Dear P House,
The radiused putter face at
R&B Putters is not new or innovative. It is based upon the simple idea that if the golfer hits the top part of the ball (i.e., contacts the ball "above the equator") the ball will start forward rolling sooner. This is two little ideas that get all confused. First, how to get the ball rolling sooner; and second, what difference does that make for line and distance.
The idea that a radiused face putter will get the ball rolling sooner is an effort in golf to make a billiards stroke thru a cue ball with a straight-down-the-line stroke of a straight cue stick to start the cue ball rolling without skid, but doing this with a putter head at the end of a stick that hangs down in order to roll the ball sideways. In 1972 CB Daish described the physics of the billiards stroke (from
my Research database):
5.01.09.05.02., Daish, C.B., The Physics of Ball Games, (London, English Universities Press, Ltd., 1972), 73: unless the linear motion matches the rotational motion of a ball, the ball will skid. The friction on the bottom of the ball will slow the ball's linear motion and impart rotational motion. At some point, the two motions will match and the ball will roll without any skid. 74: This point is always whenever the ball's linear motion slows to 5/7ths of its starting speed, regardless of the roughness of the surface or the ball. Still, on a rough surface with more friction slowing the ball and speeding up the spin, the true skidless roll begins sooner than otherwise. In the case of a long putt across a fairly fast green, it is likely to be over before the ball has traveled 1.5 to 2 meters. The sliding or skidding which may form the first part of the motion of a ball over a level surface can be avoided in some cases if one wishes to produce a smooth rolling motion right from the start. To accomplish this it is necessary to impart rotation to the ball in the form of top spin at just the right rate to match the initial velocity. 75: With a billiard ball, such topspin is imparted by striking the ball with the cue at a point 7/10th of the diameter of the ball above the surface, with a horizontal blow parallel to the plane of the ball's horizontal equator. For a standard billiard ball, this is 3.5 cm above the surface. Billiard table cushions are shaped so the rail is also at this height, to provide true-rolling rebounds of balls off the rails.
5.01.09.05.02., Daish, C.B., The Physics of Ball Games, (London, English Universities Press, Ltd., 1972), 76: Most golfers hit on the up when putting, projecting the ball a bit up in the air to start with, as seen from the dotted lines in the dew on greens, showing that the ball initially hops along the green in a series of small bounces. However, there could perhaps be some advantage in imparting initial top spin to the ball. There are two ways in which the design of a putter may help to bring this about. By providing a cylindrical head to the putter and making the diameter of the cylinder a little greater than that of the ball, it can be arranged that the ball is normally hit at a point somewhat above centre .... This will introduce some degree of top spin, as with a billiard ball cued above its centre. But it will also force the ball towards the ground at impact, so clearly the idea cannot be carried too far without disastrous consequences. Some initial top spin is also brought about in using a ping putter .... The centre of gravity of the head of this putter is low down and behind the face. The impact with the ball will normally occur at a point above this centre of gravity and hence, since the clubhead is on strings during impact, it will rotate slightly about its centre of gravity during this period. [T]his rotation about the centre of gravity C will be in an anticlockwise sense. This means that, to some extent, the face will be moving up across the ball while they are in contact, and so friction between the face and the ball will produce a degree of top spin. [similar to driver gear effect] Both these designs, then, should reduce skidding in the early stages. Whether they produce advantages of any practical consequences is another matter. [seems cannot eliminate skid entirely? what harm does skid do to line or distance? how much does either design reduce skid? what is effect of reduced skid on distance or line? is there any reason not to make the cylinder head contact the ball at precisely 7/10th of the ball diameter? what's harmful about hitting the ball towards the ground a bit? etc.]
So, a cylinder design (putter A) "may" help get the ball forward rolling sooner than some other type of putter (putters B, C, D, etc.). How about this issue: given putter B, is there a stroke dynamic the golfer can do with this tool to help get the ball forward rolling sooner? Yes, of course there is. Do the R&B Putter designers know what sort of stroke will do that? No, they don't. So, back to the original first issue: what actually helps get the ball forward rolling sooner? The radiused-face putter design is NOT the only or even the main way to accomplish this.
There are two dynamics in the stroke that helps get the ball forward rolling sooner: the vertical gear effect from the putter head design (plus using it correctly in the stroke by making sure the impact point on the putter face is above the putter head's center of gravity), and a stroke dynamic that also "rolls 'a' top (not 'the' top) over the opposite bottom in relation to the chosen 'a' top".
