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SAE J1371 Hydraulic Excavator Swing Performance and Rating Procedure (Cancelled Standard)
SAE J1371, cancelled in February 2002, was developed to provide a standardized method for calculating and specifying swing performance characteristics of hydraulic excavators. Although the standard is no longer active, its definitions, formulas, and rating procedures have influenced the design and testing of swing systems. This article covers the key aspects of the standard, including swing speed and torque calculations, performance verification, and brake requirements.
Purpose and Scope of SAE J1371
The standard aimed to unify how manufacturers determine and communicate swing performance. It defined terms like pinion ratio, gear reduction, gear efficiency, and specified test conditions for measuring time to swing 90 degrees and swing angle of deceleration. It applied to hydraulic excavators as defined in SAE J1057 and set forth minimum performance and safety requirements for swing brakes, parking brakes, and swing locks.
Key Definitions and Formulas
The core of the standard lies in the calculation of rated swing speed and swing torque. The pinion ratio (Pr) is the ratio of the number of teeth on the swing bearing gear to the number of teeth on the swing drive pinion. Gear reduction ratio (Rg) is the total reduction between the swing motor and pinion. Gear efficiency (Eg) is capped at 98% per gear set for rating consistency.
| Parameter | Symbol | Formula / Description |
|---|---|---|
| Pinion Ratio | Pr | (Teeth of swing bearing gear) / (Teeth of swing drive pinion) |
| Rated Swing Speed | Sn | Sn = Sm / (Pr × Rg) where Sm is swing motor speed |
| Rated Swing Torque | Ts | Ts = Tm × Rg × Pr × Eg where Tm is swing motor torque |
| Gear Efficiency | Eg | Product of individual gear set efficiencies, each ≤ 98% |
Performance Testing and Verification
The standard specified test conditions: machine level within 1%, working equipment extended to maximum radii, engine at full throttle. Manufacturers had to verify published values for swing speed and torque with test results exceeding 95% of the published figures. The time to swing 90 degrees could not exceed the published time by more than 5%, and the swing angle of deceleration also had a 5% tolerance.
Brake Requirements:
- Swing Brake: Must bring the upperstructure to a complete stop from rated speed ten times in rapid succession, without the deceleration angle increasing more than 20%.
- Swing Parking Brake: Required if the swing brake cannot hold the upperstructure after stopping. Must have torque capacity ≥ 105% of maximum motor torque and be applicable without engine running.
- Swing Lock: Optional mechanical lock that must withstand engagement at full throttle without damage.
⚠️ Standard Cancellation: SAE J1371 was cancelled because its test procedures relied on drum and shoe type swing brakes, which are no longer used in modern hydraulic excavators. Today’s hydraulic motors double as braking sources, and more advanced controls have rendered the original test methods obsolete.
🛠️ Engineering Design Insight: Even though the standard is cancelled, the approach of limiting gear efficiency to 98% per set provides a conservative baseline for rating. When verifying performance, the 95% threshold for speed and torque and the 5% limit on swing time and deceleration remain practical benchmarks for consistency.
Frequently Asked Questions
1. Is SAE J1371 still active?
No. It was cancelled in February 2002 and is not recommended for new designs. Modern excavators use different braking and control technologies that require updated testing procedures.
2. How is rated swing speed calculated under the standard?
Rated swing speed is calculated as Sn = Sm / (Pr × Rg), where Sm is the swing motor speed in rpm, Pr is the pinion ratio, and Rg is the gear reduction ratio.
3. What are the key test conditions for swing performance?
Tests must be conducted on a level surface (within 1%), with the working equipment extended to maximum radii and the bucket empty, engine at rated speed. The machine configuration must match that used for lift capacity testing per SAE J1097.
4. Why did SAE cancel the standard?
The standard was considered obsolete because its test methodology catered to drum and shoe brakes. Modern hydraulic excavators rely on hydraulic motor braking, making the old procedures inapplicable. The formulas, while basic, are still available for informal use but the formal test procedures are outdated.
This summary provides a historical and technical reference for engineers working with swing systems. Although SAE J1371 is no longer active, understanding its content can still offer insight into the fundamentals of swing performance rating.
