Rotating Fan Blades

Hi guys, still quite new Blender but loving the program.

I’ve run into a problem when animating a fan blade. I found a short bit of advice on here to keep the fan blades running throughout the animation by using the IPO Curve Editor.

I select the keyframes, then go Curve>Extend Mode> Extrapolation and this turns the original keyframes into a never ending line. Meaning the blades turn forever.

This is great, but the blades move very slowly, quite lethargic and lack the energy I need for a massive output of power. Any suggestions on how I should be shaping the curve or setting the keyframes up in order for the fans to spin very quickly and constantly?

One problem I have which may be leading to this is that when I set the original keyframes the rotation of the blades seem to only turn once although I put several raotations in before setting the new keyframe. I think Blender is picking the shortest route to the new position but missing out the spins inbetween… does this make sense?

Thanks for your help guys.


You want to make the slope of the IPO steeper. You can do this by scaling it upwards.

If you want your blades to rotate constantly, without accelerating or decelerating, you only need two keyframes with linear interpolation and extrapolation as the extend mode.

If this fan never stops turning, you can also fake it by a transparent disc with blades texture…
Just an idea to speed up the process. :wink:

Hmm, the fan is supposed to start up, turn (for the vast majority of the animation) and then slow to a stop. Stopping and starting I worked around by inputting more keyframes and dragging them to a horizontal line in the IPO window which kept them stationary until they were needed. This meant the fan does stop and start when I need it to but is just not fast enough.

I’ll try scaling the curve up and see if that helps, thanks very much for your help guys.

Here you have one other way to rotate your propellerblade.

Use Space + add + Curve + Bezier Circle. Select Propeller + Press Shift + Bezier Circle. Press Ctrl + P and Follow Path.

Change speed with PathLen or follow rawpigeon )advice. Press Alt + A to start the propeller.


Airoplane.blend (166 KB)