A Somfy motor does not touch the tube it drives. Between the two sits a small set of parts — a crown, a drive, and a bracket — and getting them wrong is the reason a correctly-sized motor still will not install. These parts are cheap, specific, and not interchangeable.
What each part does
- Crown (also called the adaptor ring) fits over the motor's non-drive end and centers the motor inside the tube. It does not transmit torque; it stops the motor from rattling around inside the tube.
- Drive (or drive wheel) locks onto the motor's output and engages the inside profile of the tube. This is the part that actually turns the shade.
- Bracket mounts the motor head to the wall, ceiling or shade cassette, and holds the motor against the torque it produces.
- Idler supports the opposite end of the tube. It is not a motor part, but a tube will not run true without one.
Crown and drive are always bought as a matched pair for a specific tube. Somfy sells them that way, and mixing sizes across sets does not work.
Selecting a crown and drive set
A crown and drive set is chosen by two things, in this order:
1. The motor family. LT50, LT60, LS40, Sonesse 30, Sonesse 40, Sonesse 50 and ST30 all have different output profiles. An LT50 set will not fit an LT60 motor. This is a hard compatibility boundary, not a tolerance.
2. The exact tube. Not the nominal size — the exact tube. You need three things about it:
- Profile — round or profiled (keyed / grooved). A 2 in round tube and a 2 in profiled tube take different drives, because the drive engages the internal shape.
- Outside diameter — 1.5 in, 2 in, 2.5 in and so on.
- Wall thickness — a thicker wall means a smaller bore for the same outside diameter, and the crown has to fit the bore.
If you are matching an existing tube and cannot identify it, measure the inside diameter and photograph the internal profile. Those two facts identify almost any tube in common use.
Brackets and head types
Somfy motors come with different head types, and the bracket has to match the head, not just the motor family:
- Star head — a splined head that keys into a star bracket. The most common configuration on LT50 motors.
- Round head — a smooth cylindrical head, used with a different bracket family entirely.
Beyond the head, the bracket also has to suit the mounting: face mount, ceiling mount, or into a cassette with a fixed projection. Exterior cassette awnings usually dictate the bracket, because the cassette manufacturer sets the mounting geometry.
Somfy's own LT50 Universal Motor Bracket and LT50 Star Head Motor Bracket cover most 500-series interior work.
Adaptor plates for third-party hardware
Plenty of installations put a Somfy motor into a shade system built by somebody else. Adaptor plates exist for exactly this: they mate a Somfy motor head to a bracket designed for another manufacturer's system.
Plates are stocked for Rollease (including Skyline and the R-series), ZMC, Acmeda and Louvolite brackets. If you are replacing a failed motor in an existing shade and keeping the brackets, an adaptor plate is usually what makes that possible without rebuilding the headrail.
A worked order
For a typical interior roller shade on 2 in profiled tube with a Sonesse 506S2 RTS motor, the complete parts list is:
- The motor — Sonesse 506S2 RTS (1001809)
- An LT50 crown sized for the tube
- An LT50 hard clip drive matching the tube profile
- An LT50 bracket matching the head type and the mount
- An idler for the far end
- A power cable — a fast connector pigtail or SJTW cable with the right plug
- A control — an RTS remote or wall switch
Every motor listing on this site carries a compatibility panel naming the specific crowns, drives, brackets, tubes, cables and controls that complete that motor. That panel is built from Somfy's own documentation, so it is the fastest way to assemble a correct order.
Browse all motor accessories, or start further back with How to Size a Somfy Shade Motor.
