Optimal 1200 RPM Boosts Rice Threshing Efficiency in Indonesian Farm Machinery Study
A 2026 study by Eka Putra Dairi Boangmanalu and colleagues from Politeknik Negeri Medan reveals that operating a rice threshing machine at 1200 rpm delivers the best balance of efficiency, grain quality, and fuel use. Published in the International Journal of Integrative Sciences (IJIS), the research highlights how fine-tuning machine speed can significantly improve post-harvest outcomes for Indonesian farmers, where efficiency and grain preservation are critical to income and food supply.
Rice threshing—the process of separating grains from harvested stalks—is a pivotal stage in agriculture. In many rural parts of Indonesia, farmers still rely on manual methods such as beating or trampling, which are labor-intensive and result in high grain loss. The shift toward mechanized threshing offers a major opportunity to increase productivity, reduce labor, and improve grain quality. However, machine settings, especially rotational speed, play a decisive role in determining performance.
Why This Research Matters
Indonesia is one of the world’s largest rice producers, and improving post-harvest efficiency is essential for food security and farmer livelihoods. Traditional threshing methods typically handle only 20–30 kg per hour and can lead to significant grain loss. Mechanical threshers, especially those powered by small gasoline engines, promise higher capacity and better results—but only when properly optimized.
This study addresses a key knowledge gap: identifying the most effective operating speed for a 100 kg/hour rice threshing machine using the widely cultivated Ciherang rice variety. The findings offer practical, field-ready guidance for farmers and agricultural operators.
Simple but Rigorous Testing
The research team conducted controlled experiments using a spike-tooth cylinder rice threshing machine powered by a 6 horsepower gasoline engine. The machine was tested at five different rotational speeds: 600, 800, 1000, 1200, and 1400 revolutions per minute (rpm).
Each test involved:
- Feeding harvested Ciherang rice into the machine
- Measuring output capacity (kg/hour)
- Calculating threshing efficiency (percentage of grains successfully separated)
- Recording grain loss (unthreshed or lost grains)
- Monitoring fuel consumption
The experiments were repeated three times for accuracy, and standard tools such as tachometers, digital scales, and moisture meters ensured reliable data collection.
Key Findings at a Glance
The study shows a clear relationship between rotational speed and machine performance:
- Working Capacity
Threshing Efficiency
Grain Loss
Fuel Consumption
The Sweet Spot: 1200 RPM
The most important takeaway is the identification of 1200 rpm as the optimal operating speed. At this point, the machine achieves:
- High capacity (100 kg/hour)
- Maximum efficiency (88%)
- Minimum grain loss (12%)
- Moderate fuel consumption (0.58 L/hour)
Beyond this speed, performance begins to decline. Although capacity increases slightly at 1400 rpm, efficiency drops and grain loss rises due to excessive force and airflow inside the machine.
The researchers explain that at very high speeds, grains are more likely to break or be blown away before proper separation. This reduces overall quality and increases waste.
Expert Insight
The research team from Politeknik Negeri Medan emphasizes the importance of balancing mechanical force and grain preservation.
Real-World Impact
The implications of this study are highly practical:
- Operating threshing machines at the recommended speed can reduce grain loss and improve income.
- Provides a clear benchmark for machine calibration and maintenance.
- Supports initiatives promoting mechanization in rural agriculture.
- Offers insights for designing more efficient and user-friendly threshing machines.
By simply adjusting engine speed, farmers can significantly improve both productivity and fuel efficiency—without investing in new equipment.
Design and Operational Insights
The study also highlights several technical considerations:
- The cylinder design (400 mm diameter with 40 teeth) performs best at moderate speeds
- Proper airflow control is essential to prevent grain loss
- Excessive speed creates turbulence, reducing separation efficiency
These findings can guide future improvements in machine design and agricultural engineering.
Limitations and Future Research
The study was conducted under controlled conditions using a single rice variety with a fixed moisture content of 14%. Real-world conditions may vary, including differences in:
- Rice varieties
- Moisture levels
- Feeding rates
Future research is recommended to explore these variables, as well as alternative power sources such as electric or diesel engines for improved sustainability.
Author Profile
(Co-authors: Sahat, Nisfan Bahri, Suadi, Jandri Fan HT Saragi, Angga Bahri Pratama — all affiliated with Politeknik Negeri Medan in engineering and applied sciences.)
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