Jeff Brunski’s scientific contributions

The forgiveness of golf putters is traditionally achieved through weight distribution. Putters are often designed with large footprints, which help to increase the moment of inertia (MOI), but consequently move the center of gravity (CG) farther behind the face. The use of higher MOI putters will result in less ball speed loss on impacts away from the sweet spot (i.e., more forgiveness). It has been shown that certain face properties, such as milling patterns, grooves, or soft inserts, can be leveraged to have a similar effect. This paper explores the relationships between impact location, MOI, CG depth, discretionary mass placement, and launch direction for these putters. A novel design strategy is proposed. Minimizing CG depth for putters with ball speed normalizing face properties, even at the expense of MOI, can result in more consistent launch direction and distance control for the average player.

Golf clubs are often evaluated by many methods to determine their performance. For drivers in particular, the primary performance indicator is ball speed, which is directly related to distance. Golf club manufacturers make many claims about how extra ball speed is achieved. For example, these may include: design features, face thickness, materials, center of gravity location, and moments of inertia. This paper proposes a new method to evaluate the performance of golf clubs from a single metric. With the benefits of modern launch monitors, accurate impact location data can be captured very efficiently. Using this, along with COR (coefficient of restitution) map testing, the Expected Value of COR can be calculated for a golfer or population of golfers. The “Expected COR” metric takes into account many engineering properties of a particular club that affect ball speed, along with the impact variation of the golfer, to give a single score for rating.

The forgiveness of golf putters is traditionally achieved through weight distribution. Higher MOI (moment of inertia) putters will show less ball speed loss on impacts away from the sweet spot. A very large MOI putter, however, may not be desired by a golfer due to weight or appearance. The relationship between ball speed and impact location is affected by the mass properties of the putter (i.e., CG location, mass, moments of inertia, products of inertia) and the putter face. It has been shown that certain face properties, such as milling patterns, grooves, or soft inserts, can have small effects on ball speed. This paper proposes a method to normalize the ball speed on laterally miss-hit putter impacts using a “model-specific” milling pattern of variable depth and pitch, resulting in the largest possible region of the face providing consistent putt distances, thus improving performance given the average player’s impact pattern.