Manually Measuring Swingweight

ryushen21

Legend
I don't have any current plans to develop an Android app, but if demand justifies it, I will. I did verify that Android supplies a precise timestamp with the gyroscope data, so there's a chance that it will work as well as the iPhone app. Unfortunately, it's not a simple matter of recompiling.
I totally get that and it's a bummer for me not to get one. But I also know it doesn't make sense to spend the time developing the Android version unless you have the customer base to support it.
 

Chace

Hall of Fame
Just went to order one and looks like they’re out of stock again. That was quick. 4 sold in less than an hour.
 

Irvin

Talk Tennis Guru
I just had 2 Dunlop 200g racket to re-string for a client. The last time he asked me to to put lead at 3&9 on Racket #2. Here are the measurements today:

Racket #1 SW 326.36, TW 12.67, Wt 345.72, COM 32.1
Racket #2 SW 332.77, TW 13.24, Wt 352.51, COM 32.0

The TW difference is (13.24-12.67) 0.57. The radius at 3&9 is 12.2 cm. I=mr^2 or m = I/r^2 but this is kgcm^2 instead of gcm^2 so I’d have to multiply by 1000. 1 g of my lead is 11 cm long and 4 strips at 3&9 will be needed. Sot calculation for lead strips to match the TW for both rackets is:

(((13.24-12.67)/(12.2*12.2))*11)*250 = 10.53144 or 4 10.5 cm of lead on both sides of racket #1 to match TW.

EDIT: Putting all this in an Excel worksheet if you’re going to start matching.
 

tim-ay

Hall of Fame
I just had 2 Dunlop 200g racket to re-string for a client. The last time he asked me to to put lead at 3&9 on Racket #2. Here are the measurements today:

Racket #1 SW 326.36, TW 12.67, Wt 345.72, COM 32.1
Racket #2 SW 332.77, TW 13.24, Wt 352.51, COM 32.0

The TW difference is (13.24-12.67) 0.57. The radius at 3&9 is 12.2 cm. I=mr^2 or m = I/r^2 but this is kgcm^2 instead of gcm^2 so I’d have to multiply by 1000. 1 g of my lead is 11 cm long and 4 strips at 3&9 will be needed. Sot calculation for lead strips to match the TW for both rackets is:

(((13.24-12.67)/(12.2*12.2))*11)*250 = 10.53144 or 4 10.5 cm of lead on both sides of racket #1 to match TW.

EDIT: Putting all this in an Excel worksheet if you’re going to start matching.
If the frame curvature is different towards 12 than towards 6, everything will be balanced on the frame you are adjusting, but do you think you might have to trial and error a bit to match another frame? That radius squared could throw things off a little or am I being stupid? Didn’t sleep well last night… edit, it probably won’t make much difference, even if a frame has a slightly different mass distribution in the head. Yeah, i was being stupid, lol
 

Irvin

Talk Tennis Guru
If the frame curvature is different towards 12 than towards 6, everything will be balanced on the frame you are adjusting, but do you think you might have to trial and error a bit to match another frame? That radius squared could throw things off a little or am I being stupid? Didn’t sleep well last night… edit, it probably won’t make much difference, even if a frame has a slightly different mass distribution in the head. Yeah, i was being stupid, lol
You’re not being stupid but talk about frame curvature does not make sense to me. Radius squared could throw things off? I don’t think you understand. The radius of a racket is half the diameter at 3&9 where you get the most TW increase per gram. TW increase is I=mr^2 you must square the radius.

if my client wanted to match TW of Racket #1 to Racket #2 (the one he added weight at 3&9) he could do it by adding 4 10.5 cm strips of lead at 3&9.
 

tim-ay

Hall of Fame
You’re not being stupid but talk about frame curvature does not make sense to me. Radius squared could throw things off? I don’t think you understand. The radius of a racket is half the diameter at 3&9 where you get the most TW increase per gram. TW increase is I=mr^2 you must square the radius.

if my client wanted to match TW of Racket #1 to Racket #2 (the one he added weight at 3&9) he could do it by adding 4 10.5 cm strips of lead at 3&9.
No , i understand the formula. I’m just thinking the center point may not be the center point of the added mass impact on TW due to the frame curvature( it’s not always symmetric). Doesn’t matter….the more i thought about it i realized its stupid to worry about. Lol. Maybe the COM for the TW axis rotation is really 12.1 vs. 12.2. But so what? We’ll see it in the measurements and adjust. It will matter more at 10/2 though.
 