Golfers think erroneously that there is only one "top" of a ball -- everything above the equator. But the equator is defined as the plane thru the middle of the ball that is oriented "level" in gravity OR level with reference to the tilt of the surface. Even though there are two "equators" in golfer-think, golfers don't realize this. Thus, in golfer-think, the "top" is above "the" equator. The physics definition of the "top", however, is in relation to the center of the sphere of the ball, not a plane. Given a line that aims from any point on the surface of the ball that passes thru the center of the sphere and comes out on the opposite side of the sphere (like a North Pole and a South Pole on Earth), there is a plane that includes this line that arises vertically from the surface and is oriented in the direction of the rolling, and the "equator" is a plane that is perpendicular to this vertical plane and includes the center of the sphere, the line thru the center and the back point on the surface and the front point opposite this. If the back point of contact on the ball is low on the ball in the sense of closer to the bottom of the ball that sits on the grass than the "equator" is (e.g., the back point is one dimple below the equator), then the opposite front point on the ball will be one dimple ABOVE the equator. And vice versa for entry points on the back above the equator. The "equator" that is a plane thru the center of the ball that includes this North Pole and South Pole entering the back of the ball one dimple above or on or below the equator level to the surface and exiting the ball one dimple lower than or the same as or higher than the level equator constitutes "a" dividing plane that separates "a" top from its bottom. And this equatorial plane is not level to the surface at all, but it still divides the ball into "a" top half above this specific equator plane and the rest of the ball is the bottom half. Forward roll happens when the putter hits "a" top of a ball. This "knocks a top over its bottom".
The ball acts like two sacks of potatos, both in hemisphere shapes, tied together at bthe center, with the top sack having all RED potatos and the bottom sack having all BLUE potatos. The sacks are tight, so if you hit a RED potato, all RED potatos get hit. Rolling a ball happens when a golfer hits the RED sack and the BLUE sack wants to stay put, so the RED sack heads off more or less level above the ground but the BLUE sack stays put and makes the RED sack "roll" towards the ground, and rolling starts with the RED rolling over the BLUE.
How a ball gets "hit" is determined by the direction of the force of the impact thru the sphere. A blow that is directed exactly thru the center of the ball and that is also level with the surface and the surface is also level in gravity will produce the MAXIMUM skid in the ball's motion. Hit a cue ball with a level cue stick stroke thru the level equator and thru the center of the cue ball on a slate pool table that is bubble-leveled in gravity and the cue ball will SKID. Hit one golf ball against another by sliding the ball across a billiards table into the other ball, and the struck ball will SKID to begin with, 100% skid and zero% rolling, but this state will change very quickly to SOME rolling immediately and to NO backspin (if there was any to begin with) also very soon. AND ALL SKID will be gone no matter what, once the initial ball speed after impact has slowed to 5/7th what it was at the start.
What sort of direction of the blow happens when a putter face that is flat strikes a golf ball? A fact of geometry that putter designers or teachers don't seem to know about is that a flat slab like a putter head and face CANNOT contact a sphere EXCEPT where the tangent plane on the back of the ball is EXACTLY THE SAME as the angle of the flat putter face at impact. A tangent plane is like holding a small square of hard plastic flush agaiunst a ball -- the orientation of the plane of the sqquare plastic changes as it is held below the equator, on the equator, or above the equator. On the equator, the tangent plane is oriented exactly vertical to the surface, and this corresponds to zero loft at impact. That means that whatever LOFT is actually presented to the back of the ball (e.g., 5 degrees of positive loft in relation to the surface and not to gravity), then the ONLY spot on the back of the ball where it is PHYSICALLY POSIIBLE to contact the ball is the tangent plane on the sphere that is ALSO the SAME degree off vertical (e.g., 5 degrees) or off the equator (in relation to an equator plane level to the surface, not gravity). If you made a line from the center of the ball to the back of the ball and this line aimed down beneath the equator plane by exactly 5 degrees, this line exits the back of the ball on the ONLY spot where the 5 degree lofted putter face can POSSIBLY touch the ball.
This sounds like a problem, since the direction of many blow thru ANY and ALL tangent planes must be aimed straight thru the center of the ball, and that is supposed to "knuckleball" the putt into a lot of skidding. But what ACTUALLY happens is that there is a brief period when the putter and ball remain in contact and during this time, the loft presented to the back of the ball INCREASES unless the golfer manipulates the putting stroke to keep the putter blow level thru impact. If the golfer keeps the blow level so no loft gets added during impact contact, the ball skids like crazy. But if the golfer allows the loft to increase, the direction of the blow in effect gets "averaged" and the average blow MISSES the center of the ball on "a" high side, and this starts the ball rolling "a top over its bottom".
Does this start the ball with NO SKID at all? No. Does the cylinder putter start the ball with NO SKID at all? No. Does the cylinder putter start the ball with NO BACKSPIN at all? Possibly (maybe even probably). Does a flat-faced putter start the ball with NO BACKSAPIN? Possibly, depending upon whether the stroke dynamic knocks "a" top over its bottom (and to some extent whether there is some vertical gearing of the putter face up and over the back of the ball). Does a flat-faced putter with NO gear effect and TOO MUCH loft start a ball with BACKSPIN? Probably, but it also launches the ball into the air with some BACKSPIN.
