Swingweight calculation

[FranzS]

Let's suppose I know:
- weight
- balance point
- swingweight
of a certain racquet (stock). After customization (leadtape & other) I'm able to measure:
- new weight
- new balance point
Is there any calculation to find out the new swingweight? I think it should be possible with all these data.

 

[smirker]

Let's suppose I know:
- weight
- balance point
- swingweight
of a certain racquet (stock). After customization (leadtape & other) I'm able to measure:
- new weight
- new balance point
Is there any calculation to find out the new swingweight? I think it should be possible with all these data.

There is a tool for calculating swing weight in the TW University. Have a look, it's a relatively easy process. Don't think you can calculate the SW any other way without an RDC.

 

[Cerps]

Yeah use the twu site! It's really good.

 

[Irvin]

SW = SWi + mdd

Where:
SW = new swing weight
SWi = initial swingweight
m = added mass in Kg
d = distance of mass to axis for SW in cm. if in doubt use 10 cm

EDIT: for example, if you add 8 g of mass 45 cm above the axis point your SW will increase .008*45*45 or 16.2 points.

 

[Jocke]

If we're talking swingweight as in RDC units, it might be useful to know that an added gram at 12 increases SW with about 3 Points. 1 gram at 3 (or 9) increases SW about 2 Points.

 

[stealthfighter69]

How much SW is added when adding a leather grip that's, let's say, 10 grams heavier than the grip being replaced?

 

[Irvin]

How much SW is added when adding a leather grip that's, let's say, 10 grams heavier than the grip being replaced?

Very little as the grip is very close to the axis. But is you look at the 10 g centered around the axis that would be 0.01*5*5 or 0.25 points.

 

[stealthfighter69]

Thanks for the response but can you explain what those numbers refer to?

 

[Irvin]

Inertia (SW is a calculation of Inertia around a specific axis) is the sum of all mass within an object times the square of the distance from the axis. When calculating the SW of a racket it is not practical to measure the weight of each particle so the racket has to be put into motion to determine the SW (Inertia) around an axis. If you add weight to a racket though it is a totally different matter. If you add 1 gram of mass at 12 o'clock you know that mass is .001 Kg. You know the inside of the frame is ~65 cm from the butt. You know the SW axis is generally computed around a 10 cm axis. You multiply the mass (in Kg 0.001) time the square of the distance (55 cm.) Therefore the 1 g weight at 12 o'clock is 0.001*55*55 or about ~3 point increase

Adding a leather grip that weighs 10 g more that the original means you have effectively added 5 g 5 cm below the axis and 5 g 5 cm above the axis assuming you have a grip that is ~20 cm up the handle. So the math is 0.005*5*5 + 0.005*5*5 or 0.10*5*5.

If you add 1 g of weight at 3 or 9 that is about 40 cm above the axis so 0.001*40*40 = 1.6 point increase. The actual distance of the 3&9 position may change depending on the length of the racket, but if you know the approximate locations of the mass it is not hard to compute. It is always best to measure if you can do it accurately because adding a 10 cm strip of lead tape weighing 5 g centered 40 cm above the axis is not the same at adding a point mass of 5 g 40 cm from the axis. Close but not the same.

 

[Erik van der Laan]

Is this a good calculation tool?
https://www.stringwaynederland.nl/SW-TA-online/SwingCalc/index-en.php

 

[Irvin]

Is this a good calculation tool?
https://www.stringwaynederland.nl/SW-TA-online/SwingCalc/index-en.php

SW is a secondary moment of inertia. Inertia measures how mass is distributed in a racket. That tool may five to an approximation but probably not exact. Rod Cross wrote a paper that claimed you could get within 2% with with weight, balance, and length only though. II can look it up if you want.

EDIT: Here is Rod Cross's article http://www.physics.usyd.edu.au/~cross/customising.pdf

 

[coolschreiber]

@Irwin I customized my IG Prestige MP with 4gm total at 3& 9 and 5 gm at 12. Its 310 SW stock. Now I'm assuming its -
for 12 o'clock - 5gm x 3 sw units - 15
for 3&9 o'clock - 4gm x 1.6 sw units - 6.4
About 310 + 15 +6.4 = 331 SW ? You think its approximately that?
I have a leather grip + over grip too.

