common starting range is about 1.1 to 1.5.
- Reel tip speed = 2πrN, where r is reel radius and N is rotational speed in revolutions per second.
- Crop flow improves when the reel gently guides stalks into the cutter bar instead of striking them hard.
- Reel height is usually set so the fingers contact the crop above the center of mass but below the grain heads or pods when possible.
- Moving the reel forward helps gather leaning or lodged crop, while moving it back can reduce aggressive contact in standing crop.
- Header loss increases when cutter bar speed, reel speed, and combine ground speed are not matched to crop conditions.
Vocabulary
- Header reel
- A rotating assembly at the front of a combine header that guides crop stalks into the cutter bar and feeding system.
- Reel bat
- A horizontal bar on the reel that supports fingers or tines and sweeps crop backward as the reel rotates.
- Cutter bar
- The reciprocating knife section of the header that cuts crop stalks near the base.
- Auger
- A rotating screw-like conveyor that moves cut crop material from the sides of the header toward the feeder opening.
- Lodged crop
- Crop that has fallen or leaned over before harvest, making it harder for the header to lift and cut cleanly.
Common Mistakes to Avoid
- Setting the reel speed much faster than ground speed, which is wrong because the bats can slap grain heads and increase shatter loss.
- Running the reel too low, which is wrong because the fingers can push crop down before it reaches the cutter bar or pick up excess soil and debris.
- Keeping the reel in one fixed position for all crops, which is wrong because standing, short, tall, and lodged crops need different height and fore-aft settings.
- Ignoring uneven crop flow at the auger, which is wrong because bunching at the header can reduce feeding efficiency and cause slugging inside the combine.
Practice Questions
- 1 A header reel has a radius of 0.55 m and rotates at 35 rpm. Calculate the reel tip speed in m/s using reel tip speed = 2πrN, where N is in revolutions per second.
- 2 A combine travels at 1.8 m/s and the reel tip speed is 2.4 m/s. Calculate the reel speed ratio and state whether it is within the common starting range of 1.1 to 1.5.
- 3 A field of wheat is leaning forward in the direction of travel and the header is leaving some heads uncut. Explain how you would adjust reel position and speed, and justify your choices.