Master Trader
New User
Does anyone know how to calculate a racquet's swing weight? My guess is that it has something to do with a racquet's balance point and its static weight, but I'm not sure.
Racquet's Swing Weight
- Thread starter Master Trader
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dmastous
Professional
The formula is mass times distance squared. The distance here is the distance from, usually, 4 inches from the butt end of the racquet to it's balance point.
What it's trying to do is put a number value on the amount of force it takes to get the racquet to move when you swing it. So it can be said to be related to static moment, but it's not the same thing.
What it's trying to do is put a number value on the amount of force it takes to get the racquet to move when you swing it. So it can be said to be related to static moment, but it's not the same thing.
The swingweight is basically the moment of inertia of the frame with respect to the axis of rotation which, in this case, is your wrist. What dmastous said is correct, but not fully complete.
If you do a search on my name and "swingweight", you will find several posts where I try to explain the whole thing.
In short: Balance point and total weight say nothing about the swingweight. Since swingweight is a function of the total weight distrubution of the racket, it can never be fully characterized by just the balance point and total weight.
Consider these extreme cases:
- Object 1: 70cm long, 150 grams at each end
- Object 2: 70cm long, 100 gram at each end and 100 gram in the middle
- Object 3: 70cm long, 300 gram in the middle
All object are 70 cm long, wheigh 300 grams and have a balance point at 35 cm. If you will swing them with your wrist though while holding them at one end, they will each have a distinctly different feel to them, this is basically put into a number: "the swingweight".
For each point of mass, this is indeed calculated by multiplying the mass with the square of the distance from the point of rotation. However, you have to add the outcome of this calculation of all the points of mass in the object. The total gives you the moment of intertia with respect to the axis of rotation you are considering. If you do this for all 3 objects, you will get 3 different numbers.
Since a real racket cannot be simply modelled by a few points of mass and you do not know the exact distribution of mass, it is not possible to calculate its swingweight.
As I said earlier, do a search and you will find some posts of mine where I actually show this by doing some calculations.
I hope it helps,
Regards,
Maurice-the-tennis-scientist
If you do a search on my name and "swingweight", you will find several posts where I try to explain the whole thing.
In short: Balance point and total weight say nothing about the swingweight. Since swingweight is a function of the total weight distrubution of the racket, it can never be fully characterized by just the balance point and total weight.
Consider these extreme cases:
- Object 1: 70cm long, 150 grams at each end
- Object 2: 70cm long, 100 gram at each end and 100 gram in the middle
- Object 3: 70cm long, 300 gram in the middle
All object are 70 cm long, wheigh 300 grams and have a balance point at 35 cm. If you will swing them with your wrist though while holding them at one end, they will each have a distinctly different feel to them, this is basically put into a number: "the swingweight".
For each point of mass, this is indeed calculated by multiplying the mass with the square of the distance from the point of rotation. However, you have to add the outcome of this calculation of all the points of mass in the object. The total gives you the moment of intertia with respect to the axis of rotation you are considering. If you do this for all 3 objects, you will get 3 different numbers.
Since a real racket cannot be simply modelled by a few points of mass and you do not know the exact distribution of mass, it is not possible to calculate its swingweight.
As I said earlier, do a search and you will find some posts of mine where I actually show this by doing some calculations.
I hope it helps,
Regards,
Maurice-the-tennis-scientist
Master Trader
New User
Thanks for all the input!
