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#41 | |
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Professional
Join Date: Aug 2005
Location: The crappest town in Britain
Posts: 1,145
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Quote:
The main thing is to focus on the real goal, which is the final twistweight/hitting weight at 3&9 rather than a specific amount of lead tape.
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#42 | |
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Join Date: Jun 2012
Posts: 133
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#43 | ||
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But reversing this relationship is not the goal. Equalizing the spin production so that the stringbed produces the same amount of spin on high, low and central impacts is the goal. Adding 100 grams does not achieve that goal. The TW Professor mused that, if the addition of mass at 3&9 effectively reverses the relationship in a linear way, there may be an amount of mass that one could add that would achieve this goal. Some simple calculations showed that adding about 60 grams of mass should do this, assuming there is such a linear relationship. For the sake of experiment, I'm willing to run with this assumption. Quote:
In the paper, six physical effects or phenomena were linked to the altered spin production seen at high and low impacts with and without added mass: 1. Short-side effect 2. Rotation effect 3. Friction effect 4. Bending effect 5. String movement effect 6. Weight effect Increasing hittingweight will definitely have a big impact on numbers 5 and 6 on this list. But the relationship of hittingweight and effects 1-4 on the list is not at all clear. On the other hand, increasing twistweight will almost certainly alter the rotation effect (#2 on the list) and short-side effects (#1), and the reversal in the spin-gradient from low to high seen in the experiment might be in large, or even most, part due to increasing twistweight by a huge amount because it is likely that these effects are those most amenable to modulation by the addition of mass. Adding those 100 grams to the Exo3 Red 105 pushed the twistweight to around 32.7. The greatest twistweight amongst racquets currently produced is about 21 (Wilson K4 OS), so we're definitely in uncharted territory here. Adding 60 grams at 3&9 to the Exo3 Red would bump the swingweight to around 24. So why not just add a couple grams at 3&9 to a K4 OS and call it a day? It would be tempting to attribute the results described in the paper to measures that we are familiar with and understand well, like hittingweight and twistweight. But there are several more effects on the above list that are not often considered in conventional racquet customization work using relatively small amounts of mass. The bending effects documented in the paper, for example, are not something that people usually think about when adding a little lead to a racquet. Yes, I could use the the above twistweight number and calculate the hittingweight that would result from the addition of 60 grams at 3&9, and then attempt to target both those numbers. But would that achieve the goal? Remember that the TWU experiments also included the addition of 100 grams of mass at 1&11. This would have increased the hittingweight much, much more than the addition of that mass at 3&9. So if we focus on a target hittingweight we would only need to add maybe 20 or 30 grams at 1&11 to hit that target. But, the addition of 100 grams at 1&11 did not produce the same effect on spin production at various impact locations as did mass at 3&9. Adding mass at 1&11 intensified the result observed in the stock condition - spin production was already greatest on low impacts and adding mass at 1&11 made this even more pronounced. This would suggest that increasing twistweight, not hittingweight, is most important to reverse the spin gradient observed in stock racquets. And this is what the paper, at least hesitantly, concludes by noting that the short-side and rotation effects (numbers 1 & 2 on the list) are most responsible for the differences in spin production seen in high and low impacts. Increasing twistweight to around 24 could then, be a worthy goal. It's interesting to note that the short-side effect would be reduced using an oversize frame like the K4 112, because off-center impacts would be further from the frame than they would be in a midplus and even more so than with a mid. This suggests that, at a given twistweight, the difference in spin production for high and low impacts would be less with an oversize than with a midplus. A mid would be the worst. Also, since oversize frames naturally have greater twistweights, because any mass added or existing on the periphery of the frame is located further from the longitudinal axis, you'd have to add less mass to an oversize to achieve the goal of equalizing spin production across the stringbed. Conversely, you may have to add even more mass, perhaps much more, to achieve this goal with a mid. In fact, it could be that the K4 112 achieves the goal in stock form with it's twistweight of 22. But I'm not playing with that ugly thing! Anyway, yes, it would be tempting to focus only increasing twistweight to a particular target, and in this case that target would be about 24. And in essence that's what I'm doing. What's the best location to add mass to increase twistweight the most while increasing hittingweight the least? At the frame's widest point - at 3&9. So I'm trying to find a frame with a very low swingweight so that I can add 60 grams at 3&9. The good news is that even a very light, low-swingweight frame like those kindly suggested so far have stock swingweights pretty close or only a little less than the Exo3 Red. Whew! To those who have suggested that I should come down to earth and who have kindly pointed out that adding even modest amounts of mass at 3&9 changes the performance of a racquet: Thanks, you're right. But I'm not looking for performance enhancement; I'm looking to create the ultimate control racquet. LOL The bummer, though, is that even if I do achieve the objective of making spin production uniform for all impacts across the racquet face from 3 to center to 9, I probably won't even know it. Times like these I wish I had a spin measurement rig in the basement. Last edited by corners : 02-21-2013 at 12:45 PM. |
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#44 | |
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Hall Of Fame
Join Date: Aug 2010
Location: Canada, Eh?
