As per your usual standard, the Domino Project is a very impressive piece of work. I do, however, have one question about the construction of the puzzle, in particular the segment regarding how the edge pieces are held in place. While it's true that a screw and a washer will indeed hold them to the puzzle, it looks to me like it'll also prevent the top and bottom layers from turning, since the washer would slam into the sides of the edge pieces or failing that, the corner pieces. Is there something that I'm missing? L8r.

I've taken a careful look to the original domino from my collection. Some parts of its internal construction are visible if to turn a side by 90 degrees. Springs and washers are here.
Let's imagine a sheet of plastic about 2 mm thick with square drawn on it. The square is about the same size as cube's side. Now we will bend the plastic sheet to make a hollow cylinder about two cube sides in diameter. After cutting out the "square" and drilling a hole in the center we will have the "washer". We can call it "sunken center".
All pieces, except centers, have a groove for the sunken center to go. Corners are partially held by sunken centers while turning a side. For axes aren't split, only centers and sunken centers are fixed as I can see.

Remember the part about "frustratingly restrictive"...in the puzzles wanted sections description of the Rubik's Domino?
You're not missing anything.

> Some parts of its internal construction are visible if to turn a side by 90 degrees. Springs and washers are here.

This is not the case on mine. I believe there may be two different mechanisms. Mine definitely has no springs.

> All pieces, except centers, have a groove for the sunken center to go.

This is just what I way saying. The washers must be big enough that when the top/bottom faces are twisted 45 degrees, the edge pieces are still just held by two washers. The washers will have to be near the centre, in other words the four side axes musn't be too long.

Jaap
http://www.org2.com/jaap/puzzles

I must say I agree with Tim. The original domino used a centre pieces that was split, so the four axes to the sides were also split.
If you use something like a washer, which isn't split, there will probably have to be a groove through all the pieces to allow it to pass through when the top/bottom is turned. One of the eight edge pieces should be fixed to the axis to keep the centre piece aligned.

BTW Wayne, I like the new design. Thanks also for the big link to my site!

Jaap

Apparently I've missed the boat here. I always thought the top and bottom (black and white) halves of the Domino did not turn. I think that is what I thought. after reading the posts here about it, I'm not sure I follow what is being said. I'm halfway through building Wayne's design, can somebody explain it a different way as to how this thing really works?
Thanks.

Jake

Yes, this is a problem. But as you say, an arced grove can be cut 360o around all of the pieces to allow the washer to move through. So far, it looks feesable to do this, as the pieces themselves would be affected by the cut.

No worries about the link. It's a darn good resource.

Jaap, do you mean that the washers (I guess they'd really be split washers) would be attached so that they tuck underneath the centre piece? I've been doing some thinking about the problem and that was one of the things I came up with, but using washers never occurred to me. I was thinking more along the lines of building the "washer" design right into the piece itself. The other thing I was thinking was to not cut the inside tab quite so far, but instead cut a circular groove around each side of the mechanism for the edge piece to grab on to. The problem with this would be that it might weaken the spider so much it would fall apart. L8r.

What I meant by that was from my experience using the virtual domino on the Rubik's games CDROM. I found that being so used to manipulating the 3x3x3, the 3x3x2 was frustratingly restrinctive because some movements are forced 180o as opposed to 90o movements of the cube.

Wayne

I explained it elsewhere int eh thread but in short, a cut groove 360o to allow the washer to pass through. I'll do up some pictures later to see if this is feesable and update the design on the page.

Don't worry Jake, keep going on your domino and cut the grooves at the very end.

Wayne

I distinctly remember seeing two different patents for the Domino puzzle by Erno Rubik. I'm pretty sure that some of each design were produced. One patent was a significant improvement over the original. The improved patent used a split (top and bottom) spindle with half washer-like features in each half. All I remember about the first patent design is that they were considered very flimsy and easily broken because of very small features on the cubies. I will look and see if I can find the two patent numbers. Maybe Wayne's approach will be better than either of Rubik's once he gets the bugs out.

Doug.

There's one additional problem which would have to be taken into account. In order to minimise the size of the groove, you'll need to find some way to curve the washer so it has the same radius as the groove being cut. Otherwise you may need to cut a groove so huge that the tabs would snap off the corner pieces. L8r.

I agree that cutting a circular groove in the parts will allow the two halves to rotate, but while in mid-turn (about 45 degrees) the washer will be out of place for holding the edge pieces from falling away from the spindle. They will just plop off.

I also agree with Jaap that at least 1 edge piece would need to be glued to one edge piece to keep the spindle washers from loosing their orientation with respect to the rest of the puzzle.

Doug.

I think this link will take you to the "improved" domino puzzle patent drawing:

http://131.127.219.64/spiweb/webbench.dll?cmd=DisplayPreviewImage&session_id=086f62e26cd011d580240004aca367b4&document=BP00UUUS4378116&page=1&s%65ction=0&summary=1+5&view=full&name=4378116

See the half spindle at the bottom of the page.

I can't seem to be able to track down the "first" domino patent.

Doug.

The previously given patent US4378116 actually shows both designs. Figures 1-6 are for the original design, and Figures 7-12 are for the improved design.

I had read somewhere that both were produced.

Doug.

First off, a link to my site which complements Wayne's but focuses on patents - http://www.calormen.com/TwistyPuzzles/twisty.htm. I'm missing lots, but hope to have everything listed eventually. The Domino patent is referenced there.

Next: I also am unsure how the Domino Project plans allow for a 90 degree rotation of the two halves, specifically how the corner lips avoid hitting the center spindle. I asked Wayne and he assured me that everything was kosher, but it still doesn't look right.

Lastly, addressing the subject line: this discussion forum contains three categories of people; (1) those lucky collectors who have vintage Dominos, (2) a few people capable of making custom puzzles with molds and resin, and (3) those who want to posess a 3x3x2 puzzle. I suspect there may be some overlap.

This begs the question: ignoring, for the moment, legalty issues; are any of the designs of existing dominos available to readers of this board amenable to direct copying? I've found that the trickiest part of puzzle making is crafting the originals. The mold-making and resin-pouring are comparatively trivial in comparison, and are completely harmless to the original. Given a very trusting (1) and a (2) with spare time (alas, not me), a small batch of replicas could be had if the design will hold up.

Any takers? Those of us in category (3) might be coerced into funding such an exploratory venture.

A friend has sent me a octahedron which I have just finished making the molds to all the pieces. I'm going to try a cast up to see how well they turned out, so right now it is basically possible for me to copy someones Domino.

It will be a while before I'm ready to finished the octahedron and return it to it's owner, but it might be worth someone considering in a few weeks. If there's any takers, let me know.

I'll be posting the results of the copied puzzle in an article on Twisty soon.

Hi Wayne
Are you thinking of making octahedrons and selling them? If you are, then Im very keen to buy one from you.
James.

Not sure, James. It's taken ages to create the molds (last one dries tonight). It'll take ages to make all the pieces needed so it wouldn't be cheap enough to sell. I'd probably only trade for rarer puzzles if I ever made a second one.

But... it'd be announced if I do. We'll have to see.