The Central Nervous System of the Paddy Machine
In the sprawling flooded plains of Southern Brazil (*Várzea*), the Rice Transplanter Main Gearbox (Caixa de Transmissão Principal) is the critical link between the engine and the mud. It is not merely a speed reducer; it is a complex power distribution hub. It must accept input from a diesel engine (20-30HP), manage the variable speed via a Hydrostatic Transmission (HST), and split the torque to drive the muddy wheels while simultaneously powering the precision planting arms at the rear.
The engineering challenge is twofold: Synchronization and Sealing. The planting speed must be perfectly proportional to the ground speed to ensure consistent hill spacing (e.g., 30cm), regardless of whether the machine is accelerating or bogging down in deep clay. Furthermore, the lower half of this gearbox spends its entire life submerged in abrasive silica-rich water.
EVER-POWER's TM-Series (Transplanter Main) gearboxes are designed with a “Dual-Path” architecture. They integrate a high-efficiency HST unit for smooth traction control and a mechanical PTO line for the planting section. Housed in a corrosion-resistant aluminum-magnesium alloy casing, they feature differential locks and portal axles designed specifically for the heavy, sticky soils of Rio Grande do Sul.
Technical Specifications: TM-Series (Main Transmission)
| Parámetro | Especificación | Parámetro | Especificación |
|---|---|---|---|
| Potencia de entrada | 18 HP – 45 HP (Diesel) | Traction Type | HST + 2-Speed Mechanical |
| Velocidad de entrada | 2600 – 3200 RPM | Max Travel Speed | 1.6 m/s (Field) / 15 km/h (Road) |
| Material de la carcasa | ADC12 de aluminio fundido a presión | Bloqueo del diferencial | Mechanical Dog Clutch (Pedal) |
| Axle Torque | Max 2,200 Nm | Steering Assist | Side Clutch / Power Turn |
| PTO Output Speed | Synchro with Ground Speed | Axle Shaft | Hex 35mm / 42mm |
| Material del engranaje | 20CrMnTiH (Carburized 60HRC) | Sistema de frenos | Internal Wet Disc |
| Clasificación de sellado | IP68 (Submersible) | Lubricación | Universal Tractor Fluid (UTTO) |
| Main Seal | Cassette Seal (Mud Block) | Capacidad de aceite | 7.5 Liters – 14.0 Liters |
| Enfriamiento | Finned Case + External Fan | Planting Clutch | Internal Hydraulic / Mechanical |
| Peso (seco) | 45 kg – 85 kg | Hydraulic Pump | Integrated Mounting Port |
| Montaje | Center Chassis Bolt-On | Ground Clearance | Optimized (Portal Axle Design) |
| Compatibilidad | Yanmar / Kubota / Iseki | Garantía | 24 Months / 2000 H |
Engineering the “Swamp Drive”
1. The HST Integration Advantage
Traditional mechanical gearboxes are jerky, causing seedling trays to shake and miss hills. EVER-POWER integrates a Hydrostatic Transmission (HST) directly onto the input of the mechanical gearbox. This allows for infinite speed control (0-10 km/h) with a single pedal. The operator can slow down instantly for a difficult muddy patch without declutching, keeping the engine RPM (and hydraulic pressure) high for the lift cylinders.
2. Waterproof Axle Technology
The axle seals are the Achilles’ heel of rice machines. Sand and water ingress leads to bearing failure. We utilize a “Cassette Seal” + “Mud Shield” combination. The outer shield physically scrapes mud off the axle hub, while the internal cassette seal provides a multi-lip barrier with its own integrated wear sleeve. This ensures the seal lip never grooves the expensive axle shaft, even after 3000 hours in the paddy.
3. Differential Lock for Deep Mud
In the soft “Tijuco” mud, one wheel often loses traction. A standard open differential spins the slipping wheel, stranding the machine. Our TM-Series gearboxes feature a heavy-duty Mechanical Differential Lock. Engaged via a foot pedal, it locks the left and right axles together, forcing both wheels to turn at the same speed and powering the machine out of the bog.