 

[Irvin]

@Irwin I customized my IG Prestige MP with 4gm total at 3& 9 and 5 gm at 12. Its 310 SW stock. Now I'm assuming its -
for 12 o'clock - 5gm x 3 sw units - 15
for 3&9 o'clock - 4gm x 1.6 sw units - 6.4
About 310 + 15 +6.4 = 331 SW ? You think its approximately that?
I have a leather grip + over grip too.

I'm not real sure. First of all I'm not sure the real specs are close to the advertised specs. If they are measure the distance from the butt cap to the average location of the weight at 12 (I'm assuming 68 cm. Then measure the average location of the weight at 3&9. Subtract the SW axis from each 9.75 cm. Then apply the formula for SW increase. SW = mrr or SW = .005*57.25*57.25 + .004*42.25*42.25 = 24 point increase in SW or 334

EDIT: But don't get hung up on the number if it feels right that is all that counts.

 

[coolschreiber]

I'm not real sure. First of all I'm not sure the real specs are close to the advertised specs. If they are measure the distance from the butt cap to the average location of the weight at 12 (I'm assuming 68 cm. Then measure the average location of the weight at 3&9. Subtract the SW axis from each 9.75 cm. Then apply the formula for SW increase. SW = mrr or SW = .005*57.25*57.25 + .004*42.25*42.25 = 24 point increase in SW or 334

EDIT: But don't get hung up on the number if it feels right that is all that counts.

Thanks @Irwin!
I will give it a whirl at the court and see how it goes.

 

[Karma Tennis]

OK, as a rank amateur in this area, I'm going to chime in with my two cents worth.

I think SW is a somewhat variable "variable" because it is such a personal (ie subjective) metric. So I don't compare my SW numbers with anyone else's. I know what feels good for me so I stick to what feels good.

On that basis, I can then resort to relative values rather than absolute ones, if that makes any sense.

I get consistent results using the iOS SwingTool app. It allows me to track relative changes in SW depending on how I customise racquets. And it also makes it much easier to match racquets of similar spec. Please keep in mind that I can't really detect much of a change in a few points of SW so this method works very well for me.

I think "Science" can often get in the way when "Art" is more than enough. Swingweight calculations is one area where I think "Science" often does more harm than good.

Like @Irvin says, "if it feels right that is all that counts".

 

[Erik van der Laan]

SW is a secondary moment of inertia. Inertia measures how mass is distributed in a racket. That tool may five to an approximation but probably not exact. Rod Cross wrote a paper that claimed you could get within 2% with with weight, balance, and length only though. II can look it up if you want.

EDIT: Here is Rod Cross's article http://www.physics.usyd.edu.au/~cross/customising.pdf

Hi Irvin, my English is not so good. What do you mean with "Il can look it up if you want".

 

[Irvin]

Hi Irvin, my English is not so good. What do you mean with "Il can look it up if you want".

Sorry I looked up the reference for you and included the pdf link in the edited post.

 

[Erik van der Laan]

Sorry I looked up the reference for you and included the pdf link in the edited post.

Doesn't matter. Thanks and I gonna study it

 

[Irvin]

Doesn't matter. Thanks and I gonna study it

That is actually chapter 16 out of the Physics and Technology of Tennis. Way over my head. LOL if it get too deep for you look at the conclusion at the end.

 

[Erik van der Laan]

That is actually chapter 16 out of the Physics and Technology of Tennis. Way over my head. LOL if it get too deep for you look at the conclusion at the end.

So difficult stuff pffff. I read the conclusions

 

[Erik van der Laan]

After playing for the first time with following racketspecs: Prince EXO3 Tour 16x18. SW 336 en total weight 357 grams.

Next morning I ve got some stiffy feel in my wrist en underarm. Its de first with this weight and SW. Racket is a lot heavier then my old racket EXO3 Team 16x18.
Is it better for me to low down the SW. I added about 12 grams of lead at 3 and 9 o clock en 4 grams at 12 o clock. Im thinking to pull of the 4 grams at 12 o clock.

Is this a good idea?

 

[Shroud]

After playing for the first time with following racketspecs: Prince EXO3 Tour 16x18. SW 336 en total weight 357 grams.

Next morning I ve got some stiffy feel in my wrist en underarm. Its de first with this weight and SW. Racket is a lot heavier then my old racket EXO3 Team 16x18.
Is it better for me to low down the SW. I added about 12 grams of lead at 3 and 9 o clock en 4 grams at 12 o clock. Im thinking to pull of the 4 grams at 12 o clock.

