website TennisTinker.com with the free calculation tool is online. Subscribe for an account for free, no catch or fine print. Thanks for watching and let me know what topic you would want to see next. I have loads of ideas, but you can help!
Amazing! This is the best internet has to offer: good ideas, intelligent thinking, creativity! Tennis addicts love this kind of thing. I will try to replicate the board in Brazil. Thank you!
Thanks, i know it's taking a long time. I have a huge list for videos, but currently combining it with my work isn't the easiest. I shot the next video already at the court, to hear all my audio clipping at home haha. So i have to shoot it again, it was horrible.
You're totally right! I'm ashamed of how long ago i made the first video. Currently very ill though and other life troubles which are merely weak excuses 😉. I'm not going to make precise promises currently, but I'll post at least 1 new video in the next few months. I've got a whole list of topics for many videos. My wife and daughter are pressuring me saying I'm holding back info from my viewers.
@@TennisTinker indeed. I'm gonna do one for myself, based on your instructions. Surprisingly, I have 5 head radical mp microgel, but didn't bought them all at once. The first 2 of them bought it in 2018, another 2 in 2020 and the last one in 2022. I have to say they all different in balance and SW, especially the last one came brand new already with 10 grams of silicon in the butcam, in which the other ones doesn't have. I really need to get them close to one spec. I'll keep in touch with you!
@@mariusstoica7248 silicone in the butt cap doesn't change the swing weight, but it does change the balance and static weight with the same swing weight which as a result also changes the polarisation of the racket which means that the timing of your contact punt can differ greatly between the rackets with the same swing but different racket
@@TennisTinker right. I've noticed this playing, you know breaking the strings during a game, then go to your bag and pick another one, same tension at 23-21 kg, from the first hit I felted so off, so different, but I had no choice, I had to continue the match and loose, so frustrating.. Now I'm trying to get them on spec. 330-335gr weight, 335 balance, 330 swing weight
@@mariusstoica7248 I play with 353 grams static weight, 31,0 cm balance and 332 swing weight. Now you know why the timing is difficult after changing a racket. Even with 2 rackets that you buy new in the shop, the Quality control of those rackets van be pretty off to make both rackets feel like 2 different rackets.
Very nice video! Thank you.. Would you please show us the formula that's used to calculate the swing weight? I believe it was contained in cell G3 in your spreadsheet.
If you go to TennisTinker.com you can create a free account and download the sheet. All for free as i want to encourage other people to do the same as me and tinker their specs to their liking.
@@Ignachotube i would advise to use a maximum of 15 degrees. The higher you do the faster the racket swings through the 0 degree point. Air friction increases exponentially related to speed and you don't want too much of the air friction because that can interfere with your results as it slows down the swing speed. So i would advice 10 to 15 degrees max. The trade-off is that the lower the degree is you let go for the first swing, the more difficult it becomes to exactly define the exact last frame after x swings. So as low as possible where you can still comfortably define the exact last frame after x swings. I generally use at least 10 swings for X. The higher the number of swings the less issue you have with small errors in defining the exact time for the 1st and last swing as the error is also divided by the amount of swings. I've done also more than 10 swings. So it is a trade-off between your time investment and accuracy.
Thanks, that is not needed. I have used my method on the same racket multiple times after adding lead and calculating the effect. After applying the lead and measuring, the measurement was spot on with the calculation. So the method is sound. An RDC machine does the same calculation, but then internally and is calibrated with a metal bar. That metal bar can also have imperfections, so also a RDC machine is not 100% accurate.
Yes, it works exactly the same for any length racket. Swing weight is measured with the 10cm from the butt cap point of reference. This method you measure it from the top cross string (you input the distance between the top cross string and butt cap) and the formulas automatically translate this into the swing weight from 10cm. It's an inertia calculation.
At 5:57 I see an interesting calculation can you explain? In the video of measured swings it shows actually 32.780 and you put in 42.780 then add 180 and make a correction for slow motion. Where did you get the 42,780 from and where did you get the 180 from?
For the video i had to do it rough and fast so the time in that little tool wasn't totally accurate. (Before the video i did it accurate for the exact time). It was something like 3 minutes 42 sec etc. In the sheet i add the 3 minutes by adding 180 seconds, as the sheet calculates in seconds. And the divide is to calculate back from slow motion to real time.
@tennistinker, a racquet with a lower stiffness makes a softer impact of the ball. A lower string tension makes a softer impact on the ball as well. In general, to create a similar feel of softness between a racquet with a lower en higher stiffness, what should be the difference in string tension?
