I have no idea if this would work.

What if you were to make a frame probably square with an axle through it. On the axle would light weight plastic that would take up the inside of the frame. The axle would have to be very well lubricated. Then hook up some kind of speedometer to it. As the stone passes through, it spins the plastic and axle (like the spinny things in a pin ball machine) and regesters on the speedometer. I think as long as the plastic is light enough, energy wouldn't really be lost.

Anyone think this would work? The obvious answer would be to try it. Dah

My suspicion would be that you'd end up either putting your missile through the plastic or just smashing the frame.
Light plastic would be no good. Possible if you used a thin sheet of aluminium it might work. But plastic will just get punctured. :-)

You might have problems with energy losses.  Every bit of energy that went into deforming the plastic, making a loud noise, or making the target vibrate would get lost to the system and wouldn't get measured by the speedometer.  And you wouldn't be able to use conservation of momentum for a system like this because some of the projectile's momentum would get transfered through the bearing system to the earth.

I still think a ballistic seems the best way to go.  It might suffer from energy losses as well, but if could figure out a way to track the darn thing while it twisted and swung after getting hit by an off-center shot, you could use conservation of momentum to get the projectile speed.

NOTE: In theory, if you can measure the path of the hand and sling, you can figure out the timing information, projectile speed, etc., by measuring the speed of the slinger's hand at the moment of release.  This might be well within the range of a cheapo sports radar gun.  I keep promising to post the equations... someday.  I've turned them into a PDF file, but I still haven't gotten around to scanning them in.  Maybe over Thanksgiving...

Still the easiest method for measuring average velocity is to attach a firework snapper above the rock on the release side of the pocket and have a helper with a stopwatch standing equidistant to you and a sheet of plywood or other acoustically suitable target, situated so as not to see you or the target.  Snap, he starts the stopwatch, thud, he stops it.



Bodda bing Bodda....



Bang.



TS

Nice to hear from you again TS.

In another life you must have been a sound effects man. It used to be, "badum dabum" or something similar. Now it's Bodda bing Bodda??

Probably the easiest way to get a reasonably accurate determination is to video yourself. Get a good, wide, side-on shot and use a brightly coloured projectile, preferably with a wall or fence as background. Then if you review the video frame by frame you should be able to see how far the ball has travelled against the background. A bit of number crunching with your trusty calculator should give you its velocity. You will of course have to know how many frames per second your camera opeates at.

A-S

Hey A.S.



Quote:

Probably the easiest way to get a reasonably accurate determination is to video yourself.

Having done so on numerous occasions, I feel confident in advocating the former as the easiest method by which to obtain very accurate average velocities.  



Quote:

In another life you must have been a sound effects man.

As crazy as it sounds.....some seem to consider me a 'sound' effects man in this one.



(Buddum Bum)


:o



TS

Greetings again TS,

To be honest I haven't tried the hidden stopwatch assistant method. I imagine that the idea of being unable to see the slinger is that you respond only to the audio cue and do not anticipate either the release or the strike, and presumably the response delay is the same, givng the correct interval. Over what distance do you measure? I assume that anything less than 10m would be pretty hard to catch. Have you cross checked the result by another method?

Regards,

Aussieslinger

TS is wrong again - another one to add to his collection - the timing should be from the throw (and you don't need to hear a firework to detect a throw) until the stone is SEEN to hit the target, since over a hundred yards, the sound would take approximately 1/3 of a second to cover the distance, which would interfere with an accurate estimate of projectile speed.

SV

   

well if the listener was placed equidistant between the slinger and the target - then hearing would work fine. And a snapper would give a distinct sharp sound that might be easier to distuinguish than the longer and softer sound of the sling.

lol dissing it just cos it's ts isn't terribly logical (captain) :-)
As a home use method it's as good as anything else, in that it relies entirely on the observer having very good hearing and reflexes.
Obviously a human observer free measurement method would be preferable - but you should be able to get a reasonable apporximation with ts method. Just apply commonsense to the position of the observer.

Sure if you are going to time over 100 m then a hand held stopwatch would give accurate timing ie. the human reflex factor is minimized. But how much of the stone's original velocity is lost by the time it covers 100m; perhaps 50%(?), so the calculated velocity will be well below the actual release velocity.

Whether you position yourself mid-path and use audio cues, or use visual ones, I imagine that the hardest part would be to accurately snap the stop watch, especially if the distance over which the flight is measured is small.

It has just occured to me that it would be quite possible to stand next to the slinger and still use audio cues. Just deduct the 1/3 second or whatever it may be, that the sound takes to return from the target from the measured time to give the true flight time.

