RcTek : Information & Resources for the Model Car Racer

Deep Groove Roller Bearings

Although an often overlooked and mistreated part of a radio controlled model car, the bearing is an important link in transferring motion from the engine/motor to the track surface.

In this article we have information about how they work and the parts that they are made up of so that you will be better informed when maintaining your car. We have used the term deep groove ball bearings so as to differentiate them from tapered roller bearings, cylindrical roller bearings, etc.

Different Types of Bearings

Unshielded bearing

Shielded bearing

The bearings used in model cars are available in a wide range of sizes but all are made using the same basic parts. The only differences between the bearings that are used is the type of shield that may be fitted.

The image to the left shows a bearing without a shield and the image to the right shows a bearing fitted with a shield.

More information about shields is featured in the Roller Bearing Shields article.

The Parts of a Bearing

Deep groove ball bearings consist of only three main parts, the races, the cage and the actual ball bearings. The function of each is listed below along with a detailed description.

The Ball Races

Bearing races

Bearing outer race

The ball races are the inner and outer parts of the bearing and are marked in yellow in the image to the left.

They are made from a ring of steel that has a concave groove in the inside of the outer race, which is shown in the image to the right. The inner race has a matching groove on its outer face.

Bearing Cross Section

As can be seen in the image to the left, the grooves, in combination with the cage, also provide an effective means of keeping the whole assembly together.

The Cage

Bearing shield

Bearing cage

The bearing cage, which is coloured in yellow in the image to the left, is responsible for keeping the ball bearings spaced out equally around the insides of the races. They would otherwise collide with each other and lead to the bearing seizing and possibly falling apart.

The cages can be made from different materials and in a couple of different ways. The image to the right shows one example that is made from metal.

The Ball Bearings

Ball bearings

The ball bearings are what most people would consider to be the main part of a bearing, but the other parts are equally important. The balls are usually made from steel, but harder carbide and ceramic types are available.

Bearing Shields

These items are covered in the Roller Bearing Shields article.

How Ball Races Work

Now that we have introduced and identified the parts of a bearing we will move on to how they actually work.

The grooves in the inner and outer races guide the ball bearings as the shaft that they are fitted to rotates. This is suitably demonstrated in the animation to the right in which we have straightened out the ball race for the sake of simplicity.

If you Play the animation you will see that the ball will always take the path of least resistance so that if there is a side load placed on the bearing the sides of the groove will force it back towards the centre.

This self-centering effect will only tolerate light side loadings and other types of bearings should be considered if this is an issue.

You may Stop the animation if necessary.

How the Ball Bearings Move Inside the Races

If you Play the animation of a rotating bearing (the cage has been removed for clarity) to the left you will probably unsurprised at the outcome, the inner race either revolves around the outer race or vice versa depending on the application.

If you Stop the animation we can show you what actually happens when a bearing rotates, it is simple physics and is demonstrated in the animation below.

When you Play the animation to the right you will see the yellow dots that show how the ball bearings roll around when one race revolves in relation to the other.

This provides a low friction mechanism for allowing the rotational movement to occur that only requires a minimum of lubrication to operate efficiently.

You may, of course, Stop the animation if necessary.

Bearing Lubrication

Any type of bearing requires lubrication of some type. This lubrication does not just lower the internal friction between the various parts, it acts as a medium to dissipate heat that is built up due to the loads on the bearing.

This you may wish to take into consideration if you experiment with different types of lubrication - oil is better at conducting heat than grease.

In spite of this, the majority of bearings use grease as it is very good for trapping contaminants and keeping them away from the ball bearings for extended periods of time.

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© 2001, 2009 by Darren Burnhill