That's really good question. It is also dependent on how much the difference is between the stiffness of the rackets. I have some rackets that have stiffness 59 or 60 and other rackets that are around 65. I don't play with rackets that are stiffer than that although I have one racket that is even softer than 59. Next to stiffness there are 2 other aspects that influence the feel of the setup: 1. Density of the string bed (a denser string bed, especially the center), the stiffer it feels. there are very dense 16x19 string beds as well as pretty open 18x20,. So the string pattern doesn't always tell the whole story. 2. The size and shape of the hoop. a smaller size hoop 95 inch2 will feel stiffer and the shape also influences it, a more oval narrow hoop feels stiffer as well, but the narrow shape maybe also has to do with the smaller sweet spot and my lack of always hitting the strings in the middle. So I cannot answer this objectively, just my experience with my dynamic tension measurements. I string a smaller head size racket (95 inch2) 1 to 1.5 kg lower than a 100 inch2 racket. just based on stiffness I differ 1 kg. As an example I string my pro staff 97 1.5 kg lower than say my Head Speed MP. But my radical pro I go 0.5 kg lower than the speed, but that has to do with the higher power level of the radical pro over the speed mp. Otherwise I would string it 1 kg lower, but then it gives me too much power. So you have string bed feel, but also confidence related to power (dept of your shots). So most of the time I adjust for a similar level of power 1st and stringbed feel 2nd.
Sorry but I cannot understand why it is divided by 8 could you please explain where this 8 comes from (slow motion 8 times ) how do you get that ? thank you very much
Oh that is only specific for my smartphone. My smartphone records 8x slow motion (240 fps) but stores the video as 30 fps. That's a factor 8 slower. That means the time in my recorded video is 8 times too high so that is why i divide by 8. Again, specific for my own smartphone. If your smartphone records 240 fps and stores the video as 240 fps you don't have to divide by 8.
This is not working, as i tried multiple times, filmed with a iphone 13 pro on 240FPS and i do not get a accurate sw , my time for 20 swings was on 01:49,08 , so i do no know how you get the time on 03....what FPS do you use on your phone?
@@vladmaxim 240 fps divided by 30 is 8. So you might have to divide the time of your 20 swings by 8. You have to imput the time in second. And with 1 swing i mean from the furthest front to back and back to front again. Let me know if this solved the issue.
@@TennisTinker First of all thank you for your reply, i try since February to find my SW on my HEAD Speed MP 2024 with your method but again and again i did not work, or maybe i do not understand it completely. I did all you say that includes the furthest front to back and back to front again swing, but i get the time of 01,49,08 and when i put in in the sheet it is divided by 8 it is like 60,49,09 (and your calculator does the divide it automaticaly by 8) and i get the swingweight totally wrong, my question how get 03 minutes on your video with 20 swings and i got only 01 min and 49 seconds on slowmotion 240fps ? Thanks!
@@vladmaxim on my website you can find my email. If you can share a link with me to your sheet and video file, i can have a look for you. That's the only way for me to really help you. If your video plays back at 60 fps while it is recorded at 240 fps, the divider has to be 4 in stead of 8, but I'm just guessing here. I can only really help you if you give me access to your files.
@@vladmaxim I get a swing weight of 332,01 with your data. I put 110,319 seconds divided by 4 (so not 8). 20 swings was 1 minute 50 seconds and 319/1000 The video is saved at 60 fps. So 240/60 is 4 Good luck
Great video, just one question: when you swing your racket from the hooks, you advise up to a 15 degree angle to swing it from. Does this have to be perfectly 15 degree angle? Because at what point does wind force become a factor?
It doesn't have to be exact, if you see that the amplitude of the swing decreases rapidly with every swing, then you are encountering wind drag. The less the amplitude decreases per swing the less air drag.
Really depends how you make your balance board. From the bar that the racket balances on to the side where you measure the butt cap while balancing should be minimum 35 cm as i don't know rackets with a balance higher than that, but you could be safe and use 40 cm in that direction. Of the tablet face side you should have something that the racket face can rest on otherwise while balancing it falls off. That could be a table under your balance board or you can add length to the balance board itself. Something like 30 cm should be enough. If you also incorporate measuring the distance from butt cap to the top string, you need a board of the length of a racket, plus some.
