Motor on a rim (surface-mounted) lock
A motor unit is fixed to the surface-mounted rim lock case or to its knob, driving the latch or the deadbolt. Common on UK nightlatches and on Asian surface-mounted deadlocks.
Applies to these lock types
Rim nightlatch (surface-mounted) · Australian deadlatch and deadlock · Padlock, hasp and staple
Measurements this architecture needs
- Lock case width × height × depth
- Interior thumb-turn / turn-piece size and profile
- Door thickness
Adapter interfaces to design
- Case geometry survey — rim cases vary far more than mortise cases
- Knob-to-case clearance so the motor does not foul the door stop
Design targets
Targets marked "from standard" come from the cited document. Targets marked "practice" are our engineering guidance and must be verified for your design.
| Target | Value | Basis |
|---|---|---|
| Output torque | ≥ 1.5 N·m for a spring-loaded deadlatch |
practice |
Known blockers
- Spring-loaded deadlatches need high torque and give poor battery life.
- Old rim cases are often out of square; the drive train needs radial tolerance.
- Surface-mounted electronics are easier to attack — consider the case as part of the security system.
Design checklist
- Survey at least 20 real cases before freezing the adapter geometry.
- Confirm the door still opens by hand with no power.