[Joe Hancock]

There shouldn't be much if indeed any difference in playing a 100% ball on a 100% length course to playing a say 90% ball on an 90% length course.
Same number of shots .... but on a smaller area of land.
Might be quite nice.
atb

Also, can you just imagine being close enough to those in harms way that they could actually hear someone yell fore……maybe Nicklaus and his Cayman concept was way ahead of his time!

[Ben Hollerbach]

A fractional increase in ball spin would do bupkis. I say this because even a 100% increase (doubling) in ball spin doesn't do as much as people seem to think. Plug in the numbers into a launch optimizer, you'll see. I think I posted pictures earlier up-thread.

People act like the Tour Balata spun like crazy off the driver. It didn't. And even if you could make a Pro V1x spin 500 RPM more, it'd result in a pretty small change in distance/curve, and also be worked around pretty quickly by the tour guys (reps, players, fitters, engineers).

I'll quote a friend who made these:

The main issue with what Phil is trying to argue here is that spin rate has very little to do with how much a ball will curve - that's governed primarily by the spin axis. More or less spin with the same spin axis will have very little effect on the measured curvature of a golf ball, because most reasonable spin axis values (ball not dramatically hooking or slicing) are 10% or less.

A modern high MOI golf ball, in relation to comparable balls from yesterday, does not just have a higher resistance to backspin. The modern ball is more resistant to all rotational forces applied to it.

In the simplest of terms, the force of the golf swing imparts two different forces on the ball, linear momentum and angular momentum. For the confines of this discussion we’ll view linear momentum as the force that propels the golf ball forward and focus much of our interest in angular momentum. Angular momentum is the rotational forces acted upon the golf ball; primarily back spin and yaw spin, with yaw spin being spin generated on a secondary axis different from backspin. Within current golf ball flight dynamics, angular momentum is typically characterized as ball spin and spin axis. Conservation of energy illustrates that as the MOI of a golf ball is decreased, the angular momentum would increase.To put it another way, a reduction of MOI will increase both the ball's spin rate and spin axis.

Presuming a flushly struck shot suggests a ball hit in the middle of the face with a square face angle, the flushed shot will exhibit minimal difference between a low MOI and high MOI golf ball. As the majority of force transfer will occur in the generation of linear momentum and a minimal amount of force transfer will generate angular momentum, in the form of backspin. With the major difference being an increased backspin rate in proportion to the MOI changes between the two balls. As the strike degrades, with the strike point moving further away from the sweet spot and/or the face angle becoming more deflected, the effects of the mishit will become exponentially magnified on the low MOI golf ball.

For decades, the MOI characteristics of the golf ball and increased potential for yaw spin was countered by the bulge and roll built into woods. This shot saving technology would utilize gear effect to counter the potential for yaw spin in a positive way and bring an errant tee shot back into play. A low MOI ball that is struck near the toe of the driver will have to conserve angular momentum, creating an increase in yaw spin, resulting in an increase in spin axis and a ball flight that will allow a ball starting right of the target line to curve back into play. As the MOI of the ball increases, the yaw spin on a toe struck shot must be lower to preserve angular momentum equally, resulting in the ball starting right and staying right during its flight. This is one characteristic that is easy to recognize when playing modern golf balls with vintage persimmons. Today you’re much more likely to hit high blocks and low pulls with persimmon vs. the toe draw and heel cut that was common 30 years ago.

For the average player, the gear effect influence on their shot was a godsend. For the best in the world, bulge & roll  became a tool to use to better control the golf ball. As golf ball manufacturers began building balls with higher MOI, the need for gear effect became minimized and bulge & roll was slowly reduced. Larger flat sections of the driver face replaced the sweeping faces of vintage drivers, allowing for off center hits to still start near the players intended target line. As the ball was more resistant to rotational forces, it would develop a minimal amount of yaw spin, resulting in a more neutral spin axis.

If the MOI of the golf ball was reduced it would have a noticeable, but not overall significant, impact on flushly struck shots. But the impact of the reduced MOI of the ball would be very significant for miss hit shots. The impact of the MOI change would be magnified as the swing speed of the player is increased. As good as the touring professionals may be, even they do not flush every drive. But the modern high MOI golf ball and the design of the modern driver has allowed them to swing all out and have minimal concern for the strike position at impact. If the MOI of the ball is reduced, their demand for increased strike quality must go up. When the impact of a miss hit driver is an increase in angular momentum and a resulting change in spin axis, their control of the ball becomes diminished. The practice of “swinging for the fences”, relying on modern technology to control and manage potential miss hits will become a much riskier strategy. The implication of a bomb and gouge strategy will change as mishits travel further offline. The relationship between distance and control will begin to slide back more towards control.

