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ken_adey
09-30-2006, 01:18 PM
Would adding weight in the handle and on the hoop (about 1 oz. total) affect the stiffness rating of the racquet? I would it would to some degree.

Ken....

andrew_b
09-30-2006, 01:48 PM
I don't *think* it would, but I'm not sure. I think that the devices to measure stiffness don't "swing" the frame.

Interesting question, though.

play well,
Andrew

Midlife crisis
09-30-2006, 11:00 PM
Would adding weight in the handle and on the hoop (about 1 oz. total) affect the stiffness rating of the racquet? I would it would to some degree.

Ken....

Adding weight as you describe would not affect the static stiffness measurement of the racquet, but would alter the dynamic stiffness you would experience when you hit the ball. Genenerally, adding weight in the handle makes the racquet feel more flexible.

Keifers
09-30-2006, 11:12 PM
Adding weight as you describe would not affect the static stiffness measurement of the racquet, but would alter the dynamic stiffness you would experience when you hit the ball. Genenerally, adding weight in the handle makes the racquet feel more flexible.
Hmm, very interesting thought about weight in the handle.

I was going to say that adding weight perhaps makes the racquet seem stiffer because of the added oomph.

travlerajm
10-01-2006, 02:48 AM
As midlife says, adding weight affects the dynamic stiffness. But the effects are complex.

In general, adding weight the butt will make a racquet flex more, while adding weight to the upper handle will make it feel a little stiffer. Adding weight to the hoop will generally make it feel quite a bit stiffer.

An interesting case is that of racquets that have a natural flexpoint in the throat (Yonex, O3, Fischer, etc.). These racquets normally behave like there is a hinge at the throat. For these racquets, you can actually use added mass to control the direction of the flex. For example, adding a lot of weight in both the butt and the tip will actually make the frame flex in the reverse direction, because the ends of the racquet will have more forward inertia than the throat at impact.

rich s
10-01-2006, 08:40 AM
i don't think it affects either static or dynamic stiffness as both are material and geometric properties of the racquet......added mass increases the amount of deflection due to the increased load acting on the frame at the time of ball impact.

The racquet may feel less stiff because it deflects more.

Look at a Pogo stick as an example. Let someone who weighs 50 lb jump on it and the spring inside hardly compresses. Now (with super strong majic duct tape) attach a 50 lb olympic weight/dumb bell to the pogo stick and have the same 50 lb person jump on it......it will deflect twice as much now because there is double the load acting on it.....the spring inside the pogo stick didn't getting any less stiff.....it just deflects more because a greater load is actin on it.....

The racquet frame is a spring also.....to change it stiffness you either have to add structural mass to it to make it stiffer (which lead tape is not) or you have to flex it a lot or compromise it's integrity to make is less stiff (which lead tape does not do)...

The added weight of the lead tape generates greater force on the frame a ball impact (due to inertia) and the frame deflects (bends) more which can be confused with less stiffness.

F=kx F = force....k = stiffness (spring constant) , x = deflection.

Midlife crisis
10-01-2006, 08:37 PM
i don't think it affects either static or dynamic stiffness as both are material and geometric properties of the racquet......added mass increases the amount of deflection due to the increased load acting on the frame at the time of ball impact.

The racquet may feel less stiff because it deflects more.

Static stiffness will be unaffected, but dynamic stiffness will change slightly, only because added mass tends to constrain that portion of the racquet to which it is attached, and so more of the stress from the impact goes into bending the frame rather than moving the frame.

However, I think this is a minor effect and the difference in the feel of the impact is much greater than the actual effect itself. For instance, I play with a racquet with nearly three ounces of weight added to the handle, and despite it being 78 RDC, it plays more like a classic, flexy racquet from a feel perspective.

AlpineCadet
10-02-2006, 01:15 AM
Static stiffness will be unaffected, but dynamic stiffness will change slightly, only because added mass tends to constrain that portion of the racquet to which it is attached, and so more of the stress from the impact goes into bending the frame rather than moving the frame.

However, I think this is a minor effect and the difference in the feel of the impact is much greater than the actual effect itself. For instance, I play with a racquet with nearly three ounces of weight added to the handle, and despite it being 78 RDC, it plays more like a classic, flexy racquet from a feel perspective.

I totally agree with you. I've added weight to the hoop and handle of a racket with a stiffness rating of 68, and the added racket flex was most pronounced on my serves.

travlerajm
10-02-2006, 01:17 AM
Static stiffness will be unaffected, but dynamic stiffness will change slightly, only because added mass tends to constrain that portion of the racquet to which it is attached, and so more of the stress from the impact goes into bending the frame rather than moving the frame.

