Moment of Inertia (MOI)

Equipment
21

I agree. What MOI matching does is it gets the weight of the club and the force required to swing that club the same throughout the set.

So, let’s say you go from clubs that are 2,650 MOI to 2,750 MOI (sizeable jump). After awhile…as you have pointed out, you will adjust to the heavier 2,750 MOI.

But, if you have a 3-iron that is 2,750, 4-iron that is 2,650 and a 5-iron that is 2,700…that becomes very difficult to adjust to since you are going from club-to-club and having to adjust the amount of force you put on the club.

3JACK

22

Check your PM.

3JACK

23

I think I have an idea how to work these clubs out. I will keep the 2 and 3 iron at D5; the 4 and 5 built to D6; the 6 and 7 iron to D7; 8 iron at D8; 9 iron at D9 and the PW at E0.

24

Here’s a blog post I did, re-posting Tom Wishon’s article on MOI vs. Swingweight he sent in his most recent Tech report e-mail. You have to click the charts to enlarge them. But, when you look at the charts, try to compare the MOI’s of the drivers measured at the same swingweight. For instance, a D-0 swingweight on a 46 inch driver with an 84 gram shaft will have an MOI of 2,875. But a D-0 swingweight on 44 inch driver with an 84 gram shaft will have an MOI of 2,806.

And like I mentioned earlier, you want to have the MOI within +/- 5 (for drivers, they will have an entirely different MOI than the irons).

Sooo, 2 drivers with the same shaft and the same swingweight can require vastly different amounts of force to swing them.

3jack.blogspot.com/2011/12/wisho … eight.html

3JACK

25

Interesting stuff R3J.

How hard is it to find a clubmaker with a MOI machine…do you have your own MOI machine?

Also…if you have 2 clubs with the same MOI, but one is a ladies flex shaft and the other is an Xstiff, will they really feel the same? Are you saying is doesn’t matter?

Hogan seemed to solve the shaft flex question by selecting the stiffest flex available, as apparently “hitters”, but not “swingers” should. What is your take on solving the shaft flex variable in clubfitting?

Thanks.

26

I have my own MOI maching. You can do it without a machine, but you need digital scales and to be very good at math. Even then, the error is greater.

I would either Google up ‘MOI certified’ and wherever you live…or check out the list of Wishon fitters wishongolf.com/find-a-clubfitter/

I would contact the ones in your area and ask if they can do MOI Matching.

Now, you do NOT need to have Wishon clubs to get the MOI matched. However, they will likely want to fit your for MOI and then match the rest of the set. Problem is…you will likely run into fitters saying your lie angles are too flat and your clubs are too heavy, etc. But, if you don’t mind going thru that and just get fitted for MOI…you would be all set.

I believe that MOI matching is superior to frequency matching. But, we have to remember that they are 2 different things. The reason why I think MOI matching is superior is that I can hit some great shots with a shaft that is too flexible for me. The problem is timing that kick of the shaft. It’s not that MOI matching will make it so I can time the kick of the shaft every time…but, it will make it easier and I don’t have to adjust the amount of force I apply in the swing from club-to-club. Much like Lag talked about golfer’s being able to adjust to heavier equipment over time, if you can get the MOI to match the entire set, the golfer over time can adjust to it (and have an easier time adjusting to it).

3JACK

27

Thanks R3J.

Is it fair to say that, given a set of irons, a rational way to customize them is:
1 first decide on your goal for shaft flex and length, and overall weight of the wedge( and thus the other clubs)…
2 then adjust all irons to a specific MOI number that you have determined suites you well. In other words, once you know "your"MOI, the variables become overall dead weight and shaft flex and length…and of course lie angle.
3 set lie angles.

Why would we use a different MOI for woods?
You said:

Also…the earlier era golfers, Hogan etc, played shorter shafts. What do you guys feel should be the shaft length of a 5i? Is anybody starting to lean towards keeping the shaft original short length?(doesn’t this help “hitters” fight dumping?) And given that there are two ways to adjust MOI…add weight at either end, or adjust shaft length…which is “better”?

28

…also…when adjusting MOI …one can add weight not only at either end, but also along the shaft. I think BOM made reference to that a while back, and Gerrry Hogan may have when discussing Bobby Jones’ shaft weight and balance, and how this may have affecting his great distance.

Any thoughts on this would be appreciated.

29

R3J
I think even in the MOI formula you need to measure shaft heft (by a deflection machine, guessing). So if you get frequency matching alongwith progressive swing weighting (0.7 SW per club) that should be fine???

