Generally Eclectic

Ch 12: Modeling the Swing

Chapter Twelve: Guide to the Golf Swing

I feel pain that someone is going to have to read this stuff - Wife

In Chapter 10, we presented the basic rotation equation. We noted that the equation depends on:

Chapter 10 also looked at the duration of movements in the downswing, and the factor converting the average downswing speed of the club from the movements to speed at impact.

In Chapter 11, we looked at each movement in the golf swing in terms of rotation centre, distance of the rotation centre to the ball, the angle between the line from the rotation centre to the ball and the axis of rotation.

In this chapter, we build on the foregoing to develop a "big picture" model of the golf swing. The model is necessary because the individual movements are to some extent interdependent. Changes in the way some of the movements are performed affect the performance of other movements.

Our model has three components:

  1. Parameters. These are the inputs to the model, and are based on the characteristics of the individual golfer, including physical dimensions, flexibility, equipment, swing posture, and duration of movements in the swing. For purposes of our discussion, default values based on the author are provided. Changes in some default values will be explored to determine their impact. The model is designed so that you can insert your own values into a spreadsheet to get a perspective of your swing.
  2. Calculated values. These are values determined from parameters and used as inputs into the Club Speed Calculator Table.
  3. Club Speed Calculator Table. The table consists of the application of the basic rotation equation, lateral movement and spinal tilt, for each movement in the golf swing.

The parameters used in the model are listed below, with the default values on which the conclusions of the model are based.

  1. How many frames per second in your video camera? Default=27
  2. How many frames to uncock the wrists in the downswing? Default=4
  3. How many frames to roll your forearms and rotate your upper arm in the shoulder socket? Default=4
  4. How many frames to move the upper arm in the shoulder socket? Default=6
  5. How many frames to move the shoulder sockets around the spine? Default=6
  6. How many frames to untwist the spine? Default=11
  7. How many frames to rotate the hips? Default=11
  8. Acceleration Scaling Up Factor. Default=1
  9. What is the length of your club (inches)? Default=45.5
  10. What is the length of your arms in inches? Default=24.0
  11. How many inches do you move your shoulder sockets around the spine in the downswing? Default=3.0
  12. What is the distance in inches between your two shoulder sockets? Default=13.0
  13. How many inches do your hips move laterally in the Push and Clear? Default=3.0
  14. What is the distance in inches between your hip joints? Default=7.0
  15. How many degrees do you tilt your spine/upper body forward at the hips relative to the vertical? Default=30
  16. How many inches from your shoulders to the base of the spine? Default=17.5
  17. How many inches from the base of your spine to the centre between the two hip joints? Default=7.5
  18. What is the angle in degrees between the club shaft and the arm? Default=130
  19. What is the distance from the ground to the hip joint (inches) when standing erect? Default=32.0
  20. How much distance should be subtracted to allow for knee bend, use of tee, etc.? Default=2.5
  21. Downswing Rotation of Wrists (degrees) Default=45
  22. Downswing Rotation of Forearms (degrees) Default=45
  23. Downswing Rotation of Upper Arms in Shoulder Socket (degrees) Default=45
  24. Downswing Rotation of Upper Arms Around Shoulder Socket - Basic (degrees) Default=45
  25. Downswing Rotation of Spine - Basic - Top to Start (degrees) Default=60
  26. Downswing Rotation of Hips - Pure Rotation - Basic - Top to Start (degrees) Default=45
  27. Downswing Rotation of Spine - Additional - Start to Impact (degrees) Default=5
  28. Downswing Rotation of Hips - Pure Rotation - Additional - Start to Impact (degrees) Default=10

Key observations about the parameters include:

From these parameters, a number of additional values needed to calculate club speed can be calculated as follows:

  1. How many inches does the centre of the spine move away from the target as a result of the forward lean in Pure Rotation? Answer: 8.8 inches
  2. What is the angle in degrees between the line from the shoulder socket to the ball and the ground? Answer: 53.5 degrees
  3. How many inches does the lead hip move forward in the back swing in Pure Rotation? Answer: 2.7 inches
  4. How many inches does the centre of the spine move away from the target as a result of the forward lean in Push and Clear? Answer: 4.7 inches
  5. What is the distance (inches) from the ball to the shoulder centre? Answer: 63.64 inches
  6. Downswing Rotation of Shoulder Socket Around Spine - Basic. Answer: 26.7 degrees
  7. Downswing Rotation by Hips -Push and Clear - Basic (degrees). Answer: 22.1 degrees

The following summarizes the combined effect of rotation, lateral movement and spinal tilt for each movement in the golf swing.

Club Speed Calculator

Click here to view the speed calculator: Table;Table With Fixed Header; PDF

Multiple RotationCan the results for the individual movements be added to create a total? To address this, note the rotation circles resulting from the movements in the golf swing. While the circles show some variability, note that what really matters is the instant of impact. All of the rotation circles pass through the ball, and the point when they pass through the ball is the instant of impact. Proper execution of the various movements should ensure maximum consistency among the movements in terms of propelling the ball straight down the fairway (rather than left or right) at the instant of impact. As such, while adding up the club head speeds from the individual movements may overstate the actual club head speed, the overstatement is likely to be minimal. On this basis, we shall continue to use the practice of adding up the speeds of the individuals movements to get the overall club head speed.

The Bottom Line