Posts: 4,432
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-Fuji
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I believe what he says are nuggets of truth. And I collect them. And I store them in the lock-box of my soul. -JD |
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#45 | |
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Professional
Join Date: Aug 2005
Location: The crappest town in Britain
Posts: 1,145
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Quote:
The more I think about the problem, the more I suspect that what you're really looking for is a particular distribution of mass in terms of the ratio of mass in the upper, middle, and lower hoop. That is, if you have a frame with x% of the mass in the upper third of the hoop, y% in the middle third, and z% in the lower third, you'll get that consistent spin potential across the whole string bed regardless of the overall specs. The difficult part is finding the exact values for x, y, and z, which will probably vary a bit frame by frame given differences in head shapes, flex patterns, and string spacing. If I were in your shoes, I'd start with the Exo3 Red and see if that 60 g really does give you the consistent spin potential that you're looking for (forget overall specs and personal preferences for the moment). You might find that that necessary modifications are more complicated and the results are difficult to verify. But, if you do end up finding a way to verify the results and get what you're looking for, then you can start searching for other frames that will give you the overall specs you like after you've modified them to get that consistent string bed. Basically, test the feasibility first on a well-known subject and then start looking for more ideal candidates later.
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#46 |
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Hall Of Fame
Join Date: Feb 2004
Posts: 2,901
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10 grams at 3 and 9 increase swingweight by appx 25.
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#47 | |
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Hall Of Fame
Join Date: Jul 2008
Posts: 3,805
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Quote:
But I think it's pretty clear from the paper that two effects dominate the observed difference in spin generation between high (toward the sky) and low (toward the ground) impacts: the rotation effect and the short-side effect. If hittingweight, or the hittingweight gradient from throat to tip, were the critical factor, then the 100 grams added at 11&1 should have reversed this gradient, as 100 grams added to those locations would have bumped the swingweight by about 250 units. Adding 100 grams at 3&9 "only" increases swingweight by 200 units. But the relationship is reversed in terms of twistweight. Those grams at 3&9 increase the twistweight by about 12 units, while adding at 1&11 would only increase it by about 7 units. I think it's pretty clear that the reason why mass added at 3&9 worked to reverse the spin difference is because of the twistweight increase, which makes sense if you carefully read the descriptions of the rotation and short-side effects. Looking at the experimental results, it appears that adding mass at 11&1 would work too, but you'd have to add even more mass, like maybe 150 grams, which takes me far away from the secondary goal of keeping swingweight at a swingable level. This is why I don't think it matters which frame I start with, as long as it has a twistweight of 11 or more, stock. Increasing swingweight, and thereby increasing hittingweight, should increase spin at all impact locations, but shouldn't change the observed spin gradient that much, if at all. So I'm not too concerned about the stock or final swingweight. (I might be wrong about this, however.) In addition, the experiments in the paper provide a basis for further experimentation. It would have been best if the TW Professor had tried 60 grams and confirmed his hunch; but, his results with 100 grams certainly light the way towards trying 60 grams at home. Going in another direction entirely would, in my opinion, require a controlled spin testing rig like he has, which I haven't got. So I'll restrict my wild racquet ramblings to the path already slightly tamped down. Unfortunately, all that mass concentrated at 3&9 will not equalize the throat to tip power gradient. But that's another problem, and one that Travlerjam has solved, I believe, by concentrating mass in the entire top half of the hoop, from 3 all the way round to 9. This is what Head has done too with their new Graphene Speed Pro, at least that's what their marketing says. Last edited by corners : 02-22-2013 at 08:14 AM. |
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#48 |
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Rookie
Join Date: Jun 2012
Posts: 133
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This got me inspired.
