SIEMENS
2/9
Siemens MD 50.8 · 2017
Configuring guide
Configuring a gearbox
2
■
Shaft load and bearing service life
Permissible radial force
The selection tables specify the permissible radial force
F
R2
.
The table values refer to the force application point x,
see table
"Gearbox constants for calculating the radial force"
.
Note:
For BH.39 with 25 x 35 solid shaft, the permissible radial force
F
x
must always be calculated using the conversion below
(even when x = 18 mm), because the table values apply to a
30 x 50 solid shaft.
Radial force conversion for
force application at distance
other than x
When the distance x to the shaft shoulder is other than the value
stated in the table, use the following formulas to convert the
permissible radial force.
The lowest value of
F
xperm1
(bearing service life),
F
xperm2
(strength) and
F
Rmax
is the permissible radial force
F
x
. The
calculation is applicable without axial force.
Permissible radial force according to the bearing service life
Permissible radial force according to the shaft strength
Permissible radial force for force application at distance other
than x
F
x
F
xperm1
;
F
xperm2
;
F
R2max
Condition: Available radial force
permissible radial force
Variables for defining shaft load and bearing service life
Definition of the force application point
Fig. 2/5
Force application point
Gearbox constants for calculating the radial force
F
xperm1
F
R2
y
z
x1
+
-------------------
=
F
xperm2
a
b
x1
+
---------------------
=
Code
Description
Unit
Force application angle
°
a, b, d, l, y, z
Gearbox constants
Nmm /
mm
d
0
Average diameter of the mounted
transmission element
mm
F
G
Force due to weight
N
F
R2
Permissible radial force (from power table)
N
F
R2max
Maximum permissible radial force according
to table
"Gearbox constants for calculating
the radial force"
N
F
Ravail
Available radial force
N
F
x
Permissible radial force from out of center
force application point
N
F
xperm1
Permissible radial force, limited by the
bearing service life, at a distance of x from the
shaft shoulder
N
F
xperm2
Permissible radial force, limited by the shaft
strength, at a distance of x from the shaft
shoulder
N
RWC
Running wheel center
-
x
Distance from the shaft shoulder up to the
force application point at running wheel
center for
F
R2
according to table
"Gearbox
constants for calculating the radial force"
mm
x1
Distance from the shaft shoulder up to the
force application point at running wheel
center for
F
x
mm
View Z
G_D087_EN_00317
RWC
x
Z
F
0
x
x x1
F
R2
F
X
0°
90°
180°
270°
F
R2
F
R2
F
X
α
Ød
Gearbox size
Constants
y
z
a
b
d
l
T
2
F
R2max
Force application x
mm
mm
Nmm
mm
mm
mm
Nm
N
mm
Light-load applications
BH.29
158
145
97 500
0
25
35
90
7 500
13
BH.39
170
162
216 000
0
25
35
200
12 000
18
BH.39
170
152
270 000
0
30
50
200
15 000
18
Heavy-load applications
KH.49
199
171
333 000
0
30
60
420
18 500
18
KH.49
199
171
518 000
0
35
70
420
18 500
28
KH.69
239
211
700 000
0
45
90
600
25 000
28
KH.79
257
225
1 280 000
0
55
110
820
40 000
32
© Siemens AG 2017