I’ve spoken almost exclusively about ball hits from the tee box, while this may be the location of the largest impact, a reduction of golf ball MOI will be seen in other parts of play as well. Fliers hit from the rough is not a shot outcome we see all that often today, but with a lower MOI golf ball it becomes a much larger concern. When playing from a less than ideal lie, the uncertainty of ball spin will impact strategy, both in the possibility of catching the ball high on the face producing a flier and catching the ball cleanly producing a high spinning shot.

As the increase in angular momentum is a function of swing speed. Any changes to the MOI of a golf ball would have the smallest impact to the average slow swinging player and the greatest impact to the tour level player. Putting a maximum MOI on the ball that is closer to what was common 30 years ago would initiate a greater control variable to the tour level player. It would not directly reduce possible distance players may hit the ball but it would dramatically increase the need for near perfect strike conditions to control such shots. Player's strategies would begin to reflect their confidence level in their skill to strike the ball squarely, not just their ability to swing as fast as possible.

[Steve Kline]

^^^^^^^^


Yes to this.


Thank you for explaining why I know from experience that the ball curves less today than it used to.

[JESII]

Ben,


Who is more likely to lose control of their ball under the reduced MOI rules you've laid out, the 5,000 Tour level players hitting the ball at 170+ ball speed? Or the 50,000 amateurs that can also generate that type of speed?

[Garland Bayley]

We ran test (one many thing 'unscientific' but perhaps it's instructive) with Lucas Herbert (now a top 100 player) a couple of years ago
There were 4 scenarios - new driver and new balls. New driver and old balls - balata. Old driver (persimmon) with new balls and old driver and old balls.
The spin rates respectively were:
2326 (new and new) Carry 289 yards.
3080 (new and old) 272
2968 (old and new 262
4166 (old and old) 244

It seems to me that the only instructive thing about this unscientific exercise is that it is so uncontrolled that no conclusions can be drawn from it. Or, perhaps the one conclusion is that the new driver was somewhat optimized for the golfer, but the old driver absolutely was not.

What was an 'optimised' driver in 1980?
It was a club you found that looked good, felt good and you trusted. Nothing was 'optimised' by today's standards.
It is a really good driver and exactly the type of club he'd have been using.

Of course nothing was optimized by today's standards.

However, biographies of tour pros i have read indicated they did some driver switching until they found one that appeared to work best for them. An unoptimized optimization.

Perhaps i might have offered a better explanation by suggesting that the swing that worked well for the modern driver appeared to not be the best swing for the old driver. We see in your results that the same ball performed significantly different between the two drivers. Different driver COR shouldn't cause the spin difference should it? Modern technology should result in higher clubhead speed shouldn't it? Higher clubhead speed presumably should result in more spin shouldn't it? But, yet the modern driver produced less spin. Is there anything else of significance that i am overlooking?

If I remember Sam Snead's biography correctly, he hit down on the ball with the driver to reduce spin. I assume your subject made no such effort to modify his modern swing.

[Sean_A]

Ben,


Who is more likely to lose control of their ball under the reduced MOI rules you've laid out, the 5,000 Tour level players hitting the ball at 170+ ball speed? Or the 50,000 amateurs that can also generate that type of speed?

Don't those tour players have to learn how to better control the ball at earlier stages in their life or are they born with that high ball speed and great control? I see good players blow shots miles off line. It happens when swinging hard.

Ciao

[Thomas Dai]

Unable to resist - based on comments about spin on this thread it seems like more Spin Doctors are posting on here than work in politics!
atb

[Mike_Clayton]

We ran test (one many thing 'unscientific' but perhaps it's instructive) with Lucas Herbert (now a top 100 player) a couple of years ago
There were 4 scenarios - new driver and new balls. New driver and old balls - balata. Old driver (persimmon) with new balls and old driver and old balls.
The spin rates respectively were:
2326 (new and new) Carry 289 yards.
3080 (new and old) 272
2968 (old and new 262
4166 (old and old) 244

It seems to me that the only instructive thing about this unscientific exercise is that it is so uncontrolled that no conclusions can be drawn from it. Or, perhaps the one conclusion is that the new driver was somewhat optimized for the golfer, but the old driver absolutely was not.

What was an 'optimised' driver in 1980?
It was a club you found that looked good, felt good and you trusted. Nothing was 'optimised' by today's standards.
It is a really good driver and exactly the type of club he'd have been using.

Of course nothing was optimized by today's standards.

However, biographies of tour pros i have read indicated they did some driver switching until they found one that appeared to work best for them. An unoptimized optimization.

Perhaps i might have offered a better explanation by suggesting that the swing that worked well for the modern driver appeared to not be the best swing for the old driver. We see in your results that the same ball performed significantly different between the two drivers. Different driver COR shouldn't cause the spin difference should it? Modern technology should result in higher clubhead speed shouldn't it? Higher clubhead speed presumably should result in more spin shouldn't it? But, yet the modern driver produced less spin. Is there anything else of significance that i am overlooking?

