Loads

There are no standardized calculation methods, either nationally or internationally, to calculate basic load ratings for polymer ball bearings. According to the current state of technology, an analytical life calculation is not possible.
For low speeds (n < 25 r/min), the static load carrying capacity is to be used.
Dynamic
load carrying
capacity
The dynamic load carrying capacity is an indicator for the operational load at which the bearing fulfils its function in the majority of applications. The dynamic load carrying capacity depends on the operating conditions and needs to be adjusted under the following conditions:
  • operating temperature T > 50 °C (120 °F)
  • rotational speed n ≥ 20% of the limiting speed nlim (→ product tables)

Cadj = fT fn C

Calculation example
Bearing 6301/HR11TN, n = 650 r/min, T = 90 °C (195 °F)

From the product table:
  • C   = 0,31 kN
  • nlim = 1 300 r/min
From diagram 1:
  • with T = 90 °C (195 °F) and rings made of POM
    → fT ≈ 0,87
  • with n/nlim: (650/1 300) x 100 = 50%
    → fn ≈ 0,85

Cadj = 0,87 x 0,85 x 0,31 = 0,229 kN
Static load
carrying
capacity

The static load carrying capacity is the maximum load that a bearing can accommodate at standstill without sustaining damage to the balls or raceways.

The static load carrying capacity depends on the operating temperature and should be adjusted at operating temperatures T > 50 °C (120 °F).

C0adj = fT C0

Symbols

C
=
basic dynamic load rating [kN] (→ product table)
Cadj
=
adjusted dynamic load carrying capacity [kN]
C0
=
basic static load rating [kN] (→ product table)
C0adj
=
adjusted static load carrying capacity [kN]
fn
=
adjustment factor for speed (diagram 1)
fT
=
adjustment factor for operating temperature (diagram 1)
n
=
rotational speed [r/min]
nlim
=
limiting speed [r/min] (→ product table)
T
=
operating temperature [°C (°F)]

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