30

[b]

[/b]

Yep he did. He took solder wire and wrapped it around the shaft- just below the lower hand index finger directly adjacent to the end of the grip. I suppose one could put it at the end of the grip as well if so inclined. I seem to recall that the effect of this- as oppossed to butt weighting- is the dead weight is increased with a decrease in swingweight…but more importantly the additional mass added was so close to the hands that it intesified the pressures that load into the hands.

As opposed to butt weighting which does the same thing, but may not have the same feel in the hands. That be my Mr. Bom recollection if that’s what you were getting at Eagle. Good topic going here. :slight_smile:

31

Not sure if this over simplifies things too much.

MOI.png

32

You fit for MOI last. That’s because the type of shaft and its dimensions (along with the clubhead) can drastically change the MOI. So, get fit for everything else first, then find what MOI works best. I actually think it’s probably something that the golfer will have to tinker around with, particularly if their swing improves. Still, I think if the set is MOI matched, but not fitted for MOI, that’s still better than nothing and I actually think it will help your swing over time.

Here’s what Wishon says:

TWGT testing and feedback from many of the clubmakers using MOI matching in their work has proven that because woods and irons are so different in their length ranges, better results are obtained by matching all the woods to one MOI, and then matching all of the irons to another MOI, with both chosen specifically for each golfer either on the basis of the “favorite club” or the “test club” approach. The difference in MOI measurement between the woods and irons typically is for the woods to be 50 g/cm2 higher in MOI than the irons

For an overiew by Tom on MOI matching, check out this link: wishongolf.com/clubmakers/matchi … bs-by-moi/

33

Here’s something that I got from in an e-mail from a Wishon employee a couple of months back.

[i]You can MOI match by adjusting the headweights-as you go higher in loft, headweight will increase and/or you can do internal weighting of the shaft to change the MOI. Some clubmakers do this to keep the balance point about the same and have less of a difference in the set where some clubs might feel head heavy and others feel head light. This has more to do with the waggle feel than it does the MOI and the amount of for ce it takes to swing the club, but for some feel players they prefer this.

Some clubmakers use progressively heavier shafts to achieve the similar results.

The only other thing that we do differently is go to a 3/8” or 10mm length gap between clubs which makes MOI matching much easier where you won’t have to add a ton of weight to the short irons[/i].

3JACK

34

This is the general premise and mathematical formula. However, I recently tried the 3/8" increments with 7-gram interval headweights and it doesn’t make the MOI match…and not even close. I found the dispersion slightly less, but still too off.

Plus, you can get a quirky shaft. Like my 3-iron which is at 2,625 MOI and is a D-2 swingweight while my 4-iron is at 2,702 and is at D-3 swingweight. It would be nice to know that, even if the math tells you it’s correct, when it’s off.

3JACK

35

I think it’s important not to throw the baby out with the bath water here, the baby being deadweight imo. Where will we be when they bring out the 10gm shafts that they are working on??

But as a tinkerer, it’s irresistible stuff, I am thinking about building a set to these specs. :laughing:

MOI_specs__.png

36

Thanks again R3J for your responses and the information.

NRG said:

I am not set up to do my own club fitting/repair…but it is tempting to have several sets with the same MOI at different dead weights for the set, maybe even different shaft length and flex. Sooner or later …one will win out as a preference it seems. Wonder if Lag has a favorite performer among his several sets?

The other interesting thing is what Wishon said about Hogan’s superstiff shafts…once he adjusted to them he never went back, even into his 70’s.

37

I think you can go a long way yourself with some kitchen scales and a roll of lead tape. But if you want to get into the real finer details then its going to be a costly business. I am scared to add up how much money I have spent on club making equipment over the last few years, sometimes it’s best not to know.

38

Recently, I fitted myself for MOI. Previously, I just used the ‘best club’ approach with the irons. The best club in my bag was the 4-iron, which came out to 2,700 MOI (heaviest in the set). So I used lead tape and matched the rest of the irons to 2,700 MOI. And it worked pretty well.

However, over the weekend I decided to actually fit myself for MOI. I had been told some different things from different people, but what I generally found was:

  1. The main way to fit for MOI is to find the lightest club and some impact tape. Hit shots, check the impact dispersion. Add some lead tape (or magnets), hit some shots and check the impact dispersion. Find the weight that results in the tightest impact dispersion, along with ball flight and feel…then have the MOI measured.

