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-   -   How to test tennis balls (measuring bounce) (http://tt.tennis-warehouse.com/showthread.php?t=381505)

stoneage 05-25-2011 07:13 AM

How to test tennis balls (measuring bounce)
 
According to the ITF rules a "valid" tennis ball should bounce to between 135 cm and 147 cm when dropped on a concrete floor from a height of 254 cm (53-57 in from 100 in). This means that the ball should reach between 53% and 57% of the drop height when bouncing. However, that is a little difficult to measure, unless you have a high speed camera and are prepared to spend some time analyzing the video. Probably not something worth doing for checking and old can of balls.

A simpler way is to use the sound and a basic laws of physics. If you drop the ball and measure the time "t" between the first impact on the floor and the second, you can calculate the height "h" the ball has reached through the equation (g is gravity):

h=g*t^2/8

If you want to be more precise you can include the air resistance, which is fairly small, but will reduce the height with about 3 %. So including that and g=9.81 you get:

h= 1.19*t^2

Since you take the square of the time you have to measure it fairly exactly. The easiest way to do it, is to record the sound with a computer, and get the time between the two bumps in the sound curve. Agreed that this still is a little work, but nothing that should prevent a scientifically minded tennis nerd :)

I have implemented this and some further calculation to handle low bounces in the latest version of racquetTune.

/Sten

______________________________________
racquetTune, swingTool and netHeight, tennis apps for the iPhone.

mikeler 05-25-2011 10:01 AM

You are going to put low bouncing Penn balls out of business! :twisted:

bigmalik76 05-25-2011 11:14 AM

Quote:

Originally Posted by mikeler (Post 5681505)
You are going to put low bouncing Penn balls out of business! :twisted:


:) But Penn Balls are cheap at Costco maybe they will get cheaper :)

vandre 05-25-2011 11:49 AM

dude, you're making me want an iphone! curse you!

i'm a caveman i guess, because i test the bounce of a tennis ball by holding it at eye level and dropping it. if it bounces to or above my waist, it's good.

The Matrix 05-25-2011 12:01 PM

Are you really going to do this just to see how dead a ball is??

bigmalik76 05-26-2011 03:17 PM

I'll rather open a new can then sit down and solve those equations. (Disclaimer: not a big fan of Math :twisted:)

tennytive 05-27-2011 06:56 AM

Quote:

Originally Posted by vandre (Post 5681757)
dude, you're making me want an iphone! curse you!

i'm a caveman i guess, because i test the bounce of a tennis ball by holding it at eye level and dropping it. if it bounces to or above my waist, it's good.

^^^^ Bingo!

Readers 06-21-2011 06:53 PM

I honestly think it's easier to put a line on a wall or a post, then bounce the ball next to it... takes less than a min.

ae695 06-22-2011 01:37 AM

Racquettune
 
If you have an iPhone (do not know if there is an Android version) you can use Raquettune app. The last version has a ball test.

Good luck!!

verbouge 11-17-2012 03:37 PM

The Ball Bounce feature has disappeared from my Racquettune app!
 
I was going to show it to someone last night, and lo and behold, it's no longer on the app. Anybody else have this issue? Stoneage, you have any insight or help?

Thanks,
Dave in Oregon

LeeD 11-17-2012 04:18 PM

I'd say any Dunlop bounces the lowest.
And what air temps? Balls and air temps. In 120 degrees, with heated balls, anything is too bouncy.
In 39 degrees, even Wilsons are dead as doornails.

tennisnj 11-17-2012 05:31 PM

It all depends on court surface because the courts I play most of the time are the slowest hardcourts I've ever been on & also the lowest bouncing (they weren't laid right). They play as slow as clay with the bounce of grass courts. The only way to get any pace or depth is to use Dunlop because they bounce the highest.

LeeD 11-17-2012 05:46 PM

Wait, are you saying Dunrocks bounce the HIGHEST? Higher than Wilson air balls?
Are you sure this is what you meant to say?
I hope you don't think Tretorn pressureless also bounce really high?

tennisnj 11-17-2012 06:04 PM

Again Lee, it all depends on the courts. Tretorns don't bounce @ all where I play & they ruin your arm. The ultra-slow hardcourts I play on don't allow for Penns to be used unless that's all we have handy. The Dunlops bounce the HIGHEST b/c they are the liveliest tennis balls for the courts we play on. Wilsons bounce 'in the middle' if we're comparing Penn, Wilson & Dunlop.

LeeD 11-17-2012 06:08 PM

Wow, that doesn't go on West Coast cement at all.
Wilson's are the lightest and most air, least knapp, bouncing highest regardless of court surface.
Penn's have more knapp, some are heavier.
Dunlops are what some guys here call "dunrocks", the most knapp, the heaviest, and moderate air pressure.
Tretorns are the rock, bounce the least, are the heaviest.

tennisnj 11-17-2012 06:23 PM

I figured it out---many courts on the east coast are more cushioned (not always on purpose-ours happen to be installed incorrectly & there is always a layer of water underneath the 1st few layers.) You may be familiar with the old San Jose ATP tournament the SAP Open; we supposedly use the same surface as there---Premier Court its called http://www.premiercourt.com/what_is.htm & it is god awful. Says it's not a gritty court surface but judging by the way balls look after 5 sets of doubles, I'd say they're very gritty.

