Discussion in 'Racquets' started by xFullCourtTenniSx, Jan 29, 2010.

1. ### IrvinG.O.A.T.

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A quote from that link - Mass (in kilograms, symbol M) is a measure of the racquet's "inertia," a word that means essentially its resistance to change. The change resisted by mass is change in linear (straight-line) velocity. SW is Inertia if I have a 300 gram racket what is the SW? If mass were inertia all 300 g rackets would have the same SW.

When you add mass anywhere on a racket you increase the inertia of the racket. Inertia is used to measure SW and TW so when the mass changes TW and SW changes. Mass dampens vibrations the softer the material used to add mass the more it dampens vibrations. For Instance, silicone added in the handle dampens more than lead. The nodes in a racket are changed by mass. The sweet spot is a node and when you add mass you change the locations of nodes. Pretty easy to see mass changes balance. Balance effects TW and SW.

2. ### zaliveProfessional

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For some reason I have trouble finding that quote, but it's not that important.

SW measures rotational inertia (moment of inertia), I think the author was talking about plain (linear) inertia. Rotational inertia is not the same as inertia. And the mass is indeed measure of inertia, it's in the very definition of a mass.
Don't disregard the text just like that, it relies on physics and equasions.

3. ### IrvinG.O.A.T.

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If that were true where you add 10 / 20 / 50 g of mass on a racket would make absolutely no difference what so ever. Maybe you could help yourself out if you just google Inertia. It's a lot more than just mass.

Last edited: Dec 3, 2015

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5. ### Karma TennisSemi-Pro

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For one player, we did experiment with adding weight to both the hoop and the handle. We tried different placements in the hoop but all of them made the racquet less whippy. The player wanted more heft without sacrificing the whippiness which promotes more RHS and better maneuverability at the net. The best solution for him was to increase the racquet's static weight, and the best place to add the extra weight was in the handle.

I mentioned in another thread ... the main thing about the 2013 APD is that it works best for clean accurate hitters. The racquet is very unforgiving and really bites back if ball contact on the string bed is off centre.

This particular player is usually a very clean hitter, so the racquet configuration works very well for him.

6. ### zaliveProfessional

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I found this video on youtube:

Guy adds 2.5 oz (70 g) of silicone in the handle. Ok, he took out the foam previously which also has some weight in it, maybe 0.5-0.7 oz, but still it's pretty significant added mass. According to comments, some guys were pretty upset with that .

For what I could read about the subject, these should be the general effects of adding silicone/mass to the handle:

- moving the COM (center of mass) towards more HL (which is good)
- making the Moment smaller (it's important for static balance of racquet, but also for the Torsion upon impact, because Torsion = Moment * Torque
- better dampening of vibrations of racquet (more mass means more dampening, + silicone is good for dampening)
- better stability of racquet (because Torque is proportional to r = distance between axis of rotation and COM, and Torsion is proportional to Torque)
- slightly icreased SW (almost not significant if you measure from axis of rotation positioned at the handle, as usually expressed, but significant when taking into account another axis of rotation positioned in shoulder/body; still not near as significant as the mass in the hoop)
- slightly increased power (because of the upper bullet as realistic SW has increased)

slightly increased SW/power could be significant if the mass added to the handle is significant, as in video

Formulas and explanations for Moment, Torque and Torsion can be found here:
http://www.racquetresearch.com/

7. ### EasternRocksHall of Fame

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Is 1.25 grams total (2 2.5 inch strips) placed at 12 o clock a negligible mod?

8. ### IrvinG.O.A.T.

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It's (58*58*.00125) just over 1% or 4.2 Kgcm2

9. ### EasternRocksHall of Fame

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Can you explain the math there? isn't 1 g at 12 equivalent to 3 points of sw? so 1.25 -> 3.75

10. ### zaliveProfessional

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Yes. More precisely, 1g at 12 o'clock is equivalent to 3.4 points increase of SW. Math is added SW = (added grams at 12 o'clock) * square (58.5 cm) .

