I'm starting to match 2 Tecnifibre 315 Dynacore Rackets

[Irvin]

Just for the fun of it I'm starting to match up 2 rackets and raise the SW by about 10 points. I've taken the strings out and removed the grips, so I'm down to bare rackets. The specs I have now are:

Racket #1 - Weight 305.0 g, Balance 31.3 cm, SW 284.6 Kgcm^2, and TW 13.0 Kgcm^2
Racket #2 - Weight 307.3 g, Balance 31.4cm, SW 288.2 Kgcm^2, and TW 13.2 Kgcm^2

For racket #1 I need to add 2.3 g to raise the TW 0.2 Kgcm^2, SW 3.6 Kgcm^2, and the balance by 0.1 cm. The total inertia I'm adding is 3.8 Kgcm^2 (SW + TW) and I = mr^2 so 3.8 = .0023r^2 so r^2 = 3.8/.0023 and the square root of (3.8/.0023) is 40.65 cm. That point (just below 3&9) is about 12 from the centerline of the racket which raises the TW by (12*12*.0023) 0.3 Kgcm and it is about 39 cm up from the 10 cm pivot which increases the SW 3.5 by (39*39*.0023) 3.6 Kgcm^2. The 2.3 g I added is 49 cm from the butt so the balance increases to [((305.0*31.3)+(2.3*49))/307.3} or 31.4 cm. Since I averaged all my specs down to +/-0.1 I can live with being off by +/-0.1.

The rackets are now matched up very close and anything I do to one I do to the other and they should both end up very much the same. I wanted to also raise the SW by 10 points. I'm going to remove the bumper and place 1/4" lead tape at 68.1 cm so I need [10/(58.1*58.1)] 3.0 g. Once I string the rackets I want to adjust the balance to get an MgR/I of 21.0. I should be able to do that by adding weight to the lower end of the racket.

Questions?

 

[zipplock]

Wow, that's super precise. When I match racquets I get weight to within 1 gram, balance to same HL. My experience is if I do this the SW is nearly matched as well. When I get the racquets this close I can't tell the differences because they are so small.

Your racquet matching game is next level ...

 

[Irvin]

@zipplock thank you, I believe you're right. I'm try to get the TW and SW close and after stringing I'll match the weight and balance as close as I can by adding weight only to the lower end. The weight added on the handle will change the SW very little. I'm hoping I can add just about the same weight at the same locations so it is not even noticeable.

 

[Irvin]

Wow, that's super precise. When I match racquets I get weight to within 1 gram, balance to same HL. My experience is if I do this the SW is nearly matched as well. When I get the racquets this close I can't tell the differences because they are so small.

Your racquet matching game is next level ...

That’s why I’m not a big fan of the TW tool. They usually offer 2 ways to match the rackets, placing weight at either 1 or 2 points from the butt. Assume you use the 1 point method and add 2.3 g at 44.67 cm from the butt and that raises the balance and weight to match perfectly, but that raises the SW by 0.5 pts and the TW by a hair. I could also evenly split the 2.3 g at equal distances above and below the 44.67 which will maintain the exact balance and weight but change the TW and raise the SW angst RW. Without actually knowing what you’re doing I think it is hit or miss.

 

[zipplock]

I'm a fan of heavy-ish (345 gm) and HL, so for me it's pretty simple. I buy racquets that are on the lighter side (300-310 gm) stock, then add weight to the handle (leather grip, lead tape) so I'm not really messing around with swingweight (my target is that 330-335 range).
Limitations for me are that the stock racquet needs have a target swingweight to begin with and be similar enough before I start building them up, which means I'm buying at least 2 racquets at a time.

 

[Irvin]

Same here, I like a 12.5-13 oz racket, I like the 315 because by the time I finish stringing the racket (+18 g) and putting on an over wrap (+6 g) I’m already going up to the 340 g weight. The 315 has a lower SW so I bump it up a bit (+3 g) and by the time I match up weight, balance, and MgR/I I’m assuming I’ll be in the 350 g neighborhood (12.5 oz.) I wish I were home now stringing my rackets, rather than sitting in the service department waiting on warranty work to be done on my truck.

