SG12 Series Servo Gearbox (3.8:1 Ratio, 642° Rotation, 1330 oz-in, 0.61 sec/60°)

SKU: Build System: Actobotics

This 3.8:1 Ratio, SG12 Series Servo Gearbox is driven by the goBILDA 2000-0025-0002 servo which has been altered to read feedback from a potentiometer located on the final shaft of the Servo Gearbox so that the rotation is not limited or effected by the ratio chosen. The 3.8:1 ratio will result in the large aluminum gear rotating with 3.8 times the torque of the driving servo! If the SG12-38 doesn't suit your needs, be sure to check out the other Servo Gearbox options.

The 1/2" diameter stainless steel shaft of the Servo Gearbox is supported by a pair of 1/2" ball bearings and held in place with retaining rings above and below the bearings so that it can withstand loads from any direction. An arm, disk or linkage can be fastened to the threaded holes on the Actobotics 0.77" pattern. Alternately, the 0.14" thru-holes on the perimeter of the aluminum hub gear can be used to fasten standoffs, spacers or a linkage to, or, you can slide a 1" clamping hub around the spacer on top of the gearbox for quick adjustments to the item being fastened.

The Servo Gearbox is easily attached to Actobotics Channel, given it's overall width of 1.32" (to match the internal width of U-Channel). For those of you installing in an R/C vehicle, the 585506 bracket is a popular choice as it creates ears to mount the servo gearbox down to a flat surface.

While this model does have feedback, you can actually toggle back and forth between continuous (open loop) and feedback (closed loop), using the goBILDA servo programmer.

How Far Will This Servo Gearbox Rotate?

The answer to this question is partially dependant on what you are using to control the servo that drives the gearbox. Click for a quick video explanation.

With an Average Radio System:
Your average transmitter and receiver will output a relativly narrow PWM signal range.

Radio System + Travel Tuner:
Adding a Servo Travel Tuner to your radio system setup will allow you to achieve wide PWM signal ranges.

Wide Signal Controllers:
Controllers such as the Actobotics® Servo Controller, Arduinos, and Raspberry Pi servo hats can usually send a wide signal.

Tech Tips

Gear Ratios

While we offer a variety of pre-made ratios, if you already own one of our Servo Gearboxes and want to change the ratio, here are the gears you will need to obtain the ratio you desire.

Ratio Servo Gear Hub-Mount Gear
2:1 32T (615310) 64T (615194)
3:1 24T (615306) 72T (615198)
3.8:1 20T (615302) 76T (615202)
5:1 16T (615298) 80T (615206)
7:1 12T (615294) 84T (615210)



Weight 6.9 oz (195g)
Gear Ratio 3.8:1
Voltage Range 4.8V - 7.4V
No-Load Speed (4.8V) 0.95 sec/60°
No-Load Speed (6.0V) 0.76 sec/60°
No-Load Speed (7.4V) 0.61 sec/60°
Stall Torque (4.8V) 912 oz-in (65.7 )
Stall Torque (6.0V) 1140 oz-in (82.1
Stall Torque (7.4V) 1330 oz-in (95.8
No-Load Current (4.8V) 150mA
No-Load Current (6.0V) 160mA
No-Load Current (7.4V) 200mA
Stall Current (4.8V) 2,000mA
Stall Current (6.0V) 2,500mA
Stall Current (7.4V) 3,000mA
Max PWM Range 500-2500μsec
Travel per μsec 0.321°/μsec
Max Rotation 642°
Pulse Amplitude 3-5V
Deadband Width 4μsec

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