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 Post subject: RotoPrism 2 Mechanism
PostPosted: Fri Aug 17, 2012 12:06 pm 
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I thought I should start a new thread to attempt to answer Oskar's questions regarding the mechanism of the RotoPrism 2. In the IPP32 thread, Oskar wrote the following:
Oskar wrote:
Hi Dave,

As you know, I bought a sample of your Rotoprism 2 to study it. After playing with it for quite a while, not solving it and remaining clueless about the mechanism, I took the puzzle apart.

I am deeply impressed by the elegance of the mechanism. I had expected more pieces inside. I am still not sure whether I understand the geometry of the puzzle. I noticed three shells: an inner shell, a deep-cut middle layer and the beyond-deep-cut outer shell. However, I do not understand how they interact. Could you explain it with some illustrations?

I noticed that the outer shell is quite hollow. The five triangles slides in some rails, but you did not fill up the holes in those rails, nor did you fill the voids under the corners of the triangles. Could you have filled those holes? Would that do any good (or bad)?

Finally, I think that even the deep-cut layer would already make a nice puzzle. What would that look like?

Thank you again for this great puzzle and a masterpiece of engineering!

Oskar
First, many thanks for the compliments, and for purchasing the puzzle!

Now to the questions:

The inner shell you're referring to is the hollow core. The core has a triangular stalk on either pole that serves to hold the next layer of parts in place. It also has pieces that are the equivalent of the Fracture-6 equatorial vertices rotationally attached. The screws are located inside of the core in order to save space. These rotating core parts have an additional stalk which serves to help hold the outer face centers onto the puzzle.

The next layer is the deep-cut middle layer, and this is equivalent to the remaining parts of Fracture-6. The pieces which are analogous to the Fracture-6 edges do not show on the outside of the RotoPrism 2, but they do have triangular stalks extending outward which serve to hold the outer face centers onto the puzzle. The parts which are the equivalents of the Fracture-6 face centers appear in this layer, and on the outside of RotoPrism 2 as the corner pieces. These also have an extra set of "wings" at the same height as the stalks on the non-visible "edge" pieces, to again hold the outer centers onto the puzzle.

The deeper-than-origin-cut outer layer consists of these corner pieces, plus the face centers. Due to the internal geometry, the face centers end up being very thin, but fortunately there was enough material left to create grooves where the wings on the corners and the stalks on the middle layer pieces and the core pieces can grab them. Hopefully the following images will help clarify all of that further:
Attachment:
rotoprism 2 cutaway view 2.jpg
rotoprism 2 cutaway view 2.jpg [ 109.89 KiB | Viewed 933 times ]
In the image above, the blue part is the core, and the magenta parts are screwed to the core. The orange parts are the hidden "edges" of Fracture-6, and the red and yellow parts are the analogs of the Fracture-6 faces. The remaining parts are the two different types of face centers (curved and flat).
Attachment:
fractured prism raw parts.jpg
fractured prism raw parts.jpg [ 57.81 KiB | Viewed 933 times ]
This next image shows the parts of the prismatic version of the same puzzle in the raw state (no grooves, wings, etc.), minus the core. The five (only four are visible) outer triangular pieces (face centers on RotoPrism 2) are dark green and red. They can be rotated into any one of three positions, which is why so much of these parts had to be cut away. This can be most easily understood by looking at the red pieces on the side, and imagining them rotated by 120 degrees. I did not add the cutoff pieces back in to help stabilize the puzzle, since they would interfere with each other and prevent the puzzle from turning. This is where the jumbling nature of the puzzle comes in. With Fracture-6, it is easy to tell that the puzzle jumbles since there is no way to unbandage the parts without fudging (see Constellation Six). However, on RotoPrism 2, this jumbling shows up on the inside of the puzzle, and causes the voids.

To answer the last question, the inner deep cut layer of RotoPrism 2 has already been made into three different puzzles. It is the equivalent of Fracture-6, RotoPrism 3 (round), or RotoPrism 3 (flat).

Hopefully that answers more questions than it creates about the mechanism, but please let me know if additional images or further clarification is needed. Despite its apparent simplicity, RotoPrism 2 was indeed one of the most challenging puzzles to design that I have made. It took quite some time and several different computer models to understand how the mechanism had to work. The way I was originally viewing the puzzle (before I realized that it is deeper-than-origin turning), it seemed to require axes that appeared and disappeared. Fortunately it turned out to be a bit simpler than that, but still quite interesting.

Dave

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 Post subject: Re: RotoPrism 2 Mechanism
PostPosted: Fri Aug 17, 2012 12:14 pm 
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It is just magnificent. Dave, I am very impressed with the elegance of your mechanism.

-Doug

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 Post subject: Re: RotoPrism 2 Mechanism
PostPosted: Fri Aug 17, 2012 4:00 pm 
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Hi Dave,

Thank you for sharing all the detailed info. I am understanding now a bit more of the design process, although I would not yet know how to apply it to other geometries. Very inspiring!

Oskar

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 Post subject: Re: RotoPrism 2 Mechanism
PostPosted: Fri Aug 17, 2012 6:47 pm 
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David, thanks for posting this. I was confused by this one at the IPP, and even after reading your post a couple of times, I am still working on understanding, to be honest. So thanks for the explanation!

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