However, I am sure TechStuf has it all in hand. After all he says he has done it many times, presumably with consistent results. All I asked was whether he had cross checked his results with another method.

I have done my video method only once, but it gave good results; two frames to travel 5m, giving a speed of 40 m/s. Seems reasonable.

Welcome back TS.

Why not put your camera behind a shelter with the lens coverred by wire mesh or thick glass and sling from various distances toward the camera. If the camera has a high frame rate the release should be seen quite easily and if it has sound the impact should be heard immediatly. I thinking this would give a % less error.

OR

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.

;D

why not use a chronograph and get your ammo to travel between the traps. I've used chronographs to determine the velocity of my paintball gun, so I am within allowable limits for tournements etc.  

As a kid I seem to remeber going to the county fair, seeing a booth where you could find your pitching speed. They had a back drop with a target on it. The target had some kind of meter in it that registered pressure. It would tell you your speed by the amount of force the baseball exerted on the target.

Any possible way to make something like this on a simple scale.

for all the time and energy your going to spend building this device which may or may not work. Why not buy a chronograph from ebay or a yard sale or flea market?

Chronograph?

When in doubt, ask wikipedia... ;)

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.

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.

Hmm, well edgebaston is only 40 mins drive away ;-)

http://en.wikipedia.org/wiki/Ballistic_pendulum
That's doable - make the pendulum fairly wide and sling at it from a couple of feet - could work :-)

Would iy be possible to just clock the speed of your sling in rotation?

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.

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. :-/

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. ;)

Yes I am 11 12 in January :)

wrote on Dec 30^th, 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. ;)

Good try, but it's a little harder than that unfortunately :). 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.

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.

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)

JTK wrote on Jan 8^th, 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.

JTK wrote on Jan 8^th, 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 ;).

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!

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

TS,

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

Regards,

Aussieslinger

I'll pull the audio track and see.  Don't know why I didn't try it earlier.


TS

147fps give or take.  Pulled the audio track from the video, converting it to a .wav file.  Jibes nicely with the release and impact frame time lapse on video.  Of course, I was using over 4oz ammo in an accuracy exercise which accounts for the slow velocity.  

I wouldn't be surprised to hear of double that velocity in a flat out speed exercise by some here.

Making sure the mic is at midpoint and starting the measurement where the trough meets flatline on release, and vice versa for impact sound waveform will aid in accuracy.

My rock made a buzzing sound during flight which can clearly be distinguished from release in the sine wave graphic produced by my waveform editor.  Fun stuff!


TS

8-)

Great show Aussie, so simple and effective, and here I am trying to arrange a radar gun with help from my baseball friend.  ::)

Coenie

Glad to be of service.

Thanks for the info, TS. That speed still works out to be over 100 mph, hardly slow. With a 4 oz stone it certainly put paid to the notion that it would not be possible to kill a man with a sling.

Actually with the speed of sound at around 300 m/s the error introduced by not having the microphone positioned exactly equidistant from the slinger and target will generally be fairly small, but could be as high as 20% for a fast slinger if the recording was done at either extreme. However it would be quite easy to correct the measured flight time by working out the difference in times taken for the sound to arrive from both sources, and then either adding if the target was closer, or subtracting if the slinger was closer.

You're right, the error would be small enough to hardly matter except for extreme speed exercise covering appreciable distance.   Speaking of which,  who wants to be the first person on Slinging.org to post video of themselves (heck, even a complete stranger, anybody) breaking 300fps averaged speed at say 100ft?  


Dumb question, I know.  Let me guess....


Such an 'arduous' convoluted and confusing enterprise once again, defaults to me.


::)


You know.....


Perhaps regrettably,  I've taken a 'lacksadaisical approach' to the hobby of slinging in recent years.....but compared to all the yakking and theorizing that is the rather large preponderance of slinging.org's constituency, Aussieslinger, myself and a few others here are relative 'superstars'.


The chief reason I haven't demonstrated myself breaking every record (both existent and non existent)  with the sling is to give others the opportunity to share in the fun of actually doing it and sharing the example.  Yes, I said F-U-N....as opposed to 'work'.


And I'm 40 yrs old and at least 50lbs overweight!


How pathetic is that?


We're pathetic.  The lot of us.  


Our sport is spurious, totally irrelevant.





TS

And your point is...?  :-?

If you go out and do something that is not forced upon you, and then come back and expect to be a martyr for doing it... Sorry, that doesn't work.
However, for your hard work and assistance in gathering sling information, Thank You!

