How is swing weight worked out?

StringSnapper

Hall of Fame
If a two racquets have the same head light balance and the same overall weight, but they're different brands, will they have the same swing weight?

Alternatively, if two racquets of the same brand and model have the same swing weight and head light balance, is it guaranteed they will have the same swing weight?

Thanks
 

IowaGuy

Hall of Fame
If a two racquets have the same head light balance and the same overall weight, but they're different brands, will they have the same swing weight?
Yes, if they are the same length.

Swingweight is just basically mass times the distance from a pivot point (which is why if you extend a given racket it has more swingweight).

It is measured on a machine that literally "swings" the racket. It can also be calculated theoretically (search for previous posts).

Therefore, if two rackets (of the same length) have exactly the same overall weight, and exactly the same balance, then they will have the same swingweight since they will have the same mass and same center of mass and same distance to the pivot point.
 

Big Bagel

Professional
If a two racquets have the same head light balance and the same overall weight, but they're different brands, will they have the same swing weight?

Alternatively, if two racquets of the same brand and model have the same swing weight and head light balance, is it guaranteed they will have the same swing weight?

Thanks
No and no.
Swingweight is just basically mass times the distance from a pivot point
That is a common misconception regarding swing weight. That is the calculation for pickup weight, not swing weight.

Swing weight has to deal with the distribution of weight throughout the racquet, not just the static weight and balance point. A polarized setup (weight concentrated in the handle and at 12 o'clock) can have the same static weight and balance point, but a different swing weight than a non-polarized setup (weight evenly distributed or even concentrated at the balance point).
 

IowaGuy

Hall of Fame
No and no.

That is a common misconception regarding swing weight. That is the calculation for pickup weight, not swing weight.

Swing weight has to deal with the distribution of weight throughout the racquet, not just the static weight and balance point. A polarized setup (weight concentrated in the handle and at 12 o'clock) can have the same static weight and balance point, but a different swing weight than a non-polarized setup (weight evenly distributed or even concentrated at the balance point).

 

Big Bagel

Professional
That is the basics of Statics, yes, but Dynamics is different, particularly when the object is not being held somewhere other than the balance point and it is not moving in a straight line. Check out this directly from the website of the United States Racquet Stringers Association:

"Two racquets of identical weight and balance can have very different swing weights, and therefore will perform very differently. To illustrate, imagine two poles with two weights attached. If the weights are affixed at opposite ends, the swing weight of the pole is maximized. However, if the weights are closely situated swing weight is minimized. Two racquets balanced this way will have totally different playing characteristics. Yet they will be identical in weight and balance as shown in Figure 3.

The same holds true with racquets of differing lengths. The 10-ounce (285 grams), evenly-balanced 29-inch (737 mm) racquet discussed earlier, will have a completely different feel in motion than a 10-ounce (285 grams), evenly-balanced 27-inch (686 mm) racquet. In order to equalize the swing weight of these two racquets, the balance point of the 29-inch (737 mm) racquet would need to be placed one inch (254 mm) closer to the handle, because the even-balance point is one inch (254 mm) further out than on a 27-inch (686 mm) racquet (14-1/2 inches or 368 mm vs. 13-1/2 inches or 343 mm)."

If you would like, I can do some experiments with one of my racquets and take pictures for you to observe to prove it to you if the USRSA is not a credible enough source.
 

IowaGuy

Hall of Fame
That is the basics of Statics, yes, but Dynamics is different, particularly when the object is not being held somewhere other than the balance point and it is not moving in a straight line. Check out this directly from the website of the United States Racquet Stringers Association:

"Two racquets of identical weight and balance can have very different swing weights, and therefore will perform very differently. To illustrate, imagine two poles with two weights attached. If the weights are affixed at opposite ends, the swing weight of the pole is maximized. However, if the weights are closely situated swing weight is minimized. Two racquets balanced this way will have totally different playing characteristics. Yet they will be identical in weight and balance as shown in Figure 3.

