i am a beginner and am working on a fan animation for a small project but it keeps turning from anticlockwse to clockwise and then back to anticlockwise. i have set the fan to rotate on the z axis from 0 to 72000 degrees and interpolation mode is quartic and easing mode is set to ease out. this happens from frame 54 and can be seen if you look at each keyframe carefully. it would be a great help to know why this is happening and would love to know how to resolve it. Thank you
I downloaded your .blend and opened it up. When scrubbing through the animation, the rotation value on the left kept only going up.
What you are experiencing is something called the Wagon Wheel Effect.
To summarize, this is when it appears that something switches direction when it actually doesn't. If you have ever driven on a highway, you have likely seen how it appears that the other car's wheels are spinning in reverse.
Something similar is happening with your blender file. The animation speeds up enough that each frame it is turning somewhere between 180 and 360 degrees. This means that it appears that it is spinning in reverse.
Now that you are aware that it is not actually changing direction, you could be satisfied.
If not, keep reading.
To change how it appears, you need to change the interpolation type.
To do this, hover over your timeline and press Shift+F12. This will switch your window type to the dope sheet editor.
Now, to change the interpolation mode, press A to select all, Numpad . to zoom to selection, and T to change interpolation mode.
Now, press linear on the dropdown that appears. This will make it so the fan spins at a constant speed the entire time.
If this is not satisfactory, experiment with the other interpolation modes until you get what you want.
Finally, if this was helpful, please upvote, and if it answered your question, please mark as accepted answer.
i found that first making the interpolation mode of graph quartic and easing mode as ease in and then after a few frames after the fan speed considerably fast and starts having the 'wagon wheel effect' inserting a key frame at that position(60th frame in my case) and then making the graph from the 60th to the end as linear gives me almost the desired result. hope it was helpful.