Mechanisms

Hydraulic excavator

Machines · Hydraulic linkages

How can an excavator’s arm lift a car-sized bucket of soil using nothing but oil?

An excavator’s arm has three parts — boom, stick and bucket — joined by pins like your shoulder, elbow and wrist. Each joint is moved by its own hydraulic cylinder: oil pumped in under high pressure pushes a piston out with a force of hundreds of kilonewtons. By moving the three cylinders together, the operator makes the bucket dig, lift and dump.

A hydraulic excavator positions its bucket with a planar linkage of three pinned members — boom, stick and bucket — each driven by its own hydraulic cylinder. Pascal’s principle turns oil pressure into cylinder forces of hundreds of kilonewtons, and the linkage geometry turns those straight-line pushes into rotations that cut, carry and dump soil.

Key facts

Operating mass (20 t class)

≈ 20–23 t

Maximum digging depth

≈ 6–6.7 m

Maximum reach at ground level

≈ 9.5–10 m

Hydraulic system pressure

≈ 32–35 MPa (320–350 bar)

Bucket digging force (ISO 6015)

≈ 130–160 kN

Bucket capacity

≈ 0.8–1.3 m³

Parts you can explore (14)

• Ground
• Crawler tracks
• Slewing ring
• Upper structure
• Operator cab
• Boom
• Stick
• Bucket
• Bucket linkage
• Boom cylinder
• Stick cylinder
• Bucket cylinder
• Hydraulic hoses
• Pivot pins

In the 3D model

Rotate and take apart the model, follow a guided tour of what each part does and why it’s needed, change it with a live slider, and test yourself with a short quiz. Free, no sign-up.

Open Hydraulic excavator in 3D →

OpenArc Models’ models are simplified teaching schematics. Terms · Privacy