Name: Small Excavator Rotary Actuator - Korea Small Excavator Rotary Actuator Manufacturers, Suppliers - hydraulic cylinders price
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Small excavator boom offset controlled by rotary actuator

Small Excavator · 5th of 5 · Final

Small Excavator Rotary Actuator

The sideways mover. Every other excavator cylinder works in the vertical plane — up/down, in/out. The rotary actuator swings the boom left or right, letting the operator dig alongside a wall without repositioning the entire machine. A capability that turns a 3-point-turn into a straight pass.

50–120mmBore

333 KNMax Thrust

≤1,000mmStroke

Left ↔ RightLateral Swing

Boom Offset — The Feature That Defines a Small Excavator

Boom offset enabling wall-side trenching

On a standard excavator, the boom is fixed on the machine's centreline — the bucket can only dig directly in front of the machine. To trench alongside a wall, the operator must angle the entire machine at 45° to the wall, dig at an offset, reposition, and repeat. This is slow, imprecise, and requires extra working space.

Small excavators solve this with boom offset: the rotary actuator swings the boom foot-pivot 30–60° left or right of the centreline, allowing the bucket to dig along a line parallel to the machine — but offset sideways. The operator can trench directly alongside a wall, fence, or building foundation while the tracks remain parallel to the trench. One straight pass replaces multiple angled repositions.

This capability is almost universal on small excavators (1–6 tonnes) and is the primary reason residential and urban contractors choose mini excavators over larger machines. Korea Ever-Power manufactures the rotary actuator as the fifth and final cylinder in the small excavator hydraulic cylinder family.

Technical Specifications

Parameter	Specification
Product	Small Excavator Rotary Actuator
Function	Deflection (left/right swing) of the boom assembly
Bore Diameter	50 mm – 120 mm
Rod Diameter	25 mm – 75 mm
Stroke	≤ 1,000 mm
Max Thrust	333 KN (bore 120 mm / 29.4 MPa)
Application	Small Excavator (1–10 tonne, boom offset)
Certification	ISO 9001 · 100% hydrostatic tested

Lateral Force During Digging — The Side Load Every Other Cylinder Avoids

When the boom is offset to one side and the excavator digs, the digging reaction force has a lateral component — a sideways push that tries to swing the boom back toward the centreline. The rotary actuator must resist this lateral digging force while holding the offset angle steady. This is unlike the boom, stick, and bucket cylinders, which only experience loads in their own plane of motion.

Position holding — resisting digging side-force

The actuator must hold the boom at the set offset angle against the continuous lateral push from digging. A weak or drifting actuator allows the boom to swing inward during each dig stroke — the trench wanders away from the wall, defeating the purpose of boom offset. The cylinder's internal leakage specification is critical for position-hold accuracy.

Swing motion — repositioning between digs

Between digging cycles, the operator may swing the boom left or right to reposition the bucket. This motion requires smooth, proportional control — jerky swing makes precision trenching impossible. Korea Ever-Power specifies low-friction seals for smooth breakaway and proportional flow response across the full stroke. Contact the Korea Ever-Power engineering team for rotary actuator specifications.

Excavator rotary actuator enabling offset digging

Manufacturing Process

Bore honed to Ra 0.2–0.4 µm. Chrome plating 50–80 µm. The rotary actuator mounts horizontally at the base of the boom — a partially shielded position with moderate exposure to soil and water. The mounting lugs are forged to handle the combination of axial thrust (swing force) and lateral bending (digging side-force) that the rotary actuator uniquely experiences. Seals rated -30 °C to +80 °C, polyurethane + NBR + standard double-lip wiper.

Every rotary actuator is hydrostatic tested at 1.5× rated pressure (44.1 MPa) and position-hold tested — verifying that the boom holds its offset angle under simulated lateral digging force without measurable drift over a defined period.

OEM & ODM

What You Provide

Excavator model and weight class, boom offset range (degrees left/right), required swing torque, lateral digging force specification, bore/rod/stroke, system pressure, position-hold drift limit, pin diameters, and the boom offset linkage assembly drawing.

What the Factory Delivers

Engineering drawing with bore, rod, stroke, forged mounting lugs, low-friction seal specification, chrome plating detail, and mounting dimensions. Hydrostatic + position-hold test certificate. Seal kits. Browse the mobile machinery hydraulic cylinder family and the Korea Ever-Power catalogue.

Workshop

FAQ

Is the rotary actuator a rotary-vane type?

No — despite the name "rotary actuator," this is a conventional linear hydraulic cylinder connected to the boom offset linkage. The cylinder's linear stroke is converted to rotational (swing) motion through the linkage geometry. Rotary-vane actuators are used on some excavator models for cab rotation, but the boom offset function uses a standard linear cylinder.

Do large excavators have boom offset?

Rarely. Boom offset is primarily a small excavator feature (1–10 tonnes). Large excavators (20+ tonnes) use their greater reach and wider swing to work around obstructions. The additional weight and complexity of an offset mechanism is less justified on a large machine that already has sufficient reach for most applications.

Can Korea Ever-Power supply all 5 small excavator cylinders as a set?

Yes — bucket (#1), stick (#2), boom (#3), bulldozing (#4), and rotary actuator (#5) are available as a complete 5-cylinder matched set for the same excavator model, ensuring pressure compatibility, seal standardisation, and coordinated delivery. Browse telescopic cylinders and forklift cylinders.