Updated: 07.11.2026
In brief: The motor size depends on the shaft: a 35 mm motor fits 40 mm octagonal shafts, a 45 mm motor fits 60 mm octagonal shafts and larger. 35 mm motors have less torque and suit small, light roller shutters.
Comparison
| 35 mm | 45 mm | |
|---|---|---|
| Shaft | 40 mm octagonal | 60 mm octagonal and larger |
| Torque (A-OK) | 6 or 10 Nm | 6 to 50 Nm |
| Application | small roller shutters, roller blinds, screens | standard roller shutters, awnings, small roller doors |
| Example | A-OK AM35, ab 69 € | AM45 mechanical ab 65 €, AM45 radio from €100 |
How to find your size
- Open the inspection cover and measure the shaft (width across flats), see Octagonal shaft.
- Note the roller shutter size and material.
- Determine the torque with the Roller shutter motor calculator .
- Choose the motor and suitable adapters.
Frequently asked questions
Can I install a 45 mm motor in a 40 mm shaft?
No, it does not fit. Conversely, a 35 mm motor in a 60 mm shaft is only possible with suitable adapters and usually too weak.
How much space does the motor need in the box?
Next to the shaft end there must be room for the motor head and the bracket. The motor length is in the data sheet.
All guides on roller shutter, awning and external venetian blind motors: Sun protection guide.
Advice on the right motor
Send us the shaft diameter, curtain size and material – we will name the right A-OK motor. Phone 040 50694631 (Mon–Fri 8 am–5 pm) or via the Contact form. All motors at a glance: Sun protection motors.
Technically reviewed by Dietmar Heiken, Sales, Vent Systems HDI GmbH, Hamburg – around 20 years of industry experience. Questions? Phone +49 40 50694631 or info@ventsystems.de
Last updated: 07.11.2026
