Last layer edge orientation problem - why does this happen??

[chj93]

Hello everybody, this matter has been puzzling me for a while, and does not happen on any of my other 3x3 cubes.

I have an earth cube, basically just a 3x3 super cube whereby the stickers have printed on them parts of the earth rather than just standard colours. F2L can be completed as it would be done on any other super cube, without problems. I come onto the last layer, and this is where the problems begin. As part of the solving process I use a 2 look OLL, the first part of which involves the orientation of the edge pieces.

At this stage I often get 3 edge pieces oriented correctly straight after the F2L, with one not. Therefore, this means that there is always 2 correct edge pieces opposite each other, so I take this to be the 'line' case, and hold the line from left to right on the top layer and perform FRUR'U'F' once, expecting this to then have oriented all 4 edges correctly.
(See first case: http://badmephisto.com/2LookOLL.pdf). But this never happens. The cube seems to permanently only ever have a maximum of 3 edge pieces correctly oriented regardless of how or when I perform the above algorithm.

This would be the kind of thing you would expect if the cube was not assembled properly, but I have taken it apart several times and I am certain that I re-assembled it in the correct manner.

So what do you think is going on here? Hopefully this all makes sense.
Thanks in advance.

 

[MaeLSTRoM]

Is there any edges that you wouldn't noticed if they were flipped aswell (not on LL), for example if both sides of an edge just had some ocean on them, they would both be blue.

 

[nqwe]

Maybe there's a piece on which the orientation doesn't matter.
Flip this edge and there you go

Edit:
Too late...

 

[ben1996123]

disassemble/reassemble or take an edge out and flip it

 

[AlexByard]

Try, rather than disassembling it, just taking the one incorrect edge piece then flipping it.. If that does not work, then maybe it is something to do with your F2L, maybe you do not have one of the edges (In the F2L) oriented correctly, because as you said.. It is a cube with parts of the earth printed on it wrong.. You could just simply be putting in a piece incorrectly, sometimes it's easy to get confused with super cubes/picture cubes.

 

[chj93]

Thanks for the replies so far.
In fact, there is one edge that belongs in the middle layer that is identical on both sides (just ocean). I don't know if you're familiar with a term called 'false equivocation'; I believe it basically means that although an edge/corner may seem correctly oriented in any of its rotations, there is actually only one correct orientation for it. For example - the samie cubie on a Sheperd's Cube. So perhaps it is something to do with this.

 

[MaeLSTRoM]

Thanks for the replies so far.
In fact, there is one edge that belongs in the middle layer that is identical on both sides (just ocean). I don't know if you're familiar with a term called 'false equivocation'; I believe it basically means that although an edge/corner may seem correctly oriented in any of its rotations, there is actually only one correct orientation for it. For example - the samie cubie on a Sheperd's Cube. So perhaps it is something to do with this.

Yeah, basically the number of fliiped edges must be even on a cube. This means if you flip that edge and one of your LL edges, then you will be able to continue as normal. (This is basically what I put in my first post btw... )

 

[chj93]

Yeah, basically the number of fliiped edges must be even on a cube. This means if you flip that edge and one of your LL edges, then you will be able to continue as normal. (This is basically what I put in my first post btw... )

But the issue here is that although the identical middle layer edge piece can be flipped either way, every edge in the last layer has a specific rotation i.e. it is completely obvious if an edge is not flipped correctly.

 

[MaeLSTRoM]

But the issue here is that although the identical middle layer edge piece can be flipped either way, every edge in the last layer has a specific rotation i.e. it is completely obvious if an edge is not flipped correctly.

Yes, because of this if you have an odd number of remining edges flipped, then the identical middle layer edge is also flipped, making the total an even number. If it is flipped correctly, the number of filpped edges remaining would be even aswell.

 

[chj93]

Yes, because of this if you have an odd number of remining edges flipped, then the identical middle layer edge is also flipped, making the total an even number. If it is flipped correctly, the number of filpped edges remaining would be even aswell.

In fact, I see what you mean about needing an even number of flipped edges. I have just solved a standard 3x3, but deliberately flipped one of the middle layer edges (but keeping it's permutation correct). Sure enough, when I came onto the OLL, I could not get all 4 edges flipped correctly together no matter how hard I tried. Therefore, the middle layer ocean piece which is identical on both sides does in fact have a specific orientation despite it looking fine however it is flipped - linking back to my idea of false equivocation.

The question now though is how do you know if an edge which looks the same on both sides is correctly flipped or not?

Try, rather than disassembling it, just taking the one incorrect edge piece then flipping it.. If that does not work, then maybe it is something to do with your F2L, maybe you do not have one of the edges (In the F2L) oriented correctly, because as you said.. It is a cube with parts of the earth printed on it wrong.. You could just simply be putting in a piece incorrectly, sometimes it's easy to get confused with super cubes/picture cubes.

Thank you for your input. You are right in what you say about a middle layer edge not being flipped correctly - but it is not obvious that the offending edge is flipped incorrectly because it is just ocean on both sides.

 

[Ralinda4]

In fact, I see what you mean about needing an even number of flipped edges. I have just solved a standard 3x3, but deliberately flipped one of the middle layer edges (but keeping it's permutation correct). Sure enough, when I came onto the OLL, I could not get all 4 edges flipped correctly together no matter how hard I tried. Therefore, the middle layer ocean piece which is identical on both sides does in fact have a specific orientation despite it looking fine however it is flipped - linking back to my idea of false equivocation.

The question now though is how do you know if an edge which looks the same on both sides is correctly flipped or not?

By looking at the other edges to see if an odd number are wrongly orientated.

 

[chj93]

By looking at the other edges to see if an odd number are wrongly orientated.

So if an odd number of edges are wrongly oriented, does that then mean the the middle layer edge which looks the same on both sides is correctly oriented?

Although having said this, I'd soon know if the edge was incorrectly flipped as it would be impossible to get the last layer cross as part of the 2 look OLL.

 

[AlexByard]

I think the way i would solve this problem is by using a 2 flip. on both of the identical edges (And a set up move to put the in the right place for the 2 flip). And if that didn't work... I would just swap them around and try again. I can not think of any way of instantly being able to identify the edge. like you would on a normal cube.... I guess it will always just be trial and error.

But isn't that just the beauty of a super cube

 

[sneaklyfox]

I don't really know what a super cube is as I don't have one, but if I understand it correctly then I'd say the solution would be to leave the ocean edge as one of the edges of the last layer if you can.

 

[MaeLSTRoM]

I don't really know what a super cube is as I don't have one, but if I understand it correctly then I'd say the solution would be to leave the ocean edge as one of the edges of the last layer if you can.

A super cube is a normal Rubik's 3x3x3 cube, but the centre orientation matters. That's the only difference, And it's relatively easy to solve compared to a normal 3x3x3