Bearing Equivalent Static Load Calculator

Equivalent static radial load formula

For a radial bearing whose current product method supplies static factors X₀ and Y₀, first calculate:

Then apply the exact product instruction:

The engine converts both loads to canonical newtons before applying the factors and returns P₀ in the selected display unit.

Safe default: purely radial load

The initial form uses Fᵣ = 10 kN, Fₐ = 0, X₀ = 1, and Y₀ = 0:

1. X₀Fᵣ = 1 × 10 = 10 kN.
2. Y₀Fₐ = 0 × 0 = 0 kN.
3. Catalog candidate: 10 + 0 = 10 kN.
4. The candidate equals the radial load, so P₀ = 10 kN.

This default avoids presenting a combined-load factor set as universal.

Illustrative combined-load example

Suppose the exact product method provides X₀ = 0.6 and Y₀ = 0.5, while one governing load combination contains Fᵣ = 5 kN and Fₐ = 8 kN:

1. Static radial contribution: 0.6 × 5 = 3 kN.
2. Static axial contribution: 0.5 × 8 = 4 kN.
3. Catalog candidate: 3 + 4 = 7 kN.
4. Radial floor: Fᵣ = 5 kN.
5. If the product method applies the floor, P₀ = max(5, 7) = 7 kN.

The values 0.6 and 0.5 are illustrative only. They must not be copied to another bearing, arrangement, or manufacturer method without verification.

Why the radial-floor rule is explicit

Some product instructions state that when the catalog expression is below Fr, the calculation must use P₀ = Fᵣ. Other bearing types use factors that already keep the expression at or above Fr, while special bearing types can require a different direct equation.

Select Apply P₀ ≥ Fr radial floor only when the exact method states that rule. If you select Use catalog expression directly and the result falls below Fr, the calculator preserves the arithmetic result but raises a warning for catalog verification.

Use paired loads from one governing case

SKF instructs users to insert radial and axial components for the maximum load that can occur and to consider the combination producing the highest P₀ when load direction varies.

Do not automatically combine the highest Fr from one operating condition with the highest Fa from another. Instead:

1. identify credible steady, transient, stationary, shock, and handling cases;
2. determine the Fr and Fa components that occur together in each case;
3. apply the exact factor and floor rule to each pair;
4. retain the case producing the governing P₀.

This calculator evaluates one pair at a time and does not build the bearing reaction load cases.

Find X₀ and Y₀ in exact product data

Static factors depend on bearing type and arrangement. Some radial needle or cylindrical roller bearings use P₀ = Fᵣ; some axial bearings use a direct axial expression; and some bearing types do not permit combined loading.

Before calculating, confirm:

• exact bearing designation and manufacturer;
• single, tandem, back-to-back, face-to-face, or other arrangement;
• permitted radial and axial load directions;
• product-table X₀ and Y₀ values;
• whether the radial-floor rule applies;
• whether preload, shock, clearance, or another factor must be included before P₀ is evaluated.

If axial load is positive while Y₀ is zero, the calculator warns that the axial component is ignored. It does not determine the correct Y₀.

P₀ is not dynamic P or a vector resultant

Do not substitute √(Fᵣ² + Fₐ²). P₀ is a scalar load-equivalence value based on maximum rolling-contact loading under a static method.

Dynamic equivalent load P is a separate fatigue-life input and can use different X, Y, and load-ratio branches. Use the Bearing Equivalent Dynamic Load Calculator for that calculation.

Continue to static safety factor

After verifying P₀, continue to the Bearing Static Safety Factor Calculator. The related-action link transfers P₀ and supplies placeholder values of C₀ = 30 kN and target s₀ = 2.

Replace both placeholders with the manufacturer-published basic static rating and the application-specific target before interpreting the result.

Engineering scope and limitations

This calculator evaluates one radial-bearing catalog-factor expression with an explicit optional radial floor. It excludes:

• automatic bearing identification, factor lookup, or arrangement selection;
• pure-thrust calculations or bearing types whose method does not use the radial expression;
• confirmation that combined loading is permissible;
• derivation of shaft reactions, bearing load sharing, moment load, preload, shock, or housing/shaft stiffness effects;
• automated evaluation of multiple load cases, changing load directions, reversals, oscillation, or duty cycles;
• internal load distribution, contact stress, truncation of contact area, tilt, misalignment, clearance, fits, or ISO 17956 analysis;
• basic static rating C₀, static safety factor, permanent-deformation acceptance, noise or accuracy requirements;
• dynamic P, L10 rating life, fatigue, minimum load, skidding, lubrication, contamination, wear, false brinelling, temperature, speed limits, sealing, mounting, or maintenance;
• product availability, dimensional compatibility, cost, warranty, certification, or final application approval.

Use current product documentation and manufacturer application guidance to verify every factor, load case, and rule before bearing selection.