Trajectory Model
For interested eSwing visitors and customers, we’ve provided a link to download an Excel spreadsheet to your computer that’s the engine for eSwing’s trajectory calculations. The worksheet and most of its formulae are protected; you will not be able to see the math and physics that are used to calculate how the golf ball flies. But you will be able to play “what if” with all of the data inputs that go into e*Swing’s trajectory calculations.
How does it work?
The primary inputs to the trajectory model are Initial Ball Velocity, Launch Angle and SpinRate, which are data captured by the Launch Monitor. If eSwing is used without a Launch Monitor, these data are assumed based on a mathematical relationship between clubhead velocity and ball velocity (which includes a factor for the club’s coefficient of restitution) as well as from the player’s selected club, which provides a nominal ball spin rate and ball launch angle for initial trajectory calculations. The combination of Swing Path Angle and Face Angle determines whether the ball will fly straight or will curve left or right of the Target Line.
Download instructions:
You must have Microsoft Excel available on your computer to open this spreadsheet. If you’re using a MAC computer, you may have problems opening and using the spreadsheet. After you have submitted your name and email address you will receive an email with eSwing’s Trajectory Model attached as an Excel (.XLS) spreadsheet Save the file to your desktop, then double click on the file icon to open the file in Excel. As the file opens, you may be asked to enable or disable macros that are associated with this spreadsheet: choose ENABLE.
Swing Data Inputs:
Notice that the velocity input to the trajectory model is INITIAL BALL VELOCITY, not clubhead velocity. As a rule of thumb, in an ideal collision (i.e., a ball hit “on the screws”) between the club and the ball, initial ball velocity is about 1.5 times greater than club speed. This is sometimes referred to as “Smash Factor”, which is simply a ratio of Ball Speed to Club Speed x 100. In otherwords, ball velocity of 150 mph equals clubspeed of 100 mph.
Have fun!