Getting the Ball to the Hole: Of Knuckleballs, Free Throws, and Putts (Lesson 3, Part 1)

 

Rory McIlroy after a lipout.

About this site: Golf Is Simple

A blind squirrel finds an acorn once in a while.

Exploration is discovery.

Don’t reinvent the wheel.

Somewhere between these three sayings lies the truth about how one learns just about anything.  We are here to learn, in this lesson about getting the ball to the hole — the part that comes after lining up our putt.  This is a brief comment on why the roll of a putt is so important.  And again the word roll is essential here.  The role of the roll is not only misunderstood, it is not even noticed.

Why We “Roll” the Ball (Or Try to Give it Top Spin At Impact)

It just so happens, though is never noticed, that a putt that rolls effortlessly has very, very desirable characteristics.  It’s not all in the roll, but the roll often rules.

After discussing the roll of the ball, the spin of a baseball, the rotation on a basketball, and the spiral of a football, we will return to the practical.

First, the fact that a ball rolls – that it turns end over end, usually about its center of gravity (if there is no sidespin) has an important effect on how far it travels.  A rolling ball is affected by the friction of the green’s grass to a lesser extent than would otherwise would be the case.  How can we see this?  Imagine that instead of a sphere, we were putting a cube with the same weight.  It wouldn’t go very well, would it?  Now that it has been pointed out, this is obvious.  Why?  Because a sphere, in theory and almost in practice, is touching the green at only a single point – as minimally as possible.  The cube is touching it almost everywhere.  The sphere therefore encounters less friction, the cube a lot.

Second, rolling actually has additionally desirable characteristics.  Even if we had a sphere only touching the green at one point, if it slides across the green, rather than rolls, it will move much differently.  Imagine that you have a choice – take a pool cue to make a straight, three foot putt; or putt with a standard putter of your choice.  The three footer is to win the U.S. Open, on the 72nd hole.  Which do you choose?  The putter every time, leaving aside any USGA Rules of Golf.  Why?  

Because the pool cue will tend to slide the ball across the surface of the green and it may add backspin, while the putter will get it rolling.

Rolling forward has two effects.  One is to make the ball encounter less friction. If you give a cue ball top spin (like you do a golf ball on a green, if putting well) it will roll with less resistance.  If you give it back spin, you are constantly – indirectly forcing the point that will touch the green next to push into the green.  Remove from the golf ball is spherical shape, and imagine if you put a hockey puck on the green to putt.  Wouldn’t go far?  Why?  It encounters a lot of resistance do to friction.  That’s why ice hockey and field hockey use very different “balls.”  Moreover if you roll the hockey puck on its side, forward, end over end, it goes much farther than if you give it backspin.

The reason a forward-rolling ball encounters less friction than a “backward-rolling” ball is not hard to understand.  A backward-rolling ball is moving forward and the ball is turning against the path of the ball.  It’s velocity at the surface of the green is in the opposite direction of the green, while the velocity at the center of gravity of the ball is forward.  This is why you see a ball that is “stabbed at” moves forward and “pops” a bit, and then the main thrust of the ball takes over, and it starts to roll forward.  A ball with topspin never has to overcome this counter-motion just after impact.  But, note, without friction, the angular velocity of the ball would not change.  So friction is a necessary component of the effects of the forces on the golf ball.

Where does this have a practical effect?  That’s a good question.  If you read, for example, Stan Utley’s putting books, he recommends adding some loft to your putter, above 4 degrees.  He does so because he wants you to get the ball rolling end over end.

There are golfers who, in effect do the opposite.  A golfer who “stabs” or “hits” at the ball, rather than “strokes” or “rolls” it, so that it bounces a bit after impact (a tiny bit, but visible), is trying to slide the ball across the green, not rollit across the green.  Don’t stab at the ball.  Roll it smoothly.  Stabbing at the ball puts a small amount of backspin on the ball.   The more friction, the more the ball has trouble rolling in a consistent path.

Phil Niekro throws a knuckleball – trying to miss his target.

Third, there is another, more important aspect to rolling a putt.  The motion of rolling a spherical object (a golf ball, a baseball, a basketball) adds stability to the path upon which it was initially set – that is, it rolls in the direction you hit more surely.  This is seen with all good pitchers in baseball and shooters in basketball.  Ever wonder why they put spin on the ball?

A Golf Ball Becomes a Gyroscope – No Lie

The principle at work is angular momentum, and the object in every day life that illustrates it best is a gyroscope.

Did you know that most intercontinental ballistic missiles are guided not by changes in the relative thrust of the rocket engines?  That would be a very inaccurate method.  Rather, they have gyroscopes inside, with instruments attached to the gyroscopes to help guide them.  Small adjustments to the gyroscopes make the rockets adjust gradually but accurately and clearly to their intended paths.  It is quite clever.  I learned this from my freshman physics professor, who also did research at the Fermi Lab outside Chicago.

