# Swingweight Question - MgR/I

Discussion in 'Racquets' started by normrose, Feb 4, 2011.

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Here is another link - http://tt.tennis-warehouse.com/showpost.php?p=5832348&postcount=55

Both your link and mine state that your personal optimal MgR/I go's down with wristband usage. As I explained in my post above, I don't think the 0.2 figure is accurate. Hopefully travlerajm will rebuke this.

Last edited: Apr 26, 2014
2. ### travlerajmHall of Fame

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Since you have stated yourself that you "got nowhere" when trying to tune your racquet to find your personal optimum MgR/I value, you have no basis to justify why you think my 0.2 correction factor for wrist band use is not "accurate." So there is nothing to "rebuke."

If it was not already apparent, the number was derived from 3 different methods yielding approximately the same result:

1. Analytically estimating the effect of the mass of the wristband on the angular acceleration of the upper pendulum, using estimates for the mass and length of the upper arm, forearm, and wrist.

2. Empirically measuring the effect of the wrist band on my own personal optimum MgR/I value.

3. Testing the result (determined from methods 1 and 2) by applying the 0.2 correction factor to my pro specs dataset (taking the time to search historical internet images and determine which players usually wore wrist bands during matches in prime years) and discovering that it produced a much tidier optimum MgR/I range than the uncorrected data.

Last edited: Apr 26, 2014

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In that case I was mistaken and I apologise, travlerajm. I had thought you just estimated it from the difference between the MgR/I value of pro's with a wristband and without. Do you still have the list of pro specs, perchance? I wouldn't mind trying to draw something from this. I've found some pro specs, but most don't give the swingweight. I do appreciate that you took the time to share your MgR/I findings on here. Any criticism is intended to be constructive criticism to help refine MgR/I.

Thats what I hope to do. It's a tough thing to do though, as you would need to compare players to find the link between height and MgR/I. If I can compare the players specs, I might be able to deduce how the different factors, like grip type and swingweight affect MgR/I, and ultimately the difference between players with different height/arm length. I don't think body mass (from bone, fat or muscle) matters much. Even if it did, it would be very difficult to experiment on. I'm interested in creating a spreadsheet that calculates your personal MgR/I value, based on arm length and the equipment factors.

Last edited: Sep 5, 2014
4. ### RozrozLegend

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i'm not a numbers man,
but reading through this i wonder:

can't we calculate EXACT specifications for an individual player?
maybe height, weight, mass, BMI, age?
or am i talking BS?

i'm wondering whether it's a different feel for each person,
or we could fit the best specs, only by dry numbers?

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Travlerajm, just to clarify, as me and corners are unsure on this, does wristband lower mgr/i by 0.2 or raise it? Did you take measurements for small and large wristbands? I found a post where you stated that large changes it 0.3 and small 0.1.

I've spent 16 hours of my free time analysing players specs and photos, looking for differences in MgR/I, that might reveal how the different factors affect mgr/i (arm length, swingweight etc). I'm unlikely to find anything, as not all players will have optimal MgR/I and some of the specs I've gathered may not be accurate. Worth a shot though.

Do you have the figures for how any of swingweight, choking up/down the handle, or forehand grip affect MgR/I. Just to save myself time. Thanks.

Last edited: Sep 5, 2014
6. ### slowfoxProfessional

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I've been playing around with this MgR/I stuff for the last year or so. It has made a BIG difference. I'm a believer. Thanks y'all.

21.15 rocks...!

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Okay, I've finished looking at the players specs and equipment information I collected. For the WTA players, there was no correlation between MgR/I and height, swingweight, forehand grip or wristband usage.

For the ATP players, there was again no clear link between MgR/I and swingweight, height or wristband usage. Players with more conventional Eastern grips had higher MgR/I values then players with semi-western or western grips. I couldn't put a number on it though, unfortunately.

There were plenty of players with the exact same setup, bar one difference. E.g same height, wristband and swingweight but different forehand grip. You would hope this would reveal the impact of one factor on MgR/I. In this case, the impact of forhand grip. Unfortuantely, when comparing these players, the MgR/I values varied wildly. All players choked down on the handle, so I couldn't check how choking up the handle affects MgR/I.

It was always unlikely that I would find anything. Not all players will have perfect, optimal MgR/I and some of the specs I gathered may not be accurate. Also, some of the rackets may not have had an overgrip put on yet, which would change the specs.

Last edited: Sep 5, 2014
8. ### sstchurHall of Fame

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So I'm wondering a few things.

Is ~21 still considered ideal for an extended length racquet? I'm using a Ki5x that is 27.5 in. Also, my height plays a role? I'm only 5'8" or maybe 5'9"

Based on my calculations, I'm getting about 20.32518

But using the TW customization worksheet, I'd have to add about 20g of lead around 8in from the butt to get 20.7. That seems crazy.

I did try adding about 8g to that spot, but didn't really like the feel that much.

I tried travler's suggestion about tuning by swinging with a relaxed wrist low to high (like a pendulum) and tried to take note of any torque or lag. I put some pennies at 8in to test various combinations. But honestly, it feel like the stock racquet comes closest to net zero. Maybe it's all in my head.

Thoughts?

9. ### BlueBHall of Fame

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Yes, you are right, the extended frames tend to have low numbers, often close to 20.5 for 27.5". They seem to play right. I have one that somehow is 21.25 and that one feels clubbier.

10. ### sstchurHall of Fame

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Other thing I'm wondering is how critical is the swingweight to this theory? Say I have my ratio close to the preferred value (21 or close to it) but the swingweight is below 350? Does that nullify the presumed benefits?

Is the the combination of ha having the right MgR/I value AND also have a swingweight of 350 to 370?