The same holds true with racquets of differing lengths. The 10-ounce (285 grams), evenly-balanced 29-inch (737 mm) racquet discussed earlier, will have a completely different feel in motion than a 10-ounce (285 grams), evenly-balanced 27-inch (686 mm) racquet. In order to equalize the swing weight of these two racquets, the balance point of the 29-inch (737 mm) racquet would need to be placed one inch (254 mm) closer to the handle, because the even-balance point is one inch (254 mm) further out than on a 27-inch (686 mm) racquet (14-1/2 inches or 368 mm vs. 13-1/2 inches or 343 mm)."

If you would like, I can do some experiments with one of my racquets and take pictures for you to observe to prove it to you if the USRSA is not a credible enough source.
I stated that assuming rackets are of equal length, so let's don't compare 27 and 29 inch rackets.

But yes, if you wanted to do some experiments with the same length of rackets that would be awesome!

Do you have access to a RDC?

We could also just look through a few dozen of the new rackets listed on TW's reviews, and compare to see just how different the measured SW (I believe they use RDC) is for rackets of the same static weight and balance. This is more in line with the OP's original question of whether two different rackets with the same static weight and balance will have the same SW...
 

2nd Serve Ace

Hall of Fame
TW swingweight estimator?

Sw must be more than W, bal and length, since the racquet must be put in motion as well to get an estimate.
 

Big Bagel

Professional
I stated that assuming rackets are of equal length, so let's don't compare 27 and 29 inch rackets.

But yes, if you wanted to do some experiments with the same length of rackets that would be awesome!

Do you have access to a RDC?

We could also just look through a few dozen of the new rackets listed on TW's reviews, and compare to see just how different the measured SW (I believe they use RDC) is for rackets of the same static weight and balance. This is more in line with the OP's original question of whether two different rackets with the same static weight and balance will have the same SW...
The first part of the quote is talking about those with the same length though.

Great, I will do it and get back to you. I'm not going to do a video, but I'll get pics of the racquet with polarized and non-polarized setups, showing static weight, balance point, and swing weight.

Yes, I have an RDC.

I would do it with two different racquets, but I would have to match them first which would take more time.
 

ONgame

Semi-Pro
If a two racquets have the same head light balance and the same overall weight, but they're different brands, will they have the same swing weight?
No. This will depend on how the weight is distributed. Lookup "polarized racquet vs not polarized racquet".

Alternatively, if two racquets of the same brand and model have the same swing weight and head light balance, is it guaranteed they will have the same swing weight?
In a perfect world, Yes.
In our world, they should be very close. The errors occur in quality control.
 

mxblink

Rookie
Swingweight is just basically mass times the distance from a pivot point
You’re wrong. Finding an intelligent-looking figure on the internet that relates to a completely separate topic in physics (center of mass, I imagine) won’t change that.

Look up the units for swingweight. Swingweight is measured in units kg-cm^2. What do you get when you multiply mass times distance, as you suggest? You get (after unit conversion) kg-cm. The units don’t match.

Swingweight is a measure of rotational inertia. Rotational inertia varies with the *square* of the distance from the mass to the pivot point. Thus, redistributing mass towards the poles of the racquet increases the swingweight while keeping balance and static weight the same.
 

IowaGuy

Hall of Fame
The first part of the quote is talking about those with the same length though.

Great, I will do it and get back to you. I'm not going to do a video, but I'll get pics of the racquet with polarized and non-polarized setups, showing static weight, balance point, and swing weight.

Yes, I have an RDC.

I would do it with two different racquets, but I would have to match them first which would take more time.
Will be fun to see the RDC values from polarized vs. non-polarized setup with the same static weight and same balance. My guess is that they will be within a few units of each other, for static weight/balance combos generally used by rec players...
 

