Jinsi ya Kugawanya Kutokuwa na Usawa wa Mabaki Unaoruhusiwa Jumla kati ya Nyuso Mbili
For a two-support rotor, the total permissible residual unbalance (U_{mathrm{per}}) is distributed between two correction planes based on rotor geometry and the rotor center of mass (CM) position. Below are the core rules from ISO 21940-11, including the 70:30 limitation set out in Clause 7.2.2 of the standard.
Definitions
- (U_{mathrm{per}}): total permissible residual unbalance for the rotor.
- (U_{mathrm{per}A}), (U_{mathrm{per}B}): permissible residual unbalance allocated to planes A and B.
- (L): umbali kati ya nyuso A na B.
- (L_A): umbali kutoka CM hadi uso A.
- (L_B): umbali kutoka CM hadi uso B.
- Uhusiano wa jiometri: (L = L_A + L_B).
1) Rotari ya Ulinganifu
Ikiwa rotari ni ya ulinganifu na CM iko takriban katikati kati ya nyuso hizo, gawanya ruhusa kwa usawa:
(U_{mathrm{per}A} = U_{mathrm{per}B} = dfrac{U_{mathrm{per}}}{2})
Njia hii inafaa kwa hali nyingi za kawaida ambapo rotor iko karibu na ulinganifu.
2) Rotor Isiyo na Ulinganifu (Kanuni ya Lever)
Ikiwa kituo cha uzito (CM) kinahamia upande wa msaada mmoja, gawanya ruhusa kwa kutumia kanuni ya lever, sawia na umbali kutoka CM hadi uso wa upande mwingine:
(U_{mathrm{per}A} = U_{mathrm{per}} cdot dfrac{L_B}{L})
(U_{mathrm{per}B} = U_{mathrm{per}} cdot dfrac{L_A}{L})
Hapa, (L) ni umbali kati ya nyuso mbili, na (L_A) na (L_B) ni umbali kutoka CM hadi uso A na B mtawaliwa.
Kikwazo Muhimu: Kanuni ya 70:30
To avoid extreme accuracy requirements in one plane, ISO 21940-11:2016 (Clause 7.2.2) stipulates for inboard rotors — i.e. with the centre of mass located between the bearing planes — that the split shall be limited to a 70:30 ratio. Even if the CM is very close to one plane/support:
- The smaller share should not be less than (0.3 cdot U_{mathrm{per}}).
- The larger share should not exceed (0.7 cdot U_{mathrm{per}}).
(0.3 cdot U_{mathrm{per}} le U_{mathrm{per}A},, U_{mathrm{per}B} le 0.7 cdot U_{mathrm{per}})
Note: these limits apply to inboard rotors. For outboard (overhung) rotors, Clause 7.2.3 of the standard allows the larger share to reach (1.3 cdot U_{mathrm{per}}), while the smaller share must still be at least (0.3 cdot U_{mathrm{per}}).
Calculator
Enter (U_{mathrm{per}}) and distances. The calculator supports symmetric split and lever-rule split. It also applies the 70:30 limitation when enabled.
