Intelligent Motion Systems MDriveAC - Manual (Page 60)

A-9 Appendices
Shock Load Output Torque
The nominal output torque (T
N
) is the actual working torque the Planetary Gearbox will generate. The
shock load output torque (T
AB
) is the additional torque that can be generated by starting and stopping
with no acceleration ramps, payloads, inertia and directional changes. Although the nominal output
torque (T
N
) of the Planetary Gearbox is accurately calculated, shock loads can greatly increase the dy-
namic torque on the Planetary Gearbox.
Each Planetary Gearbox has a maximum specified output torque. In this example a 7:1 single stage
MD23 Planetary Gearbox is being used. The maximum specified output torque is 566 oz-in. By calculat-
ing the shock load output torque (T
AB
) you can verify that value is not exceeding the maximum specified
output torque.
When calculating the shock load output torque (T
AB
), the calculated nominal output torque (T
N
) and the
operating factor (C
B
) are taken into account. C
B
is merely a factor which addresses the different working
conditions of a Planetary Gearbox and is the result of your subjective appraisal. It is therefore only meant
as a guide value. The following factors are included in the approximate estimation of the operating factor
(C
B
):
 Direction of rotation (constant or alternating)
 Load (shocks)
 Daily operating time
Note: The higher the operating factor (C
B
), the closer the shock load output torque (T
AB
) will be to the
maximum specified output torque for the Planetary Gearbox. Refer to the table below to calculate the
approximate operating factor (C
B
).
With the most extreme conditions which would be a C
B
of 1.9, the shock load output torque (T
AB
) is
over the maximum specified torque of the Planetary Gearbox with a 0.5 safety factor but under with a 0.7
safety factor.
The nominal output torque (T
N
) × the operating factor (C
B
) = shock load or maximum output torque
(T
AB
).
With a 0.5 safety factor, the shock load output torque is greater than the maximum output torque specifi-
cation of the MDrive23 Planetary Gearbox.
(378 × 1.9 = 718.2 oz-in.)
With a 0.7 safety factor the shock load output torque is within maximum output torque specification of
the MDrive23 Planetary Gearbox.
(270 × 1.9 = 513 oz-in.)
The 0.5 safety factor could only be used with a lower operating factor (C
B
) such as 1.5 or less, or a lower
motor torque.
Note: All published torque specifications are based on C
B
= 1.0. Therefore, the shock load output torque
(T
AB
) = nominal output torque (T
N
).
WARNING! Excessive torque may damage your Planetary Gearbox. If the MDrive/Planetary Gearbox
should hit an obstruction, especially at lower speeds (300 RPM or 1000 Full Steps/Second), the torque
generated will exceed the maximum torque for the Planetary Gearbox. Precautions must be taken to
ensure there are no obstructions in the system.
Determining the Operating Factor (C
B
)
Direction of
Rotation
Load
(Shocks)
Daily Operating Time
3 Hours 8 Hours 24 Hours
Constant Low* C
B
=1.0 C
B
=1.1 C
B
=1.3
Medium** C
B
=1.2 C
B
=1.3 C
B
=1.5
Alternating Low† C
B
=1.3 C
B
=1.4 C
B
=1.6
Medium†† C
B
=1.6 C
B
=1.7 C
B
=1.9
* Low Shock = Motor turns in one direction and has ramp up at start.
** Medium Shock = Motor turns in one direction and has no ramp up at start.
† Low Shock = Motor turns in both directions and has ramp up at start.
†† Medium Shock = Motor turns in both directions and has no ramp up at start.
Table B.1: Planetary Gearbox Operating Factor