Matching rackets weight and balance

[Irvin]

Some of you thought my previous method of matching rackets was a little over the top I guess. Well I going to show you how to match weight and balance (I hope) in easy to understand terms. I just got 2 rackets from a customer and the specs are:

Racket #1 Wt 317.4 and balance of 32.0
Racket #1 Wt 322.4 and balance of 31.6

I multiply the weight times the balance to get the torque at the butt. So Racket #1 has (317.4*32.0) 10,156.8 gcm (gram cm) and Racket #2 has (322.4*31.6) 10,187.84 gcm. Now I add weight to the lightest racket with the lowest torque to make them equal. There is a difference of 31.04 gcm and 5 g so I add 5 g to Racket #1 at (31.04/5) 6.2 cm.

 

[Irvin]

This allows you to match weight and balance of 2 or more rackets pretty easy. From this point on if you want to add weight at 3&9, 10&2, 12, etc ... do the same to every racket and you will be good to go.

 

[AMGF]

Good stuff.
But the SW could be quite different. How do you adjust for that?

 

[Irvin]

Good stuff.
But the SW could be quite different. How do you adjust for that?

If all I'm trying to match is weight and balance, like many people do, I do not adjust for inertia except that the inertia does change as I add weight. If I want to adjust for inertia (SW, TW, RW, and I) I use the formula I = mr^2. After matching inertia I used the method above (t = mr) to match balance.using that basic formula I may solve for m and r.

EDIT: if I'm adjust for inertia I only adjust using the minimum weight to match the rackets by adding up to raise only 1 racket, then I add additional weight in same weight and locations to attain the inertia I want.

 

[AMGF]

Ok thank you. Makes sense to do it that way. I always try match SW weight and balance all at once. I did it with the racquet tune app but using math saves some time.

 

[Irvin]

Here is another situation I found last night. The rackets had previously been head weighted, tail weighted and one had lead in the throat. But here are the weight*balance along with force difference / weight difference. The client was ok with the feel so I did not adjust anything.

Racket #1 344.0*30.5 = 10,492.0 / 0
Racket #2 342.3*30.0 = 10,269.0 / 1.7 (10,492-10269)/(344.0-342.3) = 131.2
Racket #3 339.1*30.1 = 10,206.91 / 4.9 (10,492-10,206)/(344.0-339.1) = 58.2

I could have adjusted Racket #3 by placing (344-339.1) = 4.9 g @ 58.2 cm but it would be impossible to put 1.7 g at 131.2 cm on Racket #2. The best way to match the weight and balance of these rackets would be to remove all the extra weight and start over. But the weight was under the bumpers / leather grips and would have been more work. I may have been able to take all (or some) the weight out of the throat on one racket but I forgot which one that was (I think is was Racket #1.)

EDIT: it becomes a lot less complicated when you use a spreadsheet and let Excel do all the math for you.

 

[Znak]

If all I'm trying to match is weight and balance, like many people do, I do not adjust for inertia except that the inertia does change as I add weight. If I want to adjust for inertia (SW, TW, RW, and I) I use the formula I = mr^2. After matching inertia I used the method above (t = mr) to match balance.using that basic formula I may solve for m and r.

EDIT: if I'm adjust for inertia I only adjust using the minimum weight to match the rackets by adding up to raise only 1 racket, then I add additional weight in same weight and locations to attain the inertia I want.

This is very interesting — would you mind providing an example of how you'd match SW, balance and weight at the same time?

 

[Irvin]

This is very interesting — would you mind providing an example of how you'd match SW, balance and weight at the same time?

Do you have an example of 2 rackets you'd like to match?

EDIT: Have you seen this thread https://tt.tennis-warehouse.com/ind...tch-2-tecnifibre-315-dynacore-rackets.660508/

 

[Irvin]

This is very interesting — would you mind providing an example of how you'd match SW, balance and weight at the same time?

I had a client bring me 2 PS97S rackets. He likes to remove the grips and install 2 overwraps so these specs may look a little funny. Specs are:

Racket #1 333.9 g, 33.6 cm, and 334.5 SW
Racket #2 328.9 g, 33.3 cm, and 328.9 SW

First I found the force of the 2 rackets

Racket #1 333.9*33.6 = 11,219.0
Racket #2 328.9*33.3 = 10,952.4

Then i divided the force difference by the weight difference to see where to add the 5 g on racket #2 (266.6/5 = 53.3 cm)

Adding 5 g to 53.3 cm which is 43.3 cm above the SW pivot add (.005*43.3*43.3) 9.4 points which will make the weight and balance the same in both rackets but racket #2 will then have a 1.5 point high SW. from this point on it will require adding more weight to both rackets or I could leave it alone and just take the 1.5 SW difference. Or I could drop the weight down slightly to bring the SW closer to matching and leave a balance off by a little.

 

[Znak]

I had a client bring me 2 PS97S rackets. He likes to remove the grips and install 2 overwraps so these specs may look a little funny. Specs are:

Racket #1 333.9 g, 33.6 cm, and 334.5 SW
Racket #2 328.9 g, 33.3 cm, and 328.9 SW

First I found the force of the 2 rackets

Racket #1 333.9*33.6 = 11,219.0
Racket #2 328.9*33.3 = 10,952.4

Then i divided the force difference by the weight difference to see where to add the 5 g on racket #2 (266.6/5 = 53.3 cm)

Adding 5 g to 53.3 cm which is 43.3 cm above the SW pivot add (.005*43.3*43.3) 9.4 points which will make the weight and balance the same in both rackets but racket #2 will then have a 1.5 point high SW. from this point on it will require adding more weight to both rackets or I could leave it alone and just take the 1.5 SW difference. Or I could drop the weight down slightly to bring the SW closer to matching and leave a balance off by a little.

