402W2 Winch Drive Planetary Gearbox Reducer

The absence of an integrated brake is not a cost reduction — it is an engineering statement. The 402W2 is designed for hoisting systems where the braking architecture is more sophisticated than a single spring-applied disc inside the gearbox. Marine deck cranes with DNV-certified counterbalance valves. Free-fall lifeboat davits with dual-independent hydraulic braking circuits. Heavy construction hoists with motor-mounted electromagnetic brakes plus separate drum-mounted calliper brakes. In each of these systems, an additional brake inside the gearbox would be redundant weight that contributes nothing to safety because the external braking system already provides the required holding capacity and regulatory compliance.

① Motor-Integrated Brake

Most axial piston motors (Rexroth A2FM/A6VM, Eaton, Parker) offer a factory-integrated spring-applied, hydraulic-release brake on the motor shaft. This brake acts through the 402W2 gear ratio: a 30 Nm motor brake at ratio 25 produces 750 Nm of holding torque at the drum. Verify that this multiplied value exceeds the maximum suspended load torque at the outer cable layer. This is the simplest and most common external braking method for hydraulic winch systems.

② Counterbalance Valves

A counterbalance valve in each motor port line prevents the load from overrunning the motor during lowering. When the pump stops, the counterbalance valve traps the oil in the motor circuit, locking the motor and drum in position. This provides a hydraulic hold that is independent of any mechanical brake. For crane applications certified to EN 13001 or FEM standards, the counterbalance valve is typically the primary hold mechanism, with the motor brake as the secondary.

③ External Drum Calliper Brake

A separate calliper brake mounted on the drum flange or the winch frame, acting directly on a brake disc welded to the drum cheek plate. This provides a completely independent mechanical hold that does not depend on the gearbox, the motor, or the hydraulic circuit. For safety-critical lifting (personnel hoisting, offshore crane certification), this third independent brake is often required by the classification society or the site safety standard as a tertiary hold mechanism.

Smaller, Lighter Motors

A 250 cc/rev orbit motor at 1,000 rpm weighs approximately 25-35 kg. A 45 cc/rev axial piston motor producing the same torque at 3,500 rpm weighs 8-12 kg. On a marine crane where weight aloft directly affects vessel stability, this 60-70% motor weight reduction matters. On a construction hoist where the motor mounts inside a confined drum housing, the smaller physical envelope may be the only option that fits.

Lower System Pressure

At higher motor speed and lower displacement, the system pressure required to produce the same output power is lower. Lower pressure means less stress on hoses, fittings, seals, and the pump — extending the service life of every component in the hydraulic circuit. The 402W2 ratio range (12.4-37.1) is specifically designed to allow the motor to operate at 2,000-3,000 rpm in the most efficient pressure band of a typical 250-350 bar axial piston circuit.

Variable Speed Without Valving Complexity

Variable-displacement axial piston motors allow infinite speed variation by swashplate adjustment — from full speed to zero — without any external valving or flow control. Combined with the 402W2 ratio, this provides precise hoisting speed control from full-speed lifting down to controlled, creep-speed positioning, all from the motor control alone. The 402W2 gears transmit whatever speed and torque the motor delivers, in either direction, without mechanical restriction.

Multi-Ratio Flexibility

The 12.4-37.1 ratio range allows the winch designer to match the gearbox to the exact motor displacement and pump flow available in the system. A crane OEM using a 40 cc/rev motor at 120 L/min pump flow selects ratio 25. A marine winch builder using a 63 cc/rev motor at 80 L/min selects ratio 15. The same 402W2 serves both, with the ratio chosen at order to match the specific hydraulic circuit design. Contact Korea Ever-Power with your motor and flow specifications for a verified ratio recommendation.

Marine Deck Cranes (5-10 Tonne SWL)

Deck-mounted knuckle-boom and telescopic cranes on supply vessels, research ships, and coastal freighters. These cranes use DNV- or Lloyd-certified hydraulic circuits with counterbalance valves as the primary hold mechanism and motor-integrated brakes as the secondary. The 402W2 brake-free design integrates directly into this architecture without adding a redundant third brake inside the gearbox. The slewing drive planetary gearbox handles the crane rotation on the same vessel.

Free-Fall Lifeboat Davit Recovery Winches

Free-fall lifeboat davits on offshore platforms and FPSOs use the winch only for recovery (hauling the lifeboat back to the stowed position after a drill or deployment). The launch is gravity-driven — no winch involvement. The 402W2 provides the 4,000 Nm needed to pull a 5-8 tonne lifeboat up a slipway at controlled speed, while the dual counterbalance valves in the davit hydraulic circuit provide all load-holding functions. Adding a brake inside the gearbox would not improve the safety case — it would only add weight to a system where davit head weight affects the platform structural loading calculation.

Heavy Construction Material Hoists

High-capacity material hoists on large construction sites lifting 1-3 tonne loads of reinforcement bar, formwork panels, and precast elements. These hoists typically use motor-mounted electromagnetic brakes (primary) plus a drum-mounted calliper brake (secondary) as the dual-brake system required by construction lifting regulations. The 402W2 delivers the drum torque while the external brakes handle the holding function, allowing the winch designer to specify each brake independently for optimal sizing and redundancy.

