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What am I trying to do?

I tried make a small motor (2cm) because I need simulate (physics, not only animation) this, but I can't its rotation correctly.

enter image description here

See in the image, I have a "Motor Body" (motor case, passive object), the "Axis" (rotor, active object), the "Brush" (passive object).

I connect in the empty object "Motor" with a rigidbody constraint the "Axis" object with the "Brush" object, respectively, of course with the "motor" constraint.

What I try do is rotate the "Axis" like a motor, of a mode that I can move it, rotate it, and it continue the rotation independently what position it be like an any object in the real world.

What am I getting?

The "Axis" move crazy outside of the "Motor Body" and sometimes back to "Motor Body", I don't know explain the movement, but it's far that the correct movement of a motor.

How to change the direction of motor rotation?

Up 1

Today I had a time to see that again, and I can rotate the motor now, but only if the "Axis" object is with transform location locked.

What was the problem? I set the parent of the object by the tools and not with CTRL-P, I don't know why it happened, however when a set the parent with CTRL-P I see the physics correctly. So, I withdrew the parentage of the objects, and I received the object with a different dimensions.

See the "Axis" object with parentage:

enter image description here

And see the "Axis" object without parentage:

enter image description here

It was the motive of the previous crazy rotation, so I used CTRL-P and setted the parentage again, and it's working, see:

enter image description here

But it only works when I lock the transform location of the "Axis" object, if I withdrew this see what happen:

enter image description here

The file updated:

The problem is that with the "Axis" object transform location locked I can't move the motor in the simulation, because the "Axis" object is locked, so I can only move the rest of the objects except the "Axis" object, what is expected, of course.

So, the question, How to I deal with this case? I thought fatten the inside of the "Axis" object, to it doens't fall, but It doesn't work, see:

enter image description here

Up 2

Now I can get the motor rotation and move this in simulation, I changed the "Motor Body" to active object. I also changed the "Brush" to use "animated" option in passive rigidbody, because without this the object doesn't fall in the floor. But now I have one small failure in the physics here:

enter image description here

What I'm doing wrong?

Up 3

I finally made it! The problem is that I couldn't parent the "Axis" object with the "Motor Body" object, because It's bug the physics simulation. I read here when you can set parent in the objects and continue with the physics working fine:

  • Either you have exactly one physics object (all others are ghost with no weight).
  • or You parent several rigid bodies with compound settings.
  • or You connect several rigid bodies with rigid body joints.

https://blenderartists.org/t/how-to-parent-object-to-another-one-which-has-rigid-body-physics-type/615570/4

So, I remove the parent of the "Axis" object, and the physics works now. See:

enter image description here

PerduGames
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  • Is the object origin off center? Or are you doing a physics simulation of a motor? – Nascent Space Jul 20 '20 at 04:23
  • @NascentSpace Sorry I can't understand what you wnat know, what object? I'm trying simulate a motor rotation with physics. – PerduGames Jul 20 '20 at 12:37
  • I can't load 2.8xx files and not sure if this is what you're wanting to achieve, but it might be worth a look. No physics are involved, just parenting and animation. See the 1st answer...

    Link: - https://blender.stackexchange.com/questions/137781/how-to-animate-a-propeller-on-the-axis-of-rotation/137897#137897 -...

     – Edgel3D Jul 23 '20 at 04:24
  • @Edgel3D Thanks, but with animation I know, I need simulate the physics of this, because is a project to simulation of mechanics parts, not only animation. – PerduGames Jul 23 '20 at 12:06
  • Is this the sort of thing you're after then? Same model as the link but with rigid body physics and the ground passive. The spinning motor casing (cube) can also be animated anywhere or at any angle, even whilst it's being dropped.

    Link - https://www.dropbox.com/s/tug4bsx8e9ern0b/Prop2.gif?dl=0

     – Edgel3D Jul 24 '20 at 11:49
  • @Edgel3D Yes, that's it if it isn't just animation, but the physics with active rigidbody, is the rotation of the axis with animation or physics? I need that be with physics, so the objects: "Axis", "Motor body", "Brush", need be rigid body objects. And the "Axis" is inside the "Motor body" like the .blend file of the question. Like a motor. – PerduGames Jul 24 '20 at 12:33
  • Hi again @PerduGames - The propeller rotation is keyframed as is the cube's rotation and ascent. It's then dropped using physics with the prop animation still running. That was the point of posting this, the 2nd link. Demonstrate that similtaneous physics and animation can co-exist without conflict when done a certain way. Placing an active object inside a passive one is not the way I would do things BTW. You could try inverting the casing's normals so they're all pointing inwards. That might fix it. Tell me - if not keyframed, how are you rotating the motor's shaft? – Edgel3D Jul 25 '20 at 01:59
  • Continued... Forget the last question. I can see you're using a motor constraint and mixing that with physics. It's a cocktail I'm inclined to avoid, lol. If it can be done without conflict I'm sure there are people in here who know how. Best of luck with your project... :) – Edgel3D Jul 25 '20 at 02:12
  • @Edgel3D yes, I'm using a motor rigid body constraint to simulate a motor, I have the rotate works now and at the same time can move this, but a new problem appeared: the object doesn't touch the passive objetct "Plane" more, as if the object had a margin, but it doesn't have any margin. – PerduGames Jul 25 '20 at 17:17
  • @Edgel3D I updated my question, see. – PerduGames Jul 25 '20 at 19:45
  • Hi again, I tried doing things your way this morning but nothing wanted to work all the way. Among other things, if the shaft didn't fall from the case, it couldn't be moved either, lol. I imagine you have a need to emulate this using physics thru & thru, no compromise? – Edgel3D Jul 26 '20 at 07:34
  • @Edgel3D Whats physics thru & thru? I don't understand. – PerduGames Jul 26 '20 at 14:44
  • @Edgel3D See the up3 of the question, it's working now. Of course, my motor is horrible, but I can work in this model now that physics is working to get something better. – PerduGames Jul 26 '20 at 17:36
  • Well, at least you're getting there! That's more than I did. :) Physics thru & thru? Using all physics, no animation. – Edgel3D Jul 27 '20 at 07:58
  • @Edgel3D so, it's physics thru & thru, I'm trying automate somethings to see the simulation test results before the real test. Because in the simulation I have infinite material, and in the real world not. But I haven't seen 3D physics in a while since I played with Unity3D three years ago. – PerduGames Jul 27 '20 at 13:15
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    A game engine usually has better or at least easier physics than Blender, which is after all, a modeller/animator. It's why I follow one contributor's philosophy - if you can't make it - fake it! lol. I thought that rather good. Best of luck with what you're doing... – Edgel3D Jul 28 '20 at 04:18

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