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I'm new to Blender. I can't figure out why the propeller mount is not rotating straight. I have aligned the face of the propeller mount to top of the base and it looks okay, but once I start rotating the mount on the z-axis, it goes up & down while rotating. What's causing this and how to fix?

Before Rotating

Rotating

Harry McKenzie
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fadi
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  • Your object is not aligned with the global XYZ, maybe you should realign it, parent to an empty and tilt the empty instead of the object itself, then it will rotate on itself correctly, maybe see here: https://blender.stackexchange.com/questions/129834/how-do-i-rotate-an-object-along-its-own-axis-windmill – moonboots Oct 04 '23 at 05:24
  • @moonboots I'm working on local axis and I aligned the object to local axis. I tried what you suggested. I re-aligned to global, added empty parent, but no matter how I manipulate the rotation using the empty parent it would still rotate upward & downward. I have attached the fbx, if you could please take a look. – fadi Oct 04 '23 at 13:30

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3D softwares struggle to calculate the rotation of an object on one axis when it's already tilted on another axis, but you can parent it to an empty and tilt the empty instead.

So first thing reset the rotation with AltR and maybe also apply the scale (CtrlA) unless you have good reason not to:

enter image description here

Now create an empty, resize it in the Object Data panel so it's smaller than its default size, parent your SM2_prop_mount_1 object to this empty:

enter image description here

Rotate the empty (X = 177.194d / Y = 3.2894d / Z = 46.7609d if you want it to be tilted exactly as your object before the rotation reset). Now you can rotate the object SM2_prop_mount_1, it will correctly rotate as you only ask it to rotate on one axis:

enter image description here

moonboots
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  • I can't thank you enough for the help. I was spinning my wheels going nowhere. You saved me ton of time. One question, how did you manage to exactly get those numbers? (X = 177.194d / Y = 3.2894d / Z = 46.7609d). – fadi Oct 04 '23 at 14:28
  • This was the rotation settings of your SM2_prop_mount_1 object before I reset with Alt R – moonboots Oct 04 '23 at 14:31
  • Question, why is it if I slightly adjust the mount rotation, it goes out of whack again? Is it because the origin point is in the center of the mount while I'm adjusting? I have four of these mounts, is there an easy way to make them sit straight on the base? – fadi Oct 04 '23 at 18:14
  • What do you mean by adjust? Blender and all 3d softwares struggle to rotate an object on several axis, so if you begin to rotate it on more than one axis it messes up the rotation, that's why it's better to create the tilt with a parent object – moonboots Oct 04 '23 at 18:25
  • Yup, I keep forgetting about the empty parent. It's a new concept to me but I will keep it in mind. Are you from the USA. I want to transfer lunch money to you as an appreciation for your time and help if that's ok with you. – fadi Oct 04 '23 at 18:36
  • No it's ok, you're welcome ;) – moonboots Oct 04 '23 at 18:38
  • such a humble person. My offer stands in case you change your mind. :-) – fadi Oct 04 '23 at 18:40