Exploring different Tractor torque testing methods
Getting accurate tractor torque readings is essential for understanding tractor performance, diagnosing issues, and ensuring optimal operation. Some agricultural machinery dealers and service providers have several methods at their disposal, each with unique advantages and limitations. But, which is the most accurate, time efficient, real life simulating option?
We’ve researched the top three tractor torque testing approaches and gathered the pros and cons for you.
Hub dynamometers
How it works:
The tractor’s wheels are removed, and the dynamometers are connected directly to the axle hubs. This bypasses the tyres but includes the drivetrain.
Pros:
- More accurate than rolling roads due to elimination of tyre slip.
- Measures drivetrain torque while excluding wheel and tyre variables such as wheel and tyre size.
- Ideal for diagnostics and benchmarking.
- Diagnosis of transmission faults.
- Allows the testing of the most powerful tractors which may not have PTO.
Cons:
- Labour-intensive setup—requires wheel removal and secure mounting.
- Not suitable for quick field testing.
- May not reflect real-world traction conditions.
- Equipment is bulky and expensive, often requiring a dedicated facility.
Rolling roads
How they work:
The tractor is driven onto rollers that simulate road resistance. Torque is measured through the wheels, capturing the entire drivetrain’s performance.
Pros:
- Measures real-world torque delivery through the wheels.
- Captures drivetrain losses, tire performance, and traction effects.
- Useful for comparing different drive modes (for example: 2 wheel drive vs 4 wheel drive).
- Useful for testing vehicle braking performance.
Cons:
- Requires precise setup and calibration.
- Tyre slip can introduce variability in results.
- Tyre size and tread pattern could influence results.
- Equipment is bulky and expensive, often requiring a dedicated facility.
PTO Dynamometers
How they work:
The PTO dynamometer connects directly to the tractor’s Power Take-Off (PTO) shaft, measuring torque and power output from the engine through the PTO system. The rotating energy of the engine drives a 3 phase AC alternator through a decrease/ increase speed gearbox. The output of the alternator is directly connected to resistors. The resistors then convert the engine power into hot air which is discharged vertically with a fan.
Pros:
- Simple and quick setup for most tractors.
- Direct measurement of PTO power, which is critical for all PTO driven implements
- Portable and cost-effective, especially for field service.
- Prove performance of power and torque curves
- Break-in (de-glazing of bores)
- Prove up-rated performance
- Simulate varying load conditions to assess fuel consumption variations
- Can be fitted to most tractors with accessible and functional PTO systems
- Test the functionality of:
- fuel pumps and injectors
- cooling system
- clutch and transmission
- Governor response
Cons:
- Only measures PTO output, not full drivetrain performance.
- Doesn’t account for wheel slip, transmission losses, or real-world traction.
comparison table
Conclusion
Each torque testing method serves a different purpose:
- Hub dynamometers provide precise drivetrain diagnostics without tyre interference.
- Rolling roads offer a holistic view of real-world performance.
- PTO dynamometers are ideal for quick checks and PTO-specific performance.
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For agricultural machinery dealers, the best choice depends on the testing goals, available resources, and customer needs. In some cases, a combination of methods may offer the most comprehensive insight into tractor performance.
Get in touch today to find out more about the Froment Dynamometers can enrich your services.
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