Radiolarian 15 – The Radio Chop – Skirting Rails Mechanism – 10/2013

The following was taken from my original announcement of this puzzle on TwistyPuzzles,.com in 10/2013.


This is the 15th and last in my series of increasingly deeper cut face turning icosahedrons. This is the deep cut puzzle and thus the series is now technically complete at 15. I still plan to release a V2 for the Radio Star (number 11), but otherwise this represents the end!

As you all know, the equivalent dodecahedral Chopasaurus was made first a few years ago by Andrew Cormier. My version uses an entirely different mechanism called “skirting rails”. In other words this is not a shells mechanism. It is closer to my Pentultimate V2.5 mechanism.

One very unique property of my version is that this puzzle does not jumble! Deep cut jumbling puzzles can sometimes block internally, which is a property I don’t find desirable. In those cases, external turns look valid, but can’t be done due to the internal state which cannot be seen. Since my puzzle does not jumble, it does not have this problem.

Turning is pretty tight, but it’s nice and stable. Actually starting a turn seems to be the hardest part as you can see in the video. I assume it’s because of so many parts having to align themselves perfectly inside.

Edge lengths are 88mm, making this a very large puzzle!

Video Here!


To understand the skirting rails mechanism, please see the Pentultimate V2 article, and the Pentultimate V3 article first.

On the Pentultimate, we were able to lock down 5 out of 6 tracks by locking them to the top center.

On the Radio chop, we can only lock down 6 out of 10 in this way.  I’ve colored these 6 tracks red in the image below:

Untitled-2 copy

The four remaining tracks we need to lock down are the equator (shown in yellow) and three tracks that sit between the equator and the locking top face.  I chose the points marked in green to attach pegs to the master layer that can interact with the special core.  Allowed paths are swept out of the core and the rest is used to collide with the pegs and prevent illegal moves.

In the following images, I have colored the pegs red.  Here we can see how the blue tracks will be blocked.  They can rotate in from above and below, but not move sideways:



Here we can see how the equator will be blocked.  The pegs can rotate in from above and below, but they cant move left-right.


These assembly photos were not revealed in the original post.

SGS4 566 SGS4 567 SGS4 568 SGS4 569 SGS4 570 SGS4 571 SGS4 575 SGS4 577 SGS4 579 SGS4 580 SGS4 583 SGS4 591 SGS4 596 SGS4 598 SGS4 603


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