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Matching shaft diameter is only one part of mechanical integration. Bearings and mounting also need to support the applied forces, their positions, speed and duty. Provide a load sketch with the shaft drawing when requesting an OEM motor review.
Identify the force directions
Radial force acts across the shaft axis. Axial force acts along it. A belt, gear, fan, coupling or assembly operation can introduce one or both, together with bending moments and transient loads.
State where the force acts
A radial-load value needs its application distance from a defined reference. For a simple force and lever arm, bending moment is M = F × d. A calculated 20 N force acting 0.03 m from a reference produces 0.60 N·m of moment about that reference. Actual bearing reactions depend on the support geometry; this example is not a Zhanye shaft-load limit.
Moving a pulley or gear further from the support can change bearing and shaft demands even if the transmitted torque is unchanged. Do not reuse a permissible-load figure without its specified position, speed and conditions.
Review coupling and alignment
Specify coupling type, retention, angular and parallel alignment, axial position and tolerance stack. A flexible coupling can accommodate defined misalignment, but it does not remove the need to check installation and load limits.
For a fan or impeller, include overhang, mass, balance, retention and expected thrust. For a belt drive, provide pulley position and belt forces, not only output torque.
Separate assembly forces from operating loads
Press-fit or retention operations can impose axial forces that differ from running loads. Agree the assembly method, support arrangement and permissible installation force with the supplier. Do not assume the motor bearings can absorb an unspecified pressing load.
Prepare a mechanical brief
- Shaft geometry, reference face, rotation viewing direction and mounting drawing.
- Radial and axial forces, their directions and application positions.
- Running speed, duty cycle, starts, reversals and shock events.
- Coupling, pulley, gear or fan dimensions and retention method.
- Alignment, runout, balance and tolerance requirements.
- Ambient conditions, contamination exposure and assembly process.
Verify the assembled mechanism
Check loaded behavior, alignment, vibration, temperature and evidence of movement or rubbing in a representative fixture. Where endurance validation is required, define the load spectrum and acceptance criteria. A shaft-load calculation alone does not prove project service life.
Motor family pages — ZU, ZB, ZD, ZI and ZS — are starting points for review. Permissible shaft loads must be confirmed for the selected configuration.
Related: custom shaft and mounting and noise and vibration validation.
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Helpful information to include: target voltage, speed, torque, duty cycle, available dimensions, project stage and estimated annual demand.