I'd say it's neither negligable, nor that much significant. More a fine tuning. But 2g at 12 o'clock is significant (SW gain of 2g at 12 o'clock is approximately as much as with 4g at 3+9 o'clock).

11. ### zaliveProfessional

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One interesting thing: adding 1 inch wide Tourna abrasion tape adds significant weight to the hoop. I covered the grommet (the one from 9.30 to 14.30) with that tape and I measured weight increase was 3g. In fact it seems to me that it may be over 3g, maybe 3.5g.

If so, then 1 inch wideTourna abrasion tape adds about half the mass of Tourna lead tape when comparing the same length. That's quite interesting and useful to know.

12. ### EasternRocksHall of Fame

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Thanks. Now, if I'm adding a leather grip to a stock grip and its adding about 12 grams, how much swing weight is added there?

I've read from different sources different things - some say it doesn't change it at all, some say it does marginally, some even said it goes down.

I'm trying to do a rough calculation of my modified frames new SW. If I'm at 324 stock and add 1.5 at 12, that should be 5 added SW pts (if I'm doing the math correctly). The leather adds how much to the 329?

13. ### zaliveProfessional

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added SW = (added grams) * square (position of mass from the tip of the handle in cm - 10 cm)

So, it's increase less than one SW point.

14. ### mortenHall of Fame

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Nothing the times i have changed from synthetic to leather.. On a swingweight machine... Done it about 20 times.

15. ### mortenHall of Fame

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I can feel 1gram at 12 ...

16. ### EasternRocksHall of Fame

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Between 1.25 at 12 and 1.5 at 12, is .75 SW. Wondering if this makes a difference...

So, I guess the consensus is that the leather grip adds a negligible amount of SW to the frame. Yes?

And correct me if I'm wrong, but if you add 1.5 grams at 12 and compare that with 3 grams at 3/9, you are adding the same amount of swing weight. Curious to know what the differences are other than the slightly more weight if you opt 3/9. Is it going to give you more plow, less stability when going for the weight at 12? Conversely true for the 3/9?

17. ### IrvinG.O.A.T.

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A 27" racket is 68+ cm long and saw axis is 10 cm so if you put weight inside frame it is about 58 cm above axis and 1 g is .001 Kg p. So 58*58*.001=3.364 Kgcm2

18. ### zaliveProfessional

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You won't get less stability with weight at 12 o'clock. But you will get more with 3+9 o'clock.
The other difference is that you move sweet spot a bit towards 12 o'clock with 12 o'clock mass. With 3+9 o'clock lead it stays at the same place (only a bit wider).
All the other things are just as you said. Unless you want to take account of the real SW (not the calculated one) which includes at least one additional axis, around the shoulder/body. But even so, mass in handle still increases real SW far less than the mass on the hoop.

19. ### mortenHall of Fame

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see my tread on weight at 3 and 9 vs 12 for plow

20. ### EasternRocksHall of Fame

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Have you ever tried 10/2? If 12 adds 3.46 and 3/9 adds 1.5....does 10/2 add the average of the two per gram?

21. ### zaliveProfessional

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@EasternRocks: measure the distance of the 10/14 o'clock from the tip of the handle on your racquet and calculate, I gave you the formula. It's the only way to determine.

22. ### Numero UnoSemi-Pro

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i have ps97,love it, but i really need a bit more stability without making it more HH... maybe i even need more HL racquet.. i guess im searching for six one 95 332gr with a little bigger head and 6,7gr less... so should i add weight at 3 and 9 and little more at handle? or maybe just like 7, 8 gr in the throat?

23. ### IrvinG.O.A.T.

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No matter where you add weight the SW of the racket is going to go up and there is no way to get around that. The closer the weight you add is to the bottom of the racket the less the SW will increase. If you add weight at 3&9 you will also increase torsional stability on off center shots. Adding weight at 3&9 increases SW and adding weight in the handle increases SW.

You may want to try putting weight below 3&9 as the closer it is to the bottom of the frame the less the SW goes up. Putting it on the outside of the frame also increases stability.

