MOI Matching Question? Weight to MOI ratio

So ive got a set of moi matched irons and wedges.

Irons are all at 2620 moi

Wedges are 2830 moi

1) If i want to increase all of my irons moi evenly is it the same amount of weight i need to add per head (i was told yes)

2) how many MOI points is roughly is 1 gram or .5gram or whatever a general rule of thumb is? I.e. is 1 gram 25moi points?

Thanks in advance

1. no

2. varies. On location where the mass is put and length of the club. An may be more variables are relevant too.

1. no

True - longer clubs would need a little less weight than the shorter clubs for the same MOI increase

But for a relatively small increase in MOI, if one does not have access to an MOI machine, I suspect it might be 'close enough' for most - at least in the context of just the iron set.

Thanks for the info.

I figured 1) was wrong. Simply fr the same reasons why on a driver about 1.4grams is a SWP vs on 2+ on a wedge.

As for 2) if i wanted to get the irons closer to 2700ish how much more weight roughly.

No i dont have an moi machine.

The MOI on my Malty U30's is 2561.7 (7 Iron - all others are within a few 10ths)

adding 2 grams of weight to my 7 iron increased the MOI to 2579.5, so I see a ratio of 1 gram=8.9 Kg Cm2

adding the same weight to my 9 iron gave a ration of 1 gram-8.85 Kg Cm2

I added 6.2 grams which increased by MOI to 2617.2, again I had a ratio of about 1g/9KG CM

So about 9 grams to get to 2700 in your case. A 1% difference in MOI between most clubs is fine, I work towards .5%, I doubt if 2% is noticeable to most players.

Randy

So ive got a set of moi matched irons and wedges.

 

Irons are all at 2620 moi

Wedges are 2830 moi

 

1) If i want to increase all of my irons moi evenly is it the same amount of weight i need to add per head (i was told yes)

 

2) how many MOI points is roughly is 1 gram or .5gram or whatever a general rule of thumb is? I.e. is 1 gram 25moi points?

 

Thanks in advance

When we change MOI the math is easy, but we need to know where weight will be added, its a difference if we use tip weights vs lead tape on the head since the distance from the end of the grip becomes longer to the head, vs the end of the shaft

Formula when changing weight

((Distance x Distance)*1)/1000) = MOI points kg/cm2 pr gram

Example TIP weight

Play lenght minus BBGM = Distance to tip wgt

1 Gram = MOI points

PW = 35.75" - 1.25" BBGM = 34.50" Net shaft included grip cap

((34.50 x 34.50))*1/1000) = 1 gram = 7.54 MOI

1 MOI point = Grams

7.54 MOI points / 100 = 0.076 grams = 1 MOI point at 34.50"

So ive got a set of moi matched irons and wedges.

 

Irons are all at 2620 moi

Wedges are 2830 moi

 

1) If i want to increase all of my irons moi evenly is it the same amount of weight i need to add per head (i was told yes)

 

2) how many MOI points is roughly is 1 gram or .5gram or whatever a general rule of thumb is? I.e. is 1 gram 25moi points?

 

Thanks in advance

 

When we change MOI the math is easy, but we need to know where weight will be added, its a difference if we use tip weights vs lead tape on the head since the distance from the end of the grip becomes longer to the head, vs the end of the shaft

 

Formula when changing weight

((Distance x Distance)*1)/1000) = MOI points kg/cm2 pr gram

 

Example TIP weight

Play lenght minus BBGM = Distance to tip wgt

 

1 Gram = MOI points

PW = 35.75" - 1.25" BBGM = 34.50" Net shaft included grip cap

((34.50 x 34.50))*1/1000) = 1 gram = 7.54 MOI

 

1 MOI point = Grams

7.54 MOI points / 100 = 0.076 grams = 1 MOI point at 34.50"

Awesome. At this point its gonna be lead tape on the back of the heads all in same spot.

So ive got a set of moi matched irons and wedges.

 

Irons are all at 2620 moi

Wedges are 2830 moi

 

1) If i want to increase all of my irons moi evenly is it the same amount of weight i need to add per head (i was told yes)

 

2) how many MOI points is roughly is 1 gram or .5gram or whatever a general rule of thumb is? I.e. is 1 gram 25moi points?

 

Thanks in advance

 

When we change MOI the math is easy, but we need to know where weight will be added, its a difference if we use tip weights vs lead tape on the head since the distance from the end of the grip becomes longer to the head, vs the end of the shaft

 

Formula when changing weight

((Distance x Distance)*1)/1000) = MOI points kg/cm2 pr gram

 

Example TIP weight

Play lenght minus BBGM = Distance to tip wgt

 

1 Gram = MOI points

PW = 35.75" - 1.25" BBGM = 34.50" Net shaft included grip cap

((34.50 x 34.50))*1/1000) = 1 gram = 7.54 MOI

 

1 MOI point = Grams

7.54 MOI points / 100 = 0.076 grams = 1 MOI point at 34.50"

 

Awesome. At this point its gonna be lead tape on the back of the heads all in same spot.

Just do the math, its really splitting hairs, but when we try to make it "spot on" and Blue print toleranmces to a minimum, that inch up or down (tip weight vs lead tape) matters when we are moving more than just a few....

If you down load my MILLIMETER APP, there is a hidden sheet (use unhide, no passwords) and you can use that one.

Just enter play lenght and how many points you want to add, and the sheet reply with grams to 1/10"

ITS hidden. because its NOT fully done for what its going to be used to, but NOT from that sheet, so its a "left over" i just hided, but its there.....

Since you was in the middle of it, and might use a little help, here is how it looks, and its ready to be used for THAT purpose, but macros to run it as a APP is disabled on that page.

