Large Excavator Tightening Cylinder
A Completely Different Job — Track Tension, Not Digging Force
The bucket (#6), boom (#7), and stick (#8) cylinders are all part of the excavator's arm — they dig, lift, and load. The tightening cylinder has nothing to do with digging. It sits inside the track frame (one per track, two per machine), pushing the front idler wheel forward along a slide rail to tension the track chain.
A crawler excavator's track chain is a continuous loop of forged steel links — 30–50 tonnes of chain per side on a 100-tonne machine. The track wraps around the drive sprocket (at the rear), the front idler (at the front), and 5–8 carrier rollers (on top) and 7–12 track rollers (underneath). The tightening cylinder pushes the front idler outward, stretching the chain to the correct tension. A grease-charged accumulator behind the cylinder maintains this tension as the track chain wears and lengthens over time.
Korea Ever-Power manufactures the tightening cylinder as the fourth and final cylinder in the large excavator hydraulic cylinder family — completing the full machine system from arm tip to undercarriage.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product | Large Excavator Tightening Cylinder |
| Function | Control the action of track tension |
| Bore Diameter | 280 mm – 380 mm |
| Rod Diameter | 170 mm – 300 mm |
| Stroke | ≤ 700 mm |
| Max Thrust | 3,967.4 KN (bore 380 mm / 35 MPa) |
| Application | Large Excavator (track undercarriage) |
| Certification | ISO 9001 · 100% hydrostatic tested |
Too Loose vs Too Tight — Why Correct Track Tension Is the Most Expensive Maintenance Decision
A slack track sags between the idler and the first roller, flaps during travel, and can jump off the sprocket during sharp turns — derailing the track. A derailed track immobilises the excavator until a maintenance crew re-tracks it (1–4 hours of lost production). Even without derailment, a loose track allows the links to hammer against the rollers — accelerating roller bearing wear and chain pin wear by 30–60%.
An over-tensioned track presses the chain pins into the roller bushings with excessive force — accelerating bushing wear and increasing the power consumed by undercarriage friction (reducing fuel efficiency by 3–8%). The idler bearings, carrier roller bearings, and track roller seals all suffer from the higher contact forces. Over-tension shortens undercarriage component life by 20–40%. Contact Korea Ever-Power for tightening cylinder specifications.
Manufacturing Process
The tightening cylinder bore (280–380 mm) is honed to Ra 0.2–0.4 µm. Unlike the digging cylinders which cycle rapidly, the tightening cylinder moves infrequently (only during tension adjustment) but must hold its position under extreme static load for months. The grease accumulator behind the piston maintains the tensioning force as the track chain elongates with wear — the cylinder compensates automatically without operator intervention.
Chrome plating 80 µm (the cylinder lives inside the track frame, exposed to the most abrasive undercarriage environment: packed mud, rock debris, and continuous vibration). Seals rated -40 °C to +100 °C. Hydrostatic tested at 52.5 MPa. Position-hold tested under full track tension force for a defined static period to verify zero drift.
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