There is a Lego Digital Design file at the bottom of this page for this project.
You will need:
Lots of LEGO pieces.
Step 1: Creating the Base
The base is probably the easiest part. I used three 4x12 plates put side-by-side to make a 12x12 square. Yours could be any size.
Step 2: Building the First Layer
Step 3: Building the Second Layer
This layer is like the first, except with one minor addition. Four Technic 1x2 pieces were added to the inside edges, two on each side. The picture explains all.
Step 4: The Final Layer
This layer is built exactly the same as the first, so no explanation is needed.
Step 6: The Mechanism
The mechanism is made up of two 2M axles. They fit into the holes of the base, as shown in the images below. The axles will slide into the piece, therefore locking it in.
Step 7: How to Set Up the Puzzle
Put the cross beams in the holes in the base. Put the piece in the base, making sure the holes are on the right sides. Put it in until only the first layer and plate are showing. Tilt the base until you hear the cross beams moving, and the puzzle is ready to go. This puzzle is very difficult to solve, because if you try to tilt one of the cross beams out of the piece, the other one will slide in. The best way to solve the puzzle is to hold it above a flat surface, and to spin in midair as you would spin a coin. Centrifugal force will ace on the pieces, causing them to move outward at the same time. The piece will also sink into the puzzle, showing that it can be removed. Have fun showing it to others!