Part 6D of the TGM Translations will only go over Section 2-H (On Plane Acceleration). This is what it sounds like, accelerating while being 'on plane' and the parts and components that play a role in that.
Homer starts of by talking about 'lever assembly.' Lever Assembly is just the alignments of the left shoulder, left arm and clubshaft. When Kelley talks about the 'turning shoulder' (note, it's singular, not plural), he's talking about the left shoulder.
Homer states that the spine is the 'center' of the shoulder turn only. Often times you will hear the spine, from the caddy view, is the 'axis.' S&T guys talk about having a 'centered' or 'reverse' axis tilt. Basically, early on Homer is trying to get into his recommended style of pivot where the head is 'centered.' The centered head abides by one of Homer's '3 Essentials' of the golf swing, the 'stationary head.' This is also a big part of the S&T method. Homer does mention that the Head Centered Pivot is recommended, but not mandatory. Homer also states tha the swing center for all swings has two ends to them. The top end is the top of the head, the bottom end is between the feet.
Homer also talks about the 'on plane' right shoulder. All that is from the DTL view is that the right shoulder goes down the plane. This pic below shows Byron Nelson and Nicklaus having their right shoulder 'on plane.' Golfers who come over the top tend to have the right shoulder above the plane. Golfers who get 'under plane' tend to have the right shoulder under the plane as well.
The important thing to note is that Homer states that 'On Plane Right Shoulder Motion is possible only by titling its axis, the spine.' This of course means that in order to get that right shoulder on plane, from the Caddy View, the 'axis' (aka the spine) has to tilt away from the target on the downswing.
A self explanatory quote from Homer:
Being part of both the Pivot and the Power Package, the Right Shoulder must reconcile them by moving with great precision of thrust, speed, direction and distance. The Right Shoulder does not flap around haphazardly -- it has many responsibilities.Homer then talks about variations in the location of the right shoulder at impact will vary the right elbow bend at impact which may alter the impact alignment of the clubface.
What Homer is talking about here, and it's VERY IMPORTANT to note, that at impact the right arm should be BENT from the elbow. Here's a dual pic of Moe Norman. On the left, he's at address. On the right, he's at impact.
Notice how at address Moe's right arm is straight and at impact the right arm is clearly bent from the elbow. Now, that's not to say you cannot bend the right arm at address (in fact, Homer Kelley recommended it), but it's to show that the right arm needs to be bent at impact for accurate and consistent clubface alignments at impact. Often you will hear TGM'ers say that they are 'running out of right arm' and all that means is that the right arm is not bent or not bent enough at impact. And to tie this all together, Homer is basically saying that you need 'axis tilt' to get the right shoulder in a good location and on plane at impact so you have enough right elbow bend at impact so you can have very precise clubface alignments. IMO, it's not a coincidence that some of the greatest ballstrikers ever, Trevino, Hogan, Moe, and O'Grady all had a tremendous amount of right elbow bend at impact.
Homer also talks about some other facets of the shoulder alignments, lever assembly radius and low points, but we'll get those later. Homer does state this of importance:
The long Backstroke shoulder turn produces arc of approach procedures. The short shoulder turn produces angle of approach procedures.
Here's what a club using the 'ARC of approach' procedure looks like.
This is obviously a diagram from the bird's eye view. As you can see, the clubhead approaches the ball from an arc. Here's the ANGLE of approach procedure.
This is a diagram for the Stack & Tilt method, but take a look at yellow line labeled 'leaning clubshaft.' Now take a look at the light green line labeled 'Angle of Approach.' Instead of showing a diagram where the clubhead and shaft come into the ball from an arc, this has them coming into the ball at an angle. Thus, the term 'Angle of Approach.' Basically Homer states:
Long Swing with Big Shoulder Turn (usually a 'swinger') = ANGLE of Approach
Short Swing with Short Shoulder Turn (usually a 'hitter') = ARC of Approach
Basically, the main purpose of 2-H (On Plane Acceleration) is to understand the importance of the right shoulder position, the 'centered swing', axis tilt' and what type of golfers should use an Angle vs. Arc Approach.