Sunday, April 9, 2017

amazon review of 5x5 rubiks cube

This is a great cube.  As an engineer, I'm really impressed by the design and quality.  I always have a complaint about product design, but I could not find any flaws in this.

Do not pay attention to the reviewer who said it came apart. It is not possible to take it apart without a screwdriver.  The center caps can be popped off with your fingernail to reveal the screw inside, one on each side.  You tighten the screws to make it a "tighter" cube.  As with other cubes from this manufacturer, I needed to make 1 to 2 turns on those screws to tighten the cube up.  It really is too flexible when you get it.

The colors are just as vibrant and nice as the picture shows.

I'm very enthralled by this 5x5 that I seem to have lost all interest in my 3x3. I wanted a 4x4 but figured my son would be more impressed with a 5x5 (he was), but now I am very happy I got the harder one.

The instructions are great becaus e they're so awful.  The bad "Engrish" and the challenge in trying to figure them out was fun and challenging. I specifically refrained from trying to do a web search to get good instructions.  "When we recover the centre block we will meet some problem, but normally have two condition. Recover the center block is agile step. You lean these 2 formular must think it's thinking." The instructions made it 3x harder than it should be.  I could really only understand the 4 patterns (the engrish was either superfluous or too bad) and one of the images is wrong, so I had to apply the patterns to see what happened.  Then I had to use a little but of thinking to get the pieces in the right place so that the 4 patterns could always be used.  Also, for what they call the 2nd step, (the 3rd of the 4 formulas) I had to apply the mirror image (or some type of "inverse") of the pattern for half of the pieces.  So after an hour I had the 4 patterns figured out.

Summary of solving:
2 patterns of 7 moves each applied to "middle" pieces (not the corners, not the sides). Each pattern is applied about 10 times each (20 move) because there are 48 of the middle pieces and you can easily solve the first grouping (or two) without the patterns and ~30% of the remaining pieces are in place by luck.

1 pattern of 7 moves, and it's mirror image, applied to get the 3 side pieces (that make up each side) together for each of the 12 sides. Barely 25% seem to be in place by luck, so (100% - 25%) x 12 x 2 =~ 18 times.  (you apply it to 2 of the 3 side pieces, for each side)

1 pattern of 15 moves applied about 6 times to the sides to orient  ~50% of the 12 sides that are not oriented correctly by luck. If you mess up, you have to go back to and apply step 1 and 2 several times, then all of step 3, losing 10 minutes of work.

Now solve like a 3x3

There seems to be a lot of room for figuring out ways to reduce the amount of times the first 2 patterns need to be applied. So there's plenty of room for fun invention.

Here's more detail on solving.

The first 3 patterns are pretty simple.  The 4th one is challenging and took me about 20 times before I remembered it well enough to not make a mistake.  After solving it 10 times this weekend, I'm down to 16 minutes, and I do not know if I can make a lot of improvement.  I can solve a 3x3 in 80 seconds using the most basic method.  40 seconds is my record on 3x3 due to some luc I still need to look at the 4th pattern to keep me on track (it's 15 moves, most of them a half turn).  Someone else said he does it in 7 minutes. k.

After you apply the 4 patterns you have it organized in a way so that you can solve the rest like a 3x3.  So it adds only 4 patterns to the 5 I use for a regular 3x3 (not counting 2 "mirror" moves of the 5 that I sometimes use to speed things up, and the 6 or so simple moves I use to get the initial white layer)

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