Is this a good idea?

I would leave the 4 grams at 12 and remove all the weight at 3 and 9. If you are having wrist issues, i would start there.

 

[Erik van der Laan]

I would leave the 4 grams at 12 and remove all the weight at 3 and 9. If you are having wrist issues, i would start there.

But the new setup gave me a lot of stability. I think it was because of the added tape at 3 and 9 o'clock.
Is removing 4 grams at 3 en 9 o'clock a option. If the problem still continuing is another 4 grams removing the second option.

I liked the stability

 

[AMGF]

After playing for the first time with following racketspecs: Prince EXO3 Tour 16x18. SW 336 en total weight 357 grams.

Next morning I ve got some stiffy feel in my wrist en underarm. Its de first with this weight and SW. Racket is a lot heavier then my old racket EXO3 Team 16x18.
Is it better for me to low down the SW. I added about 12 grams of lead at 3 and 9 o clock en 4 grams at 12 o clock. Im thinking to pull of the 4 grams at 12 o clock.

Is this a good idea?

Well I don't think your numbes are right. Having only 336sw from 28g added to the head doesn't add up. So I plugged in your numbers in racquettune app and for your frame I arrive at 357g, 378sw 2ptHL.

At 378sw, I can easily believe both the wrist pain and extra stable comments.

If I were you, I'd keep the 4at 12, put 2 at 3-9, you'll end up at 337g, 344sw. This will be more than enough sw unless you play Djokovic on a regular basis.

 

[Erik van der Laan]

Well I don't think your numbes are right. Having only 336sw from 28g added to the head doesn't add up. So I plugged in your numbers in racquettune app and for your frame I arrive at 357g, 378sw 2ptHL.

At 378sw, I can easily believe both the wrist pain and extra stable comments.

If I were you, I'd keep the 4at 12, put 2 at 3-9, you'll end up at 337g, 344sw. This will be more than enough sw unless you play Djokovic on a regular basis.

Euhh. Total 3 and 9 o clock is 12 grams. So 6 grams each side en 12 o clock was 3,6 grams.
Can you calculate it again

 

[AMGF]

Euhh. Total 3 and 9 o clock is 12 grams. So 6 grams each side en 12 o clock was 3,6 grams.
Can you calculate it again

I still get 358sw. But I don't have your exact starting specs so take that into account, because I have 345g total weight while you have 357g (probably the weight of dampener and overgrip). So my 358sw is probably underestimated. You're probably around 360sw. This is still very high.

I know some guys who play with 350+sw, but there are not that many. The best way to get to 350+sw is to add some weight over the course of many days/weeks. But one thing for sure, that wrist pain is your body telling you that it doesn't like it. Always listen to your body.

 

[Erik van der Laan]

I still get 358sw. But I don't have your exact starting specs so take that into account, because I have 345g total weight while you have 357g (probably the weight of dampener and overgrip). So my 358sw is probably underestimated. You're probably around 360sw. This is still very high.

I know some guys who play with 350+sw, but there are not that many. The best way to get to 350+sw is to add some weight over the course of many days/weeks. But one thing for sure, that wrist pain is your body telling you that it doesn't like it. Always listen to your body.

Thanks for calculatinig. I read about another calculation from Irvin

Balance point * Balance point * (weight x 0.001)

 

[AMGF]

Irvin knows his stuff, you probably just miscalculated at some point.

There is a free formula on TWU but I just bought the racquettune app for iPhone. It is cheap and very useful.

 

[Erik van der Laan]

Irvin knows his stuff, you probably just miscalculated at some point.

There is a free formula on TWU but I just bought the racquettune app for iPhone. It is cheap and very useful.

Already bought it, but I have got a Android phone.

The SW I calculated was not the formula of Irwin, but another one. When I'm home tonight I will calculate it.
What do you need of numbers to give a good SW calculation? I'm very interested now...

 

[AMGF]

If I had your starting weight, swing weight and balance before any was lead added, I would have a much more precise number for you.

But I used racquetfinder numbers so it can't be that far off. Pretty sure you're in the 360sw zone.

 

[Irvin]

I still get 358sw. But I don't have your exact starting specs so take that into account, because I have 345g total weight while you have 357g (probably the weight of dampener and overgrip). So my 358sw is probably underestimated. You're probably around 360sw. This is still very high.

