Ed Pegg Jr's Solution - 3 identical pieces:

I'm proud to say I've fit the Borromean Rings into the side-4 cube BY HAND.
Here are the top two layers. The other two are rotations of these.



Bryce Herdt
Hi Ed,

Recently I've attended the 12th WPC in the Netherlands as
the captain of the Ukrainian Puzzle Team. We achieved
a very high (for us) 10th place, and one of our boys,
Georgiy Kassabli (he's a four-time Puzzle Champion of
Ukraine) has the 13th place as an individual. All this makes
the 12th WPC and his results very remarkable for our
Puzzle Team and for me as its captain.

After the Championship I've found a lot of great new puzzles
at your site. Great job! Thank you! One of puzzles very
interesting for me was the Cubical Borromean Rings. I've
enjoyed solving its 4x4x4 version. Please note, that, specifically,
its 5x5x5 version makes a base for 3-piece burr which was
developed in several modifications in the past.

I attach both solutions - for 5x5x5 and 4x4x4 cases, respectively.
Also I attach detailed diagrams for the 4x4x4 case - every ring
separate, rings in pairs, and four layers of the composition.

In Cubical Borromean Rings "squeezed" into a 4x4x4 cube
every ring consists of 18 single cubes, and is symmetrical about
the central point of the cube. Also, there are hollows within
the cube - 10 single cubes altogether.

Serhiy Grabarchuk