Mastering the Torque Split
In the highly mechanized agriculture of Brazil, particularly in the soy and corn belts of Paraná and Mato Grosso, seedbed quality determines harvest yield. The Power Harrow (Grade Rotativa Vertical) is the premium tool for creating a perfect, granular seedbed without forming a hardpan. Unlike rotary tillers that chop soil, power harrows stir the soil vertically, preserving moisture and structure.
Le Central Gearbox (Caixa Central) is the command center of this machine. It accepts the PTO input (540 or 1000 RPM) and splits the power to the left and right drive shafts (or directly to the rotor trough). Crucially, it must allow the operator to adjust the rotor speed to match soil conditions—slow for dry, dusty soil to prevent structure loss, and fast for wet, heavy clay to ensure proper crumbling.
EVER-POWER's PH-Series (Power Harrow) gearboxes feature a specialized “Change-Gear” System. By simply removing the rear cover and swapping the position of two spur gears, the operator can change the output ratio instantly in the field. Built with a massive cast iron housing to dampen vibration and oversized bearings to handle the axial thrust of the PTO shaft, these gearboxes are the benchmark for durability in tropical agriculture.
Technical Specifications: PH-Series (Central Input Box)
| Paramètre | Spécification | Paramètre | Spécification |
|---|---|---|---|
| Puissance d'entrée nominale | 80 HP – 300 HP (60-220 kW) | Changement de vitesse | Lever Change / Gear Swap |
| Vitesse d'entrée | 540 / 1000 tr/min | Vitesse de sortie | 190 – 450 RPM (Variable) |
| Matériau du boîtier | Fonte ductile QT500-7 | Couple maximal | 3,800 Nm |
| Arbre d'entrée | 1-3/4″ Z6 or 1-3/8″ Z21 | Arbres de sortie | Dual Splined (For Side Shafts) |
| Type d'engrenage | Spiral Bevel + Helical Set | Matériel d'équipement | 20CrMnTiH (Trempe superficiellement) |
| Type de roulement | Rouleau conique lourd | Arbre traversant | Yes (Rear PTO Option) |
| Système d'étanchéité | FKM (Viton) Haute température | Refroidissement | Radiator Fin Design |
| Lubrification | Bain d'huile (SAE 85W-140) | Capacité pétrolière | 6.0 Liters – 9.0 Liters |
| Modèle de montage | Base Flange (Standard/Wide) | Indice de protection thermique | 110 °C en continu |
| Poids (à sec) | 80 kg – 150 kg | Respiration | High-Flow Filtered |
| Peinture | Époxy résistant à la chaleur | Garantie | 24 mois |
| Compatibilité | Maschio / Kuhn / Amazone | Protection contre les surcharges | Optional Cam Clutch |
Engineering the “Multi-Speed” Core
1. The “Change-Gear” Cassette
Unlike fixed-ratio gearboxes, a power harrow central box must offer versatility. We use a rear-accessible cassette system containing a pair of spur gears. By removing the cover plate and flipping the gears (e.g., placing the 19T on top instead of bottom), the ratio changes. We supply a full set of Matched Change Gears (17T, 19T, 21T, 24T) allowing the farmer to fine-tune rotor speeds from 190 RPM (for clod breaking) to 400 RPM (for fine pulverization).
2. Thermal Management for 300HP
Transmitting 300HP through a compact box generates immense heat due to friction. If the oil overheats, the film strength collapses, and gears scuff. EVER-POWER housings feature Deep Cooling Fins and an optimized internal oil flow path. For extreme duty (24h operation in Mato Grosso), we offer a “Cooling Port” option to connect an external oil cooler and pump.
3. Through-Shaft Versatility
Many power harrows operate in combination with a seed drill (Semeadora Acoplada). The central gearbox must drive the harrow rotors AND pass power through to the rear to drive the seeder fan. Our gearboxes feature a Hardened Through-Shaft (Eixo Passante) capable of transmitting full engine power to the rear PTO, enabling single-pass tillage and planting.
4. Vibration Damping Mounting
A power harrow vibrates intensely as the tines strike the soil. This high-frequency vibration can crack gearbox casings. We use High-Grade Nodular Iron (QT500) which has superior fatigue resistance compared to grey iron. The mounting flanges are reinforced with thick webbing to disperse stress loads evenly into the harrow frame.
Comparative Analysis: Power Harrow vs. Rotary Tiller Gearbox
| Fonctionnalité | Boîte centrale de herse motorisée (série PH) | Rotary Tiller Central Box |
|---|---|---|
| Type de charge | Continuous / High Inertia | Intermittent / Shock |
| Régulateur de vitesse | Change Gears (Versatile) | Fixed / Limited |
| Output Direction | Dual Lateral (Splitter) | Single Lateral |
| Cooling Need | Very High (Continuous Load) | Modéré |
| Coût | High (Precision Components) | Moyen |
*Based on durability tests in Paraná clay soil conditions.
Application localisée : Agro-industrie brésilienne
Heavy Clay (Terra Roxa)
The “Terra Roxa” soil becomes extremely hard when dry. Breaking it down requires high rotor speeds (350+ RPM). Our PH-Series gearboxes are supplied with a “High-Speed Gear Set” as standard for the Brazilian market, ensuring enough kinetic energy to pulverize clods into a fine seedbed for soybean planting.
Combo Seeding (Mato Grosso)
Large farms use 6-meter folding power harrows with mounted pneumatic seeders. The central gearbox must handle the load of the harrow AND the hydraulic fan pump. We offer a Rear PTO Adapter Plate that allows direct mounting of Gr.3 hydraulic pumps, simplifying the machine layout.
📒 Field Engineer’s Log: The “Howling” Box
“September 2025, Cascavel, PR. A farmer reported a loud howling noise from his 4-meter power harrow gearbox. The oil temperature was spiking to 120°C. We inspected the unit.”
“The issue was incorrect gear meshing. The operator had swapped the change gears but didn’t clean the contact surfaces, leaving a gap that misaligned the gear teeth.
Solution: We replaced the damaged gear set with our Case-Hardened Change Gears and demonstrated the correct installation procedure. We also upgraded the oil to a fully synthetic ISO VG 220, which maintains viscosity at high temperatures. The noise disappeared, and the running temp dropped to 90°C.”
Foire aux questions (OEM/B2B)
1. Can I switch between 540 and 1000 RPM input?
Yes, but you must change the internal input bevel gear set. The housing is designed to accept both ratios, but it requires a workshop change. We recommend ordering the specific version for your tractor fleet standard.
2. Does the gearbox come with a slip clutch?
The central gearbox does not contain a clutch. The overload protection (Slip Clutch or Cam Clutch) MUST be installed on the PTO drive shaft connecting the tractor to the gearbox. This is essential to protect the gears from rock jams.
3. Are parts compatible with Kuhn/Maschio harrows?
Our PH-Series is designed as a direct replacement for many common European central gearboxes. The mounting bolt pattern (base flange) and spline dimensions are standardized (DIN/ISO). Check our catalog for specific dimensional drawings.
4. What is the oil change interval?
For the first fill, change at 50 hours (break-in). Afterward, change every 500 hours or annually. Use only High-Performance Gear Oil (85W-140) to ensure the film strength survives the heat.
Complétez votre transmission de herse
Boîtes de vitesses d'aile latérale
The final drives for folding power harrows. Matched ratio to the central box.
Arbres de transmission transversaux
Balanced shafts with integrated cam clutches to drive the wings.
Oil Cooler Kits
External pumps and radiators for extreme duty applications.
Command Your Tillage Power
Equip your power harrows with EVER-POWER Central Gearboxes for versatility and endurance.
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