Question about Swing weight, Balance and Mass

[ndhUW]

Hi,

Would two racquets of a kind have the same swing weight if they have similar balance and mass? Thank you for answering my question.

hoang

 

[insiderman]

no - picture 2-frames = in weight & balance - both being (example) 300-grams and 320mm balance.

Frame #1 has 100-grams at the top, 100-grams at the exact middle, and 100-grams at the end of the handle = 300-grams, and 320mm balance.

Frame #2, has 50-grams at the top, and 200-grams in the exact middle, and then 50-grams at the end of the handle = 300-grams, and 320mm balance.

for sure the swingweight felt between the 2-frames is massive in difference. While the weight and balance are important, nothing is more important then inertia (swingweight)

 

[ndhUW]

Insiderman,

Thanks for the response. What you said was what I had in mind when I posted the question. But since the racquets that I have are of the same model (Prince Rebel 95), I didn't think the difference of a few grams in weight distribution would affect the swing weight that much. Would it?

Also, have you tried the swing weight calculator by TW? Maybe I should try that to see.

Anyway, thanks again for the response.

hoang

 

[Adam_mtl]

Hmm, I'm not quite convinced insiderman. If you take the end of the racquet handle as a reference point and calculate the moment of inertia for both frames (to that reference point), I'm pretty sure you would get the same answer, and therefore the same SW. I may be wrong, but thats what I think.

Anyone else have any input on this?

 

[insiderman]

Adam,

It is an easy way to try and explain inertia, ('swingweight') - as 'SW' are is commonly measured on an RDC, etc easily shows that the more the weight is towards the head, the higher the #'s - I've often made-up two racquets to be like what I mentioned prior, and used them for Clinics - quickly proving to anyone who handles them - now, if you want to discuss MOI, (moment-of-inertia) that is an entirely different but related aspect, and is a LOT more precise...

 

[cellofaan]

Hmm, I'm not quite convinced insiderman. If you take the end of the racquet handle as a reference point and calculate the moment of inertia for both frames (to that reference point), I'm pretty sure you would get the same answer, and therefore the same SW. I may be wrong, but thats what I think.

Anyone else have any input on this?

When calculating moment of inertia, the distance from the reference point gets squared, while the mass does not. So, 100 grams at 10 cm distance will provide a higher MOI than 200 grams at 5 cm distance.

In tennisracquets this means that the closer the weight is to the ends of the racquet (and therefore further away from the reference point) the higher the swingweight will be.

 

[Adam_mtl]

When calculating moment of inertia, the distance from the reference point gets squared, while the mass does not. So, 100 grams at 10 cm distance will provide a higher MOI than 200 grams at 5 cm distance.

In tennisracquets this means that the closer the weight is to the ends of the racquet (and therefore further away from the reference point) the higher the swingweight will be.

Yea thats true. My bad.

 

[insiderman]

If you don't have access to technical equipment, but you do have access to a accurate 1-gram measuring scale, there is always the 'age-old' way to check frames via "Tip-Weight" - basically, place the heard of a racquet in the exact same spot on the middle of the scale, and use something to support the butt-cap area as far to the exact end as possible, (like a nail in a piece of wood, etc) and then make sure with a 'bubble-level' that the frame is perfectly 'level' - take the reading on the scale as your "Tip-Weight" and use that vs. another frame...these #'s if same, or really close, will tell you that the actual swingweight is darn close...

 

[Adam_mtl]

Thanks insiderman, I'm gonna try that out with some of my racquets.