BIZOMAT MAKEOS · Engineering
Bearing Static Load Ratio
How does the static load on this bearing compare with its static rating?
Compare a rolling bearing’s basic static load rating with the equivalent static load it carries when stationary, oscillating slowly or under shock.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Basic static load rating C0 | kN | Basic static load rating from the manufacturer’s catalogue for the exact bearing. |
| Equivalent static bearing load P0 | kN | Equivalent static load from radial and axial loads with the manufacturer’s static factors, including peak and shock loads. Same unit as C0. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Basic static load rating C0
- What it is
- The catalogue static load that produces a defined permanent deformation at the most heavily loaded contact when the bearing is stationary or turning very slowly.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 35 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The static safety factor s0 is directly proportional to C0.
- Get it right
- Use C0 for the exact bearing designation, not the dynamic rating C, which is a different number.
What this means: Equivalent static bearing load P0
- What it is
- The single static load that has the same effect as the real radial and axial loads on a stationary or slowly turning bearing, including the peak and shock loads it will see.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 12 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- s0 = C0 ÷ P0, so doubling P0 halves the static safety factor.
- Get it right
- Use the highest load that can occur, even briefly, such as a shock or a dropped load; a steady average understates P0.
Method and formulas
- s0 = C0 / P0.
- Example: C0 = 35 kN and P0 = 12 kN give s0 = 35 / 12 = 2.916667.
Limitations
- The minimum acceptable s0 depends on bearing type, running smoothness, noise requirements and shock; it is set by the manufacturer’s guidance, not by this tool.
- Housing and shaft strength, and the bearing seat, are not checked.
- No certification or bearing selection is implied.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check slowly rotating or stationary bearings
- Check shock or peak loads on running bearings
- Compare bearing sizes for a static duty
Who it is for
- Design engineers
- Maintenance engineers
What you get
- Static safety factor s0 = C0 / P0
Interpreting the result
- s0 below 1 means the equivalent static load exceeds the static rating, at which permanent deformation of the rolling contact becomes significant.
Before relying on the result
- Compare s0 with the manufacturer’s recommended minimum for the bearing type and application.
- Include the largest peak or shock load the bearing can see, not only the steady load.
References
- Budynas R. G. and Nisbett J. K., Shigley’s Mechanical Engineering Design, 10th edition (McGraw-Hill, 2015), chapter 11, Rolling-Contact Bearings. Topic reference; no source tables or recommended settings are reproduced.
- ISO 76:2006, Rolling bearings — Static load ratings (cited by title; no content reproduced).
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