Retrofitting a roller door motor: torque, shaft and manual override

Updated: 07.11.2026

In brief: Smaller roller doors on garages, carports or storage units can be motorised with a 45 mm tubular motor. What matters is the weight of the door, the shaft diameter and manual operation for power cuts. Tubular motors are not suitable for heavy industrial doors.

Rough torque estimate

Rule of thumb: door weight in kg × shaft radius in m × 10 gives the load torque in Nm – plus a 20–30 % reserve. Example: 60 kg door, 70 mm shaft (radius 0.035 m, a bit more with the curtain): 60 × 0.05 × 10 = 30 Nm, so 40 Nm with reserve.

Suitable A-OK motors

Both fit shafts from 54 to 80 mm, for example 60 mm octagonal.

Why manual operation matters

Ist das Rolltor der einzige Zugang, sitzt man bei Stromausfall fest. Der AM45E hat ein Schneckengetriebe mit Nothandkurbel (Untersetzung 15:1) – das Tor lässt sich dann von Hand öffnen.

Safety

• The mains connection is made by a qualified electrician (see Connecting a roller shutter motor).
• Set the end positions so that the curtain does not pull against the stop.
• Doors used by people are subject to additional safety requirements – get advice.

Frequently asked questions

Is 50 Nm enough for my garage door?

Often yes for light aluminium roller doors. For heavy steel doors or wide doors, do the calculation or ask us with dimensions and weight.

Can I open the door by radio?

Yes, with the radio version of the AM45E (433 MHz) or a radio receiver in front of the cable motor.

Calculate the torque yourself: Roller shutter motor calculator. 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.