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Possible way to clock your stone speed. (Read 19073 times)
Altay
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Re: Possible way to clock your stone speed.
Reply #15 - Nov 25th, 2007 at 1:25am
 
When in doubt, ask wikipedia... Wink
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Dravonk
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Re: Possible way to clock your stone speed.
Reply #16 - Nov 27th, 2007 at 8:04am
 
The use of gun chronographs was already discussed, the problem is that you need to be accurate enough to make your projectile travel through the measure points.
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Curious Aardvark
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Re: Possible way to clock your stone speed.
Reply #17 - Nov 27th, 2007 at 10:46am
 
And you need a gun chronograph :-)
Pretty much everyone can scrounge up  amate and a stopwatch - we don't all have access to gun chronographs.

[quote]C_A should run on to the field when there is a international cricket game on, bump the bowler out of the way and sling towards the batsman's wicket. Maybe they would have recorded it on their radar and other goodies like slow motion cam, trajectory cam, birds eye view and the newest slowmotion infrared camera. You would not get more accurate than that.

[/quote]
Hmm, well edgebaston is only 40 mins drive away ;-)

[url]http://en.wikipedia.org/wiki/Ballistic_pendulum[/url]
That's doable - make the pendulum fairly wide and sling at it from a couple of feet - could work :-)
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Re: Possible way to clock your stone speed.
Reply #18 - Nov 27th, 2007 at 5:05pm
 
Would iy be possible to just clock the speed of your sling in rotation?
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macka
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Re: Possible way to clock your stone speed.
Reply #19 - Nov 28th, 2007 at 1:34am
 
I picked up achronograph for a song and a dance at a fleamarket, and all it needed was a ground wire resoldered. you can pick up a radar chronograph on ebay right now for less then 30 USD. Its not as accurate as say "shooting between the traps" but way more accurate then timing with a friend.
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Aussie
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Re: Possible way to clock your stone speed.
Reply #20 - Nov 28th, 2007 at 1:40am
 
If you have sufficiently sophisticated equipment it would be posible to measure your sling/projectile speed at any point. But I think the whole idea in this thread is to use equipment which is readily available or at least inexpensive.

In this day of electronic watches everyone has a stopwatch and lots of people have digital cameras with video capability. Whatever method you use should be as simple as possible so as not to introduce errors. The trouble with buiding your own ballistic pendulum or any other gadget is the difficulty of accurately calibrating it, even assuming it actually works as intended. Otherwise you may eventually wind up with data that has an extremely high degree of uncertainty, ie no better off than just the educated guess you started with. Undecided
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big_sling_gland
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Re: Possible way to clock your stone speed.
Reply #21 - Dec 30th, 2007 at 7:41pm
 
overhead cammera
sling folded lenth=radias
radias X 2= diameter
diameter X 3.14=circumference of overhead sling style
number of revolutions in 60 seconds devided by 60 X circumference = speed
if a sling that was 10 inches in folded lenth X 2 =20 inches
20 X 3.14 = I did the math 62.8 inches circumference
lets say in 60 seconds there where 180 revolutions
that would be 3 revolutions per second 62.8 X 3 = 188.4 fps (feet per second)

Thats just my example I never tested my knowelege typo. Wink
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big_sling_gland
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Re: Possible way to clock your stone speed.
Reply #22 - Dec 30th, 2007 at 7:43pm
 
Yes I am 11 12 in January Smiley
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wanderer
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Re: Possible way to clock your stone speed.
Reply #23 - Dec 31st, 2007 at 11:22am
 
Quote:
overhead cammera
sling folded lenth=radias
radias X 2= diameter
diameter X 3.14=circumference of overhead sling style
number of revolutions in 60 seconds devided by 60 X circumference = speed
if a sling that was 10 inches in folded lenth X 2 =20 inches
20 X 3.14 = I did the math 62.8 inches circumference
lets say in 60 seconds there where 180 revolutions
that would be 3 revolutions per second 62.8 X 3 = 188.4 fps (feet per second)

Thats just my example I never tested my knowelege typo. Wink

Good try, but it's a little harder than that unfortunately Smiley. BTW you slipped from inches to feet which rather messes things up!