I made a new one that is longer than 90cm and slimmer, on the new one the metal ruler of 1 meter that i cut 10 cm off was the base for the design. Video will come out, dunno when yet
Question about the measurement of the distance from butt cap to top tennis string. Did you use the fixed distance that you have from the rod to the butt cap and a fixed distance to the small metal plate on the other side, and measure the difference with the loose part of the ruler at the top string? @@TennisTinker
Thanks for the info, I have a question. Does the length of racquet play any role in your Excel? I have a Prince Tour Diablo which is 69,22 cm length, so a bit above standard.
Can you explain how far you should swing it? Doesn't the distance you swing the racket impact the calculation? Like if it was swinging from a very large angle versus a smaller one? Doesn't this change the timing?
Use small angles, as small as workable for being able to distinguish the correct frame in the outer position for your calculation. If you use too big angles the wind resistance will become a factor and it will influence your result as the swing will be allowed down by the wind resistance. So i use a max of about 10 degrees to one side.
It depends on 2 things what the factor is: 1. How fast is the slow motion? In X times normal speed.. 2. In what speed is the video saved? In my case the answer to q1 is 8x speed (240 frames per second) and it is saved as 1x speed (30 fps), so the saved file is 8 times longer than normal time. That's why i have to divide by 8. What you can do is record 1 minute in slow motion and when playing back see how long the video is. If it is 4 minutes, the video is 4 times as long and you have to divide by 4 to get it to normal time again.
Be creative in measuring the distance between the butt cap and the top cross string, you could knot a thin rope to the top string, let it hang down and cut it just below the butt cap, then also cut it right under the top string, measure the length of that rope. Different way: hang a little thin rope from the top of the racket over the top cross string while having the racket exactly horizontal level and use a long ruler to measure the distance from the butt cap to the hanging rope. Buy a metal thin flat stick that is sturdy enough but also skinny enough so that it fits in the holes between the main and cross strings. Bend the end 90 degrees with several cm up. Push that against the top cross string and make a marking just behind the butt cap. Measure the length. You can be creative and measure that in many different ways.
Maybe I'm just not good with physics, but I'm confused about how swinging the racquet from the top string can result in a swing weight measurement, when all the RDC machines measure by swinging from the grip. It seems like if you added a bunch of weight right at the level of the top string the swing time would not change, but the actual swing weight would be dramatically increased. Is there something I am missing/not understanding? Great video nonetheless. I am just confused.
The characteristics of the mass distribution which results in a certain swing length can be measured from any point and calculated towards the 10cm point from the butt cap. That is what the formulas do. As an analogy (which isn't exactly the same but to give you an idea) on a kids swing in the park you can measure the momentum on either side as long as the distribution (where the kids sit) of their mass is constant. That's why it is important to know what the exact swinging point is (the string it is hanging from) to do the translation calculation towards the normal point.
And to answer what would happen if you add a lot of weight right at the point of the hanging string: Your static weight increases and your balance point changes upward, so the swing time length will change. So you have 3 totally different inputs into the equation (mass, balance and swing time) for a different result. The swing time could maybe still be the same (sounds realistic yes), but then the other 2 still vary for a different end result
Hmm, im a bit confused as to how this would work. My understanding is that adding weight to the handle doesn't affect the swing weight because that at the point from when you swing the racquet...hence the machines that measured swing weight by swinging the racquet from the handle. But in this demo you swing it from the top...but i dont hold the racket head when I play, i hold the grip. So in this method if I had heaps of weight in the head it shouldn't affect the swing weight because the racket is upside down
You can measure inertia from any point swinging and with calculations recalculate it to the point you want it. Maybe not a totally correct anology, but to make it simple to understand. If you have a swing (like on the play ground) and you have a fat kid sitting on one side and a skinny kid sits on the other side, if they swing with the balance point close to the fat kid you can use those measurements and based on that you can calculate how it would swing if the balance point would be close to the skinny kid. So the swinging around the top string in combination with the other measurements (mass, balance point and the distance of that top string to the butt cap) is enough to translate the swing data to the 10cm point on the butt cap which is used for swing weight.
First i used the scale to get the mass of the racket. After that i put it on that metal rod for the balance point and i red the 31.9 cm (distance between metal rod for balancing and the end of the butt cap) from the metal ruler that is attached to the wooden plank. Third step is measuring the string that you hang the racket on for the swings.
Great video, thank you! When you go into customization (7:23), how does it make sense that 11g at butt cap would influence the Balance the same as 1g at top grip? The butt cap is much farther from the balance point so 11g there should have much more impact on balance than only 1 gram at top grip (closer to balance point). Wondering if the formula is off there?
