Training – Unit 1: Motor Torque/ Motor Limitations
Torque – defined as the tendency of a body to rotate about an axis
Torque depends on magnitude of force and effective length (or distance) of force
* An example of torque can be visualized by a torque wrench turning a fitting, pipe or fastener
What is a N·m?
N·m stands for two metric units: Newton and meter. A Newton·meter is a combination of two
units that comprises a standard metric unit for torque. The standard US unit of torque is
Foot·Pounds (ft·lb) or Inch·Pounds (in·lb). Inch·Pounds is best applied to the motors in the roller
shade industry.
How do I convert the metric unit of N·m to a US unit of in·lb?
Torque (metric units)
4 N·m
6 N·m
8 N·m
Torque (US units)
35.4 in·lb
53.1 in·lb
70.8 in·lb
Now that I can convert N·m to in·lb, how do I determine the lifting capacity of said motor?
The relationship between Torque, Force and effective length (or distance) is defined by:
Torque = Radius x Force
or
Since we know the Torque rating of each motor and we know the radius of the tube that we are
building the shade out of, we rewrite the equation so we can solve for Force as:
r,
tube
radius
F, fabric & hembar weight
Motor Torque
4 N·m = 35.4 in·lb
6 N·m = 53.1 in·lb
8 N·m = 70.8 in·lb
JDM 032410
Radius
Lifting Capacity
QMS
QIET
QMS
QIET
diam = 2.325”
diam = 2.78”
diam = 2.325”
diam = 2.78”
1.39 in
30.4 lb
45.6 lb
60.9 lb
25.4 lb
38.2 lb
50.9 lb
1.1625 in
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Training – Unit 1: Motor Torque/ Motor Limitations
How does lifting capacity translate into maximum shade size or maximum square footage?
In order to determine the maximum shade size, you have to take into account the fabric density
(or weight) of the material that you will be using for a certain application. A Sheerweave fabric
may be over 20 ounces per square yard whereas an E-Screen is 10.3. Also, you need to consider
the hem bar weight. A standard aluminum hem bar is approximated at 0.25 lbs per foot;
however a steel hem bar would be much more.
The relationship between lifting capacity, square footage and density is defined by:
The following values of maximum square footage are based off of a fabric density of 22 oz/yd2
(which is greater than most standard roll shade fabrics) and the hem bar weight is neglected as
that is dependent upon fabric width. The maximum square footage can be conservatively
calculated by:
Motor Torque
4 N·m = 35.4 in·lb
6 N·m = 53.1 in·lb
8 N·m = 70.8 in·lb
Lifting Capacity
QMS
QIET
30.4 lb
25.4 lb
45.6 lb
38.2 lb
60.9 lb
50.9 lb
Max Square Footage
QMS
QIET
199 ft2
166 ft2
298 ft2
250 ft2
399 ft2
333 ft2
What impact does a max of 45 revolutions for PC motors have on the length of shade I can build?
x: number of turns (x = 45 for PC mechanical limit motors)
d: tube diameter
t: fabric thickness (t = .01325” for a very thin fabrics to produce a conservative figure)
l: shade length
or rewritten as:
When you solve for the shade length (l), the result will be conservative figures of:
Maximum Drop due to Mechanical Limit Limitation
QMS (d = 2.325”)
QIET (d = 2.78”)
35’ 9”
41’ 2”
JDM 032410
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