Bearing load calculator: where shaft loads come from
Before you can check bearing life you need the load. The Rotec AI Load Calculator works out radial and axial loads from the machine itself, grouped by how the load actually arises.
Nine equipment types in the Load Calculator
| Group | Type |
|---|---|
| Power transmission | Belt, chain or sprocket drive · Gear mesh · Electric motor (rotor weight, magnetic pull, shaft-end pull) · Spring preload |
| Fluid and process equipment | Pump or fan (impeller or disc thrust) · Screw compressor thrust bearings · Roll nip load · Paper machine roll (wire and felt tension) · Agitator or mixer shaft |
The physics behind two common cases
Torque and tangential force
Torque in N·m = 9,550 × power in kW ÷ speed in rpm. The tangential force at a pulley, sprocket or gear of pitch diameter d (mm) is Ft = 2,000 × torque ÷ d newtons.
Gears
For a helical gear, the radial force is Fr = Ft × tan(α) ÷ cos(β) and the axial force is Fa = Ft × tan(β), where α is the pressure angle and β the helix angle. Spur gears have β = 0, so no axial force.
Belts and chains
The belt or chain pull on the shaft is larger than the tangential force because the tight side carries more than the slack side. The factor depends on the drive type and tension, which the Load Calculator applies for you.
From load to bearing life
Once you have the radial and axial loads, the equivalent load P is found with the bearing's X and Y factors. Then use the bearing life calculator to turn C and P into hours.
Related tools and guides
Questions
How do I calculate the load on a bearing?
Work out the forces on the shaft from the machine (belt pull, gear forces, rotor weight, thrust), split them into radial and axial parts, then combine them into an equivalent dynamic load P using the bearing factors.
How do I find the force from power and speed?
Torque in N·m = 9,550 × kW ÷ rpm. Tangential force = 2,000 × torque ÷ pitch diameter in mm.
Results are starting points from standard engineering practice. Confirm critical selections with the bearing or lubricant maker.