Momentum is mass times velocity. If a club which is heavier is swung with the same speed it has more momentum, does this extra momentum mean more distance?
The test we did was to hit balls with 4 different head weights. We used a 10.5 degree PXG 0811 X driver, which has 9 weight slots and can easily take 4 gram weights in each slot. This means we can alter the head weight by 36 grams.
Initially 6 shots were hit with the standard head weight to get a baseline distance. Then 3 shots were hit with the light head (all weights taken out), then 3 with the medium weight (4 4 gram weights added) and then 3 with the heavy head (9 4 gram weights added). This process was replicated until 12 shots were hit with each weight.
The shaft that was used was an Accra TZ5 M4 with a playing length of 45.75 inches. Titleist Pro V1 golf balls were used for all shots and the weather was perfect for testing with temperatures around 17 degrees and little or no wind.
Here are the club specifications
The weight of the shaft, grip and adapter was 130.8 grams. And you can see as the club head gets heavier the effective flex of the shaft gets softer.
The results were recorded on a Trackman 111 launch monitor. The results we are interested in are club head speed, ball speed, carry distance, total distance and dispersion. We also noted spin rate and face to path.
To calculate momentum we are going to simplify it, and just going to use to head weight as our mass as opposed to including some of the shaft weight too.
The standard weight driver gives the best results, most distance and best accuracy, the lighter head does give more club head speed and ball speed but the worst accuracy. As the head weight increases we do see a decrease in club head speed but a slightly better conversion of ball speed to club head speed. The smash factor (ball speed/club head speed) is 1.445 with the lightest, 1.46 with the medium, 1.45 with the standard and 1.48 with the heavy.
We can see from the simplified momentum calculation that momentum is increasing as the head weight is increasing, the slight loss of speed is made up by the increase in the weight. There is over a 20% difference in the head weight of the lightest to heaviest, with just a drop of around 4% in speed. The simplified momentum change is around an increase of 13% from light to heavy
We see a tendency of the lighter head to go left and the heavier head to go right. It could be the heavier head is slightly more difficult to release and the lighter head easier to release. The spin also tends to increase as the head gets heavier. It would make sense that the heavier head causes more flex in the shaft and adds to the spin with greater spin loft.
The increase in spin gives a less then optimal ball flight and a decrease in distance from the ball speed.
The indications are that an increase in club head weight can lead to more ball speed. In this test the smash factor or ball speed conversion went up with the heavier head. The overall distance was down due to two factors, the slight decrease in club head speed due to extra weight but more significantly the heavier head caused the shaft to flex more, adding dynamic loft at impact, increasing spin loft and spin as a result.
This could be remedied by stiffening the tip of the shaft bringing the dynamic loft and spin loft back down getting the spin rate more optimal and more distance.
The high swing weight of the heavier club might also make it more difficult to control, just as the light swing weight in the light club also made it hard to control. Decreasing the length of shaft by 2 inches would bring down the swing weight by 12 points making it a more balanced and manageable club.
Possibly a short heavy headed club could give the benefits of increased momentum. Short heavy headed clubs are what persimmon drivers used to be! We'll have to build a large titanium driver with the same specifications as the old persimmon drivers to see what it might do!
Comments and questions are always appreciated
The test we did was to hit balls with 4 different head weights. We used a 10.5 degree PXG 0811 X driver, which has 9 weight slots and can easily take 4 gram weights in each slot. This means we can alter the head weight by 36 grams.
Initially 6 shots were hit with the standard head weight to get a baseline distance. Then 3 shots were hit with the light head (all weights taken out), then 3 with the medium weight (4 4 gram weights added) and then 3 with the heavy head (9 4 gram weights added). This process was replicated until 12 shots were hit with each weight.
The shaft that was used was an Accra TZ5 M4 with a playing length of 45.75 inches. Titleist Pro V1 golf balls were used for all shots and the weather was perfect for testing with temperatures around 17 degrees and little or no wind.