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Dags

Hall of Fame
I just had 2 Dunlop 200g racket to re-string for a client. The last time he asked me to to put lead at 3&9 on Racket #2. Here are the measurements today:

Racket #1 SW 326.36, TW 12.67, Wt 345.72, COM 32.1
Racket #2 SW 332.77, TW 13.24, Wt 352.51, COM 32.0

The TW difference is (13.24-12.67) 0.57. The radius at 3&9 is 12.2 cm. I=mr^2 or m = I/r^2 but this is kgcm^2 instead of gcm^2 so I’d have to multiply by 1000. 1 g of my lead is 11 cm long and 4 strips at 3&9 will be needed. Sot calculation for lead strips to match the TW for both rackets is:

(((13.24-12.67)/(12.2*12.2))*11)*250 = 10.53144 or 4 10.5 cm of lead on both sides of racket #1 to match TW.

EDIT: Putting all this in an Excel worksheet if you’re going to start matching.
@bfroxen

This is another area where you could have an advantage over your competitors. With the power of the iPhone app, wouldn't it be great if you could measure the SW and TW of two (or more) racquets and have the calculations done for you with a simple output of where the put the weight to match them? Options to input weight and balance, target specs and so on.

And if that functionality already exists, you probably ought to emphasise it more!
 

Irvin

Talk Tennis Guru
No , i understand the formula. I’m just thinking the center point may not be the center point of the added mass impact on TW due to the frame curvature. Doesn’t matter….the more i thought about it i realized its stupid to worry about. Lol.
Ok but curvature still does matter for center balance. let’s assume the actual balance of the racket was 1 cm off. Instead of the radius being 12.2 cm it was 13.2 on 1 side and 11.2 on the other (1 cm off from center. Adding 3.83 g of lead at 3$9 would make a difference of 0.00389. Not enough to make a 0.01 kgcm^2 difference.
 

Irvin

Talk Tennis Guru
@bfroxen

This is another area where you could have an advantage over your competitors. With the power of the iPhone app, wouldn't it be great if you could measure the SW and TW of two (or more) racquets and have the calculations done for you with a simple output of where the put the weight to match them? Options to input weight and balance, target specs and so on.

And if that functionality already exists, you probably ought to emphasise it more!
Easier said than done I would imagine.
 

bfroxen

Rookie
cool - exciting. good to know you can turn around rather quickly.
so.... any idea on how us non-US people can get our grabby hands on your SW1? thanks. :giggle:
Trying to keep up. Another printer en-route and thinking of ordering another.

I definitely have some compliance work to do on the website to sell into the EU or UK. From the research I've done, the product itself doesn't seem to need anything. Also, I need to figure out how to pack it all in one box. I'm not sure how long it will take, but I won't take offense if you keep on me. :)
 

bfroxen

Rookie
@bfroxen

This is another area where you could have an advantage over your competitors. With the power of the iPhone app, wouldn't it be great if you could measure the SW and TW of two (or more) racquets and have the calculations done for you with a simple output of where the put the weight to match them? Options to input weight and balance, target specs and so on.

And if that functionality already exists, you probably ought to emphasise it more!
Definitely thought of that. No, it doesn't exist yet.

I did polish up the spreadsheet that I use. There's a link to it in the user guide. Racquet Matching Google Sheet. You can copy it and use/adjust to suit.
 

Irvin

Talk Tennis Guru
Trying to keep up. Another printer en-route and thinking of ordering another.

I definitely have some compliance work to do on the website to sell into the EU or UK. From the research I've done, the product itself doesn't seem to need anything. Also, I need to figure out how to pack it all in one box. I'm not sure how long it will take, but I won't take offense if you keep on me. :)
For ease of shipping you could provide instructions on creating a calibration rod. Then you have 1 small box and a lot of 3D printing you don’t have to do. Easier for you and a lower price for the buyer with reduced shipping.
 
