Antony, we are always exploring new materials. The problem is that a number of them will be promoted as some exotic stuff with a specific trade name attached to it and it takes some time to figure out what it realy is. Polymers are used quite a bit in the manufacture of putter inserts and iron cavity inserts. I don’t think anyone has made a complete iron head out of it as yet, although there isn’t much that the golf industry hasn’t tried. Kevlar, of course, has been used quite a bit in graphite shafts and in some wood heads to go along with the metals (kevlar crowns, etc.). It seems from your question that the new “higher density” polymers are in a completely different category regarding exotic properties.
Moment of Inertia: What Is It?
How Does It Relate to Clubhead Playability?
There is no question that the buzzword today for all golf clubs, metals, irons and putters is moment of inertia (MOI). Problem is most golfers do not understand what it is and probably a number really don’t care. Well, you need to care because an understanding of MOI can really help you play better and also help you to select equipment where increased MOI can be a big help.
MOI is a clubhead’s resistance to turning or rotating when it impacts a ball.
Moment of inertia or in our case more correctly referred to as rotational inertia is simply an object’s (clubhead) resistance to turning or rotating when acted on by some outside force (ball). If you strike a drive, a putt or an iron shot off center, the clubhead has a tendency to rotate. Its face rotates open on a toe shot and it rotates closed on a heel shot. This off center impact causes the clubhead to rotate around its own center of gravity and not around the golf shaft as most golfers think. The center of gravity of the clubhead is usually located on or very close to the clubfaces horizontal geometric center. This is obviously where we all try and hit the ball because it produces the most solid hit, solid feel and best distance.
Let’s take two different clubhead designs. One is a traditional shape muscle back iron with much of its weight placed near the middle of the clubhead. The other is a modern longer blade length cavity back iron with more of its weight distributed in the toe and heel areas. The MOI’s of these two irons will be different. The muscle back would probably have an MOI reading some 25% or more lower than the cavity back which causes the muscle back to rotate open or closed more easily on off center hits. More specifically, what this means to the golfer is that a shot hit the same amount off center on both irons would produce two different results. Using the cavity back as the comparative example, here is what the golfer would feel and see at impact; the cavity back would feel more solid, the ball would go farther, have more backspin, fly higher and it would go straighter. This would be a lot to give up for any golfer who simply must play with older design traditional blade type irons for whatever reason.
Higher MOIs are important in all golf club designs. This however is especially true for putters. Putting requires preciseness in both distance and direction control of the putt. Where the ball impact occurs relative to the center of the putters face is generally a function of how long the putt is and the golfers’ ability. The longer the putt and the lesser the golfers’ ability the more offset the ball is hit on either side of face center. Tests show impacts as much as 1” on either side of face center can occur. Touring professionals strike their putts in a ¼” circle on the putter face, but even a plus one handicap player will use a 5/16” to 3/8” circle for impacts. Touring professionals do not need higher MOI putter heads nearly as bad as all the rest of us. Remember, when I talk about face center on a putter, I am assuming that this is the putter heads center of gravity location. More simply stated, this would be the horizontal location where the putters face would balance while placed on a pointed object such as a pencil held vertically in a vise.
Look at the MOI demonstration dumbbells in the graphic built to show golfers visually what MOI is. Assume for a moment that each of these dumbbells shown are putters. They are each made up of three different parts and each part in both examples is exactly the same weight. This also means that each dumbbell is exactly the same weight. However one dumbbell has its two discs placed on the ends of the bar and the other dumbbell has its two discs placed on the inside of the bar. I put both dumbbells on my MOI machine. The result was that the dumbbell with the discs on the ends of the bar had an MOI that was over 6 times greater than the one with the discs toward the center. If these were really putters, which one would you like to putt with?
I have four different putting robots in my design studio and I have done and still do extensive putter testing. I also use a high speed camera to capture data which has the capability to shoot at 1/40,000th second shutter speed and 2000 frames per second. When I hit 24 foot putts with a very high MOI putter using toe, center and heel hits, all three balls sometimes go into the hole. The center hit always goes into the middle of the cup and the toe and heel shots will sometimes fall in on the right of left edge of the cup. If any ball misses only a tap-in is required for a two putt. With the exact same putter changed to a very low (50% less) MOI putter, the results are very different. The center hit still goes into the center of the cup, but the toe and heel hits are far short of the hole and considerably off to the right (toe hit) or left (heel hit). These are not tap-ins but 3 and 4 footers that can easily be missed.
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Article Discussion
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7:50AM - Feb 14, 2008RE: Moment of Inertia: What Is It?
#25
Report ThisRalph Maltby
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10:31PM - Feb 13, 2008RE: Moment of Inertia: What Is It?
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Report ThisAntony
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Ralph Thank you for answer. I’am an engineer on polymers and some of the newones on the market really interest me, like the kevlar. Have you explore this substrate as a possibility for heads or some others in the range of high density polymers.
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7:27AM - Feb 12, 2008RE: Moment of Inertia: What Is It?
