Engineering
Shaft Load Calculator
Estimate service-adjusted torque, simple-support bending moment, solid-shaft torsional shear, bending stress, von Mises stress, and entered allowable ratios.
Nominal transmitted torque (N·m)-
Service-adjusted torque (N·m)-
Central-load bending moment (N·m)-
Outer-surface torsional shear (MPa)-
Outer-surface bending stress (MPa)-
Combined von Mises stress (MPa)-
Torsional allowable ratio-
Bending allowable ratio-
Governing allowable ratio-
Shaft surface speed (m/s)-
Decision view
Loaded shaft, torque vector, bending diagram, and stress interaction point
Loaded shaft, torque vector, bending diagram, and stress interaction pointBearing reactions support the radial load while torque and bending stresses place the live operating point inside or outside the allowable box.
Exact scenario comparisonSolid shaft diameter (mm) changes while all other entered assumptions remain constant.
| Solid shaft diameter (mm) | Nominal transmitted torque (N·m) | Service-adjusted torque (N·m) | Central-load bending moment (N·m) | Outer-surface torsional shear (MPa) | Outer-surface bending stress (MPa) | Combined von Mises stress (MPa) | Torsional allowable ratio | Bending allowable ratio | Governing allowable ratio | Shaft surface speed (m/s) |
|---|
How to use Shaft Load Calculator
- Enter transmitted power and loaded speed.
- Apply a defensible service factor for torque peaks.
- Use the actual bearing span, radial load, solid diameter, and material allowables.
Calculator guide
Understanding Shaft Load Calculator
A rotating shaft can be acceptable in pure torsion yet overstressed when belt, gear, or coupling forces add bending. The calculation resolves power torque and a central radial load into separate outer-surface stresses.
Detailed calculation process
Detailed combined shaft-load calculation
The default solid 45 mm shaft carries 45 kW at 1,450 rpm, a 1.5 torque factor, and a 3.5 kN central radial load across 0.4 m.
General formula: T_n=9550*P/nT=T_n*K_sM=F*L/4tau=16*T*1000/(pi*d^3)sigma=32*M*1000/(pi*d^3)sigma_vm=sqrt(sigma^2+3*tau^2)R_t=tau_allow/tauR_b=sigma_allow/sigma Power torque and beam bending are calculated independently, converted to MPa using millimetres, and combined only in the von Mises result.
What each symbol means
Worked substitution with the default inputs
The default governing component allowable ratio is about 2.21 before fatigue and concentration effects.
Worked situations
Practical examples
- Forty-five kilowatts at 1,450 rpm produces 296.4 N·m nominal torque.
- A 3.5 kN central load across 0.4 m produces 350 N·m maximum bending moment.
Better inputs
Useful tips
- Model gear and belt loads at their actual positions.
- Apply fatigue concentration factors at shoulders and keyways.
- Check critical speed, deflection, bearings, and keys separately.
Before relying on the result
Limitations and common mistakes
- The shaft is solid, round, uniform, simply supported, and loaded centrally.
- No fatigue, stress concentration, axial load, deflection, dynamics, or keyway reduction is included.
- Entered allowables are not derived from material data.
Reference
Key terms
- Service torque
- Power-derived torque multiplied by the entered application factor.
- Outer-fibre bending stress
- Maximum normal stress at the solid shaft surface.
- Allowable ratio
- Entered allowable divided by calculated component stress.
Important note
Final shaft design requires material, fatigue, stress-concentration, deflection, critical-speed, bearing, key/spline, manufacture, and applicable code checks.
Frequently asked questions
Why use WL/4?
That is the maximum moment for a central point load on a simply supported span.
Is von Mises compared with the entered allowables?
No; the page reports it, while the two entered allowables are checked against their matching component stresses.
Can I use a hollow shaft?
Not directly; its polar and bending section moduli require different equations.