If you're changing the swingweight, don't you have to change the weight and/or balance?
If you're changing the swingweight, don't you have to change the weight and/or balance?
If you're changing the swingweight, don't you have to change the weight and/or balance?
Or are we talking about 2 similar frames that that have been leaded in different location yet have the same mass and balance location?
I am looking at getting a couple of frames from TW and they quoted those swing weights for two of the same frame with no modification
You are not talking about TW's published SWs for the frame? They took 2 frames from inventory and measured them for you!!! Really???
Yes, as part of the $10 racquet matching service, they pick out two with the closest specs (but they currently only have 2 in stock of the racquet i am after) . For $20 per racquet they do proper matching through customisation
Wow, that's pretty cool. Have seen variations in weight & balance but would not have expected that much of a difference in SW given that the other 2 parameters were similar.
The biggest issue between frames is NOT the weight or swingweight or balance, as dramatic as those can be, they can be corrected with lead (although it can drastically add to the weight of the frames to bring them to spec).
The biggest issue..and the elephant in the room here...is the stiffness. My favorite racquet is the Wilson KBLADE 98. With leather and some lead, that racquet and I simply click. Well, sometimes. Why do I say sometimes? Because when I used this racquet, I had 3....one with a flex of 70, one 67, and one 62. Those are 3 completely different frames. Unusable for me.
^^ How does one determine the flex of their frames? Is it trivial to do this or do you need access to special equipment? (I looked a bit around TWU and did not find this info).
Not true. There are many situation when 2 racquet cannot be matched with lead tape. That makes them - unusable. The result is pretty much the same.
This.
10 RDC Machines
Exactly. However, support your local tennis shop, and they will happily test them for no charge.
No charge? What kind of support is that?
Not necessarily. You can have 2 racquets with the same balance and weight BUT with different sw. For example:
XXX------XXX
and
---XXXXXX---
The key here is weight distribution.
I think this changes the polarization, and certainly the feel, but not the swingweight.
Not necessarily. You can have 2 racquets with the same balance and weight BUT with different sw. For example:
XXX------XXX
and
---XXXXXX---
The key here is weight distribution.
I think this changes the polarization, and certainly the feel, but not the swingweight.
BobFL is right--it will change all three. Swingweight measures rotational inertia, not just mass, and that inertia has to do not only with mass and balance, but also with mass distribution. If you have two wheels at the top of an inclined plane, both with the same diameter, both made of the same material, and both with the same mass, but one is a solid and the other is a band (think tire-shaped), the solid one will accelerate faster down the ramp when released because it has a lower moment of inertia. Racquets are the same. Polarized frames have higher MOIs and therefore higher SWs.
Look up the spec differences between Pure Drives and Aero Pros. No misprints there. The APDs have a higher SW because they are more polarized.
you're right that the mass at the top is (about) twice the distance and half the mass, but distance is squared in the formula, so twice the distance means four times as much inertia.Forgive me if I am in error, as it's been many years since I took Physics in college.
I understand the formula for rotational inertia to be I=ml^2. First I would take the first configuration, --xxxxxx--, and draw a moment of inertia 'l' from the axis of rotation at 10 cm up the grip, and make the I=ml^2 calculation, with m being the total mass of the racquet.
Next, I would look at the other configuration, xxx----xxx. We notice that for the first three x marks the distance from the axis of rotation is zero and there is no moment for those three x marks. The inertia that is left at the top of the racquet is twice the distance, l, and half the mass, m, compared to the first racquet.
So I find that half the mass at the top of the racquet holds an equal amount of inertia as all of the mass at the middle of the racquet, rotating about the axis of rotation at 10 cm up the grip.
I would say that the two racquets would certainly feel different, but they would not resist rotation differently. Thanks for providing this problem for me to delve into.
you're right that the mass at the top is (about) twice the distance and half the mass, but distance is squared in the formula, so twice the distance means four times as much inertia.
The biggest issue..and the elephant in the room here...is the stiffness. My favorite racquet is the Wilson KBLADE 98. With leather and some lead, that racquet and I simply click. Well, sometimes. Why do I say sometimes? Because when I used this racquet, I had 3....one with a flex of 70, one 67, and one 62. Those are 3 completely different frames. Unusable for me.
That is insane! Same stick, bought same year and that varied of stiffness? TW lists Stiffness: 67 for that stick so you got one perfect, one +2 and one -5 stiffness RA. That makes no sense to me.
First, how did you determine the flex of the three frames? Second, how can a frame made by a reputable company (Wilson headquarters 20 miles from my home) have such a wild variance in stiffness?
^ This is disturbing. I might expect to see slight differences in weight and balance. You would expect, with the cost of a new racquet, that the specs would be fairly consistent. However, we are seeing reported differences of 8 in RA stiffness ratings and 11-15 in SW measurements in this thread alone.
I might be willing to accept the difference between 70 and 67, but the difference between 70 and 62 just seems to be too much to tolerate. Even if the three "identical" frames had the same rating of 67, it might still not tell the whole story -- they could still feel different even if the other specs were pretty much the same. You would probably really need stiffness ratings at multiple locations to get a more complete picture.
Some tennis pro shops have a Babolat RDC machine to determine the RA stiffness index and other specs. I assume that TW does as well. Does anyone know if the stiffness index that TW publishes is their own measurement or do they accept the manufacturers stiffness numbers? If TW does measure this spec, how many of each model to they use to determine the specs?
Here is demo of the Babolat RDC machine used to measure various parameters. (Don't let the ominous face at the start of the video frighten you).
http://www.youtube.com/watch?v=67ndPgE5ITU
.