 

[zipplock]

For fun I bought a pair of Wilson Six One 95S racquets. They are out for delivery today. I'm excited to get going on those. I also have another pair of older Head Youtek Prestige Pro on their way, will do the same thing. I may be a racquetaholic ...

 

[Jouke]

Holy moly. This is next level matching! I have a head tuning center, and all I do is measure weight, swingweight, balance. So you are telling me that when i have those all matched it could still be the rackets (twistweight) is different?

 

[Irvin]

Holy moly. This is next level matching! I have a head tuning center, and all I do is measure weight, swingweight, balance. So you are telling me that when i have those all matched it could still be the rackets (twistweight) is different?

Yes but you can also measure TW with the Head tuning center. If the racket is turned 90 degrees you will get a reading that represents TW + SW. normally that reading is in increments of 0.5 Kgcm^2. So if my rackets were both measured on the the Head machine I would get different readings. There was someone not long ago that came up with a hack to get readings down to 0.1 in the stringing forum you may want to google that.

I use the SwingTool app to measure inertia, and a jewelry scale that measures in 0.01 increments. I use the weight to the closest 0.1 multiplied by 10. So if my weight is 305.3 I input 3,053 g in ST. That gives me a readout 10 times greater than actual. So if the readout is 2,846 Kgcm^2 I know to record 284.6. There are many ways to do this my way just works for me and as long as I keep my conditions the same I get very consistent and repeatable reading. For instance. I keep the swinging racket about 4” away from the camera lens on my iPad with a good deal of open space behind the racket. That way the camera does not miss any passes of the racket and my periods are generally +/- 0.002 seconds.

EDIT: But you don’t have to go this far. Like @zipplock suggested matching just weight and balance is really close enough many people can’t tell the difference. But if you’re switching from a racket with a 2.0 change in TW you may or may not like the racket and if all you’re measuring is SW you’ll never know why.

Here is a good article on TW http://www.tennisindustrymag.com/articles/2005/02/a_new_twist_on_the_twistweight.html

 

[dr. godmode]

What tools are you using to measure SW and TW to 0.1 tolerance?

Edit: oh

 

[Irvin]

What tools are you using to measure SW and TW to 0.1 tolerance?

Edit: oh

I use a jewelry scale where the readout is in 0.01 g, I use a homemade balance board where I use a micrometer to measure the distance to a stop in 0.01 cm, and for inertia (SW, RW, I, & TW) I use SwingTool with the weight set to 10x the value so my readout is 10x the inertia.

EDIT: But I never measure TW in a string racket. I use the head of the frame to measure the period of the swing with ST. With strings in the racket ST does not catch all the swings all the time. I could use a video and count frames per seconds which can be more accurate but it takes a lot more time.

 

[dawwe]

A twist to this topic is with other words: Higher twist weight will suit beginners better since it makes the racket more stable, and lower twist-weight is for the professional who can hit "dead-center" no matter what. Is that partially the reason why more recreational rackets has a bigger head and perhaps even more round shape?

I have added 4 g each at 3 and 9 on my racket, it plays great. I did take my racket to a shop who had that "Babolat machine" and balance was 3 points head-heavy (I have measured it to be around 34.5 cm), static-weight 363 g and massive (?) swing-weight of 383 g. I have played with this setup for approx 4 years, and it took me 3 years to find this setup. At one point I went too far weight wise and too head-heavy balance, at that point I stepped back again and found the sweet-spot, for me. I did measure balance-point when the sweet-spot was found, and I used a commercial scales (found in a Supermarket near your home ), it tipped the scales to 353 g, but it turns out it was 10 g more... As far as I'm concerned the only thing that matters is that the racket feels great and that you play great with it, regardless of its weight etc.

