SCHATZ Bearing Life Calculations
Load Ratings and Fatigue Life Calculations
Aircraft Control Bearings Load Limit Rating
The Limit Load Ratings listed in this catalog were developed to rate
bearings that operate in slow
speed applications such as those encountered in aircraft control
applications. For Bearing Life
Calculations, please consult the Schatz Engineering Department.
Basic Dynamic Radial Load Rating Cr
Schatz dynamic radial load ratings are the radial bearing loads that
will give a basic rating life
of 1,000,000 revolutions. The basic dynamic load ratings have been
determined in accordance
with the methods prescribed by ISO, ABMA, and ANSI.
Bearing Fatigue Life
The fatigue life of a guide wheel bearing is defined by the number of revolutions the bearing will operate before the first signs of fatigue occur. The L10 life is the basic rating life in hours that 90% of a sufficiently large group of apparently identical bearings will operate before the first signs of fatigue appear.
Use the following formula to calculate L10 life for guide wheel bearings:
Where:
Fr = Applied Radial Load
Fa = Applied Axial Load
S = Bearing Speed (RPM)
L10 = Life (hrs.)
Z = Factor
Cr = Schatz Bearing Dynamic Load Rating (See Following Table)
| Schatz Bearing Basic P/N | Cr(Lbs.) | Z |
|---|---|---|
| W1 | 500 | 2.20 |
| W2 | 910 | 2.50 |
| W3 | 1,740 | 2.25 |
| W4 | 3,260 | 2.45 |
Life Adjustment Factors
Many life adjustment factors can be applied to the calculated bearing life as stated above. These factors are simply multiplied by the bearing life to determine the final adjusted operating life of the bearing.
The three life adjustment factors that Schatz recommends using are:
A1 – life adjustment factor for reliability
A2 – life adjustment factor for material
A3 – life adjustment factor for lubrication
Reliability (A1):
All formulas are based on an L10 life. If a different
life needs to be calculated, use the following
table for the adjustment factor:
| Reliability (%) | 90 (L10) | 95 (L5) | 96 (L4) | 97 (L3) | 98 (L2) | 99 (L1) |
| Factor | 1.00 | .62 | .53 | .44 | .33 | .21 |
Material (A2):
There are several material options for use with Schatz
bearings. The following chart shows the
life adjustment factors for the materials offered:
| Material Type | 52100 | 440-C | M-50 | Schatz EMS 138 |
| Factor (A2) | 2.2 | .6 | 4.2 | 4.2 |
Lubrication (A3):
Lubrication and the presence of an elastic-hydrodynamic
lubrication film is critical to achieving
proper bearing life. Please consult the Schatz engineering department
for information on determining
the lubrication factor for a specific application.
Visit our Lubrication Options page for grease specifications.