I just did an experiment with a Pure Storm Ltd. I put two weights of 45 grams at the sides of the head and moved both up and down until I was satisfied with a constant launchangle when the tennisballs were hit across the face from 3 to 9. The most ideal spot seemed to be at 4 and 8. I know I varied not only twistweight but also swingweight and balance, but during play I also varied grip position up and down regardless of the present swingweight and balance. The interesting part is that I tried to hit with constant rackethead speed and all over the racketface from 3 to 9 and with the weights attached at 4 and 8, the launchangle, speed and depth were pretty constant, which makes me believe that the spinrate also had to be pretty much the same. Whether a 425 grams racket is really playable is another question Really looking forward to your experience, Corners. Last edited by JohnB : 02-22-2013 at 10:47 AM. |
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#49 | |
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Hall Of Fame
Join Date: Jul 2008
Posts: 3,805
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Quote:
I wonder if you found 4&8 to equalize spin the most because of the headshape of the PSL, which kind of has a Volkl headshape, wider at 4&8 than most other frames. The only negative with mass at 4&8 is that it will tend to make the frame more powerful in the lower hoop, where it is already most powerful in stock form. I have always favored mass at 10&2 or higher as this will tend to equalize the power gradient of the frame and provide more pop on serve (which I tend to hit nearer the tip), in particular. But the positive of 4&8 is that it will raise the swingweight by a lesser amount that at 3&9 or higher. It might take me awhile to get my experiment going as I'm taking my time in choosing the right platform frame, of which I'd like to get two so that I can make on-court comparisons. But thanks for the encouragement. |
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#50 | |
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Rookie
Join Date: Jun 2012
Posts: 133
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Quote:
Could you, BTW, maybe explain to me what the reasoning is for wanting the upper part of head to be more powerful? I would say that in a normal groundstoke, the higher rackettipspeed would make up for that. Or is that also a matter of finding the right massgradiënt to even things out? |
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#51 | ||
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Hall Of Fame
Join Date: Jul 2008
Posts: 3,805
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But this is all most true for very high swingspeeds and low incoming ball speeds. So on serve you really don't lose much speed if you hit near the tip, if at all, and the extra spin is very welcome. But as the swingspeed slows down and the incoming ball speed increases, the low ACOR near the tip starts to penalize you. On a hard groundstroke, like 70mph shot speed, you might lose 2-4 mph if you hit 2 inches above the center with a traditionally weighted player's stick. And on a volley, where the incoming shot might be 70 mph or so, and your racquet is traveling only 15, things are worse. And made worse by the fact that volleys are relatively linear swings, so the tip isn't usually moving much faster than the throat, unlike with serves and rotational groundstrokes. So on a volley you might lose 5-7 mph on a shot struck near the tip compared to one struck in the center. Worse still, if we instead compare a volley struck 2" above center and one struck 2" below center we're looking at a possible difference of 15 MPH or so. And now the differences in launch angle and speed start to combine to produce shots landing several feet or more apart from each other on the court. So not only are you getting widely variable shot speeds at net but you're losing accuracy unless you can hit in the center of the strings each time, which you can't. So this gradient business is mostly about volleys, but also could be important on groundstrokes if you're into equipment optimization or just generally geeking out on this stuff. And if you get the tip leaded up and ACOR improved up there you might be able to get a couple extra MPH on serve because most people tend to hit high in the hoop when serving. Stiff hoops also liven up the upper hoop, but doing it with mass is a more arm-friendly approach, (as long as your shoulder can handle the heft.) The poster Travlerajm introduced me to this topic, and if you're familiar with his experiments you'll know that he weights the hell out of the top of the hoop. He plays the net a lot so this probably really helps him achieve consistent power and accuracy up there. From that perspective it's pretty interesting. Sampras gained a lot by adding so much mass at 3&9, but I wonder if his volleys would have been even better had he put more mass higher in the hoop. On the other hand, to my knowledge Edberg used a stock PS 85 without a bumper guard, which meant his swingweight was very low, with a steep ACOR dropoff near the tip. And he maybe had the best volleys of all time. So a strong case could definitely be made that we're here ridiculously overthinking this stuff. All the "data" in the first couple paragraphs was generated with TWU's Shot Maker simulator. I've learned a lot from playing around with that thing. Last edited by corners : 02-23-2013 at 03:45 PM. |
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#52 |
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Rookie
Join Date: Jun 2012
Posts: 133
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Thanks, Corners.
