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I am trying to design a kinetic art sculpture. I want to rotate two independent planes at the same center point and control both their speed and direction independently. So I've found that having two separate motors and controlling them using an Arduino is one solution for it.

But I am unsure how to set up the second rotating plane above the first one and have it rotate at the same point using the second motor.

For reference, here is something similar to what I am trying to design.

kinetic art

In the below image, the first plane is directly attached to the motor. How and where can I attach the second motor's shaft to the second plane ? I am also open to suggestions which can further simplify this design as using two different motors feels cumbersome.

setup

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    $\begingroup$ Many ways to tackle this from concentric shafts and hollow shaft motors and planetary gearboxes and one motor to just attaching a rotor to a bearing on the same shaft. For having your blades together, it makes most sense to place the motor for the leftmost rotor at the rightmost position. $\endgroup$
    – Abel
    Nov 27, 2023 at 16:49
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    $\begingroup$ As explained a shaft within a hollow shaft. $\endgroup$
    – Solar Mike
    Nov 27, 2023 at 17:00
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    $\begingroup$ This is the same basic problem solved by every analog clock (of hour-hand + minute-hand variety). In your case you may be able to use just one motor with reverse gearing. $\endgroup$
    – Transistor
    Nov 27, 2023 at 18:59

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This is the same as what is required for coaxial propellers and rotors. They generally required a hollow shaft somewhere so another shaft can run through it, and a way to drive both shafts. That generally involves motors that also have hollow shafts or gearboxes that have hollow shafts as well. A rather custom solution and a rarity. You mostly out of luck without a machine shop, but you can also get outrunner motors that are already shaft in shaft for coaxial propellers. They are much rarer but they do exist to be bought off the shelf. However, being as they are they need to match your torque requirements since you can't add any gearboxes to them without defeating their purpose (any gearbox that could support coaxial rotors to begin with doesn't need coaxial motors and could just be made to use two normal motors).

A less elegant alternative is to place a second motor in between the discs to drive the farthest disc and route power and control to it through a slip ring.

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It seems to me that you need a two shaft solution, if you imagine one shaft is longer than the other and one goes through the other. Then imagine they are both supported by a structure with bearings. Then you can power both separately with motors, and probably a gear coupling.enter image description here

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  • $\begingroup$ Only one can be inside - the other must be outside. $\endgroup$
    – Solar Mike
    Nov 27, 2023 at 17:09
  • $\begingroup$ Sorry, what do you mean? $\endgroup$ Nov 27, 2023 at 17:36
  • $\begingroup$ He means that "... they are inside one another" would be better expressed as "... one inside the other". They can't literally be inside one another. It reminds me of a local old-boy who was given a pair of kittens. He left them in a box in front of the stove overnight and when he came out they were both gone. The conclusion he came to was that, "They must have ate each other!" $\endgroup$
    – Transistor
    Nov 27, 2023 at 18:57
  • $\begingroup$ Thanks for the anecdote and correction. $\endgroup$ Nov 28, 2023 at 7:56
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    $\begingroup$ The kittens were later found, each with its tail inside the other's mouth, looking like an embodiment of the yin yang symbol. Kidding, but as long as "inside" only has a partial encapsulation requirement, then things certainly can "literally be inside one another" $\endgroup$
    – Abel
    Dec 14, 2023 at 11:24

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