About this 3D model

The balancing bird is always interesting for students to ponder the wonders of gravity or mass. It is really challenging to design a 3D model that prints well. So I decided to focus on the main math or physical ideas by adding three bolts to both wings and the tail. It is a theoretical bird, so to speak; but it gets the ideas through. Without the bolts, the bird has a decent balance at the beak. For those who don't like using bolts, there is another one with no adjustment, which balances itself well at 20% infill. If necessary, one can add some little rubber bumper stickers to find a nice balance.