You can download it all from this adr, but remember THIS Page is HIDDEN

(was not meant to be used as it is, its for DRY FIT when you stand next to the clubs, but ive converted all to metric, so it will "be back" but in a way better and easier to use version than this)

- this sheet is called MOI DRY FIT IMPERIAL

https://uploadfiles.io/ar3l3

and dont tell anyone about it, lets keep it a secret that its there....;.)

LINK to the tread where you will find a user manual to the millimeter APP, (not explained for MOI points, i dont tell this sheet exist in the file, il come back when its fully concerted to Metric)

http://www.golfwrx.com/forums/topic/1751610-metric-irons-excel-vba-app/

Personally I wouldn't rely on the math. Get a machine or somebody that does. I have seen more people be wayyy off calculating MOI from what the machine says than I have seen be close to accurate. And it's not even close.

Most club sets don't come in at the same MOI. They usually come in at more MOI with the longer irons and less with the shorter irons. The wedges are the exceptions because OEM's always make their wedges a heavier swingweight...which is funny due to those that disparage MOI matching that are using heavier swingweight in the wedges because otherwise they feel too light.

You can keep the MOI for the irons and wedges the same. So such a discrepancy as you have is a bit alarming to me. My guess is that the irons are too light and the wedges are too heavy.

Generally, adding 1-gram of lead tape to the head will increase MOI by ~10 units. Adding/subtracting 1/16th of shaft length will also change MOI by ~10 units. However that can fluctuate more due to shaft design.

RH

Personally I wouldn't rely on the math. Get a machine or somebody that does. I have seen more people be wayyy off calculating MOI from what the machine says than I have seen be close to accurate.

RH

Dont mix up the two issues here Ricky...

Many Excel sheets out there for WHOLE CLUBS where we put together what we like will NOT be able to make that job right, UNLESS they take each components actual BP into the math, most of them ive seen take for granted that the "object" has a COG at the middle (both shafts grips and heads, but non of them has a BP on the "dead center or middle" so those return numbers will, never be right.

This OPS question is a whole different thing.

We do NOT have to consider anything except the distance from the grip end and down to where that weight is added, thats the "BP" in this math and its no way we can do it wrong, this is how MOI or change of MOI is calculated on THIS task....

So, you CANT compare it to those sheets you have seen for club composing, their issue is the BP, while in this case, we know "bp", its the place we choose to add the weight no matter where that is, so all we have to do is figure out how many grams those points is at THAT spot, and you get it 100% correct with that formula.

That means, if you have a set and wants to raise the numbers of MOI points to lets say 20 UP all the way, then this EXCEL sheet in my app is the one you should use, and the numbers will be identical with what you get from the Auditor MOI scale...just give it a try

When we KNOW BP or the exact location of weight we get it right, when we dont, we dont...thats the issues here, and the reason some of this Excel sheets for MOI dont show the same values as the Auditor.

Balance point measurement is the hardest task here, but i have a DiY tool coming up for that, because its needed in the VBA app coming now where EXCEL takes care of actual MOI on clubs with the BP correct for each component we use.

..., but if its for TIP weights or lead tape, just use the formula above, you already know BP then and CANT mess up unless you type inn the wrong values.

The sheet on that file also uses the length of tip weights, so if you choose a 9 gram, the system knows that the BP of that tip weight is 14 mm higher up than the shaft tip, if we DONT, we get in this case 2 MOI points higher return value than actual, so there is no reason to think it cant do the job right and down to 1 MOI point as precision, if you do YOUR part correct, and thats measuring the distance to where that weight will be placed and look at the gram scale...if you can do that, you can do this.

Before I began thinking about the purchase of GolfMechanix MOI system, I tried the math method and though I'm pretty adept with numbers I found it pretty laborious. I did find an app for the Iphone and used it for quite some time (https://itunes.apple.com/us/app/swingtool-swing-weight/id408209116?mt=8). It worked well, was pretty consistent and was accurate. I really wasn't concerned about accuracy as i was regarding consistency and it didn't disappoint. But again, there still ended up being a bit to involved regarding calculations.

I eventually sprung for the MOI Speed Match system, and as well as the device works, the main benefit is the software - makes it a walk in the park. Even the instruction manual presents a good read in the efforts of MOI matching (https://www.golfmechanix.com/src/updates/P070205ME.pdf).

Randy

I have used that iPhone app.

I like using it to measure the period in seconds.

For those of you who build MOI matched clubs, this charts might be handy. Its based on the norm for BBGM so if your club heads is with a different BBGM, the numbers want match.IRON HEADS CONTRIBUTION TO TOTAL MOI

IRON SHAFT WEIGHT AND CONTRIBUTION TO TOTAL MOI 50/50 BALANCE POINT

TIP WEIGHT CHART WITH GRAMS TO MOI POINTS

CHANGE or ADDING Shaft weight and contribution to MOI when the shaft has a neutral BP...

DRIVERS - HEAD WEIGHT AS CONTRIBUTION TO TOTAL MOI

- Be aware of VCOG, it vary, but this chart gives a good idea of needed head weight to get to a specific target.

DRIVERS AND WOOD SHAFTS CONTRIBUTION TO TOTAL MOI - NEUTRAL BP

We CANT use this components shafts to BUILD by, but it helps us to find the area of where we have to go to get to target.

I have TONS of charts for "whatever", and if i dont have what you need already, my excel app only uses a few seconds to make it, so feel free to ask if you need one specific.

Be aware of that for Club heads VCOG will always vary, so unless we know the exact location vs Bottom of bore, we can only get close.