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Macurt

Center axis on helicopter rotor

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Hello!

 

Probably a noob question, so sorry about that.

I just bought a model of a chinook helicopter on turbosquid, and it's not rigged. Sadly, there's not even a parent relationship for the rotors and blades. So to make the rotors spin, I put the blades and central rotor in a null, and eyeballed it to try to center it and make proper rotation. And it's almost there, but there's a wobble that shouldn't be there when you look at reference videos of chinooks.

So my question is: is there a solid method of aligning/figuring out the exact center point for something like this? Or is it just trial and error?

 

Best/

Urt

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No, no, we shouldn't have to do this via trial and error. You just gotta find the part of model that is the centrepoint (should be the main prop shaft), move the axis of that to its points center (via Axis center settings), then child a new (empty) null to that and Reset PSR, before moving it back out again, then all the components of the blades under it. Then animate the null. Make sense ? 

 

CBR

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  • Makes total sense, but I'm afraid it's not that straight forward. See image, the rotors are at an angle. I imagine if they were totally perpendicular to ground plane the approach you gave is solid. But what about in cases like these?

     

    Chinook_angle.png

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    Oh that's a nicely made model....

     

    The rotors are at an angle, but so are the main shafts they are mounted to by the looks of it.

    That's OK, we just need to fix the alignment of our axis while we're centering it. Select an edge travelling along Y on the shaft in question, then set Alignment to 'selected edge' in the Axis Centre tool. Now it should be in the right place AND at the right angle.

     

    CBR

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    Here's a scene for spinning rotors up/down by addition - keyframe the slider.

     

    arrow.c4d

     

    if you do rotation by multiplication, changing the speed can have weird effects.

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  • Cerbera, thank you for your suggestions!

    And Jed, thanks for that nifty little scene file ;) 

     

    I tried the edge alignment method, but unfortunately the shaft, or any part of the model, did not have any edge that were perfectly perpendicular to the correct angle of rotation... so what I ended up doing was just tweaking the axis numerically by hand (see image) and it got a lot better.

     

     

    Axis_numerically.jpg

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    No I absolutely refuse to believe the only way was to eyeball it :)

    If we couldn't use a Y edge on the shaft to set null alignment, presumably we could have found another axis on another object that would have been right.

    Or we could have aligned a workplane to blades and the null to that.

     

    But anyway, glad you got it sorted...

     

    CBR

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    @Macurt reading your post today inspired me to dig up an old helicopter project and add some Python keyboard controls - the project isn't for rendering out as a movie, just for flying it around the viewport. I'm on Windows so can't guarantee the keys will work on a Mac. You might find it fun to play wirh.

     

    https://www.dropbox.com/s/x5jkkafoy9c9ldm/helicopter2019.zip?dl=1

     

     

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  • Cerbera - ha ha! I'm sure there's a better way! If we were to have a closer look at the rotors I'd have to make it perfect, but in this case I can get away with it.

     

    Jed - that's awesome! The shortcuts work just fine on Mac! Except F11 that I've mapped to a OS function. I love how one can turn the rotor off and still fly around :D  And the onboard camera is great, this whole script could be really useful for flying stuff.

     

     

     

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    @Macurt the script is just for flying my legocopter in the viewport (for fun). When I used to dabble in helicopters, I had a different system for movies - a convoluted XPresso method (using similar math) where the aircraft follows a target on a spline using the distance to target to control speed.

     

    Here's a Black Hawk flying round some free buildings from Pixel Lab

     

     

    and here in Greyscalegorilla city

     

     

    free Black Hawk https://free3d.com/3d-model/black-hawk-uh-60-12229.html

    free buildings https://www.thepixellab.net/freebies

     

     

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