Solution to the 51 piece burr puzzle
Here is a sequence of pictures showing how to solve the 51 piece wooden burr puzzle pictured here.
Click on any image for a larger view.
Start with the 51 pieces, and use the three longest to make the center axis.
Then assemble several "cross" pieces and insert.
Now note the top layers. The topmost piece is the odd-ball short piece with a thin connecting piece. Again more cross pieces are placed, leaving no hidden holes.
Now some pieces are slid in one at a time across the middle. This is done layer by layer to fill it up.
After all pieces are in, the final top one is rotated to tighten up the puzzle.
Viola! You're done.