Putter designers don't distinguish among: BACKSPIN, SKID, FORWARD SPIN, and LAUNCHING, but all of these motions may be present in various degrees in the initial phase of the putt until the ball speed slows to 5/7th and all skid dissipates completely. This creates a cloud of confusion when designers start describing what they are accomplishing SOLELY with the design. The R&B guys say they produce IMMEDIATE ROLLING. BS. Their "design" used with a garden-variety stroke pattern produces SOME SKID and SOME FORWARD SPIN immediately, and then the grass does the rest. Can this be duplicated with a flat-faced putter? Absolutely.
The MAIN "badness" in the initial phase of putts is not really whether there is some backspin or no backspin or some skid or no skid. The backspin and the skidding WILL get taken care of by the grass, with the grass-ball friction wiping out the backspin and skid and producing only rolling after a certain span along the grass. Putter designers simply don't notice how brief a span it takes for grass to "equalize" the rolling state of the balls from two different putters (A versus B). The truth is that there is a standard range of bad to good initial states of the balls. Putter B (bad) starts the ball off with about 1/8th back-turn of the top of the ball of backspin and Putter A (good) starts the ball off with about 1/8th turn of the top of the ball forward (a quarter turn of starting spin state is about all that separates the best "true roll" putt from the worst "true roll" putt). For almost all impact velocities that actually happen on real golf greens, Putter B catches up to 1/8th forward turn with Putter A's start in as little as two inches; the grass usually only takes about two inches to eliminate backspin and convert the ball to 1/8th forward spin. It's in all the "high-speed photography" on all the putter company websites that show skid-roll data Pual Hurrion studies for Yes! Putters and Gel Putters, TaylorMade, Rife, Aserta, etc.), but these people designing these putters and discussing their high-speed data don't know what matters in what they are looking at.
Are there "monsters" lurking in these two inches at the start of the Putter B putt? No. The ball is usually moving at 100 inches per second or thereabouts, and it would be EXTREMELY unlikely and unlucky for that two inches at the start near the ball where the golfer has a good look at the possible problems to contain anything solid and big enough to knock a ball moving that fast off line. It's possible, but HIGHLY UNLIKELY. VERY HIGHLY. In effect, there is NOTHING TO WORRY ABOUT. There is NO MONSTER swimming in the two inches that requires Putter A to kill it. Once Putter B's ball has gotten safely thru the two inches, there is NO DIFFERENCE between the ball putted by Putter B and the ball putted by Putter A. None. After the point where ball B matches ball A, the putter has nothing whatsoever to do with what happens after that, and the grass and both ball A and ball B interact exactly the same.
This is the SECOND issue: does it matter? No, not for line (there are no monsters in the two inches to knock the ball off line), and also it does not matter for distance either (as golfers using Putter B can be consistently as good with distance control as golfers using Putter A).
So, as long as the golfer does not a) launch the ball into the air unnecessarily, and b) does not "knuckleball" the putt by stroking dead level thru the center of the ball, a stroke that starts by contacting the ball a little below the equator or exactly on the equator or a little above the equator will likely produce a ball without much backspin and with some forward roll, and this putt will match the best rolls realistically attainable in under two inches anyway. Once the putt starts the ball off outside "a little above or below", the ball gets "launched" off the ground or punched into mthe ground, so that is not good. But within a nice range of lofts presented to the back of the ball, putts don't require true roll to stay on line or get consistent distance control. It's just goofy golfer-think and bad science and not real-world physics.
The golfer needs to watch out for bad designs that launch the ball or that present too much loft to the back of the ball, as this promotes air time and also backspin. So the objective is NOT chase the dream of perfect true roll or the dream of eliminating "all that horrible skidding"; instead, the smart objective is to stay away from bad putters and learn a serviceable stroke that minimizes launching and backspin but otherwise don't worry about trying to attain "perfect true rolling immediately after impact". That ain't real or even necessary for good, accurate, consistent line and distance control.
With respect to sammy's comments on dimples: any putt that hits any golf ball cover material fast and hard enough to roll the ball 5 feet on any normal green will smush the dimple out of existence. And for any stroke less than that, the odds of the dimple being in exactly the right orientation to cause sufficient line problem that would actually hurt such a short putt where it takes a pretty BIG line error to cause a miss inside 4 feet) is too small to matter and the golfer's ability to stroke the ball with precision such that the degree of dimple error is bigger for these short putts than the golfer's usual precision variability is also not realistic. Bottom line on dimples: a dimple has a very low chance of mattering for a 3-4 footer on perfect greens at Augusta National only when the golfer is extremely good at stroking the ball where aimed, which NEVER comes up in the real world and then only comes up VERY RARELY. So forget the dimples. (Here's my study of this issue,
"The Dimple Error in Putting".)
Cheers!
Geoff Mangum
Putting Theorist and Coach