Big-Head Putters
Big-head putters have been gaining in market share ever since the Odyssey Two-Ball success. But really Jack Nicklaus’ “gi-normous” Magregor Response putter used to win the 1986 Masters was a high-MOI “big-head” putter too. Big-head putters today include the Futura, the Ben Hogan Big Ben, the Nike Oz, Tour Edge Equator, Taylormade Monza, Bobby Grace MOI, and a few others, like the Resso and the Railgun
See Chuck Stogel, Big-headed putters making impact, PGATour.com, 18 June 2003;
Brent Kelly, Big-Headed Putters a Big Hit with Golfers.
What is new in the current crop of big-head putters is combining a high MOI with a recessed and low COG. The MOI works as usual. The recessed and low COG is mostly a “roll” feature – designed to promote less backspin for more efficient energy transfer. Whereas high MOI is basically mostly a line control feature to reduce off-line rolls (and a little for energy loss), the recessed and lowered COG is mostly about backspin and efficient energy transfer for distance consistency.
Here we re-enter the always exciting but murky realm of the “True Roll” in putting. Which is better for reducing backspin and promoting forward spin, reducing skid and increasing the efficiency of energy transfer – a COG at the ball’s equator, a COG below the ball’s equator, or a COG above the ball’s equator? Not surprisingly, there are strong advocates of all three designs in putters.
Retracing the history a bit, the model for putting is the “True Roll” of a billiards ball with a cue stick. The physics of this is that a level blow of the cue thru the top quadrant of the cue ball right at 5/7th the way up the diameter of the ball eliminates all skid in the roll of the cue ball because the lateral motion of the ball’s COG over the table is perfectly matched by the rotational forward spin of the ball over the table. Skid happens when the translational motion of the COG over the table is faster than the rolling of the ball. The skid friction speeds up the rolling, so eventually they match. In billiards, because the player is able to deliver a level blow right at this height, skid can be eliminated. Table rails, incidentally, are made to match this 5/7th height, both to assist the player in finding it, and in eliminating skid when the ball caroms off the rail.
But in putting, a putter face slab is not a cue stick, and this makes the level blow at the right height problematic. Designers have approached this problem by radiusing the face (a la the Tear Drop putter), by experimenting with loft, or by raising or lowering the COG to take advantage of a “gear effect.” In addition to this, there is the question of stroke technique – that is, using a specific putter of whatever design to hit level, up, or down thru the ball’s COG. The “big-head” putters typically lower the COG and move it back from the face, promoting some “gear effect” in the impact dynamics that is intended to reduce backspin.
The overlooked question in all of this is whether reducing backspin is important or necessary, and whether there are risks with the design that outweigh any gains. Everyone assumes it is a matter of common sense that a reduced-skid putt is a more accurate putt, but I’m not so sure. Skid has two characteristics of note: the ball is in closer contact with the surface than when rolling, and skid takes energy out of the motion of the ball. So what? Perhaps it is possible that being in closer contact with the surface means the putt is marginally more likely to get knocked off line than it would when rolling higher on top of the grass, but I’ve never seen proof of this. When skidding, the ball is moving pretty fast and has considerable momentum to resist getting knocked off line, whereas a rolling ball has less momentum and is more susceptible to getting knocked off line. And skid takes energy out of the putt consistently, and consistency is far more important for day-to-day distance control than the aesthetics of the roll. So, I’m not convinced that “true roll” or reduced backspin is all that important a goal to begin with.
Regardless of that, how does the “gear effect” work? If you suspend a rectangular slab 5 inches wide and 1 inch high and 1 inch deep on a string behind a ball (so the slab COG is poised at the ball’s equator and the face of the slab is square thru the ball’s COG) and then pull the slab back and up and let go so it swings square into the back of the ball, when the slab hits the ball with its COG moving thru the COG of the ball, the energy of the moving slab transfers with 100% efficiency to the ball, and the slab does not rebound or vibrate or twist. The definition of “solid” impact is COG of one mass and shape moving straight thru the COG of the other mass and shape without deflection by surface features. This works for a slab surface with a flat face “square” to the line of motion of the COG, moving thru a ball’s sphere surface such that the flat face of the slab hits the surface of the sphere in a plane that sits tangentially on the sphere. In other words, ‘flush” contact between slab and ball with the slab’s COG moving straight thru the ball’s COG. The “gear effect” is what happens to the slab when the impact is off center.
If you moved the ball 1/4 inch to the outside of the slab’s COG and then pulled the slab back and up and released it, the point of impact would be on the slab 1/4 inch toe-ward off the slab’s COG. The slab’s surface would still hit the ball flush moving thru the COG of the ball, but right at impact, the face would start to twist “open.” That seems natural, but the actual twisting is not in a manner that leaves the slab’s COG unaffected. The COG is moving forward at the time, and the twisting effectively levers the COG in a way it would not move simply from a twisting. The COG rotates clockwise looking down. When you hit a driver on the toe, the “gear effect” of the COG of the driver moves across the back of the ball and imparts counter-closkwise or hook spin to the ball. That’s why a “toe hook” happens sometimes, and even if the basic path of the driver was a slice path from out to in, the toe-ish impact and the resulting “gear effect” can help reduce the slice.
