Vibration Sideband Modulations and Harmonics Separation of a Planetary Helicopter Gearbox with Two Different Configurations

Table 3

Bell-206-B4 gearbox modulation sidebands (assuming planets are evenly spaced).

Sidebands
−5	0	(99 − 5)/4 (NI)
−4	0	(99 − 4)/4 (NI)
−3 (550.52 Hz)	1	(99 − 3)/4 (I)
−2	0	(99 − 2)/4 (NI)
−1 (561.97 Hz)	0	(99 − 1)/4 (NI)
0 (567.71 Hz)	0	(99 − 0)/4 (NI)
1 (573.74 Hz)	1	(99 + 1)/4 (I)
2	0	(99 + 2)/4 (I)
3	0	(99 + 3)/4 (NI)
4	0	(99 + 4)/4 (NI)
5 (596.36 Hz)	1	(99 + 5)/4 (I)

0: suppressed. 1: dominance: nonzero vibration. : number of teeth on the ring gear (99 teeth). : number of planetary gears (4 planets). I: integer. NI: noninteger.