If I remember Sam Snead's biography correctly, he hit down on the ball with the driver to reduce spin. I assume your subject made no such effort to modify his modern swing.

Ben sounds like he might have a better explanation than I do for that question.
I've never read anywhere about Snead trying to hit down on the driver to reduce spin.
I've read his answer to the question: 'How do you hit it low?"
"Think low"
I think Snead was a pretty instinctive player with amazing talents.


And no, Lucas was just trying to get it on the face. But I've seen Geoff Ogilvy pick up both a hickory shafted driver and a steel shafted persimmon driver, it 3 or 4 balls with them and flush it for a whole round.

[Ben Hollerbach]

Who is more likely to lose control of their ball under the reduced MOI rules you've laid out, the 5,000 Tour level players hitting the ball at 170+ ball speed? Or the 50,000 amateurs that can also generate that type of speed?

Considering more than 43% of PGA Tour pro's don't average 170 mph ball speed, I'd like to find out where you found 50,000 amateur players that do.


As this is not a new concept in golf, the simple answer to your question is what was the game like for the am player in the past when a lower MOI ball was standard? They couldn't go after the ball as hard. There is not harm in asking players to control their ball from the tee, especially when their fairway is 50% wider than the average PGA Tour fairway.

Perhaps i might have offered a better explanation by suggesting that the swing that worked well for the modern driver appeared to not be the best swing for the old driver. We see in your results that the same ball performed significantly different between the two drivers. Different driver COR shouldn't cause the spin difference should it? Modern technology should result in higher clubhead speed shouldn't it? Higher clubhead speed presumably should result in more spin shouldn't it? But, yet the modern driver produced less spin. Is there anything else of significance that i am overlooking?

If I remember Sam Snead's biography correctly, he hit down on the ball with the driver to reduce spin. I assume your subject made no such effort to modify his modern swing.

For the longest time the average angle of attack with a driver on the PGA Tour was around -1.5, in 2019 that number rose to -1.3 and today is probably closer to -.9. The really long players on tour have an AoA around +2, but the majority of players still use a descending or flat blow. Moving to a lower MOI golf ball, you'd expect to see the AoA numbers go back to around -1.5 as players would return to hitting down on the ball to increase their control.


Sam Snead would not have hit down on the ball to reduce spin, it would have most likely done the opposite and added spin to his drive.

[JESII]

Ben,


Your post on the golf balls MOI seemed to suggest an advantage of rolling back is that players would have to swing more controlled or risk losing control of the ball. Did I misinterpret?  If so, please explain your point in all the good information provided.


The rollback conversations have focused on a couple key areas; sustainability, safety and most often design integrity/challenge.


Decreasing the MOI, as you've described the resulting challenges, would seem to make controlling the ball a challenge at higher swing speeds. Are you challenging my guestimate that there's a 10:1 ratio of amateurs with high swing speeds as top level playing professionals? Also...do you seriously feel the long hitters on Tour today swing all out? They certainly swing fast, but they also look like they have a great deal in reserve.


Your post was very informative, but does not, to me, prescribe a solution.


any guesses how much impact 3 inches additional driver length at about half the weight impact swing speed?

[Garland Bayley]

Ben,

You say AoA has gone from -1.5 to -.9. My understanding is you are referring to angle of attack. My guess is that means the path of the driver when it contacts the ball.  Negative means traveling down.

My novice view is that delofts the club producing less back spin. Why would it increase spin as you say?


The novice view

[Erik J. Barzeski]

Oh, Ben… I'm going to see a movie with my wife, but I'll have a reply for you when I get back. (Free Guy. I hope it's good.)

BTW, just curious… do you know the MOI of a Tour Balata versus a modern-day urethane covered ball? You seem to think it matters quite a bit, after all.

My novice view is that delofts the club producing less back spin. Why would it increase spin as you say?

The AoA is one piece of the spin axis puzzle. The other main one here: delivered (or dynamic) loft. If you hit down more but deliver a lot less loft, you can reduce spin. You can hit up more but deliver more loft and get more spin, too.

There are others, too: more clubhead speed = more spin, all else equal. Contact location matters. The type of ball used matters. Etc.

[Bryan Izatt]

Ben,

You say AoA has gone from -1.5 to -.9. My understanding is you are referring to angle of attack. My guess is that means the path of the driver when it contacts the ball.  Negative means traveling down.

My novice view is that delofts the club producing less back spin. Why would it increase spin as you say?


The novice view

Garland,


Spin is a function of the spin loft which is the difference between the dynamic loft and the angle of attack.  If you google those three terms you'll find lots of articles explaining.  After that you can progress from the "novice view". 