JW10S 11-17-2012 08:25 PM

Quote:

Originally Posted by stoneage (Post 5681045)
According to the ITF rules a "valid" tennis ball should bounce to between 135 cm and 147 cm when dropped on a concrete floor from a height of 254 cm (53-57 in from 100 in). This means that the ball should reach between 53% and 57% of the drop height when bouncing. However, that is a little difficult to measure, unless you have a high speed camera and are prepared to spend some time analyzing the video. Probably not something worth doing for checking and old can of balls.

A simpler way is to use the sound and a basic laws of physics. If you drop the ball and measure the time "t" between the first impact on the floor and the second, you can calculate the height "h" the ball has reached through the equation (g is gravity):

h=g*t^2/8

If you want to be more precise you can include the air resistance, which is fairly small, but will reduce the height with about 3 %. So including that and g=9.81 you get:

h= 1.19*t^2

Since you take the square of the time you have to measure it fairly exactly. The easiest way to do it, is to record the sound with a computer, and get the time between the two bumps in the sound curve. Agreed that this still is a little work, but nothing that should prevent a scientifically minded tennis nerd :)

I have implemented this and some further calculation to handle low bounces in the latest version of racquetTune.

/Sten

______________________________________
racquetTune, swingTool and netHeight, tennis apps for the iPhone.

Oh please--you have to be kidding. I can easily see if a ball bounces a little more than 1/2 way back up when I drop it--besides it's easier just to squeeze them to tell if they're dead or not. You have WAY too much time on your hands--maybe you should spend more time actually playing tennis.

scotus 11-18-2012 02:03 AM

Quote:

Originally Posted by stoneage (Post 5681045)
According to the ITF rules a "valid" tennis ball should bounce to between 135 cm and 147 cm when dropped on a concrete floor from a height of 254 cm (53-57 in from 100 in). This means that the ball should reach between 53% and 57% of the drop height when bouncing. However, that is a little difficult to measure, unless you have a high speed camera and are prepared to spend some time analyzing the video. Probably not something worth doing for checking and old can of balls.

A simpler way is to use the sound and a basic laws of physics. If you drop the ball and measure the time "t" between the first impact on the floor and the second, you can calculate the height "h" the ball has reached through the equation (g is gravity):

h=g*t^2/8

If you want to be more precise you can include the air resistance, which is fairly small, but will reduce the height with about 3 %. So including that and g=9.81 you get:

h= 1.19*t^2

Since you take the square of the time you have to measure it fairly exactly. The easiest way to do it, is to record the sound with a computer, and get the time between the two bumps in the sound curve. Agreed that this still is a little work, but nothing that should prevent a scientifically minded tennis nerd :)

I have implemented this and some further calculation to handle low bounces in the latest version of racquetTune.

/Sten

______________________________________
racquetTune, swingTool and netHeight, tennis apps for the iPhone.


There's nothing "Stone Age" about this guy.

leafscat 11-18-2012 10:22 AM

Quote:

Originally Posted by verbouge (Post 7021953)
I was going to show it to someone last night, and lo and behold, it's no longer on the app. Anybody else have this issue? Stoneage, you have any insight or help?

Thanks,
Dave in Oregon

The developer made it a stand alone app. It is called Ball Tester and is free (or was). He expanded it a bit as it will also test if basketballs or soccer (footballs) have enough air in them.

sundaypunch 11-18-2012 12:53 PM

Quote:

Originally Posted by stoneage (Post 5681045)
According to the ITF rules a "valid" tennis ball should bounce to between 135 cm and 147 cm when dropped on a concrete floor from a height of 254 cm (53-57 in from 100 in). This means that the ball should reach between 53% and 57% of the drop height when bouncing. However, that is a little difficult to measure, unless you have a high speed camera and are prepared to spend some time analyzing the video. Probably not something worth doing for checking and old can of balls.

A simpler way is to use the sound and a basic laws of physics. If you drop the ball and measure the time "t" between the first impact on the floor and the second, you can calculate the height "h" the ball has reached through the equation (g is gravity):

h=g*t^2/8

If you want to be more precise you can include the air resistance, which is fairly small, but will reduce the height with about 3 %. So including that and g=9.81 you get:

h= 1.19*t^2

Since you take the square of the time you have to measure it fairly exactly. The easiest way to do it, is to record the sound with a computer, and get the time between the two bumps in the sound curve. Agreed that this still is a little work, but nothing that should prevent a scientifically minded tennis nerd :)

I have implemented this and some further calculation to handle low bounces in the latest version of racquetTune.

/Sten

______________________________________
racquetTune, swingTool and netHeight, tennis apps for the iPhone.


Or I could just put three marks on my garage wall and drop the ball.


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