However, I think this is a minor effect and the difference in the feel of the impact is much greater than the actual effect itself. For instance, I play with a racquet with nearly three ounces of weight added to the handle, and despite it being 78 RDC, it plays more like a classic, flexy racquet from a feel perspective.

Midlife,

When mass is added to the racquet, it makes more of the stress from the impact go into deflection of the stringbed. The frame moves less and deflects less.

As for your 78 RDC stick, the weight in the handle has negligible affect on it's dynamic stiffness because the frame has almost no deflection. The frame feels soft for a different reason that has almost nothing to do with dynamic flex.

By adding so much weight to the butt, you have created a racquet with a low hitting weight. The hitting weight determines the racquet's angular momentum at impact. When the ball impacts the stringbed, it causes the racquet to pivot about the wrist axis (which is about 4cm from the butt). The lower the hitting weight, the more the frame rotates. The more it rotates, the softer the feel.

With your weight distribution, your racquet would still feel soft and cushy even if it was infinitely stiff.

AlpineCadet
10-02-2006, 01:23 AM
Midlife,

When mass is added to the racquet, it makes more of the stress from the impact go into deflection of the stringbed. The frame moves less and deflects less.

As for your 78 RDC stick, the weight in the handle has negligible affect on it's dynamic stiffness because the frame has almost no deflection. The frame feels soft for a different reason that has almost nothing to do with dynamic flex.

By adding so much weight to the butt, you have created a racquet with a low hitting weight. The hitting weight determines the racquet's angular momentum at impact. When the ball impacts the stringbed, it causes the racquet to pivot about the wrist axis (which is about 4cm from the butt). The lower the hitting weight, the more the frame rotates. The more it rotates, the softer the feel.

With your weight distribution, your racquet would still feel soft and cushy even if it was infinitely stiff.

If so, then please explain why a setup with equal amounts of lead tape to the hoop and handle have created a more flexible feel upon serving.

vkartikv
10-02-2006, 11:02 AM
I have applied a layer of headtape on the headguard of my ps 85 and it certainly feels a lot stiffer than it did without the tape. Lead has the same effects except its a little more subtle.

Ripper
10-02-2006, 11:05 AM
This question, I hadn't seen here for quite a while.

ollinger
10-02-2006, 11:31 AM
AlpineCadet(??)
You are experiencing a tactile illusion. Adding weight is not causing the racquet to necessarily flex more, but the added weight decreases vibration, making the racquet feel "softer" and, in your mind, flexier. Barring very high speed cameras, I doubt you can really surmise the flex of the racquet on serve.

AlpineCadet
10-02-2006, 12:18 PM
AlpineCadet(??)
You are experiencing a tactile illusion. Adding weight is not causing the racquet to necessarily flex more, but the added weight decreases vibration, making the racquet feel "softer" and, in your mind, flexier. Barring very high speed cameras, I doubt you can really surmise the flex of the racquet on serve.

Tactile indeed. Great post.

Midlife crisis
10-02-2006, 02:24 PM
Midlife,

When mass is added to the racquet, it makes more of the stress from the impact go into deflection of the stringbed. The frame moves less and deflects less.

As for your 78 RDC stick, the weight in the handle has negligible affect on it's dynamic stiffness because the frame has almost no deflection. The frame feels soft for a different reason that has almost nothing to do with dynamic flex.

By adding so much weight to the butt, you have created a racquet with a low hitting weight. The hitting weight determines the racquet's angular momentum at impact. When the ball impacts the stringbed, it causes the racquet to pivot about the wrist axis (which is about 4cm from the butt). The lower the hitting weight, the more the frame rotates. The more it rotates, the softer the feel.

With your weight distribution, your racquet would still feel soft and cushy even if it was infinitely stiff.

We're saying the same thing - that dynamic stiffness varies by very little with weight addition but the FEEL of dynamic stiffness varies considerably.

BTW, since you've hit with that racquet, I've removed about 10 grams from the handle and have added about 15 grams in the area around the throat, on both sides of the balance point. Still highly polarized but not quite as much, with still the same static balance and slightly higher swing weight. It's getting on the verge of being a little too powerful though. I would go back to the original configuration but this change, which should actually increase hitting weight, actually makes the racquet play a bit softer too, but the changes are small enough that I could be imagining them.