The answer to your question is that having a negative angle of attack (of the centre of gravity of the club) does not necessarily mean the the club face is delofted.  Below is a Trackman graphic that shows an example where the AoA is more negative and the dynamic loft is delofted resulting in the same spin.  Of course, if the AoA is 5* negative but the dynamic loft is higher then the spin loft and spin will be higher.  There are many charts showing empirical data about optimal launch conditions for any given ball speed, launch angle and spin rate. 

[Bryan Izatt]

A fractional increase in ball spin would do bupkis. I say this because even a 100% increase (doubling) in ball spin doesn't do as much as people seem to think. Plug in the numbers into a launch optimizer, you'll see. I think I posted pictures earlier up-thread.

People act like the Tour Balata spun like crazy off the driver. It didn't. And even if you could make a Pro V1x spin 500 RPM more, it'd result in a pretty small change in distance/curve, and also be worked around pretty quickly by the tour guys (reps, players, fitters, engineers).

I'll quote a friend who made these:

The main issue with what Phil is trying to argue here is that spin rate has very little to do with how much a ball will curve - that's governed primarily by the spin axis. More or less spin with the same spin axis will have very little effect on the measured curvature of a golf ball, because most reasonable spin axis values (ball not dramatically hooking or slicing) are 10% or less.

A modern high MOI golf ball, in relation to comparable balls from yesterday, does not just have a higher resistance to backspin. The modern ball is more resistant to all rotational forces applied to it.

Could you point us to some empirical data about the MOI of modern and Balata balls.  There's plenty of discussion on the MOI of clubs but few actual numbers.  There is zero information that I can find on MOI of balls.

In the simplest of terms, the force of the golf swing imparts two different forces on the ball, linear momentum and angular momentum. For the confines of this discussion we’ll view linear momentum as the force that propels the golf ball forward and focus much of our interest in angular momentum. Angular momentum is the rotational forces acted upon the golf ball; primarily back spin and yaw spin, with yaw spin being spin generated on a secondary axis different from backspin. Within current golf ball flight dynamics, angular momentum is typically characterized as ball spin and spin axis. Conservation of energy illustrates that as the MOI of a golf ball is decreased, the angular momentum would increase.To put it another way, a reduction of MOI will increase both the ball's spin rate and spin axis.

Introducing all these scientific physics terms - forces, linear momentum, angular momentum, yaw spin, secondary axis, conservation of energy - serves only to confuse and are not entirely correctly used.  Your last sentence would have sufficed, except that the second part is incorrect - reducing the MOI would not necessarily increase the "spin axis" whatever you intended that to mean.  The initial spin axis tilt is a function of the strike on the ball regardless of MOI.   

Presuming a flushly struck shot suggests a ball hit in the middle of the face with a square face angle, the flushed shot will exhibit minimal difference between a low MOI and high MOI golf ball. As the majority of force transfer will occur in the generation of linear momentum and a minimal amount of force transfer will generate angular momentum, in the form of backspin. With the major difference being an increased backspin rate in proportion to the MOI changes between the two balls. As the strike degrades, with the strike point moving further away from the sweet spot and/or the face angle becoming more deflected, the effects of the mishit will become exponentially magnified on the low MOI golf ball.

A strike of the clubface on the ball will impart velocity, launch angle, spin and a spin tilt axis to the ball.  Where the ball is hit on the face will affect all of those.  The only impact that the ball MOI would have is on the initial spin rate - lower MOI, higher spin rate; high MOI, lower spin rate.  Do you have any empirical evidence of the relationship between ball MOI and spin rate under any condition?  In any event, to say that a mishit would be "exponentially magnified" is silly if you understand what exponential means mathematically. 

For decades, the MOI characteristics of the golf ball and increased potential for yaw spin was countered by the bulge and roll built into woods. This shot saving technology would utilize gear effect to counter the potential for yaw spin in a positive way and bring an errant tee shot back into play. A low MOI ball that is struck near the toe of the driver will have to conserve angular momentum, creating an increase in yaw spin, resulting in an increase in spin axis and a ball flight that will allow a ball starting right of the target line to curve back into play. As the MOI of the ball increases, the yaw spin on a toe struck shot must be lower to preserve angular momentum equally, resulting in the ball starting right and staying right during its flight. This is one characteristic that is easy to recognize when playing modern golf balls with vintage persimmons. Today you’re much more likely to hit high blocks and low pulls with persimmon vs. the toe draw and heel cut that was common 30 years ago.

The gear effect of bulge and roll on woods would be impacted by differences in ball MOI but I see no empirical evidence of how much of a difference there would be.

