Question about the Philip Marshall Method

[Raven72]

The Philip Marshall Method uses U' R U R' to align the yellow cross. I have found that sometime the cross will align with just four repeats of the U' R U R' Alg. and sometimes I need to keep repeating the Alg. - but it does solve the yellow cross eventually.

My question is, Am I doing something wrong or does the Alg. sort of 'shuffle' the four yellow cubies and last edge cubie around until they fall into place, meaning there is no set number of repetitions that aligns the yellow cross?

 

[AlphaSheep]

The alg U' R U' R' cycles 3 edges. Specifically, it moves the edge in the front right location to the top right, moves the edge in the top right location to the top back, and then moves the edge in the top back location to the front right. The yellow cubies in the top front and left front locations are unaffected.

You can do the alg on a solved cube to see what it does. If you do the alg 3 times without any other turns or rotations in between, then the edges should return to their original position. If you do it 6 times, then everything (both corners and edges return to their position).

As long as you are allowed to rotate the cube in between and turn the top (yellow in your case) face, it should be sufficient to solve edges with at most 3 repetitions.

 

[Raven72]

The alg U' R U' R' cycles 3 edges. Specifically, it moves the edge in the front right location to the top right, moves the edge in the top right location to the top back, and then moves the edge in the top back location to the front right. The yellow cubies in the top front and left front locations are unaffected.

You can do the alg on a solved cube to see what it does. If you do the alg 3 times without any other turns or rotations in between, then the edges should return to their original position. If you do it 6 times, then everything (both corners and edges return to their position).

As long as you are allowed to rotate the cube in between and turn the top (yellow in your case) face, it should be sufficient to solve edges with at most 3 repetitions.

Thank you for your quick an informative reply - I see what the alg does now and have worked out how to use it correctly with U rotations to set up the yellow cross solve

Edit:- still struggling with the alg on some solves....seems building the yellow cross is easier just by intuitive solving and finishing with U (R U R' U') if needed

 

[AlphaSheep]

Edit:- still struggling with the alg on some solves....seems building the yellow cross is easier just by intuitive solving and finishing with U (R U R' U) if needed

Yes, it is easy and quite efficient in most cases to do intuitively. In fact, solving the last layer edges intuitively like that is a technique commonly used by fewest moves solvers.