Agricultural tractors. Test procedures - Power tests for drawbar
1Key Takeaways
1 Scope This document specifies test procedures for determining the power available at the drawbar on agricultural tractors of the wheeled, track-laying or semi-track-laying type.
2Expert Interpretation
An in-depth analysis of BS ISO 789-9:2018, the international standard for traction power testing of wheeled and crawler tractors, covers test conditions, measurement methods, fuel consumption assessment, and CVT-specific requirements, providing technical specifications for agricultural machinery performance verification.
Analysis of the core content of the standard
| Test items | Traditional gearbox | Continuously variable transmission (CVT) |
|---|---|---|
| Maximum power test | Must cover 3 adjacent gears | Divided into 7 speed points from 5-16km/h |
| Fuel consumption test | 7.5km/h and 7-10km/h gears | Must test in manual mode first, then in automatic mode |
| Slip ratio limit | ≤15% (dual wheel difference ≤5%) | |
Key Technical Requirements
Tire Specifications: During testing, the tread pattern height must be ≥ 65% of that of a new tire (based on the three-point measurement method in Appendix A). Manufacturer-approved weights are permitted.
Test Environment: Atmospheric pressure ≥ 96.6kPa, ambient temperature 20±15℃, and the road surface must be dry concrete/asphalt.
Special Model Processing
For tractors without PTO power output, the following additional tests are required:
- Variable traction-speed test (100r/min step)
- 1-hour continuous maximum power test (fluctuation within ±2%)
Implementation Recommendations
DPF Processing:For tractors equipped with a diesel particulate filter, regeneration should be completed before testing. If regeneration is triggered during the test, the test must be paused.
Data Recording:Twelve parameters, including engine speed, traction, and slip ratio, must be recorded according to the ISO 789-13 template. The measurement error of hourly fuel consumption must be ≤1%.