Advice needed on compact, robust motor + driver for cable winch (currently using 2 MG996R servos)

Let's Make Robots Beginners
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Hi all,

I’m building a small system to reel in and release about 25 cm of cable using a 10 mm diameter drum. The cable may experience up to 20 kg of pulling force, so I need something strong, reliable, and compact.

I’m currently using two MG996R continuous rotation servos with an Arduino to share the load (each rated at ~10 kg·cm torque), but I’m having a hard time keeping them synchronized. Even after a lot of tuning, they drift apart and make precise control nearly impossible.

I’m now looking to replace them with a single motor setup that meets the following:

  • Continuous rotation in both directions
  • Stall torque ≥ 20 kg·cm** (to handle 20 kg pull on a 10 mm drum, with margin)
  • Minimum speed of 60 RPM at the output shaft
  • Built-in encoder (or equivalent feedback) for tracking exact rotation
  • Runs on 6 V (battery-powered)
  • Motor driver that handles at least 5 A peak current
  • Compact and robust—this will eventually be used in an outdoor, real-world environment

I’d really appreciate any advice on:

  1. A suitable motor that meets these requirements
  2. A compatible motor driver
  3. Any tips for power supply and general setup

Thanks in advance—just want to make sure I head in the right direction before buying more parts!

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Hi @CaseyD and welcome to our forum!

I am not sure how many options for 6V DC motor you would have, for such high torque. I’ve had a look what RobotShop sells, and there are a lot of 6VDC geared motors with encoders, but the torque is several times lower than what you need.

Are you able to bring up the voltage to 12VDC? In that case, I think RobotShop could offer some good high torque motors.

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Hi Igor - thanks for your help - do you think this one would work?

Waveshare 30KG Serial Bus Servo, High Precision, Torque w/ 360 deg Encoder

WaveshareSKU: RB-Wav-571
Manufacturer #: ST3215 Servo

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Hi @CaseyD ,

It looks promising, but you would need to switch it to continuously rotating motor mode.

Also, have in mind that you would need to control it using serial commands since it is not a standard R/C servo.