Module 1 of 5
Torque is weight times radius
What torque is, why the load on a roller shade motor changes as it moves, and when the motor works hardest.
4 lessons, then a scenario check.
Shade Motors School · Pick the Motor · 201
How to Size a Somfy Roller Shade Motor by Torque
Match a Somfy motor to a roller shade by load and tube size. Learn why torque matters, how to read the torque in a Somfy model code, and where the Sonesse and LT50 ranges start and stop.
You will be able to: Pick a Somfy motor with the torque and tube fit a roller shade needs.
Inside this course
5 modules, one idea at a time
- Torque is weight times radiusWhat torque is, why the load on a roller shade motor changes as it moves, and when the motor works hardest.4 lessons · scenario check
- Read the torque in a Somfy model codeHow to read the torque straight from a Somfy model code, so you can shortlist motors from a part list or an old label.3 lessons · scenario check
- Tube size sets the floor before torque doesWhy the tube often decides the motor family before torque does, and what fits the motor to the tube.4 lessons · scenario check
- Where each Somfy range sitsWhere each Somfy range sits for torque, speed and tube size, using verified figures from Somfy Pro e-catalog pages.2 lessons · scenario check
- Pick with headroom, then confirm on the databookHow to pick a motor with room to spare, the final check before you order, and how to choose when two motors both fit.4 lessons · scenario check
- Final quiz10 real job scenarios, one per screen, each with a hint if you need it. Score 80% to pass and get your certificate.
Torque is weight times radius
A tubular motor turns the tube
The motor sits inside the roller tube and turns it. The shade hangs from that tube, and the turning force the motor needs is torque.
ExampleA tubular motor sits inside the roller tube. Everything the shade weighs hangs off that tube.
Torque is weight times radius
Torque is weight times radius
Torque is the hanging weight multiplied by the distance from the center of the tube to the outside of the roll.
ExampleTwo shades weigh the same, but one has thicker fabric that makes a fatter roll. The fatter roll needs more torque.
Torque is weight times radius
The load peaks with the shade fully up
Fully up, the fabric wraps in layers and the radius is at its largest. So is the load. Size the motor for that moment, with the full fabric and hem bar weight.
On the jobWhen you weigh a shade, include the hem bar. It hangs at the largest radius when the shade is fully up.
Torque is weight times radius
Somfy rates torque in Nm
Somfy rates motors in newton-meters (Nm). One Nm equals about 8.85 inch-pounds.
ExampleA 6 Nm motor is about 53 inch-pounds, since one Nm is about 8.85 inch-pounds.
Check yourself
When is the torque load on a roller shade motor at its highest?
Hint: Think about when the roll is fattest.
With the shade fully rolled up, because the roll radius is largest then.
Module 2 of 5
Read the torque in a Somfy model code
How to read the torque straight from a Somfy model code, so you can shortlist motors from a part list or an old label.
3 lessons, then a scenario check.
Read the torque in a Somfy model code
The model code carries the torque
In a code such as 506S2, the first digit names the motor size family and the next two give the torque. 506 means a 50-series motor at 6 Nm.
ExampleAn old motor label reads 510S2. The 5 is the size family and 10 is the torque: 10 Nm.
Read the torque in a Somfy model code
The pattern holds across the range
404S2 is a 40-series motor at 4 Nm. 550R2 is an LT50 at 50 Nm. 660R2 is an LT60 at 60 Nm.
On the jobUse the code on a failed motor's label to find its torque before you pick a replacement.
Read the torque in a Somfy model code
Shortlist with the code, then confirm
Use the code to shortlist. Then confirm torque, speed and tube fit on the part's Somfy spec sheet before you order.
Watch forThe code is a shortlist tool. Speed and tube fit still come from the spec sheet.
Check yourself
What torque does a 510S2 motor deliver?
Hint: Skip the first digit.
10 Nm. The two digits after the size digit give the torque.
Module 3 of 5
Tube size sets the floor before torque does
Why the tube often decides the motor family before torque does, and what fits the motor to the tube.
4 lessons, then a scenario check.
Tube size sets the floor before torque does
The motor lives inside the tube
A motor slides inside the roller tube, so every motor has a minimum tube inside diameter.
ExampleA narrow tube cannot take a large motor, whatever the load. Measure the inside diameter first.
Tube size sets the floor before torque does
Minimum tube sizes
A 1.1 Nm Sonesse 28 fits a tube as small as 1.05 in ID. An LT50 needs at least 1.85 in. An LT60 needs 2.37 in.
On the jobMeasure inside diameter, not outside. The motor sits inside.
Tube size sets the floor before torque does
Tube size often picks the family
A small, light shade on a 1.25 in tube points to the 28 or 30 range. A wide exterior screen on a 2.5 in tube can take an LT50.
ExampleA 1.5 in ID tube rules out LT50 motors, which need at least 1.85 in.
Tube size sets the floor before torque does
Crowns and drives fit the tube
The crown and drive set adapts the motor to the exact tube profile. The crowns and drives course covers it.
On the jobOrder the crown and drive with the motor. They are matched to both the motor family and the tube profile.
Check yourself
Your tube is 1.5 in ID. Can an LT50 motor go inside it?
Hint: LT50 needs a bigger tube than that.
No. LT50 motors need at least 1.85 in inside diameter.
Module 4 of 5
Where each Somfy range sits
Where each Somfy range sits for torque, speed and tube size, using verified figures from Somfy Pro e-catalog pages.
2 lessons, then a scenario check.