IowaGuy

Hall of Fame
You’re wrong. Finding an intelligent-looking figure on the internet that relates to a completely separate topic in physics (center of mass, I imagine) won’t change that.

Look up the units for swingweight. Swingweight is measured in units kg-cm^2. What do you get when you multiply mass times distance, as you suggest? You get (after unit conversion) kg-cm. The units don’t match.

Swingweight is a measure of rotational inertia. Rotational inertia varies with the *square* of the distance from the mass to the pivot point. Thus, redistributing mass towards the poles of the racquet increases the swingweight while keeping balance and static weight the same.
The question is whether a strip of lead tape can be modeled as a mass acting through its center of mass, or whether it has to be modeled as hundreds of individual points of mass, each acting through its own center of mass.

i.e. if I apply a 10g strip of lead tape from 9 to 3 across the top of the entire hoop of my tennis racket, can I just model/calculate this as one mass (10g) acting through one center of mass (its distance from the pivot point)? If so, then can you model/calculate the entire hoop as one mass acting through its center of mass?
 

StringSnapper

Hall of Fame
Thanks for the replies guys.

Im still a bit confused - but it seems like if its polarised or not has a (relatively ) minor difference, no? I wonder the percentage the polarisation effects the swingweight.
By polarised do you mean the frame itself or also the lead tape, or both? Im guessing both.

For example, im using a head youtek ig prestige midplus.

Ive added 6g in overgrips and 10g in tape using 5" strips at 3 and 9. Its overall weight is 356, and as far as my dodgy homemade balancer calculated, around 7pt headlight.

Im assuming this is relatively "non polarised" compared to lets say, the same model of racquet, same weight and headlight balance, except now imagine the 6g handle weight is not from overgrips but concentrated at the bottom of the handle. And the 10g weight in the hoop is all at 12oclock in 5inch strips (and i guess even more polarised, all at the top in 3" strips)

This more polarised second racquet will have a higher swing weight?
 

saleem

Semi-Pro
Thanks for the replies guys.

Im still a bit confused - but it seems like if its polarised or not has a (relatively ) minor difference, no? I wonder the percentage the polarisation effects the swingweight.
By polarised do you mean the frame itself or also the lead tape, or both? Im guessing both.

For example, im using a head youtek ig prestige midplus.

Ive added 6g in overgrips and 10g in tape using 5" strips at 3 and 9. Its overall weight is 356, and as far as my dodgy homemade balancer calculated, around 7pt headlight.

Im assuming this is relatively "non polarised" compared to lets say, the same model of racquet, same weight and headlight balance, except now imagine the 6g handle weight is not from overgrips but concentrated at the bottom of the handle. And the 10g weight in the hoop is all at 12oclock in 5inch strips (and i guess even more polarised, all at the top in 3" strips)

This more polarised second racquet will have a higher swing weight?
add your mods in this calculator and it will give you the answer (adding to tips of the racket will be polarized)
here is a nice tool to see your modded info http://twu.tennis-warehouse.com/learning_center/customizationReverse.php
 

IowaGuy

Hall of Fame
Thanks for the replies guys.

Im still a bit confused - but it seems like if its polarised or not has a (relatively ) minor difference, no? I wonder the percentage the polarisation effects the swingweight.
By polarised do you mean the frame itself or also the lead tape, or both? Im guessing both.

For example, im using a head youtek ig prestige midplus.

Ive added 6g in overgrips and 10g in tape using 5" strips at 3 and 9. Its overall weight is 356, and as far as my dodgy homemade balancer calculated, around 7pt headlight.

Im assuming this is relatively "non polarised" compared to lets say, the same model of racquet, same weight and headlight balance, except now imagine the 6g handle weight is not from overgrips but concentrated at the bottom of the handle. And the 10g weight in the hoop is all at 12oclock in 5inch strips (and i guess even more polarised, all at the top in 3" strips)

This more polarised second racquet will have a higher swing weight?
Well, adding the same weight at 12 compared to adding the same weight at 9 will definitely increase swingweight. The weight in the handle is negligible, as it is very close to the pivot point.