Seems awfully difficult to achieve in my case.

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Sstchur, we don't know how much height/arm length influences MgR/I yet. It would be hard to discover as you would need to compare at least two players with perfectly tuned MgR/I, and know how much various factors like swingweight influence MgR/I.

Grip type, swingweight and choking up/down the handle all influence MgR/I as well. We just don't have a figure for how much. 21 is just the number that worked for travlerajm. It might not be optimal for everyone, due to differences in height and the various other equipment factors.

You can try and find your personal MgR/I using this method - http://tt.tennis-warehouse.com/showpost.php?p=5859118&postcount=17

12. ### sstchurHall of Fame

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Thanks for the info... I'll check out the links you posted.

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Last edited: Sep 5, 2014
14. ### avinceRookie

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MgR/I higher : better for eastern grip (flat shots)
MgR/I lower : better for western grip (topspin)

Is it correct ?

15. ### mortenHall of Fame

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nope...... more like the other way around, but many exceptions...

16. ### avinceRookie

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Otherwise, could it be a relation between MgR/I and the polarization of the frame ?
- polarized frame :lower MgR/I
- depolarized frame :higher MgR/I

17. ### travlerajmHall of Fame

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By definition, MgR/I is a measure of the polarization level of the frame.

It is the ratio of the first moment to the the 2nd moment (2nd moment being the moment of inertia). Thus, the higher the MgR/I value, the lower the degree of polarization.

But the bigger significance of MgR/I is that it is a measurement of the racquet's natural swing frequency as it sweeps around the wrist axis as you swing. Optimization of the MgR/I value to match your swing makes it much easier to maintain a near-constant racquetface angle through the hitting zone, making your stroke less sensitive to timing errors and therefore more accurate and more consistent. It also allows you to hit with a relaxed wrist, enabling you to take advantage of the stability and control benefits of higher swingweight frames without tiring your arm.

Last edited: May 16, 2014
18. ### henman_fanNew User

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Thanks for compiling that. It's useful info to have. I can't find any links either, including for the big one - height. I think the only way to gather how much the equipment factors affect MgR/I would be to experiment against a wall. Comparing pro data from various sources was never going to get anywhere.

If we did ever find out the equipment factors and thus calculate peoples personal MgR/I values, I would look at somehow patenting this if I was travlerajm.

I haven't seen anyone on here who has successfully tuned their MgR/I against a wall, except travlerajm. Which makes me doubt the theory somewhat. Also, stoneage and kaiser have questioned the science. Still, I have faith that MgR/I works. I have improved slightly since changing my racket to 21 MgR/I.

Last edited: Sep 5, 2014
19. ### ShroudLegend

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I played a bit with tuning but I cant say that I felt much difference putting weight at 7". Sure there were some feeling differences shadow swinging slowly but its really hard to say when actually hitting balls. True I think I like where it is now and can't really say what value its at right now.

But if I took of the 10gs at 7" would I notice?? Not sure. Will try.

I think there is something too this but I havent found the magic formula yet. And i am weird in that I usually where a long sleeve shirt, hoodie, big sweat band. Thats when its in the 70s. But some times I wear an arm brace. Recently I went to florida and took off the hoodie and played in the long sleeves only with a brace. WTF did that do to my Mg/r1? Heck if I know and how should I compensate.

I love trav but he is just too smart and can't seem to remember that most of us are really clueless. We need simple statements and simple relations otherwise his genius is not practical.

For example I read all this stuff from several threads and cant tell you if wearing a wrist band increases MG/r1. If I don't wear one how do I compensate? Do I add lead or subtract lead and how much.

Also the thought of what I wear affecting my stroke is not comforting. HOw much does sweat in my wristband screw things up? OMG I am wearing a different hoodie than when I tuned my racket, etc.

On the other hand its great to think you can adjust your racket for your swing. I just have zero clue how to do that intelligently without willy nilly adding or subtracting weight at 7". Or lets say I am hitting long how do I tune to adjust???

And I was trying to get a lighter racket and had gone down to under 370g. But now I have a new racket and doing this tuning its up to 388g.

20. ### henman_fanNew User

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I think travlerajm is very good at explaining his experiments in simple english, while still preserving the science for those who are interested. I just wish I understood more of the science. My fault for focusing on the humanities and messing around in science classes.

I agree that unless we know the effect of the equipment factors, especially height/arm length, only travlerajm can use his MgR/I formula. I think only travlerajm could find out these factors, as only he can wall tune his racket.

I doubt a hoodie has enough weight to influence MgR/I. An arm brace or sweaty wristband might have an influence. You could probably adjust the balance pre or mid match to account for this, if you want perfect MgR/I. I just want my MgR/I within range of optimal. I'm only a weekend recreational player. My main interest in MgR/I is seeing it expand and possibly help hundreds of recreational players. If it can really increase shot accuracy and reduce arm/wrist fatigue, this could revolutionise tennis at the recreational level.

It may even help with pros, or 4.5+ players, but I think a lot of players at that level are settled with their racket and can play well with any racket.

I would give up on trying to catch travlerajm. I still have unanswered questions .I tried many to catch him when I've seen him pop up on here but failed. He doesn't seem to a regular frequenter of these boards.

Last edited: Sep 5, 2014

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Agreed.

That is why I am so interested in the formula. I just want to see the idea grow. One reason being it could reduce frustration for recreational players. I've seen people try the game, get frustrated, and quit to play other sports. This I why I've asked travlerajm so many questions. Without criticism, you can't refine something. I would like to setup a spreadsheet, where people can calculate their personal MgR/I, so it can be used by all players. Admittedly, looking back, I could have answered a few of my own questions if I'd used my own intuition.

Last edited: Sep 5, 2014