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24. ### Numero UnoSemi-Pro

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hm never heard for adding weight on the outside of the frame... i think that sweetspot of ps 97 is little bit low so i dont wanna add weight below 3 and 9..i think 2 gr on both 3 and 9 and also 6,7gr at the handle would give me more stability with a little less maneuverability right keeping the swingweight below 330 right?

25. ### IrvinG.O.A.T.

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When you add weight at 3&9 it is nearer the outside of the frame that's what I meant. Some do add weight on Head frame w/CAP grommets under the grommets on the outside of the frame. As far as Weight and balance is concerned adding 2 g @3. 2 g @9, and 6 g in the handle would about the same as adding all the weight in the throat area.

26. ### mortenHall of Fame

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I like low sw too
but never got this stick stable enough, very annoying.. They should have made a 325g version. I sold it

27. ### Numero UnoSemi-Pro

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well 325 version would be almost same like six one 95... you can get stability on ps97 but you gotta sacrifice some of maneuverability

28. ### mortenHall of Fame

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Well i leaded it a lot and it never felt right.. Lead can only do so much, but cant compensate the construction. They should have made a 325g version anyway now that the sixone is gone.. Thats the racket i chose btw . Have you tried the Textreme95, Prince ?

29. ### Numero UnoSemi-Pro

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hmm can you describe yourself as a player? ntrp? no i actually hate every prince racquet xD i played for 8 years with six one 95, and for the last 12 months i have been trying new racquets like yonex ai100, pro staff 95,pure drive, vcore tour f 310gr and some other but ps97 is the best frpm all those for me...

30. ### mortenHall of Fame

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I am 5.0 . I like mid rackets, main racket ps85 , but tried a lot of rackets throughout the years, the last months i have really enjoyed the sixone rackets, have you tried pure control ?

31. ### baoshuxiongNew User

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Added 4g at 12 today on my 18x20 racquet, huge difference - bigger serves, easier topspins, more stable volley. But still, the form needs to be correct in order to take advantage of greater spin access. Arms feels more tired naturally with extra swing weight. So, better to build up the weight gradually.

32. ### zaliveProfessional

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Static moment situation in a racquet looks similar to this pic:

For this example I used the situation where you add 4 g to the tip and 10 g to the butt. All is idealistic (perfect tip, perfect butt placements of mass). And as the centre point of hand holding the racquet I used 9 cm (never mind if this is 7, 8, or 9.5 cm in reality, it doesn't change much in terms of a principle).

Any added mass creates another static moment, and differential static moment equals (mass added) * (length between added mass position and the fixed point). The fixed point is center of your hand holding the racquet. Any moment tends to rotate the racquet around the axis in fixed point. The further the mass from this fixed point is, the bigger the moment (force) to rotate (linearly proportional). It feels in hand as a heaviness.

So, any mass added in direction closer to the tip when looking from the center point of hand increases static moment of a racquets. But also, any mass added in direction towards the butt when looking from the center point of hand also creates the differential moment opposite to racquets, moment, therefore it decreases the static moment of the racquet.

The differential moment is equal to the formula in rectangule (delta M = M1 - M2). delta M adds to the M(racquet). M1 = 4 g * 59.6 cm. M2 = 10 g * 9 cm. M1 and M2 act in opposed directions (circles). M1 acts in direction of racquets static moment, so it inreases it in fact. M2 acts in direction opposed to racquet's static moment, so actually it decreases it a bit.

M is a vector, so it must be observed as such. While mass or swing weigth are scalars.

Moment (static moment) of a racquet is what you feel in your hand as head heaviness when you hold your racquet still by the handle (with playing hand only). Whenever you feel racquet a head heavy, you feel racquets static moment. The bigger the static moment of a racquet, the heavier the feel when racquet is held still. The smaller the static moment of a racquet, the lighter the feel in your hand.

It is not directly proportional to balance point (COM) of racquet, although head lighter racquets should have smaller static moment too, and vice versa. Sometimes you have head light racquets which feel quite head heavy, more than their balance should actually suggest. This is because of their higher inherent static moment.

Static moment influences a bit of swing dynamics too, and a bit of racquets behaviour too. Because even in swing, static moment is present, so there is some additional effort needed by the hand to compensate it.