A rough rule of thumb is that 1g added at 3/9 is 2 swingweight units, whereas the same 1g added at 12 is 3 swingweight units.

So, for your example, 10g at 3/9 would add 20 SW, whereas 10g at 12 would add 30 SW.

Also note that the lead added at 3/9 increases the twistweight quite a bit, whereas the weight added at 12 doesn't add much twistweight, particularly if the lead strips are short. I personally like a fairly high twistweight racket for serve returns and 1HBH. YMMV.
 

mxblink

Rookie
The question is whether a strip of lead tape can be modeled as a mass acting through its center of mass, or whether it has to be modeled as hundreds of individual points of mass, each acting through its own center of mass.

i.e. if I apply a 10g strip of lead tape from 9 to 3 across the top of the entire hoop of my tennis racket, can I just model/calculate this as one mass (10g) acting through one center of mass (its distance from the pivot point)?
I mean, sure you *can* model the added lead as a point mass located at its center of mass, but clearly that model is an estimate, and the more spread out the added lead actually is, the less accurate your estimate becomes.

If so, then can you model/calculate the entire hoop as one mass acting through its center of mass?
That would certainly be the least accurate interpretation of your model, and it would appear the answer is no.



But really, the original question is whether two racquets with the same static weight and balance necessarily have the same swingweight.

If a two racquets have the same head light balance and the same overall weight, but they're different brands, will they have the same swing weight?
Therefore, if two rackets (of the same length) have exactly the same overall weight, and exactly the same balance, then they will have the same swingweight since they will have the same mass and same center of mass and same distance to the pivot point.
The answer, as demonstrated above, is that the same static weight and balance do NOT guarantee identical swingweights. And before you argue that my examples are contrived (which they certainly are - purposely to prove a point), we can also use real world examples:




Unless Wilson and Tecnifibre have conspired to defy the laws of physics, I don't see how this is a question any longer.

Im assuming this is relatively "non polarised" compared to lets say, the same model of racquet, same weight and headlight balance, except now imagine the 6g handle weight is not from overgrips but concentrated at the bottom of the handle. And the 10g weight in the hoop is all at 12oclock in 5inch strips (and i guess even more polarised, all at the top in 3" strips)

This more polarised second racquet will have a higher swing weight?
Yes. See examples above.
 

BlueB

Legend
I can't believe this question is still asked... there are tons of threads already explaining this on detail.

Sent from my SM-G965W using Tapatalk
 

Kevo

Legend
I can't believe this question is still asked... there are tons of threads already explaining this on detail.
I can't believe there are still people who can't believe that the same old questions are still getting asked!

Oh wait, I think I was being ironic again. ;-)
 

ONgame

Semi-Pro
Thanks for the replies guys.

Im still a bit confused - but it seems like if its polarised or not has a (relatively ) minor difference, no? I wonder the percentage the polarisation effects the swingweight.
By polarised do you mean the frame itself or also the lead tape, or both? Im guessing both.

For example, im using a head youtek ig prestige midplus.

Ive added 6g in overgrips and 10g in tape using 5" strips at 3 and 9. Its overall weight is 356, and as far as my dodgy homemade balancer calculated, around 7pt headlight.

Im assuming this is relatively "non polarised" compared to lets say, the same model of racquet, same weight and headlight balance, except now imagine the 6g handle weight is not from overgrips but concentrated at the bottom of the handle. And the 10g weight in the hoop is all at 12oclock in 5inch strips (and i guess even more polarised, all at the top in 3" strips)

This more polarised second racquet will have a higher swing weight?
polarized means the weights are concentrated at the two ends of the stick
non-polarized means the weights are evenly distributed along the stick
when all else equal, a polarized stick will have a higher swing weight than the non-polarized counterpart
 
Top