  2. Irons should be fitted separately from fairway woods, drivers (and hybrids).

  3. Fairway woods will likely have a closer MOI to the driver and the hybrids will likely have a closer MOI to the irons.

Personally, I was extremely impressed and happy and even a bit shocked with the results. I had a Wishon driver that was at 2,775 MOI, I added weight to make it a 2,820 MOI. I only used the Wishon driver because it was pretty light (D-1 swingweight and 2,775 MOI). So I figured I could just check out the impact dispersion and put together another driver with a ‘better shaft.’ Instead, not only did the impact dispersion improve, but the ball flight completely improved and I hit the driver much better. For the record, I have a Cleveland Persimmon, standard length and with a X100 True Temper Dynamic Gold shaft and the MOI came out to 2,865.

However, the impact dispersion will be greater the longer the club gets. The impact dispersion for the driver was great than it was for the 3-wood which was greater than it was for the hybrid. But when I got down to the irons, I was shocked at how good the impact dispersion was. I used a 7-iron for the fitting and got my impact dispersion to be the size of a nickel. But what surprised me was I would hit 7 balls every time I added weight and when I found the MOI for me, the first 2 shots were poor swings, but the impact was exactly in the same spot as the following shots that I flushed.

I found that my 7-iron was actually about 1* too flat. I found the same with my PW as well. However, my 3 thru 6-irons were all 1 to 2* too upright. Anyway, I added the appropriate amount of lead tape and I hit the ball incredibly better and it was much easier to hit one flush with that ‘sound’ you make when you hit one flush.

I was actually stunned with the 3-iron because I hit a couple of shot that sorta felt slightly towards the toe, but were actually towards the heel. So sometimes your feel can fool you.

Anyway, here’s some before and after specs:

BEFORE

Driver (Adams): 2,845 MOI, (D-4 swingweight)
3-wood (Adam): 2,750 MOI (D-2) swingweight)
Hybrid (Mizuno): 2,735 MOI (D-3 swingweight)

3-iron: 2,625 MOI (D-0)
4-iron: 2,702 MOI (D-2)
5-iron: 2,670 MOI (D-2)
6-iron: 2,680 MOI (D-2)
7-iron: 2,694 MOI (D-2)
8-iron: 2,678 MOI (D-2)
9-iron: 2,639 MOI (D-1)
PW: 2,665 MOI (D-2)
SW: 2,688 MOI (D-4)
LW: 2,685 MOI (D-4)

AFTER

Driver (Wishon): 2,820 MOI, D-3 swingweight
3-wood (Wishon): 2,785 MOI, D-4 swingweight
Hybrid (Mizuno): 2,747 MOI, D-4 swingweight

3-iron: 2,728 MOI, D-3
4-iron: 2,728 MOI, D-3
5-iron: 2,728 MOI, D-5
6-iron: 2,728 MOI, D-6
7-iron: 2,728 MOI, D-6
8-iron: 2,728 MOI, D-6
9-iron: 2,728 MOI, D-7
PW: 2,728 MOI, D-8
SW: 2,728 MOI, D-9
LW: 2,728 MOI, D-9

Right now, I’m experimenting with taking the lead tape off and installing hosel weights. The software program that comes with the machine can calculate how much hosel weight is needed to get the MOI to the number you want it at. I’ve only done the 3 and 4-iron so far. When the epoxy cures tonight, I will then measure the MOI and see how that goes. But, so far I’m extremely happy with this. In fact, I found it makes it easier to decipher swing issues when you fit yourself for MOI Matching.

3JACK

39

Does the program consider where on the club you add weight? Out toward the toe with lead tape, down low, up high, in into the hosel?

40

I think that’s a factor, but I don’t know how to quite explain it. It’s a very sensative machine, check out page 4 in the Instruction Manual golfsmith.com/pdf/pp_copy/24 … mation.pdf

I believe that the MOI will increase if you backweight the grip. But, it will not incease the MOI at nearly the rate than it would if you add weight towards the head.

I asked ‘where you add lead tape when fitting for woods and hybrids?’ I was told that the best spot was to add it where you would add the weight. So, with the driver wrapped lead tape around the hosel because if I were to add a hosel weight, it goes into the tip end of the shaft. But, with my 3-wood, there is a port where you add weight in the soleplate. So I added weight there. So my guess is that having more lead tape towards the toe than directly behind the club will have some sort of effect. I’m just not sure what it is. I can toy around with it tonight.

The MOI machine is made by GolfMechanix. I was just checking out their Web site…they have some really interesting stuff.

3JACK