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How to Select a Pulley Assembly

How to Select a Pulley Assembly

Tuesday, July 20, 2020
Posted in: Pulleys & Sleeves

What is a pulley?

Pulleys are among the most critical and reliable, yet elementary mechanical components used in countless motion control systems, instruments and devices. When used in mechanical cable applications, pulleys support and guide the movement of cable along a path, while reducing the amount of force necessary to lift or move a working load.

A basic cable pulley system consists of a suspended wheel with cable running over or around it, through a groove where the wire rope rests. The simplest cable pulley systems, acue single fixed pulley and pulley block, reduce the amount of force necessary to lift an object by half. This is achieved by changing the direction of the pulley and multiplying the force applied when increasing the number of pulleys in a system. As cable pulley systems become more complex, more lift mitigation benefits emerge because pulleys are designed to carry and support the weight and movement of a cable system and reduce the force needed to lift or move the working load. 

A pulley system can also consist of a fixed wheel and a movable wheel, or a combination of multiple fixed wheels and additional cables which redirect motion continually. With a movable pulley system, the force weighing an object down is cut in half rather than the force necessary to lift it. With a system of multiple pulleys, each cord added reduces the necessary force by another factor.

Before Selecting a Pulley 

Once you are selecting the pulley system you need for your operation, you should focus on the numbers. Each pulley system has its own rules and caveats to follow to ensure you choose a pulley that is sized properly for the cable you are using. Pulleys are sized based on the working load of the cable. For example, if you are working with 100 pounds, you need to select a cable with a working load of at least 10 times greater than the weight you need to lift, which would be 1,000 pounds. It is a balancing act between the cable material, the load, the maximum load on the cable, the pulley material, and the pulley diameter. Our experts at Carl Stahl Sava Industries are here to help you every step of the way to make sure you get the perfect pulley design for your operation to last as many cycles as possible. 

What to consider when choosing a pulley assembly?

When choosing a pulley system, it's essential that you choose the right materials and component sizes to handle the task at hand. Before selecting, it's useful to ask yourself the following questions:

  • What size working load(s) need lifting?

  • What pulley construction do I need to use?

  • What diameter pulley is right for my job?

  • How many cycles are necessary over the pulley's lifetime?

What can go wrong with a pulley system?

An efficient, high-quality pulley system is one that incorporates the right materials, implements the right design considerations, and ultimately stands the test of time. If your product doesn't incorporate a well-designed pulley system, you may be in for significant problems including complete cable or pulley failure.

One of the biggest problems is metal on metal grinding. Using steel cabling without any kind of heat resistant coating, such as nylon, can result in metal that warps from continuous friction, grinding itself together into a fused mess.

You also have to be wary of too much load against a fixed surface. If you anchor the cabling against a sharp enough angle when installing the pulley, the cable acts as a saw against that surface, easily cutting through anything in its path. 

Using a cable or pulley wheel that is the incorrect size or material is the root of all other potential issues. It is important to select the right pulley array to satisfy both the load you intend to lift and the number of cycles that you need the pulley system to be able to perform over the course of its life.

Partner With The Right People

Partnering with the experts at Carl Stahl Sava Industries will ensure you are getting the best pulley for your operation and we will help you design the correct cable system for your exact application. We offer a wide range of solutions for any job including both standard and bracket type pulleys in varying bore types, and a complete selection of minimum and maximum cable widths.  

As a final step, select the right material to ensure that your pulley system stands up to whatever you throw at it. Sava offers: 

  • Nylon

  • Plated steel

  • Delrin

  • Molybdenum disulfide nylon

Sava is an international manufacturer of pulleys and pulley assemblies. Contact our experts today to design the perfect cable system for your application.


July 20, 2020