I tried a Wilson Clash a few days ago (310 g version) and it played very different than my racket. Felt very head-light, and it felt like I was swinging/whipping through "too violently" on the forehand. Serve felt great, I believe its partly because of the lower weight and thicker/wider beam, but also the different string pattern and not least a softer string with much lower tension (23-24 kg). My normal racket is a control oriented racket with 21 mm beam, 95 sqi and 18/20 string pattern, full bed of RPM Blast with high tension. The way Irwin is approaching customization/matching is very very professional, I wonder if they are this professional when they modify rackets for ATP-players...

 

[Irvin]

Yesterday was a bad day for me, I couldn't get anything done on the rackets. I was able to get the weight I described in post #1 on, and I was able to rescue one bumper grommet, the other bumper I replaced. Now I am going to have to find time to string the rackets and I am going to use my Gamma DW X2 machine for that with an ATW pattern. Then I will make an attempt to set up the weight and balance to match them up and get the MgR/I on both rackets to 21.0.

 

[zipplock]

I strung single string once. Broke strings in first hour of use (mishit just right). Ever since then changed to two piece. If main breaks quickly I can salvage the racquet by just restringing mains.

 

[Irvin]

@zipplock I’m not a fan of salvaging 1/2 sets of string. I see no reason why 1 piece or 2 piece should break any faster than the other. I always use designated tie off grommets to tie strings off which means the top cross is usually tied off on a main stringing 2 piece. If you don’t use a main to tie off you must use a starting clamp, and that could damage the string right where it bends around the frame or in the knot and that could easily break the string prematurely. If the crosses are tied on main and you take the mains out you’ll have to replace the crosses anyway.

If you use a 1 piece pattern and a string breaks use the longest section for your crosses and fresh string in the mains and you will have salvaged a half set a lot easier.

 

[zipplock]

I'm not sure I understand about 1/2 sets. I string from a reel, only cut length as I need. Maybe I'm missing something.
You are absolutely correct though, string breaking has nothing to do with if it was strung single or two piece. I break strings if I've used them too long or with a misfit close to the frame. I've never broken a cross, just mains.

 

[Irvin]

Well I got my rackets strung. After stringing the racket they had a SW of 304.0 at 0 cm, balance of 33.5 cm, and weight of 317.5 and 3.7.3 g. I added 1 cm of lead on each side of the throat grommets. The next time I string the frame I’ll move the lead under the throat grommet. Now I need to add grips and over wraps and they weigh about 23 g. I’m going to add enough lead under the grip to get the total weight on both frames to 341 g. The grips and OGs with add about 1.5 points to the I (SW) at 0 cm.

To get an idea of how my MgR/I will turn out 21.0 = MgR/I = (g/I = 980.5/505.5) = 1.93966MR = 21/1.93966 = MR = 10.82662 = 10.82663/.341 = R = 31.74962. EDIT: wow that’s confusing. I used the formula 21.0 = MgR/I and I know M (mass) is 341, g (gravity) is 980.5, R (radius or balance to get to 21.0 is unknown, and I (inertia or SW at butt or 0 cm. As it turned out the R / balance point I needed was was I was going to get.

Now I need to see what adding 23.5 g of mass at 8 cm (center of grip) does to the balance ((317.5*33.5)+(23.5*8))/341 = 31.74267. That’s almost perfect damn did I get lucky. Now I need to put the grips on, check the specs, and hit when I get a chance.

EDIT: Final specs should be SW 325.0, wt 341 g, balance, 31.7, and MgR/I 21.0

 

[Irvin]

I went out to hit with my 315s today sunny and high 50s but the wind was terrible. I strung up the 315s with a multi string at 52/49. I generally play with a 18x19 frame with poly in low 40s, but the SW is 325 and MgR/I is 21. I can tell much difference between the three rackets. I can tell any difference between the 2 315s. They both have a nice smooth buttery feel, but then again that why I targeted the specs I did for the same feel I experienced before which is what I was looking for in both rackets.

I strung these rackets on a DW machine and I’m not as proficient with it as I am on my eCP Babolat machine. So I can tennis slight difference in vibration between the 2 frames. But I can’t tell any difference while hitting.