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bfroxen

Rookie
For ease of shipping you could provide instructions on creating a calibration rod. Then you have 1 small box and a lot of 3D printing you don’t have to do. Easier for you and a lower price for the buyer with reduced shipping.
That may make the most sense for international shipping. The accuracy of the calibration rod is dependent on the cleanness/squareness of the cuts. I use a router and custom jig I developed. A lathe would be ideal. A saw, file, and square could work if you have the time. Then, it needs to be measured accurately. A 24"/600 mm caliper isn't accessible, but a good meter stick and some magnification can yield a good measurement.
 

Dags

Hall of Fame
Easier said than done I would imagine.
The man designed and built a swingweight machine. I have faith. :)

I'm sure you're right that the full package of every spec matching may be an ask. But as a software developer myself, anything that could be done in an Excel spreadsheet, I could create in an app - it's just a case of understanding the logic behind it. Even if the initial goal were to 'only' match on one spec, a friendly user interface and storing the readings calculated by the machine really opens up the process to those folk who are possibly less mathematically inclined. Not quite 'Racquet Matching for Dummies', but pretty close to it. The idea that I could measure the SW and a few clicks later be told 'stick 4g of lead here' is pretty awesome. Being able to harness the computational power of the iPhone is a USP for this device.
 

PrinceYonex

Semi-Pro
I’ve never seen anywhere people talking about matching TW. But now you can easily measure TW that may start more.
I am lucky to have one of these devices on the way to me. Being able to measure and match twistweight will be a game changer. Not, obviously, in my actual tennis. But surely this will open up a whole new domain of obsessive curiosity.
 
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Power Player

Bionic Poster
I think it actually can help the tennis game to identity the ideal SW that you play with. It makes a big difference to be playing with something too heavy or too light. Once you figure out what the specs are on that ideal frame that works for you, it is a lot easier to make little tweaks on racquets that never totally worked for you, but you wish would.
 

PrinceYonex

Semi-Pro
I think it actually can help the tennis game to identity the ideal SW that you play with. It makes a big difference to be playing with something too heavy or too light. Once you figure out what the specs are on that ideal frame that works for you, it is a lot easier to make little tweaks on racquets that never totally worked for you, but you wish would.
For sure, I completely agree. To this point I’ve been measuring swingweight with that SwingTool app, hanging the racquet off a table, etc. That’s been helpful already to get me in the ballpark.
I’d also add that the ability to measure twistweight accurately, something I’ve not been able to do to this point, will add yet another criteria for indicating what specs one prefers.
 

esm

Legend
I think it actually can help the tennis game to identity the ideal SW that you play with. It makes a big difference to be playing with something too heavy or too light. Once you figure out what the specs are on that ideal frame that works for you, it is a lot easier to make little tweaks on racquets that never totally worked for you, but you wish would.
Agreed. I believe find a right SW one can handle for the longest period is important.
I believe the SW1 device will just make my life much much easier to be able to measure the SW (and now TW) quickly (for me and others). I can’t wait until the day I don’t have to spend time to setup the home rigged devices and having to enter all the parameters in the swing tool app to measure SW.
I am also keen to understand “how far off” my home rigged SW setup is compared to the SW1…. When I get get it. One day soon. I hope.
 

tim-ay

Hall of Fame
That may make the most sense for international shipping. The accuracy of the calibration rod is dependent on the cleanness/squareness of the cuts. I use a router and custom jig I developed. A lathe would be ideal. A saw, file, and square could work if you have the time. Then, it needs to be measured accurately. A 24"/600 mm caliper isn't accessible, but a good meter stick and some magnification can yield a good measurement.
The turnkey solution will probably give you more sales. Such a great device and the ease of setup will enable a broad audience to use this.

I’m not sure how much support UPS or FedEx international provide to small business, but consulting with them on a packaging solution might help you, if you are able to get to the right person. DHL may have something similar.
 

Irvin

Talk Tennis Guru
I have a funny feeling that people think matching TW, SW, weight and COM is going to be a no brainer. A racket is a stick on one end and a loop on the other and there is just so many places you can add weight. If a racket were rectangular and I could place mass at any point within that rectangle then matching SW, TW, weight, and balance would be a no brained.
 

