[airair]

mb6606,

I think you have nailed the most basic difference between hitting and swinging. When you hit, you substitute some of the pivot rotation with arms rotation.

This discussion is taking us into an area where TGM seems to be at odds with Sir Isac Newton's physics theories and laws. I wouldn't go as far as saying that TGM is wrong, but I would say that TGM is confusing and inconsistent with regards to separating hitting and swinging. Faulty assumptions and explanations that are raised here on LBG passes unnoticed ever so often.

There is unclarity with regards to the difference between rope handling and centripetal force (what was called radial force above) that is highly misleading. They are not the same, but they seem to be regarded a such very often.

When you pull the rope, you're partly pulling the club towards the swing center and partly pulling it forward. The first part of the pull carries the centripetal force and all it does is keep the club in orbit. No change in swing speed because of centripetal force, only change in speed direction. The other part - the forward part - is tangential force that adds swing speed. It works in pretty much the same way as a right hand thrust with PP#1. I really like Daryl's take on this.

This centripetal / centrifugal / rope handling mess often leads to the misconception that a swinger uses centripetal force to create clubhead speed. Centripetal force doesn't produce speed. Never has, never will. Only tangential force (linear force per TGM) produces swing speed.

I really like the G.O.L.F acronym. It says it all, really: Geometrically Oriented Linear Force. Homer is so close there. Centripetal force handles the geometry by keeping the club on a circular path. Linear Force creates speed. It's really that simple.

Then there's the implied assumption that you can't use centripetal force in a hitting procedure. While the truth is that you must if you want to create a motion that looks remotely like a golf stroke where the club moves around your body. You can't avoid doing it. And with two hands on the club you will to a large extent create clubhead speed the same way as a swinger does. The hiting stroke is in this regard a swing without pp#3 rotation and where driveloading substitues some of the swingers rope handling.

Much of this confusion is related to the description of Accumulator #4 which is incomplete in TGM.
It starts in chapter two:



From there, Homer proceeds to present the three lever forms that he uses throughout. They are supposed to be all inclusive. In doing so, he basically excludes the shoulder rotation from the equation. Instad the shoulder turn is labeled as a "carrier of motion and nothing more" when PP#4 isn't engaged.

I think Homer used PP#4 as the partner to Accumulator #4 because he made his explanations dependent on the three lever forms. The only lever force he found with regards to the left arm was the pp#4 so he used that. Doing so he missed the incredible torque that the left shoulder pull and the right shoulder push represents each of their own and together. The strong pull that you get through the left arm during the down swing is often mistaken for pp#4 pressure and the "blast-off".

There are several ways to model how the left shoulder really works. A simple torque around the swing center would be be sufficient. But none of the lever forms is fit to describe how the left shoulder actually creates swing speed. The lever forms only covers the PP#4 part of it. Same thing can be said about driveloading and the right shoulder. The part of it that is done between the ground and the right shoulder may very well be analysed in a similar manner.

I haven't been able to find where Homer describes when Accumulator #4 is inline. I don't think he did. But it seems to be assumed that Accumulator #4 is inline when the left arm has left pp#4. But in reality, Accumulator #4 is in a very good out-of line condition when the arm is at 90 degrees to the shoulders (as seen from above). That's the alignment where the pull from the left arm has the largest distance away from the swing center. Accumulator #4 isn't inline before the left arm is raised to shoulder high and pointing down the shoulder line. Something that will not happen until the finish.

TGM:


First part of this is correct. If you don't turn the shoulders, the swing center will move towards the left shoulder and you will only get centripetal force through the left arm. Yet we see a lot of hitting descriptions as if the shoulders doesn't turn.

Second part is incorrect for a stroke with a straight left arm and a left hand holding on to the club. Only with one hand can you use Accumulator #1 alone. If the rope is thight you're using Accumulator #4 also.



Admittedly, there are several paragraphs in TGM that more than hints that there's more going on with the pivot than a little pp#4 thrust. But those parts are only prosaic and lacks foundation in the theoretical framework that Homer prepared for TGM. Thus you get a lot of instances where TGM is lacking and not lacking at the same time, depending on which paragraph you read. But as a framework this is a serious omission and it does impact how we understand TGM.

TGM doesn't have the mechanisms for power transmission from the pivot to the accumulators properly outlined. No wonder then, that TGM is regarded among a few critics as underplaying the significance of the pivot drive. This is especially the case in the hitting stroke. But also in the swing, where you may get the impression that all efforts are over when the right arm has left pp#4.

Much of what I've said here may be somehow off topic, but it makes all the difference in the world towards understanding the similarities between hitting and swinging and the common requirements for producing a stroke as far as physics and geometry is conserned. And also towards understanding how some of the big horsepower is generated and leveraged in the golf stroke. I tried to start a thread a few months ago in the lab that addressed Accumulator #4 but the response was zero. There are geometrical drawing and force diagrams there that outlines how Accumulator #4 works and hopefully they do not require an MSc degree to understand. Here: http://www.lynnblakegolf.com/forum/thread7114.html

Although I don't understand much of this - it would a shame to let it die without any more comments. Shouldn't some of the big guns respond?