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Old 01-08-2013, 11:22 AM   #97
Join Date: Oct 2009
Posts: 416
Default There may be different intentions

Hi guys,
I think that it might be good to discuss our basic intention:

* I certainly understand that people with knowledge about physics will say that it is impossible to calculate the Swingweight of a racquet very accurately.

But the major question is: Do we want a system that makes it possible to compare racquets or do we need very accurate values of the SW?

If we want to compare racquets we need a “measuring system” , with an accuracy that is as high as possible.

Another fact is that test results from different SW machines differ quite a lot, which proves that this is not an easy measurement to do.
So these machines are impressive and expensive but not accurate.

So if there is a much cheaper way to do a test, with about the same accuracy, there is a good reason to choose this test method. And a scale or even 2 scales are much cheaper than one SW machine.

What is our intentions with the SW advisor?
The idea of the SW came up because we advise the Dutch Tennis *** about material for young children.
- It should avoid that players play with completely the wrong SW and especially young children.
- We want to make it very easy for coaches to advise the right frame for a certain player.

The system does 3 things:
1. It advises a Swingweight for a certain player based on type of forehand, age and build.
2. It calculates the SW of a racquet, when head- and throat- weight are entered. (Only have to weigh the weight at both ends of the racquet)
3. When the SW is too low it calculates how much weight should be added at a certain position to get the desired SW.

So for our purpose we need an advise system, a measuring (calculating system) and a way to customize racquets. This is what the Excel sheet (and the online version later) does.

And of course we wanted to know how accurate our “measuring” system is compared to the official machines.

Our conclusion out of these tests is that the difference between our system and official machines is not bigger than the difference between the different SW machines.

So the inaccuracy of our system is not worse than that of the official machines. And a difference of less than 5% of the measured value is not bad at all for a complicated test.

You will understand that we are not interested in theoretical solutions without practical possibilities.

Why would Babolat or Prince tuning machines have a special function for measuring a swingweight? Why wouldn't they just measure the weight, the balance, and the length of an object and immediately give you an accurate swingweight value based on some match formula?
There are different reasons for this:
* A swing weight test based on measuring the swing time of an object is a very logic choice. The SW can be calculated with one formula from the swing time
T = 6,28 *rt (SW/w*L)
* Calculating from the Head and throat weight is much more complicated.
* Prince and Babolat sell these machines so it generates income.
* Prince and Babolat may do it with their machine Head seems to do it with the weighing system:

At 4.10 min you can see that they do the same kind of test.

Hopes this explains our intentions.
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