A rotating gyroscope, if you’ve ever tried to move it right or left, is a very powerful instrument.  It’s all about conservation of angular momentum.

Phil Niekro could tell you why.    A knuckle-baller, he tried to remove spin from the ball.  On the one hand, he lost control of its flight.   On the other, the batter had greater trouble predicting the flight of a knuckle-ball.

This is why free-throw shooters try to spin the ball backwards to give it a gyroscope effect.  They don’t know that’s why they are doing it.  They just know it works.  Billions of basketball shots, if not trillions, by millions of humans, and we as a race learn some basic physics.  Newton figured out gravity when an apple fell on his head, during a time he was at a country house avoiding an outbreak of the plague in London.  I have no doubt that the story is correct.

Spinning a free throw works.  (It should be noted that a basketball player has another consideration in play other than a lack of friction.  In putting backspin on the ball, he gains the benefit of the gyroscope effect and the flight of the ball takes a higher arc.  If one is concerned about having a shot blocked, or having a ball fall into the basket in a ‘swish’ rather than with a rim shot, a higher arc aids in making shots.

Rolling a putt therefore makes the putt travel on a more predictable path.  Small errors in striking the ball are much less magnified.  The friction of the green at any point along the balls path – say a bump like a spike mark – is much less likely to send the ball off course.

The putt “rolls true.”  All the best putters like to watch their putts roll end-over-end toward the hole.  There is no better way to putt.  This is why, for example, hitting ever so slightly up on a putt is important.  It gives the ball its end-over-end roll, and that angular momentum is very tough to move off line.

Try an experiment on the green.  Put the ball back in your stance and take ten putts.  Mark the average distance from the target hole.

A gyroscope keeps moving objects on their intended path

Put the ball slightly forward of where the putter reaches the bottom of its arc, and try ten more.  You will be surprised.  A small but important key to good, and certainly excellent putting.

It’s a same these fundamentals are not taught, from first principles, at least before now.

A Familiar Example.

You’ve hit a putt. It stops 2, maybe 3, feet from the hole. Either it rolled just past and went too far, or you feel you mis-read: you just want to sink it quickly. So you kind of side-saddle it and quickly roll it in. Maybe you putt with one arm.

Risky, since you really should line it up, but you are half giving it to yourself?

Ever notice how these putts always or almost always seem to go in?

Why?

Here’s why (assuming we both have the same type of “putt” in mind). When a golfer does this he usually makes a quick stroke in which the putter is rising at impact. Somehow intuitively the golfer knows a downward strike on the ball would go awry. This upward finish to our “half-gimme-putt” puts extra top spin on the ball; it rotates quicker; the amount of side spin or effect of gravity is pretty much eliminated, and a read of the break on the short putt becomes much less relevant – for no one would ever do this seriously on a 2-3 footer with a lot of break. So one ends up with no effective break, even if a slower, less top-spin stroke, would end up with some break. Or little net break. That is why it seems these putts go in. We’re getting rid of some of the break with what is our own gyroscope effect, imparted to the ball, by the way we strike it on these putts.

The Practical Side of Putting:  Top-spin and your putting

In general, there are some things we can say now.

If you want to reduce the effect of gravity (slope), try to put the ball more forward in your stance.  This will have the tendency of putting more top spin on the ball.  It will appear to roll “truer.”

If you are hitting a short putt and are having trouble with a read, put the ball farther forward to get more top spin.  This will make the read less important.

Have your putter bent to add one or two degrees of loft.  This tends to promote a stroke which creates top spin.  Stan Uttley recommends this in his book, The Art of Putting:  The Revolutionary Feel-Based System for Improving Your Score.  Now we know why.  (I’m not sure Utley knows why, but we’ll say that he does.)

Putts from above the hole benefit from less spin.  Why?  Because gravity and top-spin (as we shall discuss in more detail in a later part of this lesson) make it harder for a ball coming down to the hole to drop.  (Ideally, you want gravity to pull the ball into the hole, not for the speed you impart to the ball to get it the last few inches – the steeper the slope, the more likely it will run by or spin out – with bad consequences.)

Putts from below the hole benefit, all else equal, from more top-spin, for mirror-image reasons.

The rest is left for your to experiment with.

My high school golf team.  A group definitely in need of some direction.

Conclusion

There are hundreds of subjects like this one in golf.  It is what makes it an interesting game.  Enjoy.

Einstein After a Trip to the Barber.

A. Einstein

References:

[1]

Stan Utley, The Art of Putting:  The Revolutionary Feel-Based System for Improving Your Score.

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