Irvin

Talk Tennis Guru
The man designed and built a swingweight machine. I have faith. :)

I'm sure you're right that the full package of every spec matching may be an ask. But as a software developer myself, anything that could be done in an Excel spreadsheet, I could create in an app - it's just a case of understanding the logic behind it. Even if the initial goal were to 'only' match on one spec, a friendly user interface and storing the readings calculated by the machine really opens up the process to those folk who are possibly less mathematically inclined. Not quite 'Racquet Matching for Dummies', but pretty close to it. The idea that I could measure the SW and a few clicks later be told 'stick 4g of lead here' is pretty awesome. Being able to harness the computational power of the iPhone is a USP for this device.
If matching rackets is so easy here are a pair of Dunlop 200Gs I checked this morning.
How much mass do I add where to match TW, SW, weight, and COM. I’m sure an app should be developed to calculate how it could be done, and if you’re an experienced app developer it would be easy. But what is easy for one may not be easy for another.
 

tim-ay

Hall of Fame
I have a funny feeling that people think matching TW, SW, weight and COM is going to be a no brainer. A racket is a stick on one end and a loop on the other and there is just so many places you can add weight. If a racket were rectangular and I could place mass at any point within that rectangle then matching SW, TW, weight, and balance would be a no brained.
Haha, no….I think people realize it. It’s going to take some trial and error. TWU has their tool for adding weight and that is a decent start. Really what this gives us is a way to check if we are close to what we wanted. It’s going to take iteration.
 

Irvin

Talk Tennis Guru
Haha, no….I think people realize it. It’s going to take some trial and error. TWU has their tool for adding weight and that is a decent start. Really what this gives us is a way to check if we are close to what we wanted. It’s going to take iteration.
I’m aware of that tool. Here is another example of just SW, weight and COM
How do I go about using the TWU tool to match SW, weight and COM.

SOLUTION:

EDIT: You can just match one to the other you have to match both to some unknown value.
 

Power Player

Bionic Poster
Yeah part of this process is just letting go with some frames and realizing that they will not be exact. I am personally ok with that. But knowing my target numbers is a massive help.
 

Irvin

Talk Tennis Guru
Yeah part of this process is just letting go with some frames and realizing that they will not be exact. I am personally ok with that. But knowing my target numbers is a massive help.
If the present and target specs are known you should easily be able to determine if a racket can be matching to those specs and how to do it.
 

SonRK

Semi-Pro
So my SW1 came in and I was having some fun with it, but I'm trying my best to get the calibration right. I might have missed it, but is there a set SW that the rod with and without the "up" piece should be reading? I've gotten anywhere between 292 - 305 in my multiple calibration setups for the rod + up piece measuring.

My most recent calibration resulted in 301.85 / 156.23 / 303 for a Spring Constant of: 205.728 and Apparatus Mol of 6.15764

I have a few frames that were professionally measured:

  • 3 Blade 98s from Roman Prokes that should be 302, reading 305 on SW1.
  • 1 Blade 98 from TW (plastic still in wrapper since I haven't decided to use it yet) that should be 297. I don't have the placard or the string that holds it anymore, but it measured 297 on the SW1 (so this was an exact match, unless TW measures SW with placards and string still on it)..

Trying to figure out if this is a calibration issue, or maybe ****'s method/machine for determining SW is different, etc.
 

tim-ay

Hall of Fame
So my SW1 came in and I was having some fun with it, but I'm trying my best to get the calibration right. I might have missed it, but is there a set SW that the rod with and without the "up" piece should be reading? I've gotten anywhere between 292 - 305 in my multiple calibration setups for the rod + up piece measuring.

My most recent calibration resulted in 301.85 / 156.23 / 303 for a Spring Constant of: 205.728 and Apparatus Mol of 6.15764

I have a few frames that were professionally measured:

  • 3 Blade 98s from Roman Prokes that should be 302, reading 305 on SW1.
  • 1 Blade 98 from TW (plastic still in wrapper since I haven't decided to use it yet) that should be 297. I don't have the placard or the string that holds it anymore, but it measured 297 on the SW1 (so this was an exact match, unless TW measures SW with placards and string still on it)..