I know some guys who play with 350+sw, but there are not that many. The best way to get to 350+sw is to add some weight over the course of many days/weeks. But one thing for sure, that wrist pain is your body telling you that it doesn't like it. Always listen to your body.

AMGF whenever you add weight to 3&9 you will increase TW and SW. When you add mass to 12 you increase SW. I too think you numbers are off. Have you looked at the center of mass? Wherever it was surely had to change. How are you figuring SW?

 

[AMGF]

AMGF whenever you add weight to 3&9 you will increase TW and SW. When you add mass to 12 you increase SW. I too think you numbers are off. Have you looked at the center of mass? Wherever it was surely had to change. How are you figuring SW?

Because I didn't have his starting specs, I used the specs for a stock strung frame on racquetfinder. I then added the weight Erik Van gave us. Plugged it into the app and I come up with 360sw. Of course this number is not exact, but it is probably much closer to reality than his calculated 336sw (stock his frame has 323sw according to racquet finder).

If I had his measured starting spec I could be more precise. But he has added 18g of lead to the head between 3 12 and 9!! That's a lot.

One thing for sure, forget the numbers, if his wrist hurts, he should take some weight off.

 

[Lukhas]

But the new setup gave me a lot of stability. I think it was because of the added tape at 3 and 9 o'clock.
Is removing 4 grams at 3 en 9 o'clock a option. If the problem still continuing is another 4 grams removing the second option.

I liked the stability

Well as it was alluded to, adding strips of tape isn't the same as adding it on one precise point. As a result, using long stripes of lead at 12 o'clock that spread on both sides of the racquet will increase stability. Not as much as lead atv3 and 9 of course, but it's still noticeable.

 

[Shroud]

But the new setup gave me a lot of stability. I think it was because of the added tape at 3 and 9 o'clock.
Is removing 4 grams at 3 en 9 o'clock a option. If the problem still continuing is another 4 grams removing the second option.

I liked the stability

You get stability from adding weight at 12! 3 and 9 will make the racket more forgiving to off center shots. But too much there and you can tax your wrist if you have wristy shots.

And the big thing you are missing is that lead should be slow and gradual. Not one and done! We can still add weight at 3 & 9 but starting at 12 gets you the most benefit for the least amount of weight

 

[Irvin]

One thing for sure, forget the numbers, if his wrist hurts, he should take some weight off.

Sorry I tough you were adding to your racket. If his wrist is hurting it's probably caused by pronating. That happens when you serve and hit topspin. When the racket moves in that fashion it is a combination of SW and TW. 12 g at 3&9 adds a lot of TW which adds to the SW when pronating especially when you're trying to snap down on a serve or put topspin on the ball. If it didn't hurt before and it does now I'd that that weight off.

 

[Erik van der Laan]

I'm back. The total weight of my racket is 356,4. It has van replacement grip: Yonex Hi Soft. 1 overgrip: Polyfibre Omni Grip. 1 Prince Premier Silencer damper.

I added strips of 1 cm in 3 layers * 4 at 3 en 9 o'clock. And 2 layers of 1 cm * 2 at 12 o'clock

 

[Irvin]

That's 28 cm of lead, a big difference between that and 28 g. And if the lead is about 1 cm thick (1/4") I can assume 1/4 g per cm or total of 7 g. All the grip and handle mass should account for very little SW.

 

[Erik van der Laan]

That's 28 cm of lead, a big difference between that and 28 g. And if the lead is about 1 cm thick (1/4") I can assume 1/4 g per cm or total of 7 g. All the grip and handle mass should account for very little SW.

Irvin, sorry for the mistake. It's 10 cm and ik weights 1 gram per layer

 

[Irvin]

Irvin, sorry for the mistake. It's 10 cm and ik weights 1 gram per layer

My head is spinning. How many grams of mass do you have at 3, 9, and 12 individually not cumulative.

 

[Erik van der Laan]

My head is spinning. How many grams of mass do you have at 3, 9, and 12 individually not cumulative.

3 en 9 o'clock each side 6 grams = 12 grams
12 o'clock total 4 grams

 

[Irvin]

Take the weight @ 3&9 off completely and start from there. After at least a week if you feel you need more ad 1 g at 3&9 at a time.

