Fluid Power

Learn all you need to know about telescopic cylinders from what they are and operate to the advantages you will see by using them.

Telescopic cylinders are used in a wide range of heavy-duty applications from dump trucks to sanitation trucks and drill rigs to farm machinery. With their space saving design, telescopic cylinders allow for heavy equipment and trailer beds to be raised and lowered with ease by the flip of a switch. Understanding basic telescopic cylinder designs and configurations is helpful in understanding function and operation of your hydraulic work system.

In this article, we will break-down how telescopic cylinders operate together to provide a smooth process for your heavy-duty applications.

  1. What Are Telescopic Cylinders?
  2. Types of Telescopic Cylinders
  3. When Should You Use Telescopic Cylinders?
  4. What Advantages Do Telescopic Cylinders Offer?
  5. Wheelco’s Recommendation

What Are Telescopic Cylinders?

Telescopic Cylinders, also known as multi-stage cylinders, are constructed from a simple design similar to that of a telescope. They are a type of linear actuator consisting of multiple tubular rods called sleeves, all housed within the largest outside sleeve. This large outside sleeve is known as the main sleeve or barrel. Within the main sleeve, telescopic cylinders will contain four or five internal sleeves that slightly decrease in diameter to fit within one another. This construction allows for each internal sleeve to extend outward with the help of hydraulic oil pressure.

When hydraulic oil pressure is introduced to telescopic cylinders, each sleeve extends out one at a time, starting with the main sleeve working towards the smallest sleeve. Once each sleeve has reached its maximum stroke length, a stage of the cylinder is completed and the next sleeve will begin extending for their stage. You can stop the extension of the telescopic cylinder once you have reached your desired stroke length, or once you have reached maximum stroke length for all the sleeves. This operation of telescopic cylinders is true for the extension of all three types of telescopic cylinders, but each cylinder type will compress from different forces. To better understand how each telescopic cylinder compresses, we will take a deeper look at the three different types of telescopic cylinders.

Types of Telescopic Cylinders

The three types of telescopic cylinders are:

  • Single-Acting Cylinders
  • Double-Acting Cylinders
  • Single/Double Combination Cylinders

Single-Acting Telescopic Cylinders

Single-acting telescopic cylinders are the most commonly used telescopic cylinder on the market. These cylinders work by increasing hydraulic oil pressure to extend the sleeves of the cylinder to full stroke length. To retract, the single-acting telescopic cylinder uses the weight of the application with an external force, such as gravity or springs, to push the oil out of the cylinder, resulting in the sleeves retracting back into the main sleeve.

Double-Acting Cylinders

A double-acting telescopic cylinder has a more complex design and has additional seals within the sleeves of the cylinder. These seals help to create an upper and lower chamber within with telescopic cylinder for the extension and retraction of each sleeve. With the flip of a switch or press of a button, hydraulic oil flows through passageways that are machined into the internal sleeves of the cylinder to reach either the upper or lower chamber of the cylinder. Once the hydraulic oil pressure is introduced into the lower chamber, it begins to extend out the sleeves of the cylinder. The cylinder sleeves will then retract when hydraulic oil pressure is removed from the lower chamber and introduced into the upper chamber. This design is used when gravity is not available to retract the telescopic cylinder and can be seen in applications such as aerial work platforms.

Single/Double Combination Cylinders

Single/Double combination cylinders perform as a single acting telescopic cylinder but have one or more sleeves that also perform as a double acting cylinder. What this means is that hydraulic oil pressure extends each sleeve with the single-acting sleeves still retracting from external force, like gravity or springs. The double-acting cylinder sleeves are retracted by hydraulic oil pressure, just like a standard double-acting telescopic cylinder. These types of telescopic cylinders are most commonly seen in drilling applications with a work-over rig. This combination design gives you the benefits of a double-acting cylinder with the cost-effectiveness and straightforward operation of a single-acting cylinder.

Application Use For Telescopic Cylinders

Single-acting and double-acting cylinders can be utilized throughout various industries and types of equipment. They are traditionally used for heavy-duty applications that require long stroke length but also need a short retracted length when your short for space. Some of the major application uses for telescopic cylinders include the following.

  • Dump Trucks
  • Harvesters
  • Loaders
  • Tractors
  • Bulldozers
  • Excavators
  • Trenchers
  • Sanitation Trucks
  • Aerial Work Platforms
  • Agricultural Industry
  • Construction Industry
  • Forestry & Logging Industry
  • Mining Industry

The most common application that uses telescopic cylinders is that of dump bodies, end dump trailers, or other dump applications. Telescopic cylinders can also be applied to common machinery and agricultural equipment.

What Advantages Do Telescopic Cylinders Offer?

Requires Less Space

Not all operations are going to offer an abundance of space and that’s why telescopic cylinders can help resolve space-related concerns. Telescopic cylinders typically collapse between 20-40% of their fully extended length, offering a longer working stroke than that of a single stage rod actuator. The power and space saving design of telescopic cylinders make dump trucks, lifts, and sanitation trucks some of the most common applications of telescopic cylinders handling heavy loads.

Meet Specific Angle Requirements

Telescopic cylinders allow equipment and machinery, like dump trucks and sanitation trucks, to complete tasks seamlessly without worrying about the overall load weight or internal friction. Vehicles with a hydraulic powered bed can be seen using telescopic cylinders throughout our daily lives. Heavy-duty applications, such as dump trucks and sanitation trucks, require specific angles to gradually release materials instead of dumping the materials all at once. Telescopic cylinders can achieve the specific angle of around 60 degrees, or more, that is required to completely empty truck and trailer beds. And better yet, telescopic cylinders can also collapse and return to a horizontal position for safe travel.

Wheelco’s Recommendation

At Wheelco, we trust only the highest quality parts and that’s why we recommend Custom Hoist for your telescopic cylinder needs.

Custom Hoists Telescopic Cylinders

Custom Hoists Cylinders is a diversified global manufacturing company and a leading supplier of telescopic and single stage hydraulic cylinders since 1973. They make telescoping cylinder models for every mounting configuration, including hydraulic pumps and wet kits. Custom Hoists has the broadest product offering in the industry, covering virtually any heavy-duty truck or trailer application.

Need to replace your telescopic cylinder? Or how about help identifying the right type of telescopic cylinder needed? Our experts at Wheelco are always ready to help you get exactly what you need. With an overhead hoist at our Sioux Falls, SD location, service technicians with years of experience will be able to seamlessly install telescopic cylinders in your various trucks and trailers. Simply give us a call or stop by one of our stores today to see how Wheelco can help you.

Some information in this article may be from a trusted brand we carry, Custom Hoists, Inc.