Engineering
Bearing Preliminary Design Calculator
Form the catalog X-Y equivalent load, calculate ISO 281 basic rating life, apply an entered life adjustment, convert revolutions to hours, and solve the required dynamic rating.
Equivalent dynamic bearing load P-
Basic L10 life (million revolutions)-
Adjusted rating life (million revolutions)-
Adjusted rating life at entered speed-
Required life in million revolutions-
Dynamic rating required for entered life-
Catalog C minus required C-
Calculated minus required life-
Static rating divided by equivalent static load-
Dynamic rating divided by equivalent dynamic load-
Decision view
ISO 281 load-life and rating margin
ISO 281 load-life and rating marginCatalog X and Y factors form the equivalent dynamic load; the rating-life power law is adjusted and converted from revolutions to hours before the required C rating is compared with the catalog value.
Exact scenario comparisonApplied radial load Fr (kN) changes while all other entered assumptions remain constant.
| Applied radial load Fr (kN) | Equivalent dynamic bearing load P | Basic L10 life (million revolutions) | Adjusted rating life (million revolutions) | Adjusted rating life at entered speed | Required life in million revolutions | Dynamic rating required for entered life | Catalog C minus required C | Calculated minus required life | Static rating divided by equivalent static load | Dynamic rating divided by equivalent dynamic load |
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How to use Bearing Preliminary Design Calculator
- Use catalog X and Y factors for the selected bearing and load ratio.
- Enter dynamic and static ratings with equivalent loads.
- Set speed, exponent, adjustment factor, and required hours.
Calculator guide
Understanding Bearing Preliminary Design Calculator
Bearing rating life depends on an equivalent dynamic load, the catalog dynamic rating, a bearing-type exponent, speed, and clearly stated adjustment factors.
Detailed calculation process
Detailed bearing rating-life calculation
The default case traces equivalent load through life and required rating.
General formula: P=XFr+YFaL10=(C/P)^pL_adj=aL10h=10^6L_adj/(60n)C_req=P[L_req/a]^(1/p) Life is in million revolutions before speed conversion. Required rating reverses the same power law.
What each symbol means
Worked substitution with the default inputs
Using the calculated required C in the adjusted life equation reproduces the 20,000-hour requirement.
Worked situations
Practical examples
- For a ball bearing use p=3 when the catalog method supports it.
- A lower life adjustment factor reduces calculated life and increases required C.
Better inputs
Useful tips
- Use manufacturer catalog factors, not generic guesses.
- Integrate variable duty cycles separately.
- Check minimum load and static safety as independent requirements.
Before relying on the result
Limitations and common mistakes
- Lubrication, contamination, misalignment, and clearance require manufacturer methods.
- One constant load and speed are modeled.
- Reliability is represented only by the entered combined adjustment.
Reference
Key terms
- Basic dynamic rating C
- Catalog load rating used in the rating-life equation.
- Equivalent dynamic load P
- Catalog-factor combination of radial and axial load.
- L10 life
- Basic rating life associated with 90% reliability under the standard model.
Important note
Final selection must follow the current bearing manufacturer catalog and application-specific adjustment method.
Frequently asked questions
Why is the default life short?
The entered equivalent load is large relative to C and the bearing rotates at 1,200 rpm.
Does static safety prove long life?
No. Static and dynamic criteria address different failure concerns.
Can I enter p=10/3?
Yes, when that exponent matches the selected roller-bearing catalog method.