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Report ThisRalph Maltby
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Antony. as we stand at this point in time and with current materials technology, there is very little left for more distance even if there were no USGA rules limits on drivers. My guess would be 10 yards or so. There is however more room for directional control both in shaft design and head design. How much this is, I cannot quantify it. I think what we all need to keep in mind is how much we credit better golf club technology when we also need to give the ball quite a bit of credit for improved modern day performance. The changes and improvement to golf ball performance is huge. I have no basis for this next statement other than my opinion; the changes to the game as we know it today are basically a 60% improvement to golf clubs and 40% improvement in golf balls.
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9:22PM - Feb 11, 2008RE: Moment of Inertia: What Is It?
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Report ThisAntony
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Ralph..for a moment just think that there is no regulations… any! is it possible to design and manufacture the perfect driver with the maximum forgiveness and playability ever just to hit the ball straight and 240 yards? and how do you think this Driver will looks like?
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3:05PM - Feb 10, 2008RE: Moment of Inertia: What Is It?
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Report ThisRalph Maltby
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ErikBergman, good question and I don’t have an answer. I will make a few calls tomorrow and see what I can find out. The new drivers are being used in competition (except for those that the USGA found illegal) because I see tour players using them in every tournament. If the tour players can use them, we certainly can also. The 2007 GolfWorks models were all eventually approved, but I really don’t look at any list becasue the USGA sends out conforming letters to each manufacturer.
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2:50PM - Feb 10, 2008RE: Moment of Inertia: What Is It?
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Report ThisErikBergman
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How come none of the 2007/2008 driver heads are on the USGA approved drivers list? Does this mean that they are not allowed in amateur competition?
Erik
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4:33PM - Feb 9, 2008RE: Moment of Inertia: What Is It?
#19
Report ThisRalph Maltby
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Antony, 98% of working the ball with any club ever made is a function of the clubs face angle to the clubs path angle at impact. Only three possible combinations can occur; the clubface angle is square to the path (straight shot), the clubface angle is open to the path (fade or slice) and the clubface angle is closed to the path (draw or hook). The golfer has the control of this with his or her swing. This draw bias weighting thing and also comments that the higher rated game improvement clubs are harder to work is mostly the manufacturer’s marketing attempt to segment (justify) their clubs for different golfer groups. Go ahead and close the iron face at address on your Glider X’s and swing inside out and see what happens. The result is almost always a quick snap hook (the same as with any iron design). However, the higher playability irons will aid in stability in the clubhead meaning that it is slightly harder for the golfer to rotate the club as quickly as with a 10 or 20 year old designs (lower playability). This means the clubhead is helping you, the golfer, to get better consistency in ball directional control. The tour players move up every day to higher and higher playability golf clubs and they can’t go back to the older designs once they do. The pure muscle back irons are almost gone now on tour. Yes, I realize Tiger is one of the few that still plays one and if any golfer thinks that because Tiger plays it that it must be good for all golfers, then all I can say is this is backward thinking and your game will suffer. I have worked with a number of tour players who basically looked at me like I was nuts when I asked them to try a higher game improvement club from a certain manufacturer (whomever they were on staff with). None that I know of have ever gone back, as I said earlier.
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5:39PM - Feb 8, 2008RE: Moment of Inertia: What Is It?
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Report ThisAntony
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Ralph I’am the proud owner of set of Glider X irons and I want to ask you if with this wide sole irons it is more difficult to hit a draw compared with the regular sole irons. Thanks
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4:47PM - Jul 13, 2007RE: Moment of Inertia: What Is It?
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Report ThisRalph Maltby
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C-Wills, yes, you can add heel and toe weights to a traditional blade putter and you will increase the Moment of inertia (MOI). In most cases the old traditional blades were light in weight so you will actually get two benefits from doing this. If you are playing with a 34” putter length, you really don’t want to go much over 360 grams head weight ( the swingweight will be around D-7). If you made the head 340 grams in weight the swingweight would come out to around D-2. Here is an example; Lets assume you have an older Bullseye putter which is a traditional blade style putter. These putters were usually around 280 to 300 grams in head weight for a 34” or a 35” putter. The MOI was around 9.5 ounce/inches squared. If you added 25 grams of weight in the toe and 25 grams of weight in the heel, the putter head weight would now be say 350 grams and the moment of inertia (MOI) would jump up to around 16 ounce/inches squared or a 40% increase in MOI. To show you how bad this MOI still is; when Karsten Solheim invented the Ping Answer putter, it measured 28 ounce/inches squared in MOI. Now you know why he was so successful at the time because no one else in the golf industry was even close to his much higher MOI reading. OK, the driver question; my guess is that the shaft is a great fit for you in the Dunlop driver. Of course, all the measurements of this driver would need to be taken and compared to all the new drivers you bought to check out any and all significant differences. Next time you are out to buy your yearly driver, be sure and take the Dunlop driver along and demo it along with the latest and the greatest on the market. This is the best way to find out why you like the Dunlop driver so much or if there really is something better that works for you.
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12:06PM - Jul 13, 2007RE: Moment of Inertia: What Is It?
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Report ThisC-Wills
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Can you take a more traditional blade putter or iron and place weights on the end to increase the MOI? Also, I have purchased three or four drivers (one a year for the past four years) but my cheap Dunlop driver is still in my bag while my friends are all playing my new drivers. Did I just get lucky and buy one that fit my game a little better or will I have to retrain myself to hit a new driver if I am looking for an upgrade?