Driver Design ProcessAs told by University of Vermont Engineering students

WWW.Bombtechgolf.com

We began by creating a problem statement to give our team a focused goal of what a successful design consisted of for this project and to provide guidance.

The problem statement: BombTech Golf wants a radically new golf driver head to be sold to the public. The driver head must adhere to USGA standards and must not infringe on any existing patents. It should have a loft of 10.5 degrees, be compatible with common shaft sizes and should be designed with the average golfers’ ability in mind. Wind-tunnel testing and CFD modeling should prove that this new head is aerodynamic while offering a large sweet spot. The driver head design will be manufactured out of a Ti-1188 titanium. Samples will be tested to provide physical data as well as user tested and graded to insure that a high quality club has been created.

Generating Ideas

To gain some general ideas and a starting point we researched patents and prior art for “aerodynamic” woods that had already been designed. This led us to club heads with dimples, channels, and grooves. We realized that a club head with a feature that reduced drag such as a cavity, such as these patents, would be more innovative and visually appealing than simply creating the most sleek club head possible.

We researched cars, boats, and trucks to see how they tried be more aerodynamic. We found our answer with trucks. A truck, like a golf club, has a large front surface that increases drag and cannot be streamlined like a small sports car. Everyone has heard the myth that you get better gas mileage with your tailgate up. This has been proven by different entities, most popularly Mythbusters. The tailgate creates a pocket of air to form in the bed of the truck which lets the oncoming air to travel over it instead of diving into the bed of the truck creating drag. We believed we could do something similar with a golf club head by making cavities in the sole of the club.

It was decided that two cavities was best to keep the center of mass directly behind the center of the club face. We created a 3-D model of a club head in SolidWorks, a Computer Aided Drafting (CAD) program. In this program we were able to use a Computational Fluid Dynamics (CFD) simulation to test different shaped cavities. We performed some simplified calculations to get a rough number for what our drag force should equal to prove the CFD models were accurate. We then began running dozens of tests to find which shape, depth, and angles of the triangles created the least amount of drag.

The Numbers

In order to make certain that our CDF simulations were accurate we analyzed the drag force on the club using the following equation:

The density of air is known. The drag coefficient is based on a geometrical assumption and therefore also a known constant of 1.17. Since the density of air and the drag coefficient are intrinsically predetermined, we wanted to be very precise with the projected area. Using the maximum allowable face dimensions, we arrived at an area of 0.0070939047m2. It is important to have this many decimal places, as it is a multiplier of the entire equation. We also decided on a club velocity of an average amateur golfer (85mph). This is an arbitrary number as long as we use this value for all testing, both physical and computational.

This value served two purposes. It gave us a reference number allowing us to be certain that our simulations were accurate. 7.21 Newtons also served as a target maximum. Since the projected area was exaggerated our drag values at 85mph should fall below this mark. We were pleased when our simulations of our most aerodynamic design (now the GRENADE) was returning drag values of just above 5 N, well below our calculated maximum of 7.21 N