Is This 3D Printed Third Arm Useful? Maybe?

Humans have two arms, and we do pretty good things with them. More is surely better, though, right? With that in mind, [Emily The Engineer] set out to make a third arm for popular YouTuber [This Old Tony], and our primary question is this: is it actually useful?

The basic design is based around a strapped-on arm brace, which mounts the additional appendage to the wearer’s forearm. It uses a motor-driven geared mechanism to open and close a gripper, but the first revision was incredibly slow to open and close, to the point of being almost useless. Changing out the threaded rod that drives the mechanism massively sped up the gripper, much to [Emily]’s satisfaction. Strength and mounting upgrades got it to the point where it could actually be used to lift objects like spray cans and bricks. Ultimately, though, the arm mount and controls do kind of prevent the user from using their left hand when they have the third hand fitted.

It’s a fun project, if not exactly a useful one, even if [Emily] does use it to carry extra grocery bags . It does have us wondering if some kind of shoulder or backpack-mounted arms could be useful, though. It’s certainly not up to the standards of modern prosthetic, but we do love the idea of human augmentation with additional robot limbs. Here’s hoping technology advances further to make builds like this more capable in future!

11 thoughts on “Is This 3D Printed Third Arm Useful? Maybe?

    1. I was going to post exactly this! I attended an International School in Japan for a short time in the mid-late 70s where Stelarc was in residence, and felt privileged to have him as the most amazing art teacher.
      He was working on the prototype of his third arm at that time and I recall he mentioned it being able to hang on to the ceiling railing loops on a crowded train, whilst he read a newspaper with his other hands.

  1. A semi-independent prosthetic arm could be incredibly useful, as whatever it does on it’s own reduces the need for input and control from the wearer, especially if handicapped. Put a camera and microphone on it so it can observe the wearer using the other arm/hand along with voice commands to ‘train’ the arm. Pick up a cup by just moving your body/arm close the cup; the reach, fine control and grasping would be done independently by the arm. Same with moving the cup to your mouth for drinking. Same as with a real arm, the hand would be held steady automatically while body position moves slightly. Many impossible actions for a prosthetic wearer become possible with this approach. Robot training software can already use vision for learning motion.

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