Downloaded from https://www.everyspec.com ADS-79D-HDBK AH-64 hanger bearings are single ball bearings with a fixed outer race and the following dimensions: The rotational speed of the tail rotor drive shaft ( ω shaft ) is 81.06 Hz on AH-64Ds (101%NR) and 80.25 Hz on AH-64A (100%NR). Table D-II shows the fault frequencies and harmonics for 101% NR. CFF is the rotational speed of the cage. It will be less than the rotational speed of the bearing. It is designed to capture vibrations due to defects in the cage.
If the outer race is fixed, d CFF cos 1 2 1 contact pitch RE shaft d [1] If the inner race is fixed, d CFF cos 1 2 1 contact pitch RE shaft d BSF is the frequency at which the rolling elements themselves rotate. It is designed to capture the frequency of vibrations produced by defects on the surface of the rolling elements. Twice this frequency is often used because if a defect strikes both races, an impact will occur twice during every rotation of the rolling element; however, the fundamental frequency is shown here, d BSF cos 1 2 d d pitch RE shaft RE 2 2 d contact pitch [1] BPFO is the frequency at which rolling elements pass over a point on the outer race.
It is designed to capture the frequency of vibrations produced by defects of the outer race. d N BPFO cos 1 2 [1] contact pitch RE shaft d 94 TABLE D-I. AH-64 aft hanger bearing properties No. of rolling RE diameter, d RE Pitch diameter, d pitch Contact angle, θ elements, N 9 0.5000 in 2.362 in 0°