Science of the Swing Essay"Gamma"
In the last few years, the Greek letters Alpha, Beta and Gamma have become what I call “golf instruction popular.” If you’ve read my latest books or have been on social media, I’m sure you’ve seen plenty of discussions about them. For a quick refresher, the A-B-G terms are used to describe the three dimensions of movement of the golf club throughout the swing.
Whenever the movement of a “rigid body”—a thing, like a golf club or an airplane or a pen—is being described in three dimensions, it will have six degrees of freedom that it will have the ability to be driven in. We use the word “drivers” to describe the external forces and torques that move the club during the swing. These drivers are independent of each other, but they share terms within the equations of motion, so movement in three dimensions is a mashup of all the drivers and their directions accumulated together.
These six drivers of the swing are applied by the golfer at the handle of the club. In our studies, we focus on the hub, which is the point at the center of a player’s grip. The hub is where everything you’ve done with your body and your swing gets transferred out to the club.
The dynamics of club movement are derived from the behavior of the club’s mass center. The mass center can be accelerated in three different linear directions and three different angular directions—which make up the six degrees of freedom. When you’re moving the club linearly, that movement can be transformed into three components at the club’s mass center: Alpha Force, Beta Force and Gamma Force.
When you’re driving the club with torque, you can break down the actions into three components: Alpha Torque, Beta Torque, and Gamma Torque. These are angular efforts of the golfer to twist on the club and produce angular work and power.
I want offer some practical applications for this information, and supplement what you’ve learned in The Science of the Golf Swing. I’ll cover each of the six degrees of freedom in its own essay. Let’s start with one of the easiest to visualize and learn about—Gamma Torque and Gamma Rotation.
When you think about how the club moves during the swing, the fact that you’re holding one end of it might make you think that it isn’t rotating. But it is actually experiencing quite a lot of turning and spinning as you swing it—so much so that if you let go of it during the downswing it will fly like a helicopter in the air for quite some distance.
Gamma is the rotation of the club about itself during the swing. Essentially, it is how much the golfer turns the grip and shaft around throughout the travel of the club. This is a very distinct and isolated action which needs to be understood.
Let’s look at Gamma in common everyday examples.
Barbecue season is here, so let’s use something you’d put on the grill as an example.
As ridiculous as it might seem, I made an image of a shishkebab skewered onto the shaft of a golf club. Gamma rotation, produced primarily by gamma torque, is literally the same action that would be applied to twist a kebab over the barbecue to cook it evenly all the way around.
Staying on the subject of food, another way to think of Gamma rotation is the experience of a chicken twisting around itself in a rotisserie oven.
A rotisserie oven has a steel rod that goes through the center of the chicken, which rotates it about itself. I have been using this example for many years now when describing Gamma and it is always a fan favorite. (If you’re a vegetarian, don’t worry...the example works the same way if you’re visualizing vegetables on that shishkebab)
Now that we have a better understanding of what Gamma is, how do we apply it in a golf swing? Let’s break it down into two categories: Rotation and Torque.
When we analyze gamma rotation, we are looking purely at the kinematic of how much the club turns about itself. In the rotisserie chicken example, it would be how much the chicken actually rotated around the steel rod in the oven. This gamma rotation metric is called the Gamma Swing Angle as defined in Chapter 1 of the Science of the Golf Swing. In a nutshell, the Gamma rotation is the angular displacement of the golf club around itself.
What are good rotation guidelines? With irons, 90 to 100 degrees of Gamma Rotation is common at the top of the backswing, while a driver will have 70 to 90 degrees of Gamma Rotation.
Since we use Impact as the general position to derive the gamma angular change, the address position will most likely have a number above or below zero unless the gamma angle is exactly as it would be at impact. A typical downswing is roughly .25 seconds, so in that time the player will need to apply Gamma torque to replace that Gamma angle back to zero for impact.
Gamma Torque is the pure twisting action that the golfer applies to the grip to make that club turn about itself just like the rotisserie chicken. When we move into the world of kinetics, we must identify the resistance that the golfer will have to overcome to get a response from the torque. For Gamma torque, the resistance is the moment of inertia in the gamma plane of motion. The distance from the mass center to the shaft is very small, so it depends on how much mass the clubhead has and how it is distributed. With the short distance, the resistance to gamma torque is very small. It requires very little torque from the player to rotate the club gamma wise.
As you take the time to understand these components one by one and the way they work together, you’ll start to see how you can make significant improvements to your swing with seemingly minor changes in how you move at the hub. This is an exciting time, because you’re on the road to separating what matters from what doesn’t.
Let’s stay on the journey together. Enjoy this 12 minute video on Gamma rotation and torque….