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Velocity and Penetration (Read 31573 times)
Douglas
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Re: Velocity and Penetration
Reply #15 - Apr 7th, 2004 at 1:53pm
 
There was once a chronograph on my street, one of those ones that displays the speed of passing cars in big red numerals. Late one night I crept up alongside it and threw a stone by hand. I remember it read about 68mph. Then I got out my sling and cast a stone. Nothing. The meter only went to 2 digits, so was it possible I exceeded 100mph and it blanked out? I like to think so. Smiley
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english
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Re: Velocity and Penetration
Reply #16 - Apr 7th, 2004 at 3:52pm
 
80 mph does seem a bit slow.  I remember someone telling me that the average speed for a cricket ball released from a bowler is about 90mph, which is why they hurt so much when you get hit (and why cricketers wear lots of padding.)  I think a sling could easily outdo that, surely?  And they said it had about the same power as a .22 round on the documentary.  If Yurek could do, say, 300 mph, that must be about a .45...?
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Yurek
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Re: Velocity and Penetration
Reply #17 - Apr 7th, 2004 at 4:52pm
 
That is an interesting matter. There was the discussions about the velocity and impact energy a few times before now. But I see this subiect has came back.

Quote:
If Yurek could do, say, 300 mph, that must be about a .45...?


I really don't know what release velocity I can do. I would like to know it. I'm sure Larry's velocities were quite a lot bigger, when he had surpassed the record. Once I tried to determine the averange velocity of my best shots (in that time, with my ordinary sling) with stones. For the calculations there wasn't used results of precise measurements but only my estimations. I can't say how much the results differ from the real numbers, but hope not so much.

Here is the link to the my estimations and discussion about velocities and energies:

http://www.slinging.org/forum2/yabb/YaBB.cgi?board=1;action=display;num=10670427...

Jurek

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« Last Edit: Apr 8th, 2004 at 5:22pm by Yurek »  

In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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Chris
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Re: Velocity and Penetration
Reply #18 - Apr 7th, 2004 at 5:08pm
 
It's designed to gauge the speed of cars, so it probably didn't register because your rock was too small and moving too fast. 

Chris
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Matthias
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Re: Velocity and Penetration
Reply #19 - Apr 8th, 2004 at 12:18am
 
This should be easy (haha) to figure out... Just for fun, I took Barak's video and did a frame by frame analysis. Unfortunately, at 15 (low quality) frames per second you lose resolution right at the point where you need it at the release.

The plots for his throw show a smoothly accelerating swing over the last 6-7 revolutions, with substantial acceleration in the last 2. There aren't enough data points to predict the exact point of release.

Final radial speed works out to ~45 rad/s which assuming a 25" sling gives about 110kph. Arm/shoulder motion adds 9m/s in translation for a total speed of 150kph.

This isn't too bad actually! No aero-drag gives a range of >160m It doesn't look like this demonstration throw is taking full advantage of the "snap" though like I mentioned there isn't enough data in the last bit to be sure. I'd be comfortable accepting that the instantaneous radial speed at the time of release was as much as 50% higher. Maybe Barak can vet some of this...

Interesting thing to note are that Barak's hand moves only vertically during the spin up phase, and only through about 8".

I think I might write up a little prog (Sling analyser v0.1  Cheesy ) when I get some spare time. If there is interest I'll try to post an article. If we filmed a couple of throws with the intent of crunching the video we should be able to produce some intersting results - I can probably borrow a high speed camera later this summer.

Matthias
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Douglas
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Re: Velocity and Penetration
Reply #20 - Apr 8th, 2004 at 1:56pm
 
Quote:
And they said it had about the same power as a .22 round on the documentary.  If Yurek could do, say, 300 mph, that must be about a .45...?

The "power" of a .22 round is quite different, since it's lighter and going much faster. A .45 chronos at about 500fps...

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Douglas
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Re: Velocity and Penetration
Reply #21 - Apr 8th, 2004 at 1:59pm
 
Quote:
It's designed to gauge the speed of cars, so it probably didn't register because your rock was too small and moving too fast.  

Chris

It did respond to my hand-thrown stone, so I'm inclined to take a different view...
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justin Ball
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Re: Velocity and Penetration
Reply #22 - Apr 8th, 2004 at 3:32pm
 
To work out the average speed, why not use the slinger and a helper, and sling stones into a lake. The helper uses a stop watch, starts it as they see the stone leave the pouch, and stops it when they see the splash. Do about 10. Use the average.

For short distance power shots, do the same, but against, oh, I don't know, a barn rock face, sleepy cow, tax office...Of course the timing is more critical, because it is so much shorter.

One could then compare the long shots with the short shots. One would give you an average speed over a long distance, the other would give you more closely the speed when it left the pouch.

I know this isn't accurate. There are many variables, and human reaction times- and the two shots are different- the short ones would be nearer a flat trajectory, and closer to the distance actually paced off, the long shots would actually be a...oh I can't describe it in words accurately, so lets say semi-circle- though it's not really.

Justin
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Re: Velocity and Penetration
Reply #23 - Apr 8th, 2004 at 4:11pm
 
I recommend this particular Chronograph for it's low price and quality:

http://www.competitionelectronics.com/pc%20paintball.htm

Not to mention it's extra large aiming area below the diffusers!   One has only to properly illuminate the sensors and shield the unit except for the aiming area and go to town.  I do recommend very heavy plywood or metal  sheeting with a cutout slightly smaller than the aiming area on the Chronograph as a single miscast could take out the unit by catching the diffuser/supports.  I have achieved 363fps with a basic non-compounded spectra and leather sling weighing less than 1oz. and spherical lead ammo weighing 2.5 oz.   and much more than this with a compounded sling and 1.25 oz. ammo.
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Douglas
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Re: Velocity and Penetration
Reply #24 - Apr 9th, 2004 at 12:11pm
 
Bushnell's Speedster radar gun goes for about $150 but it only measures up to 300mph. They state that it only goes up to 110mph for baseballