Lead Tape - Reverse Calculations

#1
My 15 year old son is demoing the Pure Strike 16x19 and he likes it so far other than he needs to increase the static and swing weight. I really have no idea what I am doing and made a first attempt using the racquet customization tool which were these starting values:

Weight = 11.6 oz (Up from 11.3)
Balance = 13 in (Unchanged)
Swingweight = 333 kg·cm² (Up from 323)

The results are: 4.54 g @ 22.8", 3.97 g @ 1.2" which resulted in fractional strips that I fealt made no sense in dealing with as we are just starting out.

Instead I put 2.5 g on the inner hoop on each side and put 2.75 g at 1.2" and then added an over-grip hoping that would be a gram.

Ultimately, I plan on using the TW racquet customization services:

For sake of argument let's assume he likes this setup:

1. Is there a tool to reverse these weights/positions I added into the static, swingweight, and balance values so I can provide these when we purchase the racquets?

2. Am I on the right track with what I am doing?

Thanks!
 

Irvin

Talk Tennis Guru
#2
Swing weight is actually easy, mass times distance squared. In tennis it’s customary to use Kg and cm. So assume you add 2 g at 20”. That’s 0.002 Kg at 50.8 cm. Since SW is normally computed on a 10 cm pivot the point where you add lead (50.8 cm) is 40.8 cm so the SW goes up by 0.002*40.8*40.8 or 3.3 points.

You will often see someone adding mass above and below the balance point. That is done to maintain or adjust the balance or MgR/I. Let’s say you original balance was 13” or 33 cm. When you add 2 g at 50.8 cm that is 17.8 cm above the balance point. To maintain the balance you need the save force on the other side of the balance point. You added 2*17.8 or 35.6 gcm above the balance point to the mass times the distance where you add weight below the balance point must be 35.6 gcm. If you want to put the weight at 1.2” or 3 cm (33-3 is 30 cm below balance) you must add 35.6/30 or 1.2 g to maintain a balance of 13”.

Then there is MgR/I you’re going to have to google that one but you have the formula. M is mass, g is gravity 980.5, R is balance or radius, and I is inertia or SW at 0 cm instead of 10 cm. Once you add weight at some point on a racket you need to add mass at another point to maintain your MgR/I. I hop this is not too confusing.
 
#3
Thank you for the calculations.

I suppose I could have taken my time and used our kitchen scale to measure the strips to match the calculations to begin with!!!

This will be a fun experiment to see where this gets us. I suspect as my boy gets bigger and stronger over the next couple of years I am going to be adjusting the weight based on his feedback so I think it will be handy skill to know.
 
#4
I strongly advise buying a reel of 1/4" lead tape and taking the time to experiment with the different lead tape setups, either hitting against a wall or while hitting with son. There are infinitely more ways to set up a racquet that feels wrong than ways to set up a racquet that feels right.
 
#5
I strongly advise buying a reel of 1/4" lead tape and taking the time to experiment with the different lead tape setups, either hitting against a wall or while hitting with son. There are infinitely more ways to set up a racquet that feels wrong than ways to set up a racquet that feels right.
I agree. Using the specifications above the racquet static/swing weight increases but the balance remains the same (13"). However, in swinging the racquet it feels much more evenly balanced than before (less head light).

Anyway, I am doing as you say.... He is hitting and he is providing feedback. I am adjusting.... He hits and provides feedback. I adjust... etc.
 

Irvin

Talk Tennis Guru
#6
I strongly advise buying a reel of 1/4" lead tape and taking the time to experiment with the different lead tape setups, either hitting against a wall or while hitting with son. There are infinitely more ways to set up a racquet that feels wrong than ways to set up a racquet that feels right.
Another idea if you have an idea of what you like and don't like is to create an excel file that shows how changes in a racket change the specs you may be interested in. Here is a picture of a file I create for me. In the bottom center of the file there are arrows I can use to step up or down the weight I add in cell A2



EDIT: For instance say I want to add the minimum weight to the racket I entered in this file to get an MgR/I of 21.1. I can hit the right arrow until the MgR/I graph goes to or over 21.1. Then on the left I can see where the lead needs to be added to get the MgR/I I want.
 
#7
Another idea if you have an idea of what you like and don't like is to create an excel file that shows how changes in a racket change the specs you may be interested in. Here is a picture of a file I create for me. In the bottom center of the file there are arrows I can use to step up or down the weight I add in cell A2



EDIT: For instance say I want to add the minimum weight to the racket I entered in this file to get an MgR/I of 21.1. I can hit the right arrow until the MgR/I graph goes to or over 21.1. Then on the left I can see where the lead needs to be added to get the MgR/I I want.
Wow! Thank you for sending this on! It will be very helpful!
 

Irvin

Talk Tennis Guru
#9
The graphs and data fields auto update as you increase or decrease the weight in 1 g and 1 cm increments from the butt to the head.
 
#11
My 15 year old son is demoing the Pure Strike 16x19 and he likes it so far other than he needs to increase the static and swing weight. I really have no idea what I am doing and made a first attempt using the racquet customization tool which were these starting values:

Weight = 11.6 oz (Up from 11.3)
Balance = 13 in (Unchanged)
Swingweight = 333 kg·cm² (Up from 323)

The results are: 4.54 g @ 22.8", 3.97 g @ 1.2" which resulted in fractional strips that I fealt made no sense in dealing with as we are just starting out.

Instead I put 2.5 g on the inner hoop on each side and put 2.75 g at 1.2" and then added an over-grip hoping that would be a gram.

Ultimately, I plan on using the TW racquet customization services:

For sake of argument let's assume he likes this setup:

1. Is there a tool to reverse these weights/positions I added into the static, swingweight, and balance values so I can provide these when we purchase the racquets?

2. Am I on the right track with what I am doing?

Thanks!
It's so simple....

Just put 3g+3g on 9-3 positions.
New swingweigh = 333 (from 323)
New twistweight = 16.11 (from 15.11)

To balance this:
a) add an overgrip or
b) place 3-4g in the butt cap.
New static weight = 11.6 oz. (from 11.3)
 
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