For the average player, the gear effect influence on their shot was a godsend. For the best in the world, bulge & roll  became a tool to use to better control the golf ball. As golf ball manufacturers began building balls with higher MOI, the need for gear effect became minimized and bulge & roll was slowly reduced. Larger flat sections of the driver face replaced the sweeping faces of vintage drivers, allowing for off center hits to still start near the players intended target line. As the ball was more resistant to rotational forces, it would develop a minimal amount of yaw spin, resulting in a more neutral spin axis.

If the MOI of the golf ball was reduced it would have a noticeable, but not overall significant, impact on flushly struck shots. But the impact of the reduced MOI of the ball would be very significant for miss hit shots. The impact of the MOI change would be magnified as the swing speed of the player is increased. As good as the touring professionals may be, even they do not flush every drive. But the modern high MOI golf ball and the design of the modern driver has allowed them to swing all out and have minimal concern for the strike position at impact. If the MOI of the ball is reduced, their demand for increased strike quality must go up. When the impact of a miss hit driver is an increase in angular momentum and a resulting change in spin axis, their control of the ball becomes diminished. The practice of “swinging for the fences”, relying on modern technology to control and manage potential miss hits will become a much riskier strategy. The implication of a bomb and gouge strategy will change as mishits travel further offline. The relationship between distance and control will begin to slide back more towards control.

This seems like a very convoluted way to get elite players to roll back their distance.
 It would be much easier to just mandate a slightly lighter or a slightly larger ball.  Easy to mandate and easy to enforce.

I’ve spoken almost exclusively about ball hits from the tee box, while this may be the location of the largest impact, a reduction of golf ball MOI will be seen in other parts of play as well. Fliers hit from the rough is not a shot outcome we see all that often today, but with a lower MOI golf ball it becomes a much larger concern. When playing from a less than ideal lie, the uncertainty of ball spin will impact strategy, both in the possibility of catching the ball high on the face producing a flier and catching the ball cleanly producing a high spinning shot.

There are different kinds of fliers depending on the rough and the point of contact and how much grass is between the face and the ball.  Decreasing the MOI might have some impact but who knows how much and whether it would be good or bad on any given shot.

As the increase in angular momentum is a function of swing speed. Any changes to the MOI of a golf ball would have the smallest impact to the average slow swinging player and the greatest impact to the tour level player. Putting a maximum MOI on the ball that is closer to what was common 30 years ago would initiate a greater control variable to the tour level player. It would not directly reduce possible distance players may hit the ball but it would dramatically increase the need for near perfect strike conditions to control such shots. Player's strategies would begin to reflect their confidence level in their skill to strike the ball squarely, not just their ability to swing as fast as possible.

Again, this seems a very complicated way to maybe reduce distance - a bigger or lighter ball would be much easier.

[Erik J. Barzeski]

I'm back. Free Guy was quite good. Not quite what I thought it would be. I recommend it (for seeing once).

What follows is my friend's response. Before I get to that… I'd like to thank Bryan Izatt for his post, which does a pretty good job of highlighting some of the things you… didn't get right.

The simplest is is that you said "To put it another way, a reduction of MOI will increase both the ball's spin rate and spin axis." and that's wrong: it doesn't "increase the spin axis." Or tilt it any more, or whatever. The ball just spins: it doesn't differentiate between the X and Y axis.

The rest of the text in this post is his (except the quoted parts, obviously).

A modern high MOI golf ball, in relation to comparable balls from yesterday, does not just have a higher resistance to backspin. The modern ball is more resistant to all rotational forces applied to it.

This is a good start, you recognize that both backspin and sidespin will be proportionately increased.

Conservation of energy illustrates that as the MOI of a golf ball is decreased, the angular momentum would increase.

This is where you start to go wrong - angular momentum is conserved in all cases. An identical strike will result in a golf ball with identical angular momentum at impact, no matter what kind of golf ball you're using. The total impulse imparted onto the golf ball, which equates to the total change in momentum, is the same because the force applied by the golf club and the elasticity of the golf ball are unchanged.

DeltaP (change in momentum, or impulse) = F (applied force) * T (time). The force from the golf club is the same, because the strikes are identical since we are not testing that variable. The duration of impact is the same, because elasticity of the golf ball is not the variable we are testing. The only variable we are changing here is the moment of inertia of the golf ball, and that does not have any effect on the total momentum (angular or linear) imparted upon the golf ball.

L (angular momentum) = I (moment of inertia) * w (angular velocity). Angular momentum is constant, as described above. Moment of inertia is reduced, which means that the angular velocity must be increased resulting in a higher spinrate at impact.

To put it another way, a reduction of MOI will increase both the ball's spin rate and spin axis.

