Some believe that maximum club head speed is obtained when the golf swing is executed with a very stable swing center. This has been put forward by scientists such as Cochran et al in “Search For The Perfect Swing” and also by several golf instructors like for instance Redman, Knudson or Wilson. They usually refer to this approach as being a centrifugal-force swing.
However is this notion about the golf swing really true?
Prof Jorgensen, using his simple two pendulum model, introduced the horizontal motion of the swing center to simulate the shift of the swing center of a real golfer and concluded that this resulted in an increase in clubhead spead.
Howver, what about a vertical motion? Could one expect also some beneficial efects for a vertical motion of the swing center when correctly introduced in the golf swing.
Lets look how a child handles a playground swing and how he instinctively knows perfectly how to set the swing into motion and keep it going with very little effort. He does it by raising and lowering his center of mass - com - in perfect synchronization with the motion of the swing. We all have done it when young but probably never made the connection with a golf swing.
The child's effort can be thought off equivalently as a mass at the end of a rod of which the radius is varying correspondingly as done by the child's com when swinging the swing. This action can be modeled conveniently with a pendulum having a mass M and a radius r, where Δr represent a small change in r. The corresponding DV equation is show below -
φ(t) represents the angle measured relative to the vertical, g = gravity, M = mass, r = radius of pendulum and Δr a small change in r. The idea is now to show that a specific radial motion at the center of this arrangement can pump kinetic energy into the swing and hence augment the linear velocity of the mass M.
Fig1. Ilustrates how a small change in the swing radius of only 10%, introduced at two specific times as shown by the blue curve in Fig1, increases the swing arc and hence also the kinetic energy. The radius r is decreased with the amount Δr at the bottom of the arc at maximum speed and restored to its normal value at zero speed.
When the mass M is moved through the distance Δr towards the center, positive work is expended on it by the centripetal force acting on the mass M. And since any positive work expended on a mass increases its kinetic energy, we are 'pumping' kinetic energy into the swing and increasing the linear speed of the mass M in the playground swing.
It is also interesting to note that the small radial pumping motion results in a speed increase for the mass M perpendicular to the direction of the applied disturbance.
We seem to know this mechanism instinctively. When really going for it we try literaly to jump out of our shoes. Have a look at look at Laura Davies, she really gets on her toes.
mandrin