Single Acting vs Double Acting Telescopic Cylinders: Key Differences for Performance-Critical Applications

Telescopic hydraulic cylinders are ideal when long stroke length is required in a compact footprint — think dump trucks, lift gates, agricultural trailers, or refuse vehicles. But one of the most critical decisions when selecting a telescopic cylinder is whether to use a Single Acting or Double Acting design.

This post dives into the mechanical and performance differences between the two, when to use each, and how they impact control, force, and system design.

What is a telescopic cylinder?

A telescopic cylinder consists of multiple nested tubes (or “stages”) that extend sequentially to deliver long stroke lengths from a short closed height. Depending on the application, they can be built in single acting or double acting configurations.

Single Acting Telescopic Cylinders (SAT)

Operation:

• Hydraulic pressure is applied to the base end to extend the stages.

• Retraction occurs via gravity or external load (dump bed weight).

• Each stage extends in a controlled sequence based on bore sizing and internal flow.

Design Considerations:

• One hydraulic port at the base.

• Simpler construction, fewer seals and internal passages.

• No hydraulic force on retraction.

Typical Applications:

• Dump trucks and trailers

• Agricultural grain beds

• Tilt beds

• Lift platforms with vertical retraction

  

  Single acting telescopic cylinder

Pros	Limitations
Lower cost Simpler circuit design Fewer components (lighter weight) Very reliable in vertical lift situations	Gravity-dependent for retraction Not suitable for horizontal or variable-angle retraction Limited retraction speed control

Double Acting Telescopic Cylinders (DAT)

Operation:

• Hydraulic pressure extends and retracts all stages.

• Requires porting at both the base and the rod end of each moving stage (internal passages or external hoses).

• Offers full control over movement in both directions.

Design Considerations:

• Two hydraulic ports (base + rod)

• More complex machining and internal flow design

• Requires a more advanced valve system (usually 4-way)

Typical Applications:

• Refuse trucks (packer blade control)

• Agricultural equipment with variable angles

• Mobile cranes and lifting arms

• Tilt deck trailers where retraction must be forced

  

  Double acting telescopic cylinder

Pros	Limitations
Controlled, powered retraction — not gravity dependent Better suited for horizontal or off-angle applications Reliable in icy, muddy, or debris-blocked environments	Higher cost More complex maintenance Greater number of seals = increased potential leak points

🧮 Performance & Control Comparison

Feature	Single Acting Telescopic	Double Acting Telescopic
Hydraulic control (retract)	No (gravity/external force)	Yes (powered retraction)
Number of ports	One	Two
Retraction force	Not hydraulic	Controlled & variable
Complexity	Low	High
Use in cold/dirty environments	Limited	Better suited
Ideal orientation	Vertical	Any (incl. horizontal)
Cost	Lower	Higher

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🧠 Final Thoughts

Choosing between a single acting or double acting telescopic cylinder isn’t just about budget — it’s about application-critical functionality.

If you're lifting vertically and gravity does the job on the way down, a single acting cylinder is all you need. But if you’re operating at an angle, in rough terrain, or need speed and control on retraction, a double acting system is worth the investment.

NorthStar Hydraulics stocks a wide range of high-performance telescopic cylinders and can also design custom builds for OEMs and integrators. If you’re unsure what type is best, reach out — we’ll help you spec it right the first time.

📩 info@northstarhydraulics.com