And also, physical formula states that: Torsion = Moment * Torque. Therefore, the bigger the moment, the higher the torsional force. So it affects even impact with the ball.

Now, I don't yet have a picture, but imagine adding a leather grip instead of adding 10 grams to the butt. Let's suppose for example that this leather grip is 10 grams heavier than the original grip, so we actually add the same mass to the handle if we replace original grip with leather grip.

What happens to the moment? The additional weigth of a leather grip is evenly distributed throughout the whole handle part which the grip covers. Let's suppose that this length is 18 cm. So, in this given example, exactly one half of the leather grip is in direction to the butt from the center point of hand, while the other half is in direction of the tip. And if the mass is evenly distributed, than one half of leather grip creates the moment which completely cancels the moment created by the other half of the grip, because they act in opposed directions!

Therefore delta M is equal to mass added to the tip * 59.6 cm. Static moment only increased, while adding a leather grip didn't help to cancel some of the moment at all! This is quite contrary to adding some mass to the butt, which did create moment of 10 g * 9 cm to cancel at least one part of the racquet's moment.

This is the reason why adding mass near the butt is simply superior to adding leather grip. It helps in creating lower static moment of a racquet - this means it helps in creating a racquet that feels more head light, expressed in terms of experience. It's also a bit better at moving of the balance point more to a more head light balance too (because of placement of mass which is more distant to COM than average distance of added leather grip mass).

Now in terms of swing dinamycs, for what I know, moving a balance point more to HL helps some. But I experience that with mass added to the butt racquet just feels whippier compared to adding a heavier grip which makes swing feel more sluggish. I don't know yet how to explain this by physics, yet I'm certain with this experience.

I hope some will appreciate this effort to explain this for some reason static moment of a racquet is a spec that is never taken into account and which is never measured. Unimportant? Judge for yourself.

33. ### Karma TennisSemi-Pro

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@zalive, wouldn't the static moment spec. only be of objective value if every player held the racquet in the same way all the time? In the real world, players don't do that. Not only do different players hold the racquet (grip!) differently, many of them change the way they hold the racquet from stroke to stroke.

Typical racquet specifications like Static Weight, Balance, string pattern, etc. don't change as a function of the way the racquet is used. So they are easily measured and documented.

34. ### zaliveProfessional

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Static moment is no less objective than SW and not much different in respect to what you mention. SW also has to have some referent point (which is defined at 10.16 cm from the butt), so the static moment should also have such common point to be meaningful. Different point means different static moment, but also a different SW too.

I'm not saying that it's important enough to be introduced as additional spec. But I think it's something that customizers should know about. And the solution is so simple that you need not to know anything else: just add at least the most of the mass that you add to your handle near the butt. And you'll be rewarded with a more playable stick.

Using a a heavy grip like a leather one might not be the best customizing solution. Sometimes you can still afford it. Sometimes you cannot.

Last edited: Jan 18, 2016
35. ### Karma TennisSemi-Pro

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You might notice that I deliberately didn't mention SW in my list of objective measures. And you have explained why. In any case for me the SW measurement only applies across a much broader range. (IE The difference between a 326 and a 330 SW is not that noticeable. The difference between a 316 and a 330 is!)

But I'm not wanting to get into a debate about SW specs here.

I totally agree with what you say regarding adding mass to the handle. You will see in several other posts I have made in other threads that our first point of customisation with racquets ... particularly Babolat ones ... is to add mass inside the handle under the butt cap. We get huge "value for money" doing this, especially with APDs. More stability, more plowthrough, better balance and a huge (perceived) increase in impact absorption.

For me, the best racquet Babolat never made, was a 2013 APD with a static weight of 325 grams and an unstrung Balance of 10 Points Head Light.

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36. ### zaliveProfessional

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Yeah, and we do know pretty much about SW, it's not useless to have this spec around regardless of the fact that number itself means less for our playing style. Same with moment. Because wherever this central point of our grip is, the important thing is that it still exists, and it cannot be on the butt. We'll always have two levers with some mass on it, creating static moments of opposite directions so principles do apply.

