Does this worksheet select a permissible ISO balance grade for a marine propeller?

No. Enter a residual-unbalance magnitude from the controlled balancing specification or measurement record. Grade selection, permissible magnitude, correction planes and allocation require the applicable specification and ISO 21940-11 rules.

Can total residual unbalance be divided equally by blade count?

No generic scalar division is valid. Unbalance is a vector with magnitude, angle and plane; blade correction depends on correction radius, phase, plane and the approved balancing procedure.

What force does the worksheet calculate?

It calculates the amplitude U omega squared for one documented rotating unbalance vector. It does not predict bearing force, hull vibration or structural response.

Does a low calculated force prove ISO compliance?

No. The worksheet has no acceptance limit and does not implement the ISO balancing procedure, tolerance-plane allocation or balancing-error assessment.

Does the result apply to a flexible rotor?

No ISO 21940-11 claim is made for flexible behaviour. The official scope states that flexible rotors are handled by ISO 21940-12.

General rotating-force arithmetic · no grade selection

Documented Residual-Unbalance Force Worksheet

Calculate the specific unbalance and ideal one-vector rotating-force amplitude from a residual-unbalance magnitude already established by a controlled balancing specification or measurement record.

No propeller G-grade presetsNo per-blade scalar allocationNo ISO compliance verdict

General mechanics outputs

Ideal rotating-force amplitude F

Specific unbalance e = U/m

Angular speed ω

SI unbalance magnitude

Not transmitted load or vibration: F is the ideal radial force amplitude Uω² for one rotating vector. Real bearing reactions, shaft/hull vibration, phase, multi-plane couple unbalance, hydrodynamic loading, structural modes and operating response need a system model and measurements.

One documented unbalance vector

ω = 2πn / 60
U_SI = U_g·mm × 10⁻⁶ kg-m
F = U_SI ω²
e = U_SI / m

n is rotational speed in revolutions per minute; U is the magnitude of one residual-unbalance vector; m is the represented rigid assembly mass; F is ideal rotating-force amplitude in newtons; and e is specific unbalance/eccentricity. The worksheet displays e in micrometres for metric input or mil (0.001 in) for US input.

OpenStax University Physics gives the circular-motion relation F = mrω². Because unbalance U is the product mr, substitution gives F = Uω². This is general mechanics, not an ISO tolerance equation.

The US route uses exact NIST factors: 1 oz = 0.028349523125 kg, 1 lb = 0.45359237 kg and 1 in = 0.0254 m. Thus 1 oz·in = 720.0779 g·mm exactly at the represented digits.

Former output/input	Confirmed problem
Propeller diameter	It was collected and saved but never used by any formula.
G40/G16/G6.3/G2.5 marine presets	Grades were assigned to workboats,cargo/navy/passenger/submarine applications without a verified current ISO table or project/OEM/classification-society basis.
Permissible ISO unbalance	The page selected a grade and returned acceptance without implementing the rigid-behaviour decision,correction-plane count,allocation or balancing-error procedure in ISO21940-11.
Per-blade allowance U/N	Residual unbalance is a vector with magnitude,angle and plane. Scalar division by blade count does not define correction mass,radius,phase or plane and is not a generic balancing tolerance.
In-situ compliance claim	A scalar calculator cannot establish ISO compliance or authorize attaching trial/correction masses to a marine propeller. Equipment access,hydrodynamic state,correction method and approvals are project-specific.

The replacement accepts a controlled U value and performs only general mechanics. It makes no claim that U is permissible.

ISO 21940-11

The official ISO 21940-11:2016 page identifies Edition1 as current but under systematic review, with Amendment1:2022. Its scope covers procedures and unbalance tolerances for rotors with rigid behaviour, including permissible residual-unbalance magnitude, necessary correction-plane count, allocation to tolerance planes and balancing-process errors. It excludes flexible-behaviour rotors, which are handled by ISO21940-12.

Those procedure,grade/application and allocation details are licensed and are not inferred here. A project specification,OEM,class rule or authorized calculation must establish the applicable balance requirement and whether the assembly behaves rigidly at balancing/service speeds.

Propeller manufacturing standards are separate

ISO 484-1:2015 covers manufacturing tolerances for ship screw propellers greater than2.50m and is marked to be revised; ISO 484-2:2015 covers0.80m to2.50m inclusive and is current but expected to be replaced. Their closed tolerance content is not copied or treated as a G-grade table.

Published mechanics check

OpenStax University Physics, Section6.3 publishes an example with900kg,25m/s and500m radius giving1125N. Representing mr as U=450000kg·m and ω=v/r=0.05rad/s (n≈0.477464829r/min), this worksheet independently reproduces1125N. This validates the mechanics transformation only; it is not a rotor tolerance example.

ISO lifecycle and sources accessed13 July2026. No closed grade/application table,clause value or permissible residual unbalance is asserted.

This worksheet does not select one. Use the exact controlled project,OEM,class or licensed-standard basis and document its edition,rigid-behaviour assessment,planes and allocation.

No generic scalar division is valid. Correction needs vector phase,plane,radius,available locations and an approved procedure.

No. It is the ideal one-vector rotating-force amplitude. Bearing and structural response depends on the complete rotor-bearing-foundation/fluid system.

No. There is no permissible limit or acceptance comparison. ISO procedures,planes,allocation and error assessment are not implemented.