A roller bearing is a cylindrical unit that is used to provide low-friction movement for a bushing or bearing block. A ball bearing is a spherical unit that accomplishes the same objective as a roller bearing. The real difference has to do with the contact surface between the bearing and the rail

A roller bearing is a cylindrical unit that is used to provide low-friction movement for a bushing or bearing block. A ball bearing is a spherical unit that accomplishes the same objective as a roller bearing. The real difference has to do with the contact surface between the bearing and the rail. For ball bearings (assuming a perfectly spherical bearing and no deformation), the contact surface is just a single point. Even once deformation is accounted for, the amount of surface where the ball is contacting the rail is limited. This creates an inherent strength limit for the balls. Roller bearings on the other hand, have an entire line of contact. This greatly increases the rigidity, stability, and maximum load capacity of the system.

Also unlike ball bearings, roller bearings are not made to handle thrust loads. The main difference is the type of contact. For a ball bearing, the type of contact is a point whereas for a roller bearing is a line. ... Difference between roller bearing and ball bearing lies in the type of rolling element

How Bearings Work

In general, bearings are all composed of the same basic mechanics: a ball set within an internal or external ring. This setup allows for force to be placed on the ball, referred to as loading. There are two different types of loading with bearings; thrust and radial. If your bearing is working with a radial load, this means the bearing will rotate, or roll when put under tension. Alternatively, a thrust load will be subject to force dependant on the angle. Bearings have been around for hundreds of years and have many different uses, some of which include aiding in rolling (a tire), pulling, applications in hard drives, skateboards, and more.

Ball Bearings

In small amounts of weight, this extremely common bearing is able to handle both thrust and radial load, making it a popular bearing with engineers. When ball bearings are in motion their main job is to transfer the load from the outer raceway to the inner raceway. This allows for a smooth spin. Ball bearings are commonly used in small wheels and hard drives, as well as other everyday applications, but are prone to deformation when under too much pressure.

Roller Bearings

Unlike ball bearings, roller bearings are designed with heavy loads in mind. These bearings are primarily based around a cylinder, meaning this bearing is able to distribute a load over a large area, carrying heavy weights. Also unlike ball bearings, roller bearings are not made to handle thrust loads.

While there are dozens of ball bearings available on the market, that doesn’t mean that the automotive industry doesn’t have their favorites. Mechanical bearings are used between two automotive parts that allow for rotation or liner movements. These bearings will enhance the vehicles performance, bear heavy loads, and reduce friction. Today we’re looking at the top 3 bearings used in the automotive industry and why they just won’t turn anywhere else

1: . Ball Bearings

As a general overview, ball bearings are rolling bearings that allow for a decrease in friction rotating between two surfaces; likely a vehicle and the pavement. This bearing will allow for changes in speed, by supporting radial and axial loads. They are essential in automotives and are one of the most common bearings used in the automotive industry.

2: Plain Bearings

Regular, plain old bearings that contain no rolling elements are widely used in the automotive industry. This is mainly because they have the ability to bear heavy loads and large carrying capacities. Not to mention they are usually the least expensive. Plain bearings also have a long life-span in comparison to other rolling bearings.

3: Thrust Bearings

Thrust bearings consist of three main parts. Like most other ball bearings they assist in the support of an axial load and allow for rotation between two parts. There are many different variations of thrust bearings available, such as: tapered roller thrust bearings, cylindrical bearings, and spherical bearings. These bearings are often used in automotive and aerospace applications.

Different applications [ see the three pictures below of various types of bearings]

Plain Bearings

The earliest (and original!) blocks used plain bearings, but they have slowly given way to higher-performing bearings. Plain bearings have the least number of moving parts. A long lifespan and low maintenance with heavy load applications are the main benefits of plain bearings.

Metal or plastic sheaves roll directly on metal pins or bushings. Plain bearings are often comprised of a plastic surface and a metal shell. Another common kind of plain bearing will use a soft bronze bushing and a polished steel shaft. Their static and high-load capability make plain bearings suitable for vangs, backstay, runner and halyard turning blocks. However, full contact between two surfaces results in more friction, reducing their potential running speed.

Ball Bearings

Ball bearings were the response to reduce this friction and they do this job extremely well. However, the small contact surface of the balls, which reduces the friction so much, is also their biggest weakness i.e. the point loading of the balls can lead to compression, at high loads and the block jamming. Ball bearings are high performance blocks suited to running at high speeds, but their size and weight increase significantly as loads rise. So, the R+D for block bearings wasn’t finished at this stage.

Roller Bearings

Roller bearings were the compromise between plain and ball bearings. Rollers facilitate low friction at high working loads. Heavily-loaded lines run faster, smoother and are more easily adjusted compared to a plain bearing block. They can also be smaller and lighter than a ball bearing block, for the same working load, due to the increased contact between the rollers and the hub.

Found on sailing boats of 35’+, these blocks are optimal for mainsheets, guy leads, backstays, after guys and tack lines.

For larger boats, blocks use a blend of ball and roller bearings. Roller bearings take the main line loads, leaving the ball bearings mounted around either edge to keep the sheave running smoothly, even with off-axis loads. This can be seen in the ‘2 stage bearing system’of the Ronstan Core Blocks.

[Roller bearings: ‘Rollers’ are small tubes arranged around the centre of the bearing. Rollers are a ‘compromise’ between the plain and balls. Rollers wear faster than ball bearings, but can carry higher loads as they have a higher contact area.]

What are bearings made from?

Ball and roller bearings are commonly manufactured with the following materials:

Delrin- Commonly found in deck blocks and known as ‘acetal’. This is a thermoplastic specially designed for high compression, but low tension, thus suitable for low loads.

Torlon- Is the commercial name given to the high-performance thermoplastic composite material and offer a performance upgrade to Delrin balls.

Ceramic- Ceramic ball bearings are incredibly strong and can be polished to incredibly smooth surfaces. This enables them to handle extraordinary heavy loads with very low friction but their cost generally limits them to grand prix level blocks.

For many years, the backbone of most block ranges were heavy plastics with aluminium or stainless steel structural side plates, which were used to transfer loads. As computing power advanced, designers modelled crucial load paths accurately to ensure sufficient strength from modern, lightweight composite materials. Today, blocks are lighter and smaller than those used a decade ago, making them perfect for the thinner hi-tech lines / ropes.