As equipment owners look for ways to cut fuel costs and routine maintenance on legacy machinery, repowering a classic Ferguson tractor with an electric drivetrain has moved from experiment to practical upgrade.
In a recent customer project, the goal was simple but demanding: replace the tractor's original 26 HP internal combustion engine with a DC traction motor, keep the existing 4-speed manual gearbox intact, and add a matched motor control system.
This article breaks down the engineering challenges, the motor selection process, and how our XQ-18-7P 96V 18kW DC series-wound traction motor delivered a drop-in electric solution that seamlessly interfaced with the stock gearbox splined shaft.
Why Repower a Ferguson Tractor with an Electric Motor?
A small Ferguson utility tractor is a legendary workhorse—used for mowing, dragging, loading, plowing, and light farm work. However, its original gasoline or diesel engine carries real disadvantages as it ages:
- Fuel and Oil Costs: Fuel costs continue to rise with every hour of operation, and lubricating oil requires regular changes.
- Recurring Maintenance: Maintaining spark plugs, filters, belts, water pumps, radiators, and exhaust systems takes considerable time and money.
- Noise and Emissions: Internal combustion engines produce exhaust fumes and high-decibel noise, which can be problematic when operating inside barns, greenhouses, stables, or close-quarters yards.
- Sourcing Vintage Parts: Sourcing replacement engine parts for vintage tractors becomes increasingly difficult and expensive.
Replacing the engine with a DC traction motor eliminates the complex fuel, cooling, and exhaust systems, while keeping the tractor's physical chassis and mechanical utility fully intact.
The Core Challenge: Matching the Stock 4-Speed Gearbox
The tractor's original internal combustion engine drove a 4-speed manual gearbox through a splined input shaft. To minimize conversion costs and complexity, the customer wanted the new electric motor to bolt directly onto that existing splined shaft without modifying the transmission.
This requirement established four key engineering constraints for the replacement motor:
- High Starting Torque: The motor needed to deliver high torque at low speeds to move the heavy tractor from a standstill, especially under load.
- Matched Speed Range: A continuous operating speed range of 0 to 2500 RPM was required to align with the safety and design limits of the stock gearbox.
- Direct Mechanical Coupling: The motor's output shaft had to match the specific splined shaft configuration of the tractor gearbox, avoiding the need for expensive custom-machined adapters.
- Precise Control: A matched motor control system was necessary to ensure smooth acceleration and variable speed control throughout the RPM range.
Retaining the stock gearbox was a key design decision. It preserved the tractor's proven final-drive gear ratios for pulling and towing, while keeping the overall conversion process simple and highly cost-effective.
Why a DC Series-Wound Traction Motor Fits a Tractor
A 26 HP internal combustion engine produces its rated peak power at relatively high RPMs. In contrast, utility tractors require high torque at very low speeds for heavy pulling.
A DC series-wound traction motor is an excellent match for this application because of its native electrical characteristics. In a series-wound motor, the field winding is connected in series with the armature winding. This design provides:
- Maximum starting torque when the armature is at 0 RPM.
- An inherent torque curve that automatically increases torque as the load increases and the motor slows down.
- Excellent durability and overload capacity, making it perfect for heavy-duty agricultural and utility tasks.
The XQ-18-7P Motor Solution
After assessing the mechanical and electrical requirements, our engineering team selected the XQ-18-7P 96V 18kW DC Series-Wound Traction Motor.
This motor was a clean fit for several reasons:
- Perfect Power Match: The 18 kW (approx. 24.1 HP) continuous rating closely aligns with the original 26 HP engine power.
- Compatible Speed Range: The 0–2500 RPM range perfectly fits the input limits of the existing 4-speed gearbox.
- Splined Shaft Integration: The output shaft of the XQ-18-7P can be configured to mate directly with the tractor's gearbox splined shaft.
- High Efficiency: It runs on a 96V DC system, keeping operating currents at highly efficient levels.