Speaking of, I'm reminded about 7'' position for lead placement, which cannot quite easily be explained physically, but comes from experience. It would be interesting to do empirical comparations between 7'' point and, say, average point of about 0.5-1'' from the butt. And from the physical point of view I could only see one point of comparative advantage if mass was used near the grip spot (center point of holding the racquet), which is closer to 3'', as this spot should be less inert for wrist action (acceleration).

37. ### djnemoRookie

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Customized a Graphene Speed S. Racquet was 290 grams unstrung (good old Head QC - 5 grams over spec), and the balance was 4 pts headlight. I added 17 grams of silicone through the trap door with cotton ball dams, and 3 grams of lead under the bumper from 11-1. Unstrung specs are now 310 grams, and 315 balance. I am guessing the swingweight is around 330. Can't weight to string it up and hit!

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38. ### lulzprimeRookie

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The whole 7" from buttcap for counterbalance is I think; just a very general rule.

I moved my tapes from 7" to 4" instead and guess what? I loved my racket way more than I have ever did.
Numbers are just numbers. Tennis isn't rocket science.

39. ### zaliveProfessional

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7'' lead placement seems to have something to do with MgR/I , as described in travlerajm's thread. It's the way to increase MgR/I towards a more natural value (at least when dealing with polarized setups) for the racquet to be used as a pendulum, which is very useful in ATP type preparation and stroke.

On the other hand, the closer you move lead to the butt, the more maneuverable and statically easier racquet you get, because of most effect of moving the balance point towards the handle and because of best static moment counterbalancing.

On the third hand, placement like at 3-4'' is perhaps the best for the wrist action, giving the lower added real swing weight from the wrist position, and may also represent a compromise between the upper two,

At the end of the day, it seems that there is hardly one direction which can be pointed as the right one. I guess it's just best to know this all, and then try in a real given situation what works best for you.

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40. ### Stick-manNew User

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Any recommendations for a pure aero to increase stability, control and plow through specifically in a forehand but not impact serve characteristics? 3 and 9 or 12 and some in handle? If 3 and 9 should I put in handle too?

41. ### psyvecNew User

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one gram @ 3 & 9... maybe 2 - 3 grs in the handle. You will create the babolat pure aerodrive :v

42. ### psukheNew User

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I purchased 2 volkl pro stock rackets (Tour 10 V-Engine with DNX 9 paintjob) several years ago from TW and I am wondering if its "Sensor Tour Handle System" will prevent me from putting silicone foam in the handle. Using TW University's tool, I would need 32.5g in the handle. I put this off for years because I didn't want to damage the frames while customizing them.

43. ### Pleb123Rookie

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Yes, it will prevent it so long as it remains. If you are willing to remove it completely and use a different butt cap then maybe...

44. ### Pleb123Rookie

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Silicone in the handle greatly improves plow and comfort of the Pure Aero. I prefer lead at 11-1 for stability and control.

45. ### movdqaG.O.A.T.

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Is it a gel? It sounds like it's similar to silicone. Does yours have the Sensor cap? If not, maybe you could just drive two nails through it to add an ounce.

46. ### Pleb123Rookie

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Sensor thingy is a plastic or firm rubber insert about the length of a pinky finger that fits into a channel inside the handle.

47. ### movdqaG.O.A.T.

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I saw a cross-section diagram of it. If yours has that plug then it would appear difficult unless you could easily remove it. If the other stuff that it sits in is foam or very soft, you could just drive two four inch nails in and then replace the cap.

48. ### Pleb123Rookie

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It is just hollow inside. I gave up trying to modify Volkl racquets a long while ago.

49. ### JboRookie

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Sorri if it has been asked guys, but if i already have 2g each at 3 and 9 in 1/4 inch wide strips and wanted to try adding another gram to each side, should i throw a couple more strips on top of the middle of the current lead strips or should i take it all off and add 1.5g strips again? Does it make a difference?

50. ### wmrhawkRookie

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I've done one on top of the other before without any problems.

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