4. Synchronized PTO Output
To maintain a constant planting distance (e.g., 30cm per hill), the planting arms must speed up or slow down exactly with the ground speed. Our gearbox features a Ground-Driven PTO option. A dedicated gear train takes speed reference from the final drive ring gear, ensuring that even if the wheels slip slightly, the planting rhythm stays mechanically linked to the forward motion logic.
System Comparison: HST vs. Belt Drive Transmission
| Característica | HST Transmission (EVER-POWER) | Mechanical Belt Drive |
|---|---|---|
| Control de velocidad | Smooth / Infinite | Stepped / Jerky |
| Reverse Shifting | Instant (Single Pedal) | Stop & Shift Lever |
| Torque at Low Speed | High (Hydraulic Advantage) | Low (Belt Slip Risk) |
| Planting Accuracy | Muy alto | Medio |
| Mantenimiento | Fluid/Filter Change | Belt/Clutch Replacement |
*Analysis based on field efficiency tests in Santa Catarina rice estates.
Localized Application: Brazil Rice Belt
High-Speed Planting (Uruguaiana)
Large farms in the border region demand speed. Our TM-Series allows planting speeds up to 1.8 m/s while maintaining stability. The aluminum housing reduces the machine’s total weight, preventing it from sinking too deep into the soft clay, while the reinforced internal gears handle the high torque of 8-row operation.
Corrosion Defense (Coastal Lagoons)
Saline water intrusion is common near Lagoa Mirim. Aluminum gearboxes can suffer from “white rust” (corrosion). EVER-POWER applies a triple-layer Epoxy-Acrylic Coating and uses stainless steel external hardware. The breather is elevated via a snorkel tube to prevent saline water from entering the case during deep wading.
📒 Field Engineer’s Log: The “Slipping” Transplanter
“November 2025, Pelotas. A farmer called in panic. His 6-row transplanter wouldn’t move in the mud once the oil got hot. We checked the transmission oil temperature: 110°C.”
“They were using standard 10W-30 motor oil in the transmission. The viscosity broke down under heat, causing the HST pump to bypass internally (loss of pressure).
Solution: We flushed the system and refilled it with Universal Tractor Transmission Oil (UTTO) which has specific anti-foaming and high-heat viscosity stabilizers. We also cleaned the mud-caked cooling fins on the case. The machine returned to full power immediately, running 20°C cooler.”
Preguntas frecuentes (OEM/B2B)
1. Can I retrofit this gearbox to an older Yanmar model?
Yes, our TM-Series is designed with mounting points that match the standard Yanmar VP and Kubota NSP chassis configurations. It is a popular upgrade for older mechanical machines to convert them to HST drive (requires engine coupling adaptation).
2. What oil should I use for the HST system?
For integrated transmission cases (where HST and gears share oil), use high-quality UTTO (Universal Tractor Transmission Oil). Do not use standard hydraulic oil (AW-46) as it lacks the extreme pressure (EP) additives needed for the gears. Do not use Gear Oil (SAE 90) as it is too thick for the HST pump.
3. Does the gearbox include the portal axles?
We offer two configurations: The Central Transmission Case only, or the complete “Rear Axle Assembly” which includes the transmission plus the left and right portal chain cases (axle housings). The complete assembly is recommended for new OEM designs.
4. How do I engage the differential lock?
The differential lock is engaged mechanically via an external lever/pedal. It should only be engaged when driving straight in slippery conditions. Disengage it before turning to avoid damaging the internal dog clutch or axle shafts.
Complete Your Transplanter Drivetrain
Portal Chain Cases
Final drive drop-boxes that provide ground clearance. Sealed oil bath.
Paddy Wheels
Narrow profile rubber wheels (900mm diameter) for minimal crop damage.
Planting Arm Units
Rotary planting cases that connect to the rear PTO output.
Reliability When the Field is Flooded
Equip your fleet with EVER-POWER’s waterproof transmission technology.
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