Is it safe to operate a winch drive without an internal brake?

Yes, provided the external braking system meets the redundancy and holding capacity requirements of the applicable lifting standard. The 402W2 is not intended for systems that rely on a single internal gearbox brake as the sole load-holding mechanism. It is designed for systems where the braking is distributed across multiple independent components — motor brakes, counterbalance valves, and/or external drum brakes — each sized to hold the full suspended load independently.

What is the difference between the 402W2 and the 403W2?

Same torque (4,000 Nm), same two-stage architecture, same FEM M5 duty classification, same 3,500 rpm input speed. The 403W2 adds a 270 Nm multi-disc negative parking brake inside the housing, adding approximately 5 kg to the dry weight (120 vs 115 kg) and the ratio range shifts slightly (15.4-40 vs 12.4-37.1) due to the internal space consumed by the brake assembly. If the application needs an internal brake, specify the 403W2. If the external braking system provides all required holding capacity, the 402W2 is lighter and offers slightly lower ratios.

Why does the 402W2 accept 3,500 rpm when the 400/401 only accept 1,000 rpm?

The single-stage 400/401 models use a single large sun gear that produces high tooth peripheral velocity at high input speeds. The two-stage 402W2 distributes the total reduction across two smaller gear sets, each operating at lower peripheral velocity than a single stage would at the same input speed. This allows the 402W2 to accept 3,500 rpm safely — the tooth velocity at each stage is comparable to the 400/401 at 1,000 rpm. The two-stage design simultaneously unlocks higher input speeds and higher total ratio.

Can the 402W2 be used for crane hoist certification under EN 13001?

Yes. EN 13001 requires the hoist mechanism to have at least two independent means of preventing uncontrolled load descent. The 402W2 provides the torque transmission function; the braking function must be provided by at least two external components (for example, motor brake + counterbalance valve, or motor brake + drum calliper brake). The gearbox itself is a torque transmission component, not a safety-holding component, in this system architecture. Provide the complete braking system design to the notified body for EN 13001 certification.

What counterbalance valve pilot ratio is recommended for the 402W2 in a lowering application?

The counterbalance valve pilot ratio depends on the system operating pressure and the load-induced pressure at the motor ports. As a starting point: select a pilot ratio of 3:1 to 4.5:1. A higher pilot ratio provides smoother lowering control but requires more pilot pressure to open the valve. A lower pilot ratio is easier to open but may produce jerky lowering at low speeds. The optimal setting is determined by testing on the actual crane — adjust in 0.5:1 increments until the lowering speed is smooth and controllable at all load levels from zero to maximum.

How does the winch drive planetary gearbox efficiency compare to a worm gear winch drive at the same torque?

The 402W2 at 95% efficiency wastes 5% of input power as heat. A worm gear reducer at the same ratio range (12-37:1) operates at 55-75% efficiency, wasting 25-45% of input power as heat. For a 4,000 Nm winch lifting a 2-tonne load at 20 m/min, the 402W2 requires approximately 14.0 kW of hydraulic input power. The worm gear would require 18.7-25.5 kW for the same lift — 33-82% more power, all of which converts to heat inside a sealed drum housing. At this power level, the worm gear thermal management challenge becomes the limiting factor long before the torque rating is reached.

8-tonne SWL knuckle-boom crane on a platform supply vessel. The 402W2 at ratio 28 paired with a 45 cc/rev Rexroth A2FM motor and dual counterbalance valves. The brake-free design was the correct choice for this application — our DNV-certified hydraulic circuit provides motor brake plus counterbalance hold, and adding a third brake inside the gearbox would have required re-certification of the entire braking system. The 402W2 passed the DNV type approval survey without any additional documentation beyond the standard product data sheet and material certificates. Clean and simple.

Free-fall lifeboat davit recovery winch for an FPSO project. The winch only operates in the hoisting direction — recovering the 6.5-tonne lifeboat after a drill deployment. The 402W2 at ratio 18 with a 63 cc/rev variable-displacement motor gives us 15 m/min recovery speed at full load. The brake-free design was specifically requested by the platform operator because their maintenance procedure treats gearbox-internal brakes as an inspection item that requires drum removal — which on an FPSO means a crane and three-day work permit. No internal brake means no brake inspection means no drum removal. The counterbalance valves provide all holding functions and are accessible from outside the drum housing.

2.5-tonne materials hoist for high-rise construction. The 402W2 at ratio 25 with a motor-mounted electromagnetic brake (primary) and a drum calliper brake (secondary). Mechanically the drive is solid and the hoisting speed control through the variable-displacement motor is smooth. The 4-star reflects a documentation issue: the product data sheet lists "external braking system required" but does not specify the MINIMUM brake holding torque needed at the drum for various load scenarios. We calculated it ourselves from the torque and ratio, but a pre-calculated table showing "at X load on Y drum PCD, minimum external brake torque = Z" would have accelerated our safety case submission by a week.