Mass Moment of Inertia. MOI. It’s key to Newton’s Laws of Motion, and for the sake of simplicity, it’s the measure of an objects “stability”.
Unfortunately, MOI (as a term) has been hijacked by the Marketing Whizzes and used to confuse, not to enlighten. Such as claims by other putter companies… “Our Brand X 8572 g-cm2 MOI beats the other guys Brand Y 8463!”
Well, all that bull ends today.
Let’s start with a basic fact… measuring MOI of putter-heads in “grams x centimeters squared” is a bit silly. Of course, when typical putters were 3000 – 4000 g-cm2, maybe it made sense. But… you can’t sense the MOI differential (blindfolded) in typical putters even if you were a cyborg. To sense in increments of 1000 gm-cm2, with your eyes closed, is difficult, much less in 100, 10, or 1 unit increments.
So let’s stop the nonsense in metric incremental “fine-ness”. Putter heads (for purposes of comparison) should be measured in kilograms-centimeters squared, not grams. We do this. Our Black Swan is 23 kg-cm2, the Balck Hawk is 21 kg-cm2. Typical putters are between 3 (old style) to maybe 7 (most high-MOI putters) kg-cm2.
Sweet spot size is dictated by MOI. So, we have roughly 7 times to 3 times the effective “sweet spot” of other putters. Think it doesn’t matter? Think again.
The USGA governs MOI (vertical axis, heel & toe twist) in Drivers at 5900 gm-cm2. They do it for a reason. More is Better. Period. (… again Tom, this might stress you a bit to hear, so you better go take your statins).
Think of it as though Our Creator actually could make the “perfect putter”. Using the USGA limits on putter design, and of course, God’s Own Laws (described so elegantly by Isaac Newton), what would it be?
Let’s first take maximum concievable “MOI”, about the vertical axis of a putter, that has a mass of 440 grams.
Well, if it was God, he could add two elements to “Mendeleev’s Table”, he’d add a metal (call it “Toskiite”, after Bob Toski) that was as light as helium, but a solid, not a gas (that we would use as the putter’s “body” or “frame”), and another (call it “Oliverite”, after Ed ‘Porky’ Oliver) that was about as dense (heavy) as the center of the Sun (162 g/cc, or about 9 times denser than tungsten, but solid at atmospheric pressure), to be used as a “pin”. We’d make a putter body of Toskiite, and post four pins of Oliverite (each would be 110 grams) on the extreme corners…
The MOI in such case? About 60,000 g-cm2, or 60 kg-cm2. Theoretical max, only acheivable by God himself, by adding fanciful elements Toskiite and Oliverite to our choice of materials.
Well, what about using the materials we actually have available? Use tungsten for the pins, and design a thin wall composite frame, and you might get one that is about 55,000 g-cm2, or 55 kg-cm2.
Would you putt with such a putter? Probably not. But you shouldn’t putt with a putter one-tenth as capable as to sweet spot size, either.
This brings us to these questions…
Do you design simply to extend MOI higher, to the detriment of the other design features or putting success factors? Heck no.
How much MOI is too much? There is no such thing, so long as you don’t compromise good design and physics principles in achieving it.
How much MOI is enough? Good question. Is 3 kg-cm2 enough? No chance. Is 9 kg-cm2 enough? Not likely. Is 21 kg-cm2 enough? You tell us… putt with a well designed putter that has 21 kg-cm2 MOI or higher. We have two for you to try. The Swoosh has one that doesn’t work very well, admitted by their own designer’s public statement to the press. Chances are, they won’t let you try it.
Now, we’ve told you, (and all those wanna-be golf club designers out there, including in R&D labs) about all you need to know about MOI & putters (well, not all, but that’s for a future post!).
We like full disclosure, and open source thinking. We’re not afraid of the truth being known. We don’t have Marketing Whizzes spinning the buzzwords to advantage. You come to our site, you just get me, an engineer who couldn’t putt, but now, makes 90 footers at insane frequency in front of pros, while telling them it’s going to happen in advance.
Truth is a wonderful thing. So is making long putts. We give you both… so get a Black Swan or Black Hawk, and go have fun.
For more on MOI… https://one-putts.com/putting-science/moment-of-inertia/