Today, I moved the weights to 10 and 2 and tried to be as precise as possible to achieve the same twistweight. No matter how I shifted the weights around 10 and 2, I could get a predictable launchangle. No comes the interesting part. When attached the weights to spots around 10 and 2 where the launchangle was least unpredictable, I added 12 grams total also at 10 and 2 (on top of the weights), the launchangle, speed and depth were constant again. This makes me believe that with higher swingweights, higher twistweights are needed to generate a constant spinrate across the face from 3 to 9. Estimated final specs. 437grams, 39cm, sw.600+, so not very playable obviously. |
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#53 | |
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Hall Of Fame
Join Date: Jul 2008
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#54 | |
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Rookie
Join Date: Jun 2012
Posts: 133
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Although the swingweight increase is enormous, the twistweight increase isn't that much higher, relatively speaking. So it might be that a certain twistweight is optimal for this purpose and that just a little finetuning is needed. If you want to combine this experiment with a proper power gradiënt towards to tip, you have to start with a very, very light frame. |
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#55 | |
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Join Date: Jul 2008
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i wish I was that clever.
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#56 |
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Rookie
Join Date: Oct 2011
Location: (Stony Brook/ Brooklyn )NY
Posts: 269
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How to add 60 grams at 9&3? That is 120inch of .5gram,or 240 inch of.25 gram lead?? If you use the .5gram/inch, thats 30layers of lead
Last edited by tyu1314 : 02-26-2013 at 07:51 PM. |
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#57 | |
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Professional
Join Date: Aug 2005
Location: The crappest town in Britain
Posts: 1,145
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Quote:
It's a fairly sizable stack of lead, but it's still doable.
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#58 | |
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#59 |
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Professional
Join Date: Aug 2005
Location: The crappest town in Britain
Posts: 1,145
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Maybe a combination of liquid and lead tape. Squirt the silicone and measure the mass gained. Then add the remaining mass with layers of lead tape.
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#60 |
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Join Date: Mar 2006
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I just found this thread. It’s an interesting topic.
I discovered 5-6 years ago an interesting phenomenon, and I confess that I still cannot fully explain the physics of it. If you start with a stock racquet (doesn’t really matter what the starting specs are, it could be a light tweener, or it could be a players racquet, as long the swingweight is in the typical range), and then proceed to add mass gradually to the upper hoop, it will tend to become more powerful and less spin-friendly. But as you continue to add mass, eventually you reach a “tipping point”, where further additions of mass start to have the opposite effect on spin and power level a groundstroke. Continued addition of mass beyond this tipping point result in a heavier, spinnier response from the stringbed (I had previously termed this zone beyond the tipping point as “SW2”). I found it uncanny that the tipping point almost always occurs at a swingweight near 360 (but it can vary, depending on the starting specs of the frame). It seems to be at least in part a swingweight effect, because the “spin reversal” (that is, the increased spin with further mass increase) happens regardless of whether I place the extra lead at 3-&-9 or at 12. But I have also noticed that the heavy ball effect (seemingly effortless natural spin) is most pronounced when a significant fraction of the added mass is at 3 and 9. I had presumed in the past that this “spin reversal” effect must be somehow related to the effects of ball flattening. But now I’m not so sure – I think ball flattening is part of the story, but these other effects discussed by TW professor (rotation effect, shortside effect, could also be contributing to this phenomenon). The TW Professor’s experiment looked at what happens when you add 100g, which pushes you far past the tipping point, into the realm of very spin-friendly racquets. But I think the experiment is jumping over the more interesting question of what is happening in between. In my experience, it doesn’t take 100g addition to enjoy these heavy-spin effects – all it takes is pushing the swingweight of your racquet up to around 370 SW. Doing the experiment on court (or even against a wall) is fun and easy to do. Just grab a roll of lead tape, and start adding a couple grams at a time, and observe the difference in ball response. When you finally get past the tipping point, and the ball starts to really dip after it leaves your stringbed, it is a strange sensation. As for creating more consistent spin across the face from 3 to 9, I have never specifically tried to optimize that. However, I can tell you that whenever I try to play with a frame of stock swingweight (325 or so), I am never completely comfortable with the predictability of spin and launch angle. For me, the difference in control (with ‘control’ defined here as predictability of ball response) between 325 SW and swingweight in high 360s is night and day. Maybe part of the reason is that the high 360s swingweight range is where spin rate is nearly equalized across the face from 3 to 9? Once you combine predictability of ball response (which for me comes with combining high enough swingweight and stiff enough stringbed) with the ability to control the racquetface through the contact point (which for me can be achieved by carefully tuning the MgR/I parameter), tennis becomes a lot easier.
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BLX Blade 98. 13.74oz., 12.55", 370.5 SW. Pre-Stretched Ashaway Kevlar 18g/Zyex Monogut Red 16g, 55 lbs Last edited by travlerajm : 02-27-2013 at 06:54 AM. |
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