The same action of the putter COG is at work in the impact with the ball when the putter COG is lowered. But in this case, the action is vertical, not sideways. Thus, having the COG of the putter lower than the point of impact on the ball levers the putter face up across the back of the ball a little, and this “forward” spin reduces backspin a little. How much?
Tom Olsavsky of Taylormade says:
“Just like with drivers, a lower center of gravity in the face (CG down) and as far back as possible in the head (CG back), gives putters improved launch conditions. With the Rossa putter, the shift in CG caused by the lightweight Titallium insert allows for a high launch angle with very low spin.
"Putters usually produce between 40 and 400 rpms when it comes to backspin," said Tom Olsavsky, Rossa's director of product marketing. "All putters in the Rossa line are on the lower end of that rpm range, measuring between 0-100 rpm.one of the lowest ever seen in the industry."
Rossa’s Unique Putter Line, Golf-Industry.com.
The T-Roll putter has the putter’s COG at the same height as the ball’s COG. Here’s their explanation:
“The T-Roll golf putter is designed with most of the weight located away from the center of mass, creating a very high moment of inertia. (The T-Roll Defiant with Brass plug inserts is 4699 gm*cm^2. The T-Roll Defiant with Tungsten plug inserts is 6431 gm*cm^2.) Also, the 'T' shaped mass on the T-Roll golf putter shifts the center of mass towards the top of the putter head, aligning itself horizontally with the center of mass of the golf ball. By aligning the 'Sweet Spot' on the putter head perfectly with the center of mass of the golf ball, this creates the most solid feeling putter possible. The shaft is connected to the 'T' shaped mass near the sightline. The putter head does not twist or rotate upon contact with the golf ball. Due to its high moment of inertia, even off-center hits cause minimal twisting or rotation of the putter head.”
T-Roll putter technology.
The Aserta putter places the COG higher than the equator. Using what they call Inverted Mass Technology (abbreviated IVM instead of IMT), the Aserta folks explain:
“A traditional putter with its low center of gravity adds backspin to every putt causing the ball to hop and skid before it starts rolling. If a ball is hopping or skidding, it's going to go off line, not where you aim! The IVM inverted mass putter raises the center of gravity into the perfect position and automatically imparts topspin instead of backspin so the ball starts rolling accurately toward its target the instant it leaves the clubface. The truest possible roll!“
Aserta putter technology.
The Aserta site compares backspin rates of several putters with impact speeds for a 10-foot putt, while claiming a Forward Spin rate of 129 revolutions per minute (a phenomenal rate if true). For the Futura, the backspin rate is said to be 45 rpm and 2 feet of skid over 10 feet; the Nike Oz has 45.5 rpm and 2 feet 4 inches of skid; the Odyssey two-Ball has 34 rpm and 2 feet of skid.
Aserta putter comparisons.
Norman Lindsay in England uses the “Roll Ratio” to quantify the backspin characteristics of putter designs. He states flatly that all putters impart some backspin. The “Roll Ratio” is Spin Speed divided by Translational Speed. That is, since a ball has a circumference of about 5.3 inches, a Spin Speed of 1 revolution per second is 5.3 inches per second; if the movement of the COG across the ground is also 5.3 inches per second, then the Roll Ratio is +1 and there is no skid or backspin. Roll matches Translational Speed. A negative Roll ratio indicates backspin.
Using this Roll Ratio, the Odyssey two-Ball tested at a spin rate of 0.5 rps at a translational velocity of 7.2 feet per second. That is 5.3 inches * 0.5 rps = 2.65 inches per second Spin Rate versus 7.2 feet * 12 inches / foot = 86.4 inches per second. The Roll Rate for this putter is 2.65 / 86.4 = 0.031. That’s a –3% Roll Rate for Odyssey’s Two-Ball, and this backspin rate is the same regardless of how fast the ball is putted. The faster the putt, the more the backspin, but it is always 3% of the translational speed.
Lindsay All-Top Spin Putter technology.
The first test of the Two-Ball has the putter sole 1/8th an inch above the surface coming into impact. He repeated the test with the sole raised over 1/2 inch. This time, the Roll Ratio of the putter was –10%, and a loss of 34% of its energy due to skid. Lindsay explains: “The higher the putter head at impact, the lower the impact point on the putter face and the greater the backspin. This shows that putting the ball on the upswing does not induce topspin (as might be expected) but actually increases backspin since an upswing stroke tends to contact the ball near the bottom of the putter face. … Hitting below the sweet spot affects the length ‘forgiveness’ of a putter. As the impact height varies, impacts furthest from the sweet spot suffer greatest loss of launch velocity and highest backspin. These two factors combine to reduce putt length.”
Lindsay also addresses recessed COG as promoting the “gear effect” as well as shaft attachment in line with the COG. Combined with low COG and a radiusing of the face, Lidsay putters aim for improved distance control by reducing backspin and reducing energy loss from skid to as low as 20% of the initial energy of the roll. He writes:
* Vertical gear effect
It’s well known that hitting the ball off the heel or toe of a driver puts sidespin on the ball, even if the clubface is square at impact. The same happens with a putter. What’s less well known is that vertical spin changes with impacts above or below the sweet spot. Hits above the sweet spot (on a putter) give topspin. Hits below the sweet spot give backspin.