Martyr?  Martyrs require causes.  


Slinging hardly qualifies as a cause.  In it's current collective form, it hardly qualifies as anything more than an excuse to share collective outgassing.


Martyr.  LOL!


Yakk Yakk....

Sooo... Being on this site irritates you? I see an extremely easy solution...

Or is it that most of the people on this site aren't so into slinging that they work hard to transform it into a "cause"? That solution isn't quite as accessible...

Seriously, if seeing people sit around and yakk about random slinging stuff bothers you, don't read it!! If you want people to be more serious, then create your own site, or petition the mods to eliminate all random banter.

In which case these last few posts would be deleted.

Quote:

Seriously, if seeing people sit around and yakk about random slinging stuff bothers you, don't read it

I only stopped in because I forgot my hat.


And of course, Aussieslinger's admirably unflagging enthusiasm caught my attention as did Kristal's amazing book!  


Ethan, I see I've touched a nerve....I'll leave you in peace.


And don't worry, I'll try not to let that revolving door, powered by the droning winds of complacent mediocrity hit me in my dismal, fat caboose, on the way out.




TS

From Aussie...


Quote:

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)

a slinger down in Arizona did a thing a while back using this same technique with the following modification...

He hung two full size sheets of newspaper a known distance apart (don't know if he framed the top and bottom or not) and set his notebook computer equi-distant between them with the program running... stepped back and threw several stones through the papers... retrieved the computer and analyzed the data.  "whap" "whap" then dividing the distance with the time interval between whaps and you've got it aced.

I think he was getting velocities in the mid 40's (in M/s).

Where do you get that program?

BSG,

The program I used is called "Audacity". http://audacity.sourceforge.net/

Mate, computers are hardly my strong point. If I can use it anyone can!


GOW,

The sheets of newspaper idea may be good to measure how much velocity drops at any given distance but it just adds unnecessary complication. I just picked 8.1 m at random, there happened to be a mark on the ground that was easy to measure to. Also I didn't have to worry about aiming at a target just whack at the garage wall. I wasn't trying to etablish any speed records, only to see if the method worked, which it certainly does.

Regards,

Aussieslinger.

So the methods certainly are accessible to anyone... There just needs to be a set system for measuring, to make sure everyone is as accurate (or inaccurate) as the rest of us.

I'm curious, how would that be set up?

Quote:

breaking 300fps averaged speed at say 100ft?

What is meant with that? Getting a stone or whatever to break 300fps at a 100ft away from you? To me that does not sound possible.

Meanwhile I am still going on with my arrangements to aquire a radar gun to measure velocity at release, ooooooohh how painfull.  ;)

Coenie

Quote:

We're pathetic.  The lot of us.

 :o

Speak for youself, if you do not want to send a rock ripping through the air @ 300fps a 100ft away from you, please do not do it. Who would put that terrible burden on your shoulders etc. yakk, yakk, yakk

Coenie

Ethan wrote on Jan 10^th, 2008 at 10:28pm:

So the methods certainly are accessible to anyone... There just needs to be a set system for measuring, to make sure everyone is as accurate (or inaccurate) as the rest of us. I'm curious, how would that be set up?

Tricky!  For distance something between 5 and 10 yards (or meters!) is probably OK. Just measure out a distance to something that you can hit (barn door - good for me ;D) and throw while recording.

For the moment - I would hope people would just get out there and do it. When enough see how interesting it is, the standardisation will come. Until then I expect to see some 'optimistic' estimates, but that's the way of it.

Your distance you can measure to probably about 10-20 cm  at best - the uncertain part is locating the point of release. For that reason you need a 'reasonable' distance to get good accuracy. On the other hand, go too far and air drag will have significantly reduced the speed and you will read low. I feel that at least 5m is needed to get a 'reasonable' result. It is possible to make compensations for air drag, but it's probably not what most people want.

The nice thing about timing with a sound recording is that the precision is far higher than any other easily available approach, With care it can be significantly better than 1/1000th second. The difficulty is relating the sounds one records to the events one is timing. The sound of an impact is easy to pick out, less so the sound of the release, at least with my slings.

That was where things like slinging through newspaper came into the earlier proposal. No one at the time (T_S included!) took the bait as far as simplifying it further, although 'informal tests were conducted' :).

BTW - all of this stuff can get almost arbitrarily complicated, as an earlier thread suggested. If you split the sites of the microphones in a stereo recording you can easily get doppler shift measurements. Add one or two more channels and you get enough to keep a physics/engineering graduate student happy (or miserable!) for years. ;)