In most people's throw, the hand is also moving pretty fast when you release the stone. That combines with whatever rotational speed you have. Also the rotational speed at release is hard to measure because it is usually increasing pretty fast only towards the end of the motion.

That's why we want to actually measure the speed rather than infer it from the math.
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Aussie
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Re: Possible way to clock your stone speed.
Reply #24 - Jan 8th, 2008 at 6:55am
 
This afternoon I tried some experiments recording the sound of the sling with my daughter's computer using "Audacity". This program not only records the sound but produces a sound wave graph with a time scale. The swish of the sling release and the whack of the ball hitting a brick wall are very distinctly heard and the time between them easily read from the graph. Over several readings I got quite consistent measurements.

0.21 sec to travel 8.1 metres giving a velocity of 38.6 m/s. (approx. 85 mph)

This matches up nicely with the video method I tried before. Very happy with the consistency of results.
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JTK
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Re: Possible way to clock your stone speed.
Reply #25 - Jan 8th, 2008 at 4:39pm
 
ok. i have a VERY simple answer to this.  At most indoor archery ranges you can find a thing ( i cant remember the name, ill ask my dad when he gets home and edit) that you shoot the arrow throuh and it measures fps.  all you need to do is find one of those local to you and sling a ston through it and you would find the EXACT speed. there is  also a formula that determines the foi (force of impact)
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Aussie
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Re: Possible way to clock your stone speed.
Reply #26 - Jan 9th, 2008 at 4:09am
 
JTK wrote on Jan 8th, 2008 at 4:39pm:
ok. i have a VERY simple answer to this.  At most indoor archery ranges you can find a thing ( i cant remember the name, ill ask my dad when he gets home and edit) that you shoot the arrow throuh and it measures fps.  all you need to do is find one of those local to you and sling a ston through it and you would find the EXACT speed. there is  also a formula that determines the foi (force of impact)


Sure there are chronographs and all sorts of fancy equipment around that will enable extremely accurate measurements to be taken. I have just been watching the tennis here in Australia and as soon as the players serve a large screen shows the exact ball speed without them even being aware of it. But few of us have access to such equipment whereas we all have computers, stop-watches and digital cameras. The aim is to get good results with readily available equipment and little or no expense.

Incidentally the results cited above were with a 26" long sling and an ordinary tennis ball using overhead Greek style. I have yet to measure it but just from hearing the sound I am sure Fig. 8 style will give a significantly faster release velocity.
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Re: Possible way to clock your stone speed.
Reply #27 - Jan 9th, 2008 at 8:53am
 
JTK wrote on Jan 8th, 2008 at 4:39pm:
ok. i have a VERY simple answer to this. ......


It's only simple if you have access to such a device. Also, are you sure the device has a large enough capture area to sling through it? It's hard to guarantee the accuracy needed for most of these when using a sling - particularly because there is a temptation to sling as hard as possible Wink.

I think using sound cards on computers is definitely the way to go for most of us. Precision of much better that 0.01s is certainly possible - far better than digital cameras.

Well done Aussieslinger!

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Re: Possible way to clock your stone speed.
Reply #28 - Jan 9th, 2008 at 1:42pm
 

Well, done indeed.   My son's mp3 player has a built in mic and the recorded waveform clearly delineates release and impact.

One person with a recorder.  Can't get any easier than that! 

Average velocities are now an unpardonable cinch....




TS
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Aussie
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Re: Possible way to clock your stone speed.
Reply #29 - Jan 9th, 2008 at 3:38pm
 
TS,

In that case it would be nice to know how fast you were slinging when punching holes in your plywood Goliath.

Regards,

Aussieslinger
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