I think you are looking at the wrong numbers. When i change the 0 into a 1 at the 11g butt cap, you see a delta balance of -0.96 After that when i activate the line at the top of the grip the Delta balance jumps to -0.1 so only -0.04 extra. So that is in line with what you would expect. The increase at the top of the grip has much lower impact on the balance than an increase at the butt cap.
The column with balance impact at each line cannot have the exact balance change as this is dependant on the current balance and each change would also have an interfering impact on other changes. I wished i could have programmed it like that, but that's way too complex. The swing weight and mass contribution is easier in that regard. So i understand that you concluded what you did based on the line item.
Why do all my rackets turn out with a very similar weight yet they are meant to be totally different ?? I do everything exactly as you have shown on video. I don't understand why they are all within a few grams of each other. I am talking about an ncode 289 gram pro staff 95(modded with 3.6 grams of weight on top and 2 overgrips increasing its weight to 337), a blade v5, a rf97a, an ncode six one 95 that is way heavier than the other ncode and yet all swingweights are within a few grams of each other only, always around 289-290 grams. The funniest thing is that the heaviest ncode turned out with a swingweight of 286. The heaviest of all rackets RF97A turned out with a swingweight of 284 grams. I have 0 idea what I'm doing wrong. How is this even possible ? Edit number 1: We were 2 people doing this experiment and we have accidentally counted 20 swings instead of actual 19. The difference is a bit bigger now between all the models but the biggest grams difference between them was just 4 grams. Is this possible ?! Edit number 2: Adding 5 grams to the top of the six one 95 ncode (2.5 at 11 o clock and 2.5 at 13 o clock) made its swingweight increase from 339.69 to 353.88. Your formula works, sir ! Thank you for saving me at least a couple hundred euros !
I don't totally understand your issue. If you are talking about grams, you are talking about static weight. Swing weight numbers are not in grams. But is it solved now? As a rule of tumb (very rough one), adding 3 grams at 12 adds 10 swing weight points. So 5 grams could be right indeed. It is always handy to have some rule of thumbs so that you can have an idea when something is really off. A strung base (not customized racket) swing weight below 300 or above 335 is also suspicious. Not impossible, but for most normal rackets (that are not beginners rackets or old vintage rackets) very unlikely.
I answered this question already 👇 below. Yeah it sounds counter intuitive, but with maths you can translate that movement to the point that you want. That's why it is important to measure the exact distance between the top string and the butt cap. Inertia and momentums can be measured from different points to get information about the system as a whole. The formulas in my excel sheet do that work for you. What you could wonder then is the following case. What if you add mass to exact the position of the top string. Then the swing speed of the butt will not change. But the total mass will change and the center of mass (balance point) will change and those changes are also variables in the calculations which changes the outcome accordingly.
![Racquet Customization [Swingweight Measurements - Machines & DIY]](http://i.ytimg.com/vi/xvPuRMZ8rEU/mqdefault.jpg)
website TennisTinker.com with the free calculation tool is online. Subscribe for an account for free, no catch or fine print. Thanks for watching and let me know what topic you would want to see next. I have loads of ideas, but you can help!
Id love how you made the balance board, materials etc
Great i am subscribed and can't wait to see your new material
Amazing! This is the best internet has to offer: good ideas, intelligent thinking, creativity! Tennis addicts love this kind of thing. I will try to replicate the board in Brazil. Thank you!
Nice
Thank you so much for the video and the excel calculation sheet! I hope to see a new video soon!
This is great, Lars, thanks for sharing.
I look forward to seeing what you've got cooking for us next.
Thanks, i know it's taking a long time. I have a huge list for videos, but currently combining it with my work isn't the easiest. I shot the next video already at the court, to hear all my audio clipping at home haha. So i have to shoot it again, it was horrible.
Time for a Swingweight setup V2 video? Would love to see it!
You're totally right! I'm ashamed of how long ago i made the first video. Currently very ill though and other life troubles which are merely weak excuses 😉. I'm not going to make precise promises currently, but I'll post at least 1 new video in the next few months. I've got a whole list of topics for many videos. My wife and daughter are pressuring me saying I'm holding back info from my viewers.
Thanks - subscribed and looking forward to trying the tool
👍 Let me know if you have feedback.
More of this. Great video and insights…
Tnx
Tanks for sharing this, helps me alot.