Here are the club specifications
|
Club Head
|
Club Head Weight
|
Total Weight
|
Swing Weight
|
Shaft Flex /cpm
|
|
Standard
|
193.4
|
324.2
|
D6
|
259
|
|
Light
|
181.2
|
312
|
C8
|
266
|
|
Medium
|
197.7
|
328.5
|
D8
|
256
|
|
Heavy
|
218.3
|
349.1
|
F1
|
244
|
The weight of the shaft, grip and adapter was 130.8 grams. And you can see as the club head gets heavier the effective flex of the shaft gets softer.
The results were recorded on a Trackman 111 launch monitor. The results we are interested in are club head speed, ball speed, carry distance, total distance and dispersion. We also noted spin rate and face to path.
Results
|
Club Head
|
Club Speed MPH
|
Ball Speed MPH
|
Carry Yards
|
Total Distance Yards
|
Dispersion Feet
|
Spin Rate
|
Face to Path
|
|
Standard
|
103.1
|
149.9
|
239.5
|
264.6
|
21.65
|
2292
|
-0.3
|
|
Light
|
104.4
|
150.9
|
232.6
|
260.6
|
52.19
|
2402
|
-2.0
|
|
Medium
|
102.9
|
150.4
|
237.6
|
259.5
|
51.03
|
2712
|
-0.6
|
|
Heavy
|
100.4
|
149.0
|
236.2
|
256.8
|
37.89
|
3013
|
0.2
|
To calculate momentum we are going to simplify it, and just going to use to head weight as our mass as opposed to including some of the shaft weight too.
|
Club Head
|
Club Head Weight/kg
|
Club Head Speed m/s
|
Momentum P=M x V
|
|
Standard
|
.1934
|
46.089
|
8.91
|
|
Light
|
.1812
|
46.671
|
8.46
|
|
Medium
|
.1977
|
46
|
9.09
|
|
Heavy
|
.2183
|
44.883
|
9.80
|
Discussion of the Results
The standard weight driver gives the best results, most distance and best accuracy, the lighter head does give more club head speed and ball speed but the worst accuracy. As the head weight increases we do see a decrease in club head speed but a slightly better conversion of ball speed to club head speed. The smash factor (ball speed/club head speed) is 1.445 with the lightest, 1.46 with the medium, 1.45 with the standard and 1.48 with the heavy.
We can see from the simplified momentum calculation that momentum is increasing as the head weight is increasing, the slight loss of speed is made up by the increase in the weight. There is over a 20% difference in the head weight of the lightest to heaviest, with just a drop of around 4% in speed. The simplified momentum change is around an increase of 13% from light to heavy
We see a tendency of the lighter head to go left and the heavier head to go right. It could be the heavier head is slightly more difficult to release and the lighter head easier to release. The spin also tends to increase as the head gets heavier. It would make sense that the heavier head causes more flex in the shaft and adds to the spin with greater spin loft.
The increase in spin gives a less then optimal ball flight and a decrease in distance from the ball speed.
Conclusion
The indications are that an increase in club head weight can lead to more ball speed. In this test the smash factor or ball speed conversion went up with the heavier head. The overall distance was down due to two factors, the slight decrease in club head speed due to extra weight but more significantly the heavier head caused the shaft to flex more, adding dynamic loft at impact, increasing spin loft and spin as a result.
This could be remedied by stiffening the tip of the shaft bringing the dynamic loft and spin loft back down getting the spin rate more optimal and more distance.
The high swing weight of the heavier club might also make it more difficult to control, just as the light swing weight in the light club also made it hard to control. Decreasing the length of shaft by 2 inches would bring down the swing weight by 12 points making it a more balanced and manageable club.
Possibly a short heavy headed club could give the benefits of increased momentum. Short heavy headed clubs are what persimmon drivers used to be! We'll have to build a large titanium driver with the same specifications as the old persimmon drivers to see what it might do!
Comments and questions are always appreciated