This is where you go off the deep end, reducing the MOI of a golf ball will have no effect on the spin axis because the increase in both backspin and sidespin are proportionate. Let's go back to fundamental physics here to show exactly why:

A sphere with a uniform relationship between density and radius, which a golf ball is, has the same moment of inertia for all possible axis of rotation. This means that the vertical axis of rotation (sidespin) and the horizontal axis of rotation (backspin) have the same moment of inertia. The total angular momentum is equal to the sum of angular momentum along these two axis

L = I * ⍵

L_Total =  L_Sidespin + L_Backspin

(I_{Golf Ball} * ⍵_Total) = (I_{Golf Ball} * ⍵_Sidespin)+ (I_{Golf Ball} * ⍵_Backspin)

⍵_Total = ⍵_Sidespin + ⍵_Backspin

⍵_Sidespin = Δ L_Sidespin  / I_{Golf Ball}  = (F_Sidespin * T ) / I_{Golf Ball}

⍵Backspin = Δ LBackspin  / IGolf Ball  = (FBackspin * T ) / IGolf Ball

All forces and times are constant - Because we're comparing identical strikes, only changed variable is Moment of Inertia

From here it's easy to see that any change to the golf ball's moment of inertia (IGolf Ball) will have a proportionate effect on both sidespin and backspin. Halving the moment of inertia will double the backspin, and also double the sidespin.

Spin axis = ArcSin( |⍵_Sidespin|  /  |⍵_Backspin| )

Spin axis = ArcSin{ [ (F_Sidespin * T ) / I_{Golf Ball}] / [ (F_Backspin * T ) / I_{Golf Ball}] }

Spin axis = ArcSin{ [ (F_Sidespin * T ) / I_{Golf Ball}] /  [ (F_Backspin * T ) / I_{Golf Ball}] }

Spin axis = ArcSin{ (F_Sidespin * T ) /  (F_Backspin * T ) }

All forces and times are constant - Because we're comparing identical strikes, only changed variable is Moment of Inertia

The spin axis is based off the angular speed of both backspin and sidespin, with (Sidespin/Backspin) equal to the Sine of the spin axis' angle. If you double both the sidespin and the backspin, by halving the moment of inertia, the spin axis will remain unchanged.

As you can clearly see, changing the moment of inertia does not change either the total angular momentum (Force and impact duration are kept constant) nor does it change the spin axis. Literally everything you have written is debunked by the most basic of kinematics taught to freshmen collegiate students and high schoolers around the globe.

For good measure, here are some excellent illustrations from the FlightScope simulator showing exactly how little difference even a monumental increase in spinrate (2500 RPM to 5500 RPM) would have for professional golfers with 180mph ballspeed and a 5 degree spin axis:




Not only are you wrong about what measured values would be different by changing the moment of inertia, you're wrong about what the effects of a monumental difference in spinrate would even look like. You can double the spinrate off the tee and you will barely see any difference in curvature, because magnitude of curvature is primarily dictated by spin axis - not spin rate.

[Ben Hollerbach]

In the early 2000's, right around and shortly after the release of the Pro V1, Titleist filed multiple patents for High MOI golf balls.

In the patent Golf ball having a high moment of inertia, they wrote:

• "When a club head strikes a ball, an unintentional side spin is often imparted to the ball, which sends the ball off its intended course. The side spin reduces the player's control over the ball, as well as the distance the ball will travel. A golf ball that spins less tends not to drift off-line erratically if the shot is not hit squarely off the club face. The low spin ball will not cure the hook or the slice, but will reduce the adverse effects of the side spin."
• "...employ selective variation of the ball's moment of inertia to create a progressive performance ball which exhibits low spin when struck by the driver, and high spin when struck with the wedge."]
• "The present invention is directed to a golf ball with a controlled moment of inertia".

In the patent Golf ball having a high moment of inertia and low driver spin rate, they wrote:

• "In accordance to one aspect of the invention, ball 20 is a high moment of inertia ball comprising a low specific gravity inner core... Ball 20, therefore, advantageously has a high moment of rotational inertia and low initial spin rates to reduce slicing and hooking when hit with a driver club."

The Pro V1, the ball that started the entire distance revolution, was specifically design to be a high MOI ball.  Titleist literally patented that concept in order to allow driver shots to spin less and fly straighter and further.

Everyone who plays golf knows that the Pro V1 was longer and straighter than the Professional and Tour Balata. Probably everyone on this blog saw it and experienced it with their own hands and eyes. Everyone knows that this ball changed everything.  Titleist says, the Pro V1 does what it does because it has a high MOI.

Per Titleist, limit the MOI on a golf ball, and you immediately get shorter drives that drift off line more "erratically".

[A.G._Crockett]

In the early 2000's, right around and shortly after the release of the Pro V1, Titleist filed multiple patents for High MOI golf balls.