Well done Lars. Thanks!
Hi and thank you for this very interesting video. Can you make a video of how to build this ckever board you made? Thanks
I will make a new even better one and I'm glad you liked the video. You can download the sheet on my website
nice video, very helpful for those who dont want to spend extra money on sophisticated machines!
No reason not to customize your own ranger and get the best out of it
@@TennisTinker indeed. I'm gonna do one for myself, based on your instructions. Surprisingly, I have 5 head radical mp microgel, but didn't bought them all at once. The first 2 of them bought it in 2018, another 2 in 2020 and the last one in 2022. I have to say they all different in balance and SW, especially the last one came brand new already with 10 grams of silicon in the butcam, in which the other ones doesn't have. I really need to get them close to one spec. I'll keep in touch with you!
@@mariusstoica7248 silicone in the butt cap doesn't change the swing weight, but it does change the balance and static weight with the same swing weight which as a result also changes the polarisation of the racket which means that the timing of your contact punt can differ greatly between the rackets with the same swing but different racket
@@TennisTinker right. I've noticed this playing, you know breaking the strings during a game, then go to your bag and pick another one, same tension at 23-21 kg, from the first hit I felted so off, so different, but I had no choice, I had to continue the match and loose, so frustrating.. Now I'm trying to get them on spec. 330-335gr weight, 335 balance, 330 swing weight
@@mariusstoica7248 I play with 353 grams static weight, 31,0 cm balance and 332 swing weight. Now you know why the timing is difficult after changing a racket. Even with 2 rackets that you buy new in the shop, the Quality control of those rackets van be pretty off to make both rackets feel like 2 different rackets.
Very nice video! Thank you.. Would you please show us the formula that's used to calculate the swing weight? I believe it was contained in cell G3 in your spreadsheet.
If you go to TennisTinker.com you can create a free account and download the sheet. All for free as i want to encourage other people to do the same as me and tinker their specs to their liking.
from how many degrees should I drop the first swing? or it doesn't matter?
@@Ignachotube i would advise to use a maximum of 15 degrees. The higher you do the faster the racket swings through the 0 degree point. Air friction increases exponentially related to speed and you don't want too much of the air friction because that can interfere with your results as it slows down the swing speed. So i would advice 10 to 15 degrees max. The trade-off is that the lower the degree is you let go for the first swing, the more difficult it becomes to exactly define the exact last frame after x swings. So as low as possible where you can still comfortably define the exact last frame after x swings. I generally use at least 10 swings for X. The higher the number of swings the less issue you have with small errors in defining the exact time for the 1st and last swing as the error is also divided by the amount of swings. I've done also more than 10 swings.
So it is a trade-off between your time investment and accuracy.
@@Ignachotube if you started too high for you licking you can also select a later start for your first swing in your video of course.
Epic video!! awesome!!!
Great video. Would be amazing if you could get hold of an RDC machine and compare the SW values?
Thanks
Thanks, that is not needed. I have used my method on the same racket multiple times after adding lead and calculating the effect. After applying the lead and measuring, the measurement was spot on with the calculation. So the method is sound. An RDC machine does the same calculation, but then internally and is calibrated with a metal bar. That metal bar can also have imperfections, so also a RDC machine is not 100% accurate.
Does this work exactly the same way with extended racquets?
Yes, it works exactly the same for any length racket. Swing weight is measured with the 10cm from the butt cap point of reference. This method you measure it from the top cross string (you input the distance between the top cross string and butt cap) and the formulas automatically translate this into the swing weight from 10cm. It's an inertia calculation.
At 5:57 I see an interesting calculation can you explain? In the video of measured swings it shows actually 32.780 and you put in 42.780 then add 180 and make a correction for slow motion. Where did you get the 42,780 from and where did you get the 180 from?
For the video i had to do it rough and fast so the time in that little tool wasn't totally accurate. (Before the video i did it accurate for the exact time). It was something like 3 minutes 42 sec etc. In the sheet i add the 3 minutes by adding 180 seconds, as the sheet calculates in seconds. And the divide is to calculate back from slow motion to real time.
awesome video! Can you please share a template of your spreadsheet ?
You can download it from my tennistinker.com website after a free subscription
And tnx for your replying
@tennistinker, a racquet with a lower stiffness makes a softer impact of the ball. A lower string tension makes a softer impact on the ball as well. In general, to create a similar feel of softness between a racquet with a lower en higher stiffness, what should be the difference in string tension?
