Gear Motor
Multiplies motor torque (and divides motor speed) by a fixed ratio between 5:1 and 10 000:1, delivering the controlled, deliberate rotation that conveyors, robot joints, peristaltic pumps, and door actuators require.
A DC brushed, brushless, or AC induction motor is bolted to a metal gearbox housing. Inside, multi-stage spur, planetary, helical, or worm gears step down speed and step up torque proportionally. Planetary gearboxes (sun + planets + ring) give high efficiency and concentric output; worm drives give very high reduction in one stage and self-locking behaviour. Output bearings handle the radial and axial load, isolating the motor shaft from external forces.
In plain terms
Like a bicycle's lowest gear bolted directly to the pedals — the rider spins fast and easy, but the rear wheel turns slowly and pushes hard against a steep hill.
Why designers use it
- Most loads need torque, not speed — a 3 000 rpm motor at 10 mNm becomes a 30 rpm output at 1 Nm through a 100:1 gearbox, the right shape for a conveyor.
- Gearing cuts motor current at a given output torque, so a small motor can drive a heavy load without overheating.
- Worm gearboxes self-lock when unpowered, holding a load (door, valve, lift) in place without continuous current.
- A sealed gearbox with proper lubrication runs 10 000+ hours unattended in industrial environments where bare motors plus belts would fail in months.
Best for
- Conveyors
- Robot joints
- Actuators
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- High-bandwidth servo positioning under 100 ms — gearbox backlash and elasticity dominate the loop dynamics, use a direct-drive torque motor.
- Quiet office equipment — even precision planetary gearboxes radiate 50 dB at speed, picked up easily in still rooms.
Common mistakes
- Sizing for stall torque without checking the gearbox's catalogue acceleration torque rating — peak torque is what destroys gears, not continuous.
- Ignoring the radial-load curve at the output shaft — sprocket pulleys hung off a long lever arm exceed the bearing limit and grind the output gear in months.
Where you will find it
- A Universal Robots UR5e cobot's elbow joint uses a Maxon EC-i 52 brushless motor coupled to a Harmonic Drive CSG-25 component-set strain-wave gearbox at 100:1: the strain-wave geometry gives near-zero backlash, letting the controller hit ±0.03 mm tool-tip repeatability across the 850 mm reach.
- A Liftmaster 8500W jackshaft garage door opener uses a 24 V DC brushed gear-motor with a roughly 200:1 worm gearbox: the worm's self-locking characteristic holds the door's weight on the spring even when power fails, and the gearbox drops the motor's 2 000 rpm to a 10 rpm shaft pulling the cable drum.
- A Watson-Marlow 530S peristaltic pump for laboratory dosing pairs a brushless DC motor with a sealed planetary gearbox at roughly 30:1: the gearbox's smooth 8 rpm output drives the rotor head's three rollers compressing the silicone tube, and the tight backlash gives ±0.5 % volumetric repeatability dose to dose.
A short history
A gear motor pairs an electric motor with a gearbox whose meshing gears reduce the motor's output speed while increasing torque, letting it supply higher force at lower speed. This trade-off makes gear motors useful in conveyor systems, where they move loads at controlled, steady speeds. Various gear arrangements, such as spur, helical or worm, suit different needs.