391:1 Metal Gearmotor 20Dx46L mm 12V CB with Extended Motor Shaft

391:1 Metal Gearmotor 20Dx46L mm 12V CB with Extended Motor Shaft


These small brushed DC gearmotors can deliver a lot of power for their size. This version has a 12V brushed DC motor with long-life carbon brushes combined with a 390.6:1 metal spur gearbox. The gearmotor is cylindrical with a diameter of 20 mm, and the D-shaped output shaft is 4 mm in diameter and extends 18 mm from the face plate of the gearbox. This version also has a 6 × 2 mm extended motor shaft.

In Stock

These cylindrical brushed DC gearmotors are available in a wide range of gear ratios, from 25:1 up to 488:1, and with three different motors: 6 V and 12 V motors with long-life carbon brushes (CB), and a 6 V motor with shorter-life precious metal brushes. All three motors offer similar performances at their respective nominal voltages, just with the 12 V motor drawing approximately half the current of the 6 V motor and with the carbon brush versions having longer lifetimes than the one with precious metal brushes.

The CB versions can be differentiated from versions with percious metal brushes (shown on the left) by their copper-colored terminals.

These gearmotors are optionally available with an additional 2 mm-diameter output shaft that protrudes 6 mm from the rear of the motor (see the middle picture below). This rear shaft rotates at the same speed as the input to the gearbox and offers a way to add an encoder, such as our magnetic encoder for 20D mm metal gearmotors, to provide motor speed or position feedback.

The gearmotors all have 20 mm diameter gearboxes and 4 mm diameter gearbox output shafts, so it is generally easy to swap one version for another if your design requirements change (though the length of the gearbox tends to increase with the gear ratio).


Size: 20D × 47.7L mm
Weight: 47 g
Shaft diameter: 4 mm

General specifications:

Gear ratio: 390.625:1
No-load speed @ 12V: 36 rpm
No-load current @ 12V: 0.08 A
Stall current @ 12V: 1.6 A
Stall torque @ 12V: 21 kg·cm
Max output power @ 12V: 1.7 W
No-load speed @ 6V: 18 rpm
Stall current @ 6V: 0.8 A
Stall torque @ 6V: 11 kg·cm
Extended motor shaft?: Y
Long-life carbon brushes?: Y
Motor type: 1.6A stall @ 12V CB (carbon brush)

Performance at maximum efficiency:

Max efficiency @ 12V: 29 %
Speed at max efficiency: 30 rpm
Torque at max efficiency: 3.5 kg·cm
Current at max efficiency: 0.31 A
Output power at max efficiency: 1.1 W

Specific References

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