In the patient Golf ball having a high moment of inertia, they wrote:

• "When a club head strikes a ball, an unintentional side spin is often imparted to the ball, which sends the ball off its intended course. The side spin reduces the player's control over the ball, as well as the distance the ball will travel. A golf ball that spins less tends not to drift off-line erratically if the shot is not hit squarely off the club face. The low spin ball will not cure the hook or the slice, but will reduce the adverse effects of the side spin."
• "...employ selective variation of the ball's moment of inertia to create a progressive performance ball which exhibits low spin when struck by the driver, and high spin when struck with the wedge."]
• "The present invention is directed to a golf ball with a controlled moment of inertia".

In the patient Golf ball having a high moment of inertia and low driver spin rate, they wrote:

• "In accordance to one aspect of the invention, ball 20 is a high moment of inertia ball comprising a low specific gravity inner core... Ball 20, therefore, advantageously has a high moment of rotational inertia and low initial spin rates to reduce slicing and hooking when hit with a driver club."

The Pro V1, the ball that started the entire distance revolution, was specifically design to be a high MOI ball.  Titleist literally patented that concept in order to allow driver shots to spin less and fly straighter and further.

Everyone who plays golf knows that the Pro V1 was longer and straighter than the Professional and Tour Balata. Probably everyone on this blog saw it and experienced it with their own hands and eyes. Everyone knows that this ball changed everything.  Titleist says, the Pro V1 does what it does because it has a high MOI.

Per Titleist, limit the MOI on a golf ball, and you immediately get shorter drives that drift off line more "erratically".

Ben,

This is impressive science AND research; thank you.  Forgive me in advance for the lack of science in what I'm about to write.  And I agree that the ProV1 changed everything; long, durable, and enough spin off irons. 


But aren't we conflating two different issues here?  The ProV1 changed distance for pros and elite ams, without question, by giving them access to what amounted to a Pinnacle ball that would still spin off irons.  The distance FOR THEM, though, came from the solid core, moreso than the lack of spin off the driver, didn't it?  They opted for balata over surlyn because they needed spin, and they could control that spin off the driver just fine.  I just don't think there is much real world reason, at least in MY experience, to believe that a ball that spins more, or has a lower MOI, is going to go offline more for elite players and cause them not to swing as hard; they're better than that.


The material you've cited above applies much more to me than it does to them, I think, because elite golfers just don't hit curve balls like I do.  There is a mountain of data about this, compiled mostly by Mark Broadie and discussed here many times.  When a pro hits a drive into the next county over, it tends to be the vector that the ball starts on moreso than a 30 yard hook or slice.  They still flush it, for the most part; they just flushed it on the wrong line.  (It would be interesting to know the spin rates of Tour shots in and out of the fairway off the tee, but I doubt that data exists.


There is NO question that the ProV1x balls that I use have really reduced the hook that I used to fight.  But people that aren't great ball strikers just don't become pros anyway (or even elite amateurs, for that matter) and as Broadie has proven, the same skill set that allows a player to hit the ball FAR also determines that typically they will hit the ball STRAIGHT.  There's really no other way to hit the ball far except to square up the club at impact, right?  That doesn't mean it can't be offline, but it's not because of spin; it's because it STARTS offline.

It seems to me that what you are proposing would "penalize" less skilled and recreational players who DO hit curveballs, without having the desired impact on elite players.  I apologize if I've misunderstood the science.

[Ben Hollerbach]

The distance FOR THEM, though, came from the solid core, moreso than the lack of spin off the driver, didn't it? 

The solid core and spin rate is inherently linked through the change in the balls MOI. That is one component that the Titleist patents speak to in great detail. How the change ball composition adjusted the MOI and the impact that MOI change has on launch conditions

They opted for balata over surlyn because they needed spin, and they could control that spin off the driver just fine. 

Another point reference in the Titleist data, The ball cover material properties have a much greater connection to feel of the ball vs. direct spin performance.

I just don't think there is much real world reason, at least in MY experience, to believe that a ball that spins more, or has a lower MOI, is going to go offline more for elite players and cause them not to swing as hard; they're better than that.

This is true for perfectly struck shots, but even missing the center of the face by just a few dimples can produce a significant change in spin axis.

When a pro hits a drive into the next county over, it tends to be the vector that the ball starts on moreso than a 30 yard hook or slice.

This would be heavily influenced by the MOI of the ball. The higher the MOI, the more the ball will hold the starting line regardless strike conditions at impact.

It seems to me that what you are proposing would "penalize" less skilled and recreational players who DO hit curveballs, without having the desired impact on elite players.  I apologize if I've misunderstood the science.

The magnitude of influence would relate to the swing speed of the player. In the Titleist patent Golf ball having specific spin, moment of inertia, lift, and drag relationship, they wrote:


"An average professional can generally drive a golf ball at a speed of approximately 235 feet per second (ft/s) or 160 miles per hour (mph). Most amateur golfers, however, have a “lower swing-speed,” i.e., slower club head speed at impact compared to a professional golfer, and are able to drive the ball at a speed of about 130 mph and a distance of less than about 200 to about 240 yards. When compared to a ball hit by a high swing-speed player, a similar ball that is hit by a low swing-speed player travels along a more ballistic trajectory than the trajectory typically achieved by tour caliber players.