That's really good question. It is also dependent on how much the difference is between the stiffness of the rackets. I have some rackets that have stiffness 59 or 60 and other rackets that are around 65. I don't play with rackets that are stiffer than that although I have one racket that is even softer than 59. Next to stiffness there are 2 other aspects that influence the feel of the setup: 1. Density of the string bed (a denser string bed, especially the center), the stiffer it feels. there are very dense 16x19 string beds as well as pretty open 18x20,. So the string pattern doesn't always tell the whole story. 2. The size and shape of the hoop. a smaller size hoop 95 inch2 will feel stiffer and the shape also influences it, a more oval narrow hoop feels stiffer as well, but the narrow shape maybe also has to do with the smaller sweet spot and my lack of always hitting the strings in the middle.
So I cannot answer this objectively, just my experience with my dynamic tension measurements. I string a smaller head size racket (95 inch2) 1 to 1.5 kg lower than a 100 inch2 racket. just based on stiffness I differ 1 kg. As an example I string my pro staff 97 1.5 kg lower than say my Head Speed MP. But my radical pro I go 0.5 kg lower than the speed, but that has to do with the higher power level of the radical pro over the speed mp. Otherwise I would string it 1 kg lower, but then it gives me too much power.
So you have string bed feel, but also confidence related to power (dept of your shots). So most of the time I adjust for a similar level of power 1st and stringbed feel 2nd.
Sorry but I cannot understand why it is divided by 8 could you please explain where this 8 comes from (slow motion 8 times ) how do you get that ?
thank you very much
Oh that is only specific for my smartphone. My smartphone records 8x slow motion (240 fps) but stores the video as 30 fps. That's a factor 8 slower. That means the time in my recorded video is 8 times too high so that is why i divide by 8. Again, specific for my own smartphone.
If your smartphone records 240 fps and stores the video as 240 fps you don't have to divide by 8.
This is not working, as i tried multiple times, filmed with a iphone 13 pro on 240FPS and i do not get a accurate sw , my time for 20 swings was on 01:49,08 , so i do no know how you get the time on 03....what FPS do you use on your phone?
@@vladmaxim 240 fps divided by 30 is 8. So you might have to divide the time of your 20 swings by 8. You have to imput the time in second. And with 1 swing i mean from the furthest front to back and back to front again. Let me know if this solved the issue.
@@TennisTinker First of all thank you for your reply, i try since February to find my SW on my HEAD Speed MP 2024 with your method but again and again i did not work, or maybe i do not understand it completely. I did all you say that includes the furthest front to back and back to front again swing, but i get the time of 01,49,08 and when i put in in the sheet it is divided by 8 it is like 60,49,09 (and your calculator does the divide it automaticaly by 8) and i get the swingweight totally wrong, my question how get 03 minutes on your video with 20 swings and i got only 01 min and 49 seconds on slowmotion 240fps ?
Thanks!
@@vladmaxim on my website you can find my email. If you can share a link with me to your sheet and video file, i can have a look for you. That's the only way for me to really help you. If your video plays back at 60 fps while it is recorded at 240 fps, the divider has to be 4 in stead of 8, but I'm just guessing here. I can only really help you if you give me access to your files.
@@TennisTinker Hey Lars, thanks for your response, i just send you a email with the files and my racket data.
Thanks a lot for the help!
@@vladmaxim I get a swing weight of 332,01 with your data.
I put 110,319 seconds divided by 4 (so not 8).
20 swings was 1 minute 50 seconds and 319/1000
The video is saved at 60 fps. So 240/60 is 4
Good luck
Great video, just one question: when you swing your racket from the hooks, you advise up to a 15 degree angle to swing it from. Does this have to be perfectly 15 degree angle? Because at what point does wind force become a factor?
It doesn't have to be exact, if you see that the amplitude of the swing decreases rapidly with every swing, then you are encountering wind drag. The less the amplitude decreases per swing the less air drag.
@@TennisTinker okay thank you. It makes sense now 👍🎾
Hello, I wanted to ask what is the measurement of the board that you are using in length?
Really depends how you make your balance board. From the bar that the racket balances on to the side where you measure the butt cap while balancing should be minimum 35 cm as i don't know rackets with a balance higher than that, but you could be safe and use 40 cm in that direction. Of the tablet face side you should have something that the racket face can rest on otherwise while balancing it falls off. That could be a table under your balance board or you can add length to the balance board itself. Something like 30 cm should be enough.
