3 ms·

I'm actually more enamored with the cool look of the thing rather than the fact that it can balance.

• ayhanfuat 3y ago
  Same. Immediately checked if it is for sale (apparently it costs $2500 if you do it yourself).
  • pavel_lishin 3y ago
    I wonder what the cheapest possible build for something like this is, if you loosen enough constraints - let's say, if we allow it to be externally powered, and agree that size doesn't matter. Would it be cheaper (and/or safer) to build a larger one, allowing for larger-but-slower flywheels? Could you make one out of a couple of scrap bicycles?
  • JKCalhoun 3y ago
    Would be fun to try and low-cost it. I can already imagine replacing the aluminum face parts with laser-cut acrylic. It also sounds like the motors are another expensive part that likely can be low-costed. The stainless steel flywheels though..... No ideas.
    • newaccount74 3y ago
      If you can make the flywheels flat, you could cut them with a waterjet, which would be cheaper and faster than milling. And I assume that you can use normal steel instead of stainless steel.
    • pavel_lishin 3y ago
      I wonder if it would be possible to balance this thing by sloshing fluid around, or with linear actuators moving weights around. Or maybe a pair of motors, moving two circles with weights on their rims around, to shift the center of gravity around until it's stable enough to park them on opposite sides?
      • duskwuff 3y ago
        > I wonder if it would be possible to balance this thing by sloshing fluid around, or with linear actuators moving weights around. No. The reaction wheels are generating torque to change the orientation of the cube, not just shifting its center of gravity.
        • s0rce 3y ago
          Not really sloshing but you can pump fluid in tubes to mimic a reaction wheel https://ntrs.nasa.gov/citations/19910016066 https://ntrs.nasa.gov/citations/19910016066 Can also probably provide some thermal advantages as well. Oh neat, you can use a direct current electromagnetic pump to implement this with liquid metal as the fluid 10.1016/j.actaastro.2013.11.030
          • duskwuff 3y ago
            > Not really sloshing but you can pump fluid in tubes to mimic a reaction wheel https://ntrs.nasa.gov/citations/19910016066 https://ntrs.nasa.gov/citations/19910016066 I think that's a little different -- it's pumping liquid around to change attitude (i.e. to point the satellite in a different direction), not to affect its rotational velocity. To get a sustained rotation, you'd have to keep pumping the liquid around continuously, which isn't terribly practical. Neat idea, though! I wonder if it's being used anywhere, or if reaction wheels won out.
            • jdiez17 3y ago
              That’s exactly the same principle as reaction wheels. Indeed they have to keep spinning to maintain a certain angular rate.
        • pavel_lishin 3y ago
          Right, that's how this cube - and how satellites - work. But would other approaches be feasible for a desk toy or an art object?
    • johndough 3y ago
      What are cheap alternatives for motors/drivers? I imagine there are cheap brushless RC motors which might work, but not sure about the electronic speed controller.
      • YZF 3y ago
        I suspect motors and drivers used for drones/quadcopters will work in this application as well. Those should be pretty cheap. You can do all the controls in software, you just need the right (I guess sensorless) driver.
    • YZF 3y ago
      Just brainstorming here but I don't think they need to be particularly precise or strong. You can likely use many materials as long as you can get enough weight (lead weights?) on the circumference. E.g. 3d print the flywheel structure (can be made thicker for rigidity if that's an issue) and glue some lead weights on. Looks like you can have slightly larger wheels too.
      • dutchkiwifruit 3y ago
        I spent quite some time (almost) perfectly aligning my reaction wheels. Vibrations at multiple thousands of RPMs are no joke. Then again, such speeds are typically unnecessary once the cube has settled into its equilibrium position. ReM-RC on YouTube has built a similar cube which uses 3D-printed wheels with steel bolts in the circumference [1]. My wheels are oversized when you just consider the balancing application, but I want to add jump-up functionality later, and the wheels need significant inertia (and also need to run at significant speeds) to accomplish that. [1] https://youtu.be/AJQZFHJzwt4 https://youtu.be/AJQZFHJzwt4
        • YZF 3y ago
          Cool. The 3d printed wheels presumably would have some dampening properties vs. the steel ones. You can also attempt to balance them at speed (moving/adding/removing the weights) to try and minimize vibrations like you do with motorcycle or car wheels (I guess there's multiple modes though). Fun project!