For example, when a player strikes a ball, a portion of the energy from the club head is transferred to the ball as ball speed, and another portion of the energy is transferred to the ball as ball spin. Players with low swing-speed will have less energy available to transfer to both ball speed and ball spin. When club speed becomes very low, the resulting ball speed can be low enough that the effect of ball spin does not significantly increase lift (FL), which, in turn, generates a low ball speed (V) and low lift (FL). Thus, the advantages of a golf ball designed to have beneficial flight properties, such as high spin and high lift, are minimized when hit by a low swing-speed player."

Titleist is saying that this ball helps the high swing speed player (the tour pro) more than the low swing speed player.

The same low effect of ball spin on lift for a slow swing speed player would also apply to horizontal gear effect for the same player.

[Mike_Clayton]

Ben,

They could have added -'When a club head strikes a ball, an unintentional side spin is often imparted to the ball which sends the ball off its intended course, thus exposing faults in the strike and the player's method"

[A.G._Crockett]

Ben, I must be reading the Titleist quote differently than you are.  I’m reading it to mean that a very low swing speed player doesn’t transfer much energy to the ball in either ball speed or spin, which we know.  I see nothing there that makes me understand why a pro would have trouble hitting a higher spin ball long AND straight.


The fact that a ball could curve more doesn’t mean it will unless it’s struck that way.

[Jim Sherma]

It’s not about what happens when the ball is struck on the screws. It’s about what the penalty for marginal misses are. The new equipment does not differentiate small misses. All pros are almost always within the small miss range. The old spiny ball did differentiate small misses. Everyone on tour drives like Norman did because the size of the sweet spot is now a quarter as opposed to a dime. Slow swing speeds don’t get impacted as much because the spin along all axes are less.

[Bryan Izatt]

Ben,

Re the following quote:

"An average professional can generally drive a golf ball at a speed of approximately 235 feet per second (ft/s) or 160 miles per hour (mph). Most amateur golfers, however, have a “lower swing-speed,” i.e., slower club head speed at impact compared to a professional golfer, and are able to drive the ball at a speed of about 130 mph and a distance of less than about 200 to about 240 yards. When compared to a ball hit by a high swing-speed player, a similar ball that is hit by a low swing-speed player travels along a more ballistic trajectory than the trajectory typically achieved by tour caliber players.

For example, when a player strikes a ball, a portion of the energy from the club head is transferred to the ball as ball speed, and another portion of the energy is transferred to the ball as ball spin. Players with low swing-speed will have less energy available to transfer to both ball speed and ball spin. When club speed becomes very low, the resulting ball speed can be low enough that the effect of ball spin does not significantly increase lift (FL), which, in turn, generates a low ball speed (V) and low lift (FL). Thus, the advantages of a golf ball designed to have beneficial flight properties, such as high spin and high lift, are minimized when hit by a low swing-speed player."

.................... consider the chart below from PING.  It shows that the slow swing-speed players with low ball speeds achieve maximum distance at spin rates that are the same as or below those of even elite players who can achieve 180 mph ball speeds.  Mind you the slow swing-speed players need to generate a significantly higher launch angle to achieve maximum distance.  It sort of indicates that the modern high MOI ball should work just as well for short players and long players alike.

Personally, at my advanced age, I fall into the Titleist "lower swing-speed" category with a ball speed just over 130 mph and distance around 200-240 yards.  I can assure you that my ball flight is quite flat - not ballistic at all.  In fact, I think it is silly to say that any golf shot is ballistic in trajectory.  Spin of any sort create lift which flattens out a ballistic parabola.  Very high spin can create an up-shooting shot.  You can't believe everything you read in patent (not "patient") applications.


 

[Bryan Izatt]

Ben,

Since you're into Titleist patents, should we fear the latest Acushnet patent approved this week - "multifaceted dimples comprising two discrete geometries including a circular perimeter and a depression or protrusion based on a polyhedral prismatoid."  Will they claim it flies further?  Will the USGA regulate it?  Fear the polyhedral prismatoid!

[Garland Bayley]

Since many of the old time pros claimed that they dialed back their swings to keep the ball under control, I don't think it is true that the reduction of spin off the driver did not benefit their accuracy. Even as highly skilled players they were negatively affected by the side spin component.

[Garland Bayley]

...

The Pro V1, the ball that started the entire distance revolution, was specifically design to be a high MOI ball.  Titleist literally patented that concept in order to allow driver shots to spin less and fly straighter and further.

...

The ProV1, the Johnny come lately to the distance "revolution", the ball that saved Tileist from becoming a minor player in ball sales.

 

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