VEM A21 Serie Instructions De Montage, D'utilisation Et D'entretien page 24

Additional Installation, Operating and Maintenance Instructions (Translation)
Important note:
Radial forces below the minimum value can lead to bearing damage within a few hours. Test runs in no-load state
are only permissible for a short period. If the specified minimum radial force is not achieved, we recommend the
use of deep-groove ball bearings (so-called "light bearing arrangement"). The bearing arrangement can be re-
arranged on request.
3.3 Bearing loading and shaft end loading
Due to the international standardisation of asynchronous motors, dimensioning of the bearing arrangement and
shaft is only variable within limits; a constructional optimum has thus been selected.
3.4 Admissible shaft end loading
The size of the permissible shaft end loading is determined using the following main criteria:
permissible bending of the shaft
shaft end fatigue strength
bearing service life
The admissible shaft end loading (radial and axial forces) is based on a bearing service life of 20,000 hours and
resistance to fatigue of >2.0.
The loading diagram is specified in the following illustration:
F = radial shaft end loading
r
F = axial shaft end loading
a
l = length of the shaft end
x = distance of the application point F
The type-related data for the permissible axial shaft end loading F
(at the application point x : l = 0.5), F
bearing arrangement in horizontal and vertical mounting position of the motor are specified in the product cata-
logue.
The permissible radial forces are depicted as a function of the position of the application point on the shaft end for
motors in horizontal and vertical mounting position of the motor (taking into account the effective direction of the
radial force in relation to gravity).
The permissible forces given are valid for practically vibration-free mounting of the motors.
The shaft loading for frame sizes 315 L and LX and frame size 355 can be verified by the manufacturer on request.
The loadings F and F are generally dependent on the transmission elements used, i.e. on the axial and radial
r a
forces arising from these transmission elements, including their weights.
The forces are calculated using mechanical formulas, e.g. for belt pulleys
2 10
F =
r
where
F = radial force in N
r
P = rated motor output in kW (transmission output)
n = nominal motor speed
D = belt pulley diameter in mm
c = pretension factor as stated by the belt manufacturer (for V-belts preferably 2.5)
In practice, the radial force F
the range x : l = 0.5 up to x : l =1.0 can be done by linear interpolation.
If the calculated shaft loadings exceed the permissible ones, the drive elements must be changed. There are the
following possibilities, among others:
selection of a larger belt pulley diameter,
use of V-belts instead of flat belts,
selection of another pinion diameter or skew angle of the teeth,
selection of another coupling version, etc.
Generally, care must be taken that the resulting load application point of F
solution has still not been found, the manufacturer would be happy to check special constructions which can be
used to deal with problems of this kind.
from the shaft shoulder
r
(at the application point x : l = 1.0) for the basic version and for the heavy
r1.0
P
7
c
n D
does not always act at x : l =0.5. The conversion of the permissible radial force within
r
and the permissible radial shaft end loading F
a
will not be outside the shaft end. If a
r
23
English
r0.5