Animation of a Helicopter

[Joe Clay]

Cut the wings out and make them into a 3D layer or redraw them from a side profile. Use the orientation to get the rotors in the proper position and animate the y-rotation property. I think helicopter engine RPM is about 1600 from prior research (it’s pretty varied from what I can tell, but if you want extra realism, stick to 1600 or so). For an additional bit of realism, animate or wiggle the z-rotation slightly. Make sure you have motion blur checked.

You could do the same with a solid in the shape of the rotors (add a little color to the blades for a nice touch). Or, you might just be able to get away with simply directional blur in a pinch.

I hope this was clear and useful.

Joe Clay

Animator
gra-phix.com

[Carl Larsen]

One way to simplify the animation of your helicopter blades is to use an expression instead of keyframes. This way you’ll never have to think about RPM’s or start and end values. Just define a velocity and let it run.

Option-click on the Z rotation of your blades layer and add the following expression:

time*5000

Change the numerical value to fit your needs, and make sure motion blur is enabled for both the layer and composition. 5000 was a value I thought looked good when I tried it out.

If you’re still not getting the results you’re looking for, double check your composition settings (command-k, composition settings>advanced>motion blur) and increase your samples per frame and shudder angle until you get the look you’re after.

[Tobias Schrenk]

Thanks to both of you.

Finally I did it with a 3D Layer. Worked out pretty well. I think expression would also work but I read it too late and i am not really familiar with it.

Thanks again

[Joe Clay]

That’s a good tip. I would have mentioned it, but if he needed to stop it and start it, it’s a little more complicated and would almost always have to be keyframed anyway. Although it should go on the y-rotation unless it’s from above, in which case you wouldn’t need a 3D layer anyway.

I see that the OP has found his solution, but here’s another way for posterity.

You could still do RPMs with the expression method, however. The calculation would be:
RPM*6

In case you wonder where I got that, it is simplified from RPM/60s*360°. Time is expressed in seconds and fractions thereof in After Effects. Because of this, we have to multiply by 360 so that at 1 second the value is 360, or 1 revolution. Then we figure out how many revolutions per second and multiply the previous part by that. It’s convoluted, but if you’re going for realistic motion, that’s how you do it.

Thus 1500 RPM would be 9000. Which explains why 10,000 looks good (it’s about 1667 RPM). So the final expression that would go on the y-rotation property would be: time*9000. For a second rotor offset by 90°, you could either parent it and make the y-orientation 90, or use time*9000+90.

If you need to start and stop this, look into expression controls or check out Dan Ebberts’ site for info on starting and ending expressions on a certain frame.

Joe Clay

Animator
gra-phix.com