 

[Erik van der Laan]

Take the weight @ 3&9 off completely and start from there. After at least a week if you feel you need more ad 1 g at 3&9 at a time.

Okay I will take off the weight @ 3 & 9.
1 gram each time is not much. What means 1 gram adding @ 3 & 9 for the SW of a racket.

I read that 1 gram @ 12 increase SW with 5. Is that correct?

 

[Irvin]

The SW increase is the mass times the distance squared. Adding 1 g at 3&9 is like ad dinging 2 g. Now sure about your racket but let's say 3&9 is 52 cm up from the butt. That makes it 42 cm above the 10 cm SW axis so .002*42*42 = 3.528 Kg cm^2

 

[Erik van der Laan]

The SW increase is the mass times the distance squared. Adding 1 g at 3&9 is like ad dinging 2 g. Now sure about your racket but let's say 3&9 is 52 cm up from the butt. That makes it 42 cm above the 10 cm SW axis so .002*42*42 = 3.528 Kg cm^2

The middle of my strips was at 55 cm from the butt. So I added .012*45*45 = 24.3
And 4 gram @ 67 from the butt is .004*57*57 = 12.996

My SW was 37 point higher than before. . This method is simple en effective to match 2 the same rackets with a different SW.

What is the maximum advice to somebody to increase the SW ?

 

[AMGF]

Don't chase sw numbers.
Go with what feels good.
Then measure and match all your frames.

It sounds like you want a particular sw number. That's going backwards. You can try a 360sw for the fun of it. But the best way is find something you like first, then measure SW.

 

[Erik van der Laan]

Don't chase sw numbers.
Go with what feels good.
Then measure and match all your frames.

It sounds like you want a particular sw number. That's going backwards. You can try a 360sw for the fun of it. But the best way is find something you like first, then measure SW.

I'm looking for the SW number. Everybody knows his SW but I still don't know. When I have a number it's better to know what is best for myself.
If I know the numbers of the rackets it's easier to match my rackets

Its still a hell of a job to know my SW

 

[AMGF]

I'm looking for the SW number. Everybody knows his SW but I still don't know. When I have a number it's better to know what is best for myself.
If I know the numbers of the rackets it's easier to match my rackets

Its still a hell of a job to know my SW

If you only want to know your SW go here:
http://twu.tennis-warehouse.com/learning_center/swingweight_calc.php

That's the only way to know for sure.

 

[rlau]

Dont obsess too much about knowing your swingweight Erik. Only true tennis geeks know theirs. Before joining this forum I had never even heard about the concept. Oh, how simple life was back then....

 

[Irvin]

What is the maximum advice to somebody to increase the SW ?

that really depends on the player. Some people need to stay below 300 while others may be pushing 400. Taking someone else's advise could ruin your game it it is not for you. First off the racket you have before you added weight was a good start. Adding a grip you wanted, over wraps, and dampener may have made it better for you. I can guarantee you it increased swing weight, twist weight, and recoil weight. But at the same time the added mass in the handle of the frame and lowered the center of mass. That probably made it more maneuverable for you and faster to swing. You could at this point add mass into the handle too. All This will raise the mass and drop the center of mass. This will make the racket very heavy and tire you out running around with it. You then need to find a happy medium from where your were with all the head weight and where you will be then.

 

[Erik van der Laan]

that really depends on the player. Some people need to stay below 300 while others may be pushing 400. Taking someone else's advise could ruin your game it it is not for you. First off the racket you have before you added weight was a good start. Adding a grip you wanted, over wraps, and dampener may have made it better for you. I can guarantee you it increased swing weight, twist weight, and recoil weight. But at the same time the added mass in the handle of the frame and lowered the center of mass. That probably made it more maneuverable for you and faster to swing. You could at this point add mass into the handle too. All This will raise the mass and drop the center of mass. This will make the racket very heavy and tire you out running around with it. You then need to find a happy medium from where your were with all the head weight and where you will be then.

Irvin, the start was okay, but to heavy for me. I put off all the added leadtape @ 3&9. Today I'm gonna play again with my wife to know how it feels. The balance off the racket is low but I want more power then before. Im thinking adding tape at the head side wil give me more power from the baseline. Only I added to much tape so I feel my arm the day after.

My plan is to play now 2 times with a racket and then made a deciscion to add 1 gram of tape @ 3&9. Is this a good plan?