Ball bearing pulleys are commonly known to provide lower friction than their non-ball bearing counterparts. But is this always true? Are ball bearing pulleys always better than pulleys without ball bearings, regardless of the application or specific function?
Advantages of ball bearings
In certain applications, ball bearing pulleys can absolutely offer lower friction than pulleys featuring only a solid bearing or bushing. However, the efficiency gained by ball bearings is often greatest in applications with lower relative loads. If the pulley is not well-designed or made from the proper materials, the ball bearings can deform, seize, or slide instead of roll, which can actually reduce efficiency in higher load applications. With clever design and use of high quality materials, it is possible to create a ball bearing system that allows for high efficiency across the full load range.
One example of this is Ronstan’s 2-Stage bearing system, which is designed for the load to be carried by ball bearings under moderate load. As the load increases and reaches a certain threshold, the ball bearings shift outwards, acting as thrust bearings and allowing the load to be carried by a polished stainless hub.
Pulley design, materials, and other considerations
A well-designed pulley, such as the above mentioned 2-stage bearing system, will remain highly efficient across the full working load range. However, some ball bearing pulleys may produce great results at a low load, then rapidly lose efficiency as the load increases. These ball bearing pulleys will become less efficient than their non-ball bearing counterparts at loads well below their stated maximum working load. Surviving under load is not the same as thriving under load!
For extremely high loads, alternative bearing designs such as needle bearings can disperse the load, often made with high strength materials like Torlon®. However, the cost of the pulley will quickly become an important consideration as it relates to the given application.
Many factors need to be considered in the design of a pulley for it to be both strong and efficient. Materials, bearing design, and the proportional dimensions of components all play major factors in this equation. At its most basic concept, a block with a large sheave and small hub will result in low friction and low maximum working loads. Conversely, a pulley with a small sheave and large hub will result in a high working load and high friction (more friction = less efficient). Therefore, balancing these dimensions is a critically important design consideration.
Choosing the right pulley
Are you looking for a reliable and economical solution? Consider a standard solid bearing pulley.
Looking to minimize friction in a low load application? Sounds like a great fit for a ball bearing pulley system.
Do you require the best performance across the full working load range? You may be interested in a high performance pulley with sophisticated bearing design.
Learn more about Ronstan’s extensive range of pulleys