Where each Somfy range sits
Torque climbs as the tube grows
| Motor | Torque / speed | Min. tube ID |
|---|---|---|
| Sonesse 28 WireFree RTS (1003297) | 1.1 Nm / 20 rpm | 1.05 in |
| Sonesse 30 RTS 24V (1241142) | 2 Nm / 25 rpm | 1.13 in |
| Sonesse 40 RTS 404S2 (1240380) | 4 Nm / 36 rpm | 1.46 in |
| Sonesse 506S2 RTS (1001809) | 6 Nm / 32 rpm | 1.85 in |
| LT50 Altus RTS 550R2 (1038170) | 50 Nm / 14 rpm | 1.85 in |
| LT60 Altus RTS 660R2 (1162271) | 60 Nm / 14 rpm | 2.37 in |
On the jobRead across a row. Torque, speed and minimum tube size move together: a higher torque usually means a bigger tube.
Where each Somfy range sits
Speed falls as torque climbs
The LT50 and LT60 Altus motors both run 14 rpm. That suits heavy exterior screens and awnings more than fast interior shades.
ExampleA heavy exterior screen suits an LT50 at 14 rpm. A fast, light interior shade suits a smaller Sonesse.
Check yourself
Which motor in the table fits the smallest tube?
Hint: Look for the smallest number in the tube column.
The Sonesse 28 WireFree RTS Li-ion (1003297), at 1.05 in minimum tube ID.
Module 5 of 5
Pick with headroom, then confirm on the databook
How to pick a motor with room to spare, the final check before you order, and how to choose when two motors both fit.
4 lessons, then a scenario check.
Pick with headroom, then confirm on the databook
Never size at the edge
Fabric weights vary and hem bars get swapped for heavier ones. A motor working at its limit runs hotter and trips its thermal protection sooner.
ExampleA customer later swaps to a heavier hem bar. A motor sized at its limit now struggles.
Pick with headroom, then confirm on the databook
Pick the first motor with room to spare
Choose the first motor that clears the load with headroom, not the one that just meets it.
On the jobIf the load sits close to a motor's rating, step up to the next torque.
Pick with headroom, then confirm on the databook
The databook is the final check
Somfy's databooks chart the largest shade each motor can lift for a given fabric and tube. Every motor page on ShadeMotorsDirect links its databook or spec sheet under Official Somfy documentation.
On the jobOpen Official Somfy documentation on the motor's page and find the chart for that fabric and tube.
Pick with headroom, then confirm on the databook
Two motors fit? Decide on the rest
If both clear the load, choose by power (WireFree battery, 24V DC or 120V AC), control (RTS, Zigbee or wired) and noise.
ExampleTwo motors both lift the shade. No wiring at the window points to WireFree. A home on Zigbee points to a Zigbee motor.
Check yourself
Two motors both lift the shade. Which do you choose?
Hint: Torque is covered, so look at the other specs.
Decide on power source, control type and noise, since both clear the torque.
Final quiz
10 questions. Score 80% to pass.
Each question is a real job scenario, one per screen. Stuck? Tap the hint. You see the right answer and why right after you choose. Pass and you get a printable certificate, plus a 10% code for your first ShadeMotorsDirect order.
Question 1 of 10
On the job: You are explaining to a customer why a bigger shade needs a stronger motor.
What two things multiply to give the torque a roller shade needs?
Hint: Force times distance.
Torque is force times distance: the hanging weight times the roll radius.
Question 2 of 10
On the job: A motor struggles at one point in its travel and is fine at the others.
At which point is the motor working hardest?
Hint: When is the roll at its largest?
A full roll has the biggest radius, so the torque need peaks there.
Question 3 of 10
On the job: A spec sheet lists a motor at 6 Nm and your customer thinks in inch-pounds.
About how many inch-pounds is 6 Nm?
Hint: Multiply by about 8.85.
6 x 8.85 is about 53 in-lb.
Question 4 of 10
On the job: You find an old Somfy motor labeled 506S2.
A motor is coded 506S2. What torque is it?
Hint: Skip the first digit and read the next two.
After the size digit, the next two digits give torque: 06 means 6 Nm.
Question 5 of 10
On the job: A part list shows a 550R2 for a large exterior screen.
What does the 550R2 code tell you?
Hint: The first digit is the family, the next two are torque.
5 is the LT50 size family and 50 is the torque in Nm.
Question 6 of 10
On the job: You measure a roller tube at 1.5 in inside diameter.
Your roller tube is 1.5 in ID. Which family is out?
Hint: One family needs at least 1.85 in.
LT50 needs at least 1.85 in inside diameter.
Question 7 of 10
On the job: The motor is right, but it needs to grip a specific tube profile.
What adapts a motor to the exact tube profile?
Hint: It is a set of two adapters.
The crown and drive are the adapters between motor and tube.
Question 8 of 10
On the job: You are quoting a very large shade on a big tube and want the LT60.
Per the Somfy figures, what is the LT60 Altus RTS 660R2 minimum tube ID?
Hint: It is the largest figure in the tube column.
The 660R2 (1162271) needs at least 2.37 in.
Question 9 of 10
On the job: The load is just under a motor's rating and the customer wants to save money.
Why avoid sizing a motor right at its torque rating?
Hint: Think heat, and future changes to the shade.
Headroom covers heavier fabric or hem bars and keeps the motor cooler.
Question 10 of 10
On the job: You have a shortlist and you are ready to order.
What is the final check before ordering?
Hint: Somfy publishes charts for each series.
Somfy databooks publish the largest shade each motor lifts for a fabric and tube.
Almost done
Where should we send your certificate?
Your score shows on the next screen. The certificate goes to your inbox so you can download it again later.
Parts used in this course
Genuine Somfy parts, 5-year warranty
Parts used in this course
