Air Rams: What is a Telescopic Cylinder?

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A telescopic cylinder is a specially designed hydraulic cylinder or pneumatic cylinder with an air rams pulley system that provides an exceptionally long output length from a very compact retracted length. The collapsed length of a telescopic cylinder can be 20 to 40% of the fully extended length, depending on the number of stages. Some heavy-duty pneumatic telescopic cylinder units can be powered by oil hydraulics, but most medium to light units are powered by compressed air.

Another way to describe a telescopic cylinder is a hydraulic cylinder arranged as a compact envelope, with several cylinders built inside one another.

Design and work

Consisting of several cylinders that decrease in size, the main cylinder accommodates the number of cylinders arranged one inside the other. An inlet is provided in the main cylinder so pressurised oil can enter. Corresponding inlets are also provided for each cylinder.

During the extension stroke, when pressurised oil enters the main cylinder, this pushes the other cylinders outward or upward when sufficient oil pressure is generated. Each cylinder is pushed out or up in turn until the full length of the telescopic cylinder is achieved.


Telescopic cylinders are used where there is less space available for a full-length hydraulic cylinder. These are usually used in forklifts, dump trucks, hydraulic cranes, and other commercial vehicles, especially in the construction and mining industries. Telescopic cylinders are also used in lifting platforms and tipping platforms. 

With some special applications, the telescopic cylinder is required to extend with a constant speed or constant force. Therefore, the cylinder is designed so all cylinder extension stages extend or come out at the same time. 

While these cylinders are commonly restricted to a maximum of six stages – six being the practical design limit to avoid stability problems – some pneumatic cylinder designs can incorporate up to nine stages. Telescopic cylinders require careful design since they can be subjected to strong side forces, especially when fully extended.

The best example of a telescopic cylinder is that used for dump trucks in which the dump body needs to be tilted some 60° to empty its contents completely. If the body or trailer dump is fitted with a conventional rod-type cylinder, the dump body cannot return to a horizontal orientation for travel because of the cylinder’s length.

Air rams or pneumatic cylinders from MasterMac2000

MasterMac2000 P/L is one of Australia’s largest privately-owned pneumatic and process automation distributors. We have a comprehensive database and complete stocks of quality brands of air rams, pneumatic valves, flow control valves, and other pneumatic valves, such as Univer, Mack, and Tolomatic. Call us on 07 3344 4711 or visit us at

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