Just a short note to let you know how I made the animated gears movies.
Firstly, I entered two gears, both having the same pitch diameter and number of teeth, but a helix angle of 20 degrees on one, and -20 degrees on the other. Using the Info palette, I set the z coordinate of both gears to zero, and used the up and down arrow keys to adjust the x and y coordinates so the gears meshed together correctly.
I then calculated that if there were ten teeth on the gears, I only had to rotate the gears by 36 degrees, so that when the movie looped it would appear that the gears were continually rotating. I set the Animation Tweener palette tween increment time to be 0.1 seconds, then added 15 or so tween points. For each tween point I rotated one gear 4 degrees clockwise and the other gear 4 degrees anticlockwise (holding down the control key and hitting the left arrow key will rotate the selected object one degree, hitting the right arrow will rotate it the other way).
Once I had entered the tween points I added colors to the gears, set the shininess of the surfaces and adjusted the camera position to the required location. I then recorded a QuickTime movie using the Animation Player palette set to record at 30 frames per second.
I then loaded the new movie into Apple's Movie Player application and set the duration of the output movie to be 27 frames in length (27 frames = 0.9 seconds = 9 x 4 = 36 degrees). I did this by stepping forward 27 frames and then, holding the Shift key down, continue selecting frames to the end of the movie. I then cleared the selected frames at the end of the movie by selecting Clear from the Edit menu. Finally I set the play mode to be "Loop", and saved it.
The second movie was recorded just like the first, using the same tween points, the only difference being that I changed the colors of the gears and the cameras location.
