Whether four-wheeled standard or inline type, roller skates rely on bearings to make their wheels turn freely and easily. The resistance that would normally be created by a wheel turning on a bare axle is greatly reduced by skate bearings, allowing the skater to glide smoothly and with little effort. Constructed of steel and plastic, skate bearings are designed to withstand high pressure and tolerate millions of revolutions, providing a long-lived friction-reducing device.
Concept
The concept behind skate bearings is relatively simple. When an object slides across a surface, it produces friction that slows the object down. It also produced heat, which can damage the material from which the object is made. Objects tend to roll more easily than they slide. When an object is rolled, there is little friction generated. No friction means smoother movement and reduced risk of damage.
Construction
Skate bearings consist of several parts that work together in a self-contained bearing set. The outer part is called the outer race, which acts as a casing for the bearing and has a groove in which the ball bearings will ride in. A plastic retainer is then inserted into the outer race to hold ball bearings in place. The ball bearings fit into little clips in the retainer. Next, a metal ring called the inner race fits in the center of the bearing. The entire assembly is then covered with a rubber shield. This assembly forms a single skate bearing.
Operation
The axle, the threaded metal rod attached to the skate that holds the wheel in place, and the wheel itself. The axle fits through the inner races of the bearing and is the bearing is then bolted to the axle. The inner and outer race of the bearing roll over the surfaces of the ball bearings. This reduces the friction between the inner race and the outer race, allowing the wheel to turn freely and easily.
Installation and Maintenance
Roller skates use two bearings per wheel. The bearings are pressed into the inside and outside rims of the rubber wheel. Once seated properly, the wheel will spin evenly. Bearings are not maintenance free. They do need regular lubrication to further cut down on friction. They also get dirty and need to be cleaned occasionally to keep the operating at optimal performance. They also wear, despite the best maintenance and need to be replaced, on occasion.
Ratings
There are several systems for determining the manufacturing tolerances of bearings. The most widely recognized is the ABEC system from the American Bearing Engineering Council. ABEC has created a system for rating the quality of precision bearings, which are used in a wide range of applications, including skate bearings. Skate bearings are rated from one to nine as to their level of precision in manufacturing. The higher the number, the tighter the tolerances and the more expensive and, supposedly the more effective the bearing. Debate continues in the skating community as to the value of rating systems when compared to individual manufacturer standards and quality.
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