Build a Moving Bike using Flash in InDesign, Part 2
For this second installment in the Build A Moving Bike series, I’m going to explain how the pedals work. Click the picture below to see the pedals in action.
The whole pedal assembly is made up of six main parts. I’ve made these a little fancier than the originals, but they work the same way.
The most involved piece to draw is the chain ring. There are a few different ways of making gears. I made this one by starting out with a 30-sided star. Then I created two circles and used them to chop off the pointy parts of the star with a couple Pathfinder operations. I used Intersect with the bigger circle to trim the outer points and Add with the smaller circle to fill in the inner points.
To create the holes, again I started with some simple shapes and used Pathfinder > Intersect. Then I made a compound path from the holes and the outer gear shape.
For the finishing touch, I filled it with a radial gradient and pasted a small black circle in the middle. Fun stuff.
OK, so how does this all move?
The challenge is to make the pedals revolve around the chain ring while staying parallel to the ground. The solution is to use two animations. First, select both pedals and apply a 4 second long rotate counter-clockwise animation with a value of -360 degrees.
Then group the pedals with the rest of the parts and apply another rotate animation. This time, make it go in the opposite direction: clockwise 360 degrees. Make sure the duration is also 4 seconds.
Use the Timing panel to play all the animations together.
The resulting pedal rotation is zero (360 – 360 = 0), so they stay put while revolving around the chain ring. Neato! Without applying the counter-clockwise rotation directly to the pedals, the whole thing would have rotated like a propeller.
So again you can see the cool effects you can create by combining animations. In this case, the coolness came from combining two opposite animations to change the angle of rotation and make parts of a group move differently from the rest.