Bearing basic rating life means when a batch of bearings rotate separately under the same condition, the 90% total turn number which not including the turns produced by rolling fatigue, which is called “basic rated life of the bearings”. Please see below equation of the calculation of the bearing life on the basic rated load.

 
 
Lh: Bearing basic rating life; Unit is Hour
P: Equivalent dynamic bearing load
C: basic dynamic load rating
FT: Temperature-coefficient. Bearing working temperature is within 80°, FT normally is 1
Fw: Loading factor. (see sheet 1)
n: Rotation speed
 
 

Torque M=m1gxl+m1W2xh
I: Radial excentricity
V: Angular velocity of bearing operatioin
N: Bearing rotation speed
H: Axial distance from deviator load to bearing center, M
 
Sheet 1. (Loading factor)

Service Condition 1.2	Fw
No impact and in smooth movement condition	1~1.2
Normal operation condition	1.2~1.5
Hard impact condition	1.5~3

 
Harmonic reducer rigid bearing (cross roller bearing) equivalent dynamic load
 
 
P: Equivalent dynamic load, N
Fr: Radial Load, N
Fa: Axial load, N
M: Torque, N-mm
X and Y is the Radial and Axial loading factor(see sheet 2)
Dp: Pitch diameter, mm

Sheet 2. (Loading factor)

Category	X	Y
	1	0.45
	0.67	0.67