What is a Nm?
A single Newton meter (1 Nm), is exactly 8.8 inch pounds (4 kg), leveraged to a 1 inch swing.
This is the torque developed by the motor (at exactly 1" leveraged), away from the centerline of the motor's axis point (also known as the swing radius, of the motor).
The 4 kg (8.8 pounds), is a factor that is relatively easy to compare, given both US, and Metric units of measurements. Thus it is the basis of measurement standard, for calculating torque. Actual lift however, is calculated given the point of lift, as compared to the 1" leverage standard.
Example 1: If 52.8 inch pounds is realized (6 Nm), but the swing (radius) is 2" (half of a 4" tube), then maximum lift is limited to 26.4 pounds. That principal also works in reverse, if the tube is less than 2" in diameter, then the swing radius, is less than 1"........
Rarely, does the radius of a motors tubular axle, equate to exactly 1", excluding the circumstance of a small window shade's motor tube (which in fact, can be even smaller). Some window shade tubes are 1.5" in diameter, which can increase the lift capacity, of the tubular motor (by 1/3), given the fact that the lifting point of the tube, is less than a 1" radius.
Example 2: A 1.5" diameter tube, gives a .75" radius. The excess of the inch pound, as compared to .75", is 1/3 greater, than the .75" swing radius, so actual lift can be 11.704 pounds per Nm.
Thus, a 6 Nm motor (52.8 inch pounds), leveraged at 0.75", should lift 70.224 pounds.
The above however, is an unusual situation, as it is not effected by a swing greater than 1". Or, does the shade travel in a given set of tracks, that provide drag (also known as systems loss).
In most circumstances however, the lifting points of a motors tubular axle, is greater than a 1" radius, greatly reducing actual lift capacity of a motor, as compared to its 1" theoretical lift (also known, as " Available Torque").
This multiplication factor (or possible division factor), stands true, no matter if you are speaking of a few Nm, or hundreds of Nm, but adding systems loss to the formula, also is a must.
Many factors play into systems loss, inclusive of friction, and drag, as well as increased leverage, over a fixed fulcrum. In the case of rolling storm shutters, the top of a roll shutter track, is a fixed fulcrum...
The shutter does not rise or fall straight off of the girth of the bundle (excluding perhaps, at the greatest girth of it), but it usually is pulled away from the axle, where it turns downwardly, to be guided into a vertical track. To do this, it has to travel over a fulcrum, located at or very near, the point of entry to the tracks.
Note the fulcrum can be a bend in the open end of the tracks, or even a roller.
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Calculating Nm.........
10 Nm is exactly 88 inch pounds, and 50 Nm is 440 inch pounds, 100 Nm is 880 ip, etc., etc.
Usually the Nm of a motor is not written on the motors label, but the inch pounds are given. A motor that is reated for 352 inch pounds, is exactly 40 Nm (divide 352, by 8.8 = 40)
By the same token however, most motor brands list the motors model number, by both the barrel size, and by torque. As an example a Somfy 504, is a 45mm barrel motor, that is 04 Nm (Somfy always uses the "type 5" to indicate a 45 mm barrel, and a "type 6" to indicate the larger 59 mm motor barrels). Thus a Somfy 680, is an 80 Nm motor, in the type 6 motor barrel (59 mm in diameter)
Confused? You should be.......
The Elero brand uses a "type 9" to indicate the 45 mm motor barrel, and a "type 11" for the larger 59 mm motor barrel. Thus a type 940 Elero motor, is a 40 Nm motor, with the 45 mm motor barrel. The 1180 Elero, is the larger 59 mm motor barrel, with a 80 Nm motor.
These model types are confusing, for a reason......... Because they do not want you to understand it!
In our case, we try to simplify things. We list a model 4506, to indicate a 45 mm motor barrel size, and 06 for the 6 Nm motor strength.
A larger model 4540 would be the same size barrel diameter, but a 40 Nm motor (capable of a 200 pound lift, in a 60 mm axle).
Our 59100 motor, has the 59 mm motor barrel, and a 100 Nm (880 inch pound) torque.
We could call it a 6-100, or a 60-100, but that would further confuse you!
The motor's barrel, is 59 mm, and the torque is 100 Nm, so, it is a model 59100 motor!
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Given the situation were the leverage factor is many times the 1" multiplier/divider factor, and systems loss plays a factor, the expected 440 pound lift of the 50 Nm motor is cut nearly in half, as we calculate actual lift capacity.
As long as the swing of the tubular motor is 1" (radius), and no greater, the lift capacity of that motor should equal it's available torque. If the swing is greater, lift is greatly diminished (especially after calculating systems loss. for drag).
In larger motors yet, even a greater systems loss is usually experianced.
Why?
Well first off, you wouldn't have needed the larger motor, unless the load was dramaticly increased, or the height of the roll didn't cause an even greater girth of the rolled load. (increasing the weight to be lifted, at an even wider point of leverage, in relationship to the swing from motor's centerline of axis).
Thus in most cases a 100 Nm motor, will provide around 330 actual lift pounds.
Note the above are examples, and every given circumstance, is different.