If you also incorporate measuring the distance from butt cap to the top string, you need a board of the length of a racket, plus some.
I made a new one that is longer than 90cm and slimmer, on the new one the metal ruler of 1 meter that i cut 10 cm off was the base for the design. Video will come out, dunno when yet
Iets om naar uit te kijken!@@TennisTinker
Question about the measurement of the distance from butt cap to top tennis string. Did you use the fixed distance that you have from the rod to the butt cap and a fixed distance to the small metal plate on the other side, and measure the difference with the loose part of the ruler at the top string? @@TennisTinker
Thanks for the info, I have a question. Does the length of racquet play any role in your Excel? I have a Prince Tour Diablo which is 69,22 cm length, so a bit above standard.
I already saw your answer in previous questions. Thanks.
@@tennisking75 otherwise i would have answered it again. Answer is indeed that length in this case doesn't matter, regardless what she said 😄
Can you explain how far you should swing it? Doesn't the distance you swing the racket impact the calculation? Like if it was swinging from a very large angle versus a smaller one? Doesn't this change the timing?
Use small angles, as small as workable for being able to distinguish the correct frame in the outer position for your calculation. If you use too big angles the wind resistance will become a factor and it will influence your result as the swing will be allowed down by the wind resistance. So i use a max of about 10 degrees to one side.
@@TennisTinkerdoes a 10 degree angled swing have to be exact?
@@woodyhewitson i think I've answered your question already in your other comment?
Is the iPhone the same slow motion speed? Divide by 8?
It depends on 2 things what the factor is:
1. How fast is the slow motion? In X times normal speed..
2. In what speed is the video saved?
In my case the answer to q1 is 8x speed (240 frames per second) and it is saved as 1x speed (30 fps), so the saved file is 8 times longer than normal time. That's why i have to divide by 8.
What you can do is record 1 minute in slow motion and when playing back see how long the video is. If it is 4 minutes, the video is 4 times as long and you have to divide by 4 to get it to normal time again.
how do i figure out the top string distance?
Be creative in measuring the distance between the butt cap and the top cross string, you could knot a thin rope to the top string, let it hang down and cut it just below the butt cap, then also cut it right under the top string, measure the length of that rope.
Different way: hang a little thin rope from the top of the racket over the top cross string while having the racket exactly horizontal level and use a long ruler to measure the distance from the butt cap to the hanging rope.
Buy a metal thin flat stick that is sturdy enough but also skinny enough so that it fits in the holes between the main and cross strings. Bend the end 90 degrees with several cm up. Push that against the top cross string and make a marking just behind the butt cap. Measure the length.
You can be creative and measure that in many different ways.
Maybe I'm just not good with physics, but I'm confused about how swinging the racquet from the top string can result in a swing weight measurement, when all the RDC machines measure by swinging from the grip. It seems like if you added a bunch of weight right at the level of the top string the swing time would not change, but the actual swing weight would be dramatically increased. Is there something I am missing/not understanding? Great video nonetheless. I am just confused.
The characteristics of the mass distribution which results in a certain swing length can be measured from any point and calculated towards the 10cm point from the butt cap. That is what the formulas do. As an analogy (which isn't exactly the same but to give you an idea) on a kids swing in the park you can measure the momentum on either side as long as the distribution (where the kids sit) of their mass is constant.
That's why it is important to know what the exact swinging point is (the string it is hanging from) to do the translation calculation towards the normal point.
And to answer what would happen if you add a lot of weight right at the point of the hanging string:
Your static weight increases and your balance point changes upward, so the swing time length will change. So you have 3 totally different inputs into the equation (mass, balance and swing time) for a different result.
The swing time could maybe still be the same (sounds realistic yes), but then the other 2 still vary for a different end result
@@TennisTinker aaahhh ok, That makes sense now. Thank you!!
@@ncbassplayer thank you for your good question. That is something that was also crossed my mind in the beginning until i figured it out.
Hmm, im a bit confused as to how this would work. My understanding is that adding weight to the handle doesn't affect the swing weight because that at the point from when you swing the racquet...hence the machines that measured swing weight by swinging the racquet from the handle.
But in this demo you swing it from the top...but i dont hold the racket head when I play, i hold the grip.
So in this method if I had heaps of weight in the head it shouldn't affect the swing weight because the racket is upside down
You can measure inertia from any point swinging and with calculations recalculate it to the point you want it.
