Roller Blind Crown & Drive Adaptors Explained

A tubular motor can be the correct diameter and still be wrong for your roller blind. The missing piece is often the crown and drive. These two adaptors are what physically connect the motor to the inside of the roller tube, so they have to match both the motor and the tube profile.

What is the crown on a roller blind motor?

The crown sits around the motor body near the motor head. It supports and centres the motor inside the tube and follows the tube as it rotates. In systems that use electronic or mechanical limit sensing through the crown, correct engagement is also important for reliable position control.

What is the drive adaptor?

The drive fits on the output end of the motor. Its job is to lock into the roller tube's internal ribs, splines or keyways and transfer motor torque into the tube. When the motor turns, the drive turns the tube and the blind rolls up or down.

Why the internal tube profile matters

S45, S40 T-Spline, 38mm Standard, S60, HD50, S35 and L45 all have different internal geometry. That is why a generic statement such as 'fits a 45mm tube' is not enough. L45 and S45 can be close in outside diameter while requiring different crown and drive parts.

What happens if the drive is wrong?

• The motor may spin without properly turning the tube.

• The adaptor may slip under load.

• The motor may sit off-centre or bind inside the roller.

• Limits and stopping positions can become inconsistent.

• You can damage adaptors by forcing parts that were never designed to fit together.

Does every motor use the same crown and drive?

No. The adaptor set is selected around a specific motor family and tube profile. Even within the same brand, different motor diameters may use different adaptor systems. The safe sequence is always tube first, confirmed motor second, correct crown and drive third.

How do you know which adaptors you need?

Start with the MMB tube identifier. Select the tube that matches your internal profile and then use the compatibility page for that tube. This removes the need to guess from motor diameter or tube size.

If you are doing the installation yourself, our step-by-step retrofit guide shows where the crown and drive fit in the overall conversion process.