AKB Report
Radial and axial loads of motor and gearbox
1) Introduction
For certain drive dimensioning processes, radial and axial loads have to be checked. Fig. 1.1
shows the radial and axial forces acting on a gearbox shaft in an application. At present,
DSD does not contain any radial and axial load check.
In Fig. 1.2 / 1.3, you can find an overview of the Lenze motor and gearbox families.
Fig. 1.1 Radial and axial forces on the motor shaft
Fig. 1.2: Overview of Lenze motor families
Fig. 1.3: Overview of Lenze gearbox families
Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
2) Typical applications with radial loads
Typical applications include:
- Cable drum directly mounted onto a gearbox shaft (e.g. hoist drives)
- Omega belt pulley for linear conveyor sections
- General toothed belt, V-belt, flat belt ratios (e.g. winders, fans, compressors, conveyor belts)
- Sprocket on gearbox or motor shaft (e.g. materials-handling technology)
- Rack module (materials handling)
- Monorail overhead conveyors
- Eccentric and crank drives
Fig. 2.1: Toothed belt ratio at the gearbox
Fig. 2.2: Omega belt ratio with stationary drive
Fig. 2.3: Belt drive of a center winder
Radial_Axial_Load_Check_17.03.2015.docx
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Fig. 2.4: Traction drives in a storage and retrieval unit
Fig. 2.5: Hoist drive cable drum on the gearbox shaft
Fig. 2.6: Belt positioning system
Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
Fig. 2.7: V-belt transmission fan for air conditioning in buildings
Fig. 2.8: Rotating tangential chain of a roller conveyor with sprocket at the gearbox shaft
Fig. 2.9: Crank drive
Fig. 2.10: Monorail overhead conveyor
Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
3) Typical applications with axial loads
Fig. 3.1: Stirrer
Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
4) Determination of radial and axial loads
Fig. 4.1 describes how to proceed to check radial and axial forces acting on the gearbox or
motor shaft. Fig. 4.2 / 4.3 provide further information. The permissible limit loads can be
obtained from the gearbox and motor catalogues.
construction
M, d
d, X
determination
radial-/axial forces
(Fig. 4.2)
FR, FA, X
catalogue data with
standard/ reinforced
bearing
NOK
· reinforced drive
components
· changed
construction
OK
Fig. 4.1: Workflow – radial and axial load check
2M
F
Ft 
F F 
d
2
F
F  F   0 ( Fig. 4.3 )
2
Fr  F1 ²  F2 ²  2F1  F2  cosß
t
pulley
Fv, d, ß
1
v
2
v
t
Fr
sprocket
d T, α
F
r
friction wheel
d
F1=
F2=
Fv=
Ft=
Fr=
2M
d
load side
slack side
prestressing force
tangential force from
transmitting torque
radial force
β=
d=
M=
angle of wrap pulley/
sprocket
effective diameter pulley /
sprocket
torque to be transmitted
Fig. 4.2: Determination of radial and axial loads
Radial_Axial_Load_Check_17.03.2015.docx
Author: KH Weber, B. Obergöker
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AKB Report
MAntr
F1
d2
Fr
d1
ß
F2
C
F 
F ²  F ²  2 F  F  cos ß

ß  2 * (0,5  d 2 d 1 )
2  c
r
1
2
1
2
Fig. 4.3: Determination of angle of wrap β and radial force Fr for belt and chain drives
Dimensioning example for determining the radial force:
Pretension
Torque
Diameter
Sprocket distance
(
√(
)
)
(
)
Radial_Axial_Load_Check_17.03.2015.docx
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Author: KH Weber, B. Obergöker
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AKB Report
5) Reinforced bearings for high radial / axial loads
For the following gearboxes and motors, you can optionally select reinforced bearings with
increased values. For all other gearboxes and motors, the next bigger drive component is to
be selected as an alternative.
Gearbox families
Reinforced bearings
GST
GST04……GST09
g500-H100…g500-H450
GKS, g500-B
Only as C type
GKR
Only as C type
GFL, g500-S
Not provided for
Motor families
Reinforced bearings
MCA
Only as C type
MH
Only as C type
MD
Only as C type
Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
6) Dimensioning example – eccentric lifting device for materialshandling technology
Via simulation and DSD, an eccentric lifting device has been dimensioned with a GST 07-2M
gearbox. In an additional check, the radial load of the selected gearbox has to be checked to
see if the gearbox is suitable for the occurring radial load.
Gearbox:
GST07- 2M-VBR-100-32; i= 32.267
Shaft:
40 x 80  d=40 mm; l = 80 mm
Chain pinion: 12 teeth; d = 98.14 mm
Pinion-shaft shoulder distance (Fig. 1.1) x = 46 mm
Results from DSD dimensioning:
Fig. 6.1 Eccentric lifting device in the bottom
dead center (left) and in the top dead
center (right)
Calculation of the radial force
Maximum radial force
Equivalent radial force
Determining the permissible radial force according to the gearbox catalogue:
(
Radial_Axial_Load_Check_17.03.2015.docx
)
Author: KH Weber, B. Obergöker
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AKB Report
Determining the additional load factor fw from the gearbox catalogue diagram (see Fig. 1.1).

;
Fig. 6.2 Additional load factor
catalogue)
fw =0.95
at the output shaft for GST04…09-1, 2, 3 (… GST gearbox
The average gearbox output speed is nav = 11.3 min-1.  selection column n ≤ 16
Fig. 6.3: Permissible radial forces at the output with standard bearings (extract from the GST gearbox
catalogue)
According to the gearbox catalogue, the max. permissible radial force must not exceed 9500 N.

Radial_Axial_Load_Check_17.03.2015.docx
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AKB Report
Result: Load is not permissible with standard bearings
Selection of a gearbox with reinforced bearing:
Fig. 6.4 Permissible radial forces at the output with reinforced bearing (… from GST gearbox catalogue)
Peak value
Result: Load is permissible with reinforced bearing
Radial_Axial_Load_Check_17.03.2015.docx
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