# How to animate a propellor?

I need some help with a propellor animating. I tried and the result was the propellor moving forth and back. Thanks for answers.

If you want to animate it rotating, you move your time to specific frame.
Press I to set a key frame, select rotation from the pop-up window.
Move to another frame (15 frames after the previous frame), rotate the object around it's axis, press I again to set another key frame (select rotation again).

This will cause it to 'spin' for 15 frames. Without more details regarding your goal, this is the simplest way to animate.

• I did this, but for some reason it keaps slowing down and speeding up (four or five times pro 250 frames). Is this because it is just preview and will not hapen when redered? – aky-her Sep 22 '15 at 20:46
• It could depend on the rotation amount at each key-frame. Suggest looking at this to make it spin repeatedly if that is your goal - blender.stackexchange.com/questions/440/… – 3Duser Sep 22 '15 at 20:51
• I tried to slow it down a bit and works well. thanks – aky-her Sep 22 '15 at 20:51

You've tried pressing 'I' and you didn't like it because it was speeding up and slowing down. This is because blender tries to make everything smooth. If you want to make it the way you want, follow these steps.

1. Change view to 'Animation'
2. Click in the box with the lines, press 'T' and click 'Linear'
3. OPTIONAL If you want to make it propel forever, you can click on Channel -> Extrapolation mode -> Constant Extrapolation.
4. If you want to get back to the normal blender, change the view back to 'Default'
• it was because I wanted it to spin too fast, not because of the curve – aky-her Sep 23 '15 at 12:40

Another way is to set up a driver

spin * frame


where frame is the current frame, and spin is a custom property, which can be keyframed.

This way you can fiddle the speed, or key in speed changes to get differing strobing effects. (If you rotated 360 degrees each frame you would see no rotation)

There are a couple of small sample files here http://blenderartists.org/forum/showthread.php?229688-Helicopter-Rotor&p=1937512&viewfull=1#post1937512