Trying to figure out if this is a calibration issue, or maybe ****'s method/machine for determining SW is different, etc.
there is a sticker on your rod. ha.
 

Irvin

Talk Tennis Guru
So my SW1 came in and I was having some fun with it, but I'm trying my best to get the calibration right. I might have missed it, but is there a set SW that the rod with and without the "up" piece should be reading? I've gotten anywhere between 292 - 305 in my multiple calibration setups for the rod + up piece measuring.
There is a label 10 cm from the end of your calibration rod. Mine says "C01-33 324.3 167.6". Not sure what the C01-33 if probably just a rod number but with the weight on the end of the rod the inertia is 324.3 kgcm^2 and the rod without the weight is 167.6 kgcm^2. Make sure you SW1 is sitting on a solid surface. I sit mine on my pool table with the 2 front feet resting on the bumpers. Then level and calibrate.

I swing a racket a few times before I read any racket to warm up the spring. Make sure you push racket to one side and hold it steady before you press measure button. Then make a clean release. You can put the phone in the cradle on either side but I only use the right side and push the butt to the left. Using the right side will cause the SW1 to bump the stops. I never use that side because the motion is not smooth.

After calibrating the rod measure the rod the readings should be very close. Good luck.

EDIT: I assume the end with the label is always the end I place into the cradle on the SW1. If your would like to calibrate your SW1 to some other machine take your calibration or to the other machine and measure your rod on the other machine and record the SW with and without the weight. You can then overwrite the values in the app and go through your calibration again. From that point readings on the SW1 should match the other machine.
 
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SonRK

Semi-Pro
Duh - makes sense. I saw the sticker but thought it was just a "this goes on the handle" identifier and didn't look at the text on it.

I actually was letting the springs cooldown each time before doing a calibration. Is that what you guys recommend or prefer swinging the rod a few times and then going through calibration?
 

HitMoreBHs

Professional
1 Blade 98 from TW (plastic still in wrapper since I haven't decided to use it yet) that should be 297. I don't have the placard or the string that holds it anymore, but it measured 297 on the SW1 (so this was an exact match, unless TW measures SW with placards and string still on it)..
They don’t. The placard especially adds wind resistance which will cause a significant positive error in the SW reading.

As an interesting aside, most manufacturers’ placards and strings mounted on unstrung frames are 15-18g. I’m sure this was no accident and it does give a reasonable feel of the overall weight and balance of the frame with strings.
 

bfroxen

Rookie
The two values for the calibration rod, with and without the weight, are listed on the label and encoded on the NFC tag on the SW1. The label should go in the cradle.When you add the device, they're read into the app. You can see them, and change them if you have a reason to, on the top of the Calibrate tab.

As @Irvin mentioned, be sure to release the racquet cleanly. It's best to push gently on the cradle or handle of the racquet, not further out on the racquet. The machine comes setup for left-side release, but that can be changed. You need to remove, flip over, and swap the two spring stops AND change the "Release from" setting in the app. There's a small triangle on the spring stop to indicate the release side.
 

Irvin

Talk Tennis Guru
Another point I might mention is not to be too quick to release the racket. at first I would try to press the Measure buttonand release the racket immediately. Press the Measure button and then release the racket the SW1 will not start Recording until it recognizes the racket starts in motion.
 
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Power Player

Bionic Poster
I calibrated my sw1 and it was super close to the listed numbers on the rod. All checkmarks. Good to go there.

So i measure my vcore 95. SW is 317. That was somewhat stunning, but ok. The twistweight is under 13 though which is surprising.

Same with the vcore pro 97 - 322 sw and a twistweight under 13. Now im wondering if i am doing something wrong. Lol. The vcore pro feels super stable so this is wild.

Ill keep measuring frames to see how this goes. Im going with my v7 blades next since i know they swing around 340ish


Edit- v7 blades at 334 and 335. Twistweights are still seeming a bit low at 13.88.