Wow, it seems like there's a bit of an art to it. How are you getting your SW out of curiosity? Also how did you get 43.3?

 

[Irvin]

Wow, it seems like there's a bit of an art to it. How are you getting your SW out of curiosity? Also how did you get 43.3?

I used SwingTool and allowed the rackets to pivot of the 8th cross string which was 53.9 cm from the butt of the racket. Instead of inputting weights of 333.9 and 328.9 g I used 3339 and 3289 g to get a value 10x greater than actual then I divide the result by 10.

When I divide force/weight it tell me where to put the weight. That is the distance from the bit of the racket. SW is calculated from 10 cm so to determine how mass added at 53.3 cm I used 43.3 cm.

 

[Irvin]

Unless you’re going to be using the SW in your calculations I think it is easier to just match weight and balance. As long as you don’t get crazy and start to add weight all over the place SW will be close. That’s why many people just match Weight and balance. The difference in 1.5 SW point I see above could easily be errors in the measurements I made.

 

[itsstephenyo]

Is a 1.5 difference in SW actually detectable? I mean 330 and 331.5 are gonna swing 99.5% the same

 

[tlm]

Is a 1.5 difference in SW actually detectable? I mean 330 and 331.5 are gonna swing 99.5% the same

I really don’t think many players would be able to tell that small of a difference.

 

[oldno7]

@Irvin how would you approach scenarios where the lighter racquet has higher torque at the butt, assuming unstrung frames and no way to take off weight?

 

[zipplock]

Unless you’re going to be using the SW in your calculations I think it is easier to just match weight and balance. As long as you don’t get crazy and start to add weight all over the place SW will be close. That’s why many people just match Weight and balance. The difference in 1.5 SW point I see above could easily be errors in the measurements I made.

In your experience, what are people going to notice more, a difference in weight, balance or swingweight? Also, how much difference for each to be noticeable?
Me for example, I can feel the difference in balance first, then weight, then swingweight. Balance doesn't need to be very far off for me to tell the difference (can feel difference once it's more than a point difference). I start to feel swingweight difference around 10 difference.

 

[oldno7]

In your experience, what are people going to notice more, a difference in weight, balance or swingweight? Also, how much difference for each to be noticeable?
Me for example, I can feel the difference in balance first, then weight, then swingweight. Balance doesn't need to be very far off for me to tell the difference (can feel difference once it's more than a point difference). I start to feel swingweight difference around 10 difference.

I find difference in balance throws off volleys and overheads more while swingweight affects groundstrokes more.

 

[Irvin]

In your experience, what are people going to notice more, a difference in weight, balance or swingweight? Also, how much difference for each to be noticeable?
Me for example, I can feel the difference in balance first, then weight, then swingweight. Balance doesn't need to be very far off for me to tell the difference (can feel difference once it's more than a point difference). I start to feel swingweight difference around 10 difference.

IME I would say weight is the single most noticeable factor, then balance, followed by SW. many women I know want a racket under 300 g but they are more than happy with a 300+ SW. as a matter of fact is the isn’t over 300 it is too easy to push around and there is no power. More often than knot is you can match up 2 like racket weight and balance not many can tell there may or may not be a difference in SW because they are so close.

 

[Irvin]

@Irvin how would you approach scenarios where the lighter racquet has higher torque at the butt, assuming unstrung frames and no way to take off weight?

Just tell the owner to go away and don’t come back any more. LOL Just kidding, if the lighter racket has the highest torque it will also have the highest balance point. The first thing I would do is check to see if the heavier racket has any add ons to make it heavier and more head light. For example does the heavier racket have a build up sleeve, a leather grip, or an extra overwrap? If everything look normal you have to add weight to the lighter racket and raise the balance point. The more mass you add and the higher you add it raise the torque the most. Add enough mass to raise the torque And mass a little higher than the lighter racket. Then add the appropriate mass to the other racket to get the torque to match.

EDIT: I would not add mass too far off the centerline unless I knew the TW was also off. Once the weight and balance are matched you can add mass at 3&9 if you want but do the same to both rackets.

 

[oldno7]

Just tell the owner to go away and don’t come back any more. LOL Just kidding, if the lighter racket has the highest torque it will also have the highest balance point. The first thing I would do is check to see if the heavier racket has any add ons to make it heavier and more head light. For example does the heavier racket have a build up sleeve, a leather grip, or an extra overwrap? If everything look normal you have to add weight to the lighter racket and raise the balance point. The more mass you add and the higher you add it raise the torque the most. Add enough mass to raise the torque And mass a little higher than the lighter racket. Then add the appropriate mass to the other racket to get the torque to match.

EDIT: I would not add mass too far off the centerline unless I knew the TW was also off. Once the weight and balance are matched you can add mass at 3&9 if you want but do the same to both rackets.

Thanks Irvin, I haven't had a chance to re-visit these racquets. They're a pair of Wilson Classic 6.1s I bought used and I did notice something after reading your post - they have different brands of leather grip. I'll remove those grips and recheck specs. Thanks again for your ideas.