Rubik's Revenge

VI. Solve the Bottom Edges

All 8 bottom edges are in the bottom layer, and chances are they are pretty much scrambled. The first step is to arrange them in the correct positions. Randomly choose a front side, and proceed to solve the back edges; starting with the back-left edge first and the back-right second.

Note: these diagrams look strange. The first one appears to take 4 edges and cram them into one. What the first diagram actually means is that if an edge cube is coming from ANY edge-side, then you must repeat the sequence until it appears in the back-left edge. You may have to repeat this sequence four times before that happens.

The second diagram represents any edge from the front moving to the back-left edge. You may have to repeat that squence twice before it lands there. The dark squares on both diagrams are edges cubes that do not move at all during the process.

Now continue to...

~~~ Move an edge to the back-left ~~~
______________________________

Move an edge
from either side

Repeat the
sequence:

...until the edge lands
on the back-left

M- B- M+ B2
M- B- M+

You may have to
repeat the sequence
as many as 4 times.
______________________________

Move an edge
from the front

Repeat the
sequence:

...until the edge lands
on the back-left

M- B2 M+ B-
M- B- M+
N- B2 N+ B+
N- B+ N+

You may have to
repeat the sequence
as many as 2 times.

Now continue to...

~~~ Move an edge to the back-right: ~~~
______________________________

Move an edge
from either side

Repeat the
sequence:

...until the edge lands
on the back-right

N- B+ N+ B2
N- B+ N+

You may have to
repeat the sequence
as many as 4 times.
______________________________

Move an edge
from the front

Repeat the
sequence:

...until the edge lands
on the back-right

N- B2 N+ B+
N- B+ N+
M- B2 M+ B-
M- B- M+

You may have to
repeat the sequence
as many as 2 times.

If you are lucky, the edges going to the back are already paired. You can still move them one at a time, or you can use these shortcuts:

~~~ Move an edge-pair ~~~

...from the left:

...from the front:

...from the right:

N- B+ N+ B2
N- B+ N+
M- B- M+ B2
M- B- M+

M- M- B2
M- M- B2
M- M-

M- B- M+ B2
M- B- M+
N- B+ N+ B2
N- B+ N+

All sequences only have to be performed once to accomplish the move.

Both back edges
should now be
in place....

...rotate the entire
puzzle so that
the fixed edges
are in the front...

...and solve the
"other" back side.

Once again, you have to use the same sequences as before, except this time, the edges are coming from the sides only.

Move a single
edge to the
back-left:

Move a single
edge to the
back-right:

Swap the left
pair of edges
with the back
pair of edges:

Swap the right
pair of edges
with the back
pair of edges:

M- B- M+ B2
M- B- M+

(4 times max.)

N- B+ N+ B2
N- B+ N+

(4 times max.)

N- B+ N+ B2
N- B+ N+
M- B- M+ B2
M- B- M+

(1 time only)

M- B- M+ B2
M- B- M+
N- B+ N+ B2
N- B+ N+

(1 time only)

The back and
front edges are
now in place....

...rotate the entire
puzzle so that
the fixed edges
are on the sides...

...and solve the
back side again.

This time, you only have to use the sequences that move the edges from the front to the back:

Move a single
edge to the
back-left:

Move a single
edge to the
back-right:

Swap the front
pair of edges
with the back
pair of edges:

M- B2 M+ B-
M- B- M+
N- B2 N+ B+
N- B+ N+

(2 times max.)

N- B2 N+ B+
N- B+ N+
M- B2 M+ B-
M- B- M+

(2 times max.)

M- M- B2
M- M- B2
M- M-

(1 time only)

Once you solve the back side (for the third time), the remaining 2 edge cubes are forced in the front side, where they belong! Therefore, all 8 bottom edges are in place. Now for the next step: inverting.

Inversion

There are 5 different inversion schemes:

  1. Invert 2 edge-pairs on adjacent sides
  2. Invert 2 edge pairs on opposite sides
  3. Invert 4 edge pairs
  4. Invert 3 edge pairs
  5. Invert 1 edge pair

For each inversion scheme, you must rotate the entire puzzle so that the inverted pairs are positioned exactly like the ones in the diagrams, before attempting the sequence of moves!

~~~ Case #1: Invert two adjacent edge-pairs ~~~

[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2
[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2

Result:

The bottom edges
are solved.

________________________________________

~~~ Case #2: Invert two opposite edge-pairs ~~~

[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2
[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.
________________________________________

~~~ Case #3: Invert four edge-pairs ~~~

[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2
[MN]- B- [MN]+ B-
[MN]- B2 [MN]+ B2

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.
________________________________________

~~~ Case #4: Invert three edge-pairs ~~~

M- B- M- B2
M- B2 M+ B+ M+
N- B- N- B2
N- B2 N+ B+ N+
M- B- M- B2
M- B2 M+ B+ M+

Result:

The bottom edges
are solved.
________________________________________

~~~ Case #5: Invert one edge-pair ~~~

M- B- M- B2
M- B2 M+ B+ M+
N- B- N- B2
N- B2 N+ B+ N+
M- B- M- B2
M- B2 M+ B+ M+

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.

As it turns out, only two different sequences were used throughout all five cases. Now that the bottom edges are solved, the only thing left are the Middle Centers.

@ Notation / Top Centers @ Top Corners @ Top Edges
@ Middle Edges @ Bottom Corners @ Bottom Edges @ Middle Centers

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