Wonder if i should start from scratch and recalibrate or if these are the actual specs. Lol. I feel like the SWs may be 3-4 pts off and that affects the twistweight as well. This is wild.
 
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Power Player

Bionic Poster
You can put the phone in the cradle on either side but I only use the right side and push the butt to the left. Using the right side will cause the SW1 to bump the stops. I never use that side because the motion is not smooth.

After calibrating the rod measure the rod the readings should be very close. Good luck.
Ok so you dont follow the video and put the phone in the left side? And then you push the buttcap to the left. So you are doing the opposite of default?

The velcro fastener is rather long and gets in th way, so id have to flip the entire device to get that setup.

All that said, i just measured the rod and it is indeed 295. The exact specs are 295.3 on the sticker. That works for me.

I guess the rdcs i have been using are a bit off then.
 

PrinceYonex

Semi-Pro
I calibrated my sw1 and it was super close to the listed numbers on the rod. All checkmarks. Good to go there.

So i measure my vcore 95. SW is 317. That was somewhat stunning, but ok. The twistweight is under 13 though which is surprising.

Same with the vcore pro 97 - 322 sw and a twistweight under 13. Now im wondering if i am doing something wrong. Lol. The vcore pro feels super stable so this is wild.

Ill keep measuring frames to see how this goes. Im going with my v7 blades next since i know they swing around 340ish


Edit- v7 blades at 334 and 335. Twistweights are still seeming a bit low at 13.88.

Wonder if i should start from scratch and recalibrate or if these are the actual specs. Lol. I feel like the SWs may be 3-4 pts off and that affects the twistweight as well. This is wild.
One thing I’m very curious about— we are used to measuring the swingweights of our racquets and aren’t at all surprised when they don’t match with the average specs listed on TW. We have come to expect qc variance, even with Yonex, when it comes to swingweight. But I don’t think many of us have been measuring twistweights. I’ve always just gone by the listed specs on TWU. I am wondering what sort of qc variance we will all see with twistweights, when we start measuring the actual number.
 

Power Player

Bionic Poster
One thing I’m very curious about— we are used to measuring the swingweights of our racquets and aren’t at all surprised when they don’t match with the average specs listed on TW. We have come to expect qc variance, even with Yonex, when it comes to swingweight. But I don’t think many of us have been measuring twistweights. I’ve always just gone by the listed specs on TWU. I am wondering what sort of qc variance we will all see with twistweights, when we start measuring the actual number.
Yep. I think im getting the actual numbers now. TWUs are high. My test was finding my old extreme pro. It has a 330 Sw and whopping 16 TW on the sw1 machine. So while i thought something was wrong before i do not believe that is the case now.

Also my doppio measured dead on spec at 322 sw and 13.6 tw. So i am simply uncovering a lot of qc variance here that i did not expect.
 

bfroxen

Rookie
I feel like the SWs may be 3-4 pts off and that affects the twistweight as well
If the swingweights were 3-4 pts off, that would be ~1%. Since both the swingweight and spinweight would have the same error, the TW would off by the same 1% (0.14 kg·cm²).

Left and right can sometimes be confusing, since the front of the cradle moves one way and the rear moves the other way. The SW1 comes setup for left-side release, where the head of the racquet is moved to the left (if facing the decal) prior to release. That's how I do it in the videos.

Here's the small triangle on the spring stop that indicates the release position. I have the left dowel at the front of the cradle against the stop, ready for release.
 

Power Player

Bionic Poster
If the swingweights were 3-4 pts off, that would be ~1%. Since both the swingweight and spinweight would have the same error, the TW would off by the same 1% (0.14 kg·cm²).

Left and right can sometimes be confusing, since the front of the cradle moves one way and the rear moves the other way. The SW1 comes setup for left-side release, where the head of the racquet is moved to the left (if facing the decal) prior to release. That's how I do it in the videos.

Here's the small triangle on the spring stop that indicates the release position. I have the left dowel at the front of the cradle against the stop, ready for release.

Awesome. I think i dialed mine in. Its crazy how adding lead at 12 (measures dead on btw) can bump the twistweight up. My vcore 95 went from 14 tw and then i added 2 grams at 12 and now its 15.4.
 
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