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1. yea, got my axes mixed up.

2. Wow, thanx 96382 and amleto, this is now getting very interesting!

3. Ok I just tried it.

Using the racket as a standalone pendulum really gives me problems due to the friction at the mounting bracket points.

Fast build up with the two string 'torsion-pendulum' (referring to the definitions from the picture):

- it is easy to get L big (around 2m indoor)
- with strings and grip you can determine the BP by balancing the racket on a small edge (uncertainty around 3-5mm)
- biggest Problem: Get b big enough to stabilize the racket. I didnt try to attach the strings on handle and racket face. Attached them a few cm along the shaft
- Therefore I had to move the racket about 20-30 degree instead of keeping it under 10 degree.

Results:
MOIs of the handle should be around 3 g m^2 to under 15 g m^2 (estimation interval).
160g Training Racket was around 23 g m^2. This was around 3 times the moi of another racket

Maybe someone can provide some more detailed results.

4. The bifilar pendulum seems too complicated.

For only \$1, I'll be trying out the SwingTool app, but haven'td figured out how to attach the handle to swing the racket freely.

Do you think I can just tie a short piece of string and swing from a point, taking into account the new length in the app?

5. Originally Posted by j4ckie
All that being said, the head weight is a better approximation of the racket's expected behaviour than the BP and weight alone, although it can be derived from those measurements. Measuring the head wt of the rackets you're most comfortable with will give you a good estimation of what to look for when you're browsing the shelves in a badminton store
This.

Further to what I said earlier, if something like this doesn't have some sort of universal application, or cannot potentially act as a paradigm shift in the description of badminton racket models for new and existing racket companies, then all you guys are doing is having some amateur physics fun that at the end of the day will only act as a divisive tool between 'those that get it' and 'those that don't'.

6. I don't quite get why you're acting this negatively - 'amateur physics fun' is hardly a fair assessment of what visor's trying to do and what we're trying to help with. It's already an improvement as you can go to the store with a small scale and actually get an estimate of whether or not you're gonna like a racket based on the apparent head weight.

While I actually have a different approach myself I think that this is actually helpful for those who want more than 1 or 2 models that are similar in heaviness. While we have some more theoretical discussions in this thread, the idea of just measuring the apparent head weight is still valid and will give an approximation of a racket's heaviness.

Pardon me if I misunderstood your post, but if you find that the discussion doesn't interest you or is of no (practical) importance, you're welcome to just ignore it

7. See the part where I said "This". That's the part where I agree with your hypothesis of the importance of swing-weight. It's another tool to assist people to find a racket that is better suited to them, which is a good thing from an anthropological perspective.

However. How do we increase the mass appeal of this? How do we use this tool to effect more than that .001% of buyers who are anal enough go to badminton shops with a scale and a ruler?

THAT'S what I'm interested in.

Remember, we live in a world where Yonex doesn't even list the balance point of their rackets.

So for me, the real issue is about the democratisation of this information. I couldn't care less how you boffins come up with it, the question is how do we implement it?

Is anyone for example thinking of approaching Adidas to see if they would be interested in using this new information as a selling point for their rackets? What about talking with Dan and see if he's interested in adding this spec to the DC rackets?

Make sense now? Sorry if I was being ambiguous.

8. We'll, it wouldnt be too much work or money for the companies to extend their description with some sort of swing-weight. But if you give people too much information and make everything very technical and objective, then a lot of the marketing strategies will probably fall apart. Mystery and obscurity is like '*** sells'

Still, this amateur physics is fun actually.
@visor : Try to clip something stiff and stable to your handle which has a hole in it that can be used as the fulcrum point (hang it on some metal rod with little friction as possible. you can use oil if you want. rotation in in direction of racket face.). Then you can just add the extra length with the parallel axis theorem.

9. @Maklike Tier and others who're getting lost with all the physics and equations in this thread so far:

Just ignore the esoteric stuff.

The main purpose of this thread is to let others know that you don't have to leave it to chance if you're looking to replace or get backups of your favourite racket. Once you've decided on the shaft flex/stiffness, then all you need is to measure your racket and then go to the store with digital scale and a ruler to find the one that is the closest in swing wt.

And to make things even simpler, it seems that you don't even need to measure "head wt" as was done on the first post. All you need is the bp and wt of the racket, preferably in bare dry state, ie. without strings, grip, or handle shrink wrap.

Then, "head wt" will be equal to: ( bp x wt ) / 675
675 being the length of the racket.

So, with this number, you can easily estimate your swing wt and heaviness feel of any racket. Just remember to keep constant any variables like string and grip, if any.

Can it get any simpler than this?

10. And as a side result of knowing "head wt"...

It annoys me to no end when rackets are reviewed and compared without any stated specs of wt and bp. With the possible variations that come from the factory, just because someone in their comparison says that "x" racket is more powerful than "y" racket doesn't mean anything to me if their "x" sample has much more head wt than "y".

/end rant

Anyways, just providing more info out there so that we take racket reviews and comparison tests with a large grain of salt. And to educate buyers so that they can choose the right racket the first time around instead of going thru multiple rackets like me.

Found some patents from Wilson where they actually give some swing weights (and yes, same result as my measurement). Maybe more companies need to do this by defending/legitimating new inventions to the authorities...?

12. I'd still add a word of caution about using only one number (e.g. pseudo swing weight) to base decisions on - I have two examples of TPro, weights are different by ~ 5g, however the pseudo swing weight is close, but the rackets are massively different to swing.

13. Originally Posted by 96382

Found some patents from Wilson where they actually give some swing weights (and yes, same result as my measurement). Maybe more companies need to do this by defending/legitimating new inventions to the authorities...?
How the hell did that patent pass, and the tennis racket one, AND the squash racket one!? The invention being 'a head heavy racket with similar MoI to current rackets'.

14. I dont know, but I couldnt find more serious ones ..there should be more from yonex, victor etc where they have to reveal some of their measurements, i guess.

15. Originally Posted by amleto
I'd still add a word of caution about using only one number (e.g. pseudo swing weight) to base decisions on - I have two examples of TPro, weights are different by ~ 5g, however the pseudo swing weight is close, but the rackets are massively different to swing.
@amleto

You mean like eg. 90g x 283mm= 85g x 300mm, they would not swing the same? Hmmm, I'll have to think about that and try it out.

16. Originally Posted by visor
@amleto

You mean like eg. 90g x 283mm= 85g x 300mm, they would not swing the same? Hmmm, I'll have to think about that and try it out.
We've covered this already - MoI is what is important for this 'feeling'. pseudo swing weight cannot describe this.

17. Originally Posted by amleto
We've covered this already - MoI is what is important for this 'feeling'. pseudo swing weight cannot describe this.
Hmmm... yep... but I'm always one to experience it for myself.

Btw, what were the measured specs of the two T Pros in question?

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