Over the next few months, as we lead up to a new golf season for everyone, the topic of my newsletter will be how new Driver Technology provides greater distance to us all.

If there is any topic you would liked explained and presented in my upcoming newsletters, just email me. I'll attempt to cover your topic in a future newsletter.

If you'd like one on one explanations about the topic, sign up for the PGI Member Select Club and I'll answer all your questions. Now on to this week's topic.

     Clubhead weight (or more correctly, clubhead mass) is one of the key contributors to distance off the tee. The greater the mass of the clubhead and the great its speed, the farther the ball will go. Unfortunately, the greater the clubhead's mass, the slower will be its speed at impact. One can't swing a more massive (heavier) clubhead as fast.

     The physics of the interaction between club and ball is quite well understood. At play are the laws of momentum and energy. A given player (let's say you) is capable of swinging a club with a some maximum speed. The more massive the club, tthe slower will be this maximum speed. The speed of the ball is a result of the mass of the clubhead and its speed. So, as the mass increases, so will the resulting ball speed. But, since the clubhead is more massive, its maximum speed is less. There is actually an optimum mass for each golfer that produces the greatest ball speed. For most golfers, that mass is about 200 grams. A physics equation that determines the resulting ball speed is:

V = U*(1+e)/(1+m/M)

where U = clubhead speed, m = mass of ball, M = mass of clubhead

e is called the coefficient of restitution which is a measure of the efficiency of the kinetic energy transfer between club and ball. e has a value between 0 and 1. A collision with e=0 would be like a club hitting a putty ball, with the ball sticking to the club (maximum loss in kinetic energy). A collision with e=1 is called a perfectly elastic collision (no loss in kinetic energy). There would be no heat or sound produced at all, so of course is completely hypothetical.

    In the past 10 to 15 years, club and ball manufacturers have made great leaps in increasing the e of the collision due mainly to the hollow, metal faced drivers whose faces can "spring back" upon collision. So much so that the USGA has put in place a legal maximum which is about 0.83. Club testers have found that e decreases with increased clubhead speed. Tiger Woods' drives, therefore, are not as efficient as yours or mine. He makes up for this by having significantly more clubhead speed.

     Let's take the example that your clubhead speed is 110 mph (48.9 m/s), which means you are a relatively long hitter. A typical value of e (exact value depends on the club) would be about 0.83. According to the equation above, the resulting ball speed (assuming a solid hit) would be:

V = 110*(1+0.83)/(1+46/190) = 110*1.47 = 162 mph

assuming a 190 g clubhead hitting a 46 gram ball. The ball speed ends up being
1.47 times the original clubhead speed. Let's assume the amount of energy you can deliver to the club is same no matter what the mass of the club. Light clubs would have high speed, heavy clubs would have low speed, but the kinetic energy of the club would be the same in each case. The equation for kinetic energy is:

KE = 0.5*m*v*v = 0.5*0.19*48.9*48.9 = 227 Joules

where mass must be in kg and speed in m/s. In the table below are the resulting values for clubhead speed, e, and ball speed using different mass clubs, assuming constant kinetic energy of 227 Joules.

Note that it appears that the less the mass of the club, the greater the ball speed. The assumption made, however, is that the kinetic energy of the club is the same in all cases. Realistically, a golfer cannot obtain such speeds with light clubs. As determined by tests published in "Search for the Perfect Swing," the speeds of the clubs and the resulting ball speeds would be:

Ball speed actually peaks when using a clubhead with mass 0.210 kg or 210 g. This result is for a kinetic energy of 227 Joules. Different players with different swings and strengths would all have a slightly different optimum clubhead mass. For most, it is around 200 g, thus most drivers have clubhead masses that correspond to this.

     For most, experimenting to find the optimum mass would not yield very many extra yards. And, it's not as simple as adding a little lead tape to the clubhead because that would also change the center of mass of the club and the relative stiffness of the shaft, both also determiners of distance (future topics). If you happen to be quite strong and fit, you might be able to swing more massive clubheads with greater energy, thus resulting in more distance. One can only experiment.

     If you are serious about trying to optimize your distance through clubhead mass, go to a facility that has a club/ball monitor (one that measures clubhead speed, ball speed, trajectory, spin, etc). You can experiment with different clubhead masses and shafts to find the one that produces optimum ball speed, trajectory and spin (the effects of which will be discussed in a future newsletter).

A list of resources that have been used to produce this newsletter can be found on my website here.

The next newsletter's topic will be the driver shaft. What is its optimum mass and stiffness for greatest distance?

The focus of my site is utilize science and math to lower your score. New technology is one way to achieve this, but to be honest, the technology is one small piece of the puzzle.

To actually improve significantly, we all need to:

1. Improve our swings. Hit Down Dammit!

2. Improve our physical fitness and strength.
The Golf Trainer Power Performance Program™

3. Improve our mental games. Golf Mind Software

Click on the links above to take a look at ways that I personally use myself and recommend you try as well.

One last mention of my latest study on amateur golf scores and handicaps.