* Low centre of gravity
The sweet spot must be low to ensure vertical gear effect works to give topspin. In most putters the CG is not low enough to place the sweet spot below the centre of the striking face. Lindsay putter-heads have exceptionally low CG with the sweet spot well below centre. For hits at or near the centre, topspin compensates for linear ball velocity changes, giving superb putt length consistency.
* Deep centre of gravity
Gear effect is proportional to the depth of the CG behind the putter face. For good topspin you need the putter-head CG positioned from half to two inches behind the face.
* Low minimum inertia
Low minimum inertia (front-back weighting) assists vertical gear effect, giving higher topspin. At the same time it’s important to have high heel-toe weighting (i.e. high maximum inertia).
* Variable face loft
Gradual loft reduction (face roll) can be used on the bottom of the putter-face to introduce a small amount of negative loft. This generates topspin by oblique impact, even though the ball is hit on the upswing on this part of the putter-face. This arrangement is especially beneficial for length control on long putts.
* Centred shaft axis
Lindsay’s recent pioneering research into putter impact has revealed a major problem - the position of the shaft axis is critical for vertical gear effect. Aligning the shaft axis with the putter-head CG ensures the best performance for topspin and feel.
Lindsay further says that face grooves and added “dwell time” don’t add to reducing backspin.
Lidsay putters, Topspin. Although the Odyssey Two-Ball has a recessed COG, the COG is not low. In comparison, the C-Groove putter has a low COG and gives a high-face Roll Rate of +1 (no backspin) and a low-face Roll Rate of –2%. He also says that face loft should be as little as you can get away with, and that offset hosels raise the COG:
* Face loft
Some loft is necessary to lift the ball at impact, particularly on slow greens. But loft generates backspin and raises the sweet spot, so choose a putter with the minimum loft that suits you. As well as imparting topspin, vertical gear effect lifts the ball slightly so less loft is required.
* Offset neck and hosel
Offset hosels on long neck extensions joined to the front flange are a very common feature in putters. This design increases minimum inertia and raises the effective sweet spot, making backspin more likely.
Lindsay also offers the ONLY explanation I’ve ever seen as to why backspin would matter to the line of the putt, assuming a uniform surface without obstacles hitting the ball as it rolls. He says: “Topspin helps the ball track more accurately compared to backspin, since backspin tries to reverse the direction of the ball so any slight off-line movement is magnified sideways.”
Lindsay All-TS putters. Whether and to what extent this is fact could use a little science data, but I’m definitely interested in this line of thought.
Taking everything into consideration, and acknowledging that some further data needs to be gathered, it appears that Lindsay has the most persuasive explanation of the design features that promote less backspin. Some of the “big-head” putters do a better job than others at incorporating and blending these features. Lindsay himself does not have a “big head” design, and focuses most on low COG with some recessing of the COG by virtue of the low flange off the rear. The Futura putter, in contrast, has 75% of its total mass back in the rear horseshoe feature, spread out sideways so as not to alter the MOI feature. The Nike OZ design is similar. Chuck Stogel comments: “The stainless steel, rearward ring contains 66 percent of the club's weight, to help reduce skidding.”
Big-headed putters making impact.
I would love to test the
Aserta putter to compare its claims of 129 rpm of forward spin. That sounds pretty inconsistent with all else, so it should reveal a deeper level of understanding to get a better handle on the Aserta technology.
The
Tad Moore Make Everything belly putter looks like a high-MOI recessed-COG putter, but I can’t tell about whether its COG is low, middle or high. And this is the key feature for reducing backspin, moreso than recessed COG – at least it seems this way.
But back to my initial issue of whether reducing skid is important. Common sense says, sure if it’s free. Does reducing skid by putter design cost anything? Partly. I think the “big head” putters are ugly to look at and don’t do all that great a job for helping alignment and stroke. The improved physics comes at a cost. Is the “big head” necessary for reducing backspin? Apparently not, or the C-Groove and Lindsay putters would not work. What really seems to matter for reducing backspin and energy loss is hitting the ball on the face of the putter above the COG of the putter.
What gets left out in all this is the golfer’s technique. To use the Odyssey Two-Ball effectively, it is necessary to deloft the face to lower the COG for impact. That’s awkward when the backside of the putter is as big as your Aunt June’s bustle! And in Harold Swash’s technique for the C-Groove putter, he emphasizes a hands-ahead delofting for use with his low-COG putter.
I use low-COG, high-MOI putters that look like normal flange putters (not big-headed). But I hit UP on the ball by playing the ball well forward of the bottom of the stroke without delofting by hands-ahead action. My rolls look pretty good and I have very, very consistent distance control. Perhaps my impact is low on the face yet still above the COG?
Some putter designs would not work well with my technique. In the final analysis, your technique and your putter design ought to “gel’ together. However, the technique takes priority, as the dog wags the tail.
Geoff Mangum
Putting Theorist and Instructor
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