Follow the explanation
Back to the model ↑How the parts work together
Find the two contacts
Hide the cage and inspect a ball against the inner and outer raceways. The outer ring stays fixed while the inner ring drives the ball.
Separate orbit from spin
Show the cage and follow one marked ball. Its center moves with the cage, but the mark rotates around the ball itself in the opposite sense.
Change the ball size
Select a larger ball-to-pitch-diameter ratio. At the same shaft speed, the cage travels more slowly. Compare the displayed cage speed with the 20% case.
The main parts
- Inner race
- The ring attached to the rotating shaft. Its raceway drives each ball at the inner contact.
- Outer race
- The stationary housing-side ring. The outside contact of each ball has zero velocity in the ideal no-slip model.
- Rolling balls
- Eight spheres carry motion between the raceways. Orange dots and blue bands make their own rotation visible.
- Cage
- A separator that keeps the ball centers evenly spaced. It follows their orbital speed, not the shaft speed.
Questions worth exploring
How fast does a bearing cage turn compared with the shaft?
With a fixed outer ring, radial contact and no sliding, cage speed is shaft speed × ½ × (1 − d/D). Here d is ball diameter and D is the diameter of the circle through the ball centers. At d/D = 0.20, the cage turns at 40% of shaft speed. This is an ideal relationship, not a universal measured speed.
Schaeffler — Vibration analysis of rolling element bearings, section 3 (PDF page 5)
What does the cage do while the balls rotate?
The cage guides and separates the balls so neighboring balls do not touch. It travels with their centers around the bearing, while each ball also spins. Follow a colored mark to distinguish spin from orbit. The model’s spin readout is relative to the moving cage; it is a different quantity from cage speed.
evolution.skf.comSchaeffler — Vibration analysis of rolling element bearings, section 3 (PDF page 5)
Do ball bearings eliminate friction?
No. Real bearings still have friction, and their behavior depends on lubrication, contact deformation and sliding as well as geometry and loading. This generic bearing shows ideal rolling motion only. It does not predict friction, temperature, load capacity or service life; changing the ball size here demonstrates a motion relationship rather than selecting a bearing for a machine.