Technical Comparison: Original Engine vs. XQ-18-7P Electric Drivetrain
The following comparison table highlights how the XQ-18-7P electric conversion stacks up against the original internal combustion engine:
| Feature / Parameter | Original Ferguson Engine | XQ-18-7P Electric Drivetrain |
|---|---|---|
| Power Output | 26 HP (Peak) | 18 kW / ~24.1 HP (Continuous) |
| Torque Curve | Peak torque at mid-to-high RPM | Maximum torque at 0 RPM (Series-wound) |
| Speed Range | 800 – 2200 RPM (Idle to Redline) | 0 – 2500 RPM (Fully variable) |
| Gearbox Coupling | Direct clutch to splined shaft | Direct splined shaft coupling (No clutch required) |
| Maintenance Requirements | High (Oil, spark plugs, filters, belts, coolant) | Low (Occasional carbon brush inspection) |
| Emissions & Noise | High exhaust emissions, noisy (~85+ dB) | Zero emissions, near-silent operation (<65 dB) |
Pairing the Motor with a Control System
To ensure safe and reliable operation, a traction motor must be paired with a high-quality motor speed controller. Since the customer required highly precise throttle response from standstill up to 2500 RPM, we supplied a matched DC motor speed control system based on our 600A High Power DC Motor Controller, which provides the current capacity and thermal headroom needed for heavy starting loads and continuous traction duty.
The control system provides the following functions:
- Smooth Throttle Control: Delivers variable speed from 0 RPM via an electronic foot pedal or hand lever.
- Current Limiting: Automatically limits peak current to protect the motor windings during heavy starting loads.
- Reverse Commutation: Allows the motor direction to be reversed easily via the controller, expanding options beside the stock gearbox gears.
- System Diagnostics: Monitored voltage and thermal protection prevent overload issues.
Drivetrain Benefits and Final Outcome
With the XQ-18-7P motor securely mounted to the original 4-speed gearbox splined shaft and the matched controller integrated with the 96V battery pack, the conversion was highly successful.
The customer achieved all design goals:
- No Clutch Required: Because the motor can stop completely at standstill (0 RPM) and start under load, gear shifting can be done easily while the vehicle is stopped without needing a traditional mechanical clutch.
- Silent Barn Operation: The tractor can now operate indoors, in stables, and in greenhouses with absolutely zero exhaust fumes and minimal sound.
- Lower Operating Costs: Electricity costs are significantly cheaper than diesel/gasoline, and routine engine maintenance is completely eliminated.
- Instant Torque: The tractor pulls heavy loads easily due to the immediate low-end torque of the series-wound DC motor.
Frequently Asked Questions
Can any DC motor replace a Ferguson tractor engine?
No. The motor must be rated for heavy-duty traction (like a series-wound DC motor), must match the gearbox input splined shaft, and must operate safely within the speed limits (typically 0–2500 RPM) of the stock gearbox.
Why is 96V selected instead of 48V or 72V?
Higher system voltage reduces the current (Amperage) required to achieve 18 kW of power. Using a 96V system allows for smaller cabling, lower heat generation, and improved overall controller and motor efficiency.
Do I need a clutch for an electric tractor conversion?
Generally, no. Since an electric motor can sit at 0 RPM when the tractor is stopped, you can select your gear (1st, 2nd, 3rd, or 4th) while stopped and simply press the accelerator. The motor will spin and drive the tractor without needing a clutch to slip.
How long do the carbon brushes in the XQ-18-7P last?
In typical utility tractor applications, high-quality carbon brushes can last for thousands of operating hours. Regular inspections every 6 to 12 months are recommended to ensure optimal brush wear and commutator contact.
Conclusion
Repowering a classic Ferguson tractor by replacing its 26 HP engine with a 96V 18kW DC traction motor is a highly practical and modern upgrade. The XQ-18-7P traction motor provides the perfect mechanical and electrical match, seamlessly integrating with the stock 4-speed gearbox splined shaft and delivering massive low-end torque where a tractor needs it most.
Are you planning an electric vehicle conversion or repowering vintage agricultural equipment? Contact the Baoluo Motor engineering team to discuss your project requirements.