Maybe not a totally correct anology, but to make it simple to understand. If you have a swing (like on the play ground) and you have a fat kid sitting on one side and a skinny kid sits on the other side, if they swing with the balance point close to the fat kid you can use those measurements and based on that you can calculate how it would swing if the balance point would be close to the skinny kid.
So the swinging around the top string in combination with the other measurements (mass, balance point and the distance of that top string to the butt cap) is enough to translate the swing data to the 10cm point on the butt cap which is used for swing weight.
Where did you get 31.9g balance? I dont get this.
First i used the scale to get the mass of the racket.
After that i put it on that metal rod for the balance point and i red the 31.9 cm (distance between metal rod for balancing and the end of the butt cap) from the metal ruler that is attached to the wooden plank.
Third step is measuring the string that you hang the racket on for the swings.
can you share the excel spreadsheet?
You can download that for free from my website tennistinker.com
Great video, thank you!
When you go into customization (7:23), how does it make sense that 11g at butt cap would influence the Balance the same as 1g at top grip? The butt cap is much farther from the balance point so 11g there should have much more impact on balance than only 1 gram at top grip (closer to balance point). Wondering if the formula is off there?
I think you are looking at the wrong numbers. When i change the 0 into a 1 at the 11g butt cap, you see a delta balance of -0.96
After that when i activate the line at the top of the grip the Delta balance jumps to -0.1 so only -0.04 extra. So that is in line with what you would expect. The increase at the top of the grip has much lower impact on the balance than an increase at the butt cap.
@@TennisTinker Thank you so much, indeed looked at the wrong cells. Fantastic.
The column with balance impact at each line cannot have the exact balance change as this is dependant on the current balance and each change would also have an interfering impact on other changes. I wished i could have programmed it like that, but that's way too complex. The swing weight and mass contribution is easier in that regard. So i understand that you concluded what you did based on the line item.
Why do all my rackets turn out with a very similar weight yet they are meant to be totally different ?? I do everything exactly as you have shown on video. I don't understand why they are all within a few grams of each other. I am talking about an ncode 289 gram pro staff 95(modded with 3.6 grams of weight on top and 2 overgrips increasing its weight to 337), a blade v5, a rf97a, an ncode six one 95 that is way heavier than the other ncode and yet all swingweights are within a few grams of each other only, always around 289-290 grams. The funniest thing is that the heaviest ncode turned out with a swingweight of 286. The heaviest of all rackets RF97A turned out with a swingweight of 284 grams. I have 0 idea what I'm doing wrong. How is this even possible ?
Edit number 1:
We were 2 people doing this experiment and we have accidentally counted 20 swings instead of actual 19. The difference is a bit bigger now between all the models but the biggest grams difference between them was just 4 grams. Is this possible ?!
Edit number 2:
Adding 5 grams to the top of the six one 95 ncode (2.5 at 11 o clock and 2.5 at 13 o clock) made its swingweight increase from 339.69 to 353.88.
Your formula works, sir ! Thank you for saving me at least a couple hundred euros !
I don't totally understand your issue. If you are talking about grams, you are talking about static weight. Swing weight numbers are not in grams. But is it solved now? As a rule of tumb (very rough one), adding 3 grams at 12 adds 10 swing weight points. So 5 grams could be right indeed. It is always handy to have some rule of thumbs so that you can have an idea when something is really off.
A strung base (not customized racket) swing weight below 300 or above 335 is also suspicious. Not impossible, but for most normal rackets (that are not beginners rackets or old vintage rackets) very unlikely.
@@TennisTinker There is no problem, at first i thought there was but in the end i figured your method works just fine.
@@experiencewithmartin972 Good to hear
Nice you also have a string instrument on the wall. OCD and music.
Exactly. Electric cello, electric guitar and a piano sized workstation.
Great video. Thanks. I will go to your website and subscribe for an account.
Master
One big problem here Lars.. you don't test swing weight by having the butt of the racket swinging... The head of the racket has to be free
I answered this question already 👇 below. Yeah it sounds counter intuitive, but with maths you can translate that movement to the point that you want. That's why it is important to measure the exact distance between the top string and the butt cap. Inertia and momentums can be measured from different points to get information about the system as a whole.
The formulas in my excel sheet do that work for you.
What you could wonder then is the following case. What if you add mass to exact the position of the top string. Then the swing speed of the butt will not change. But the total mass will change and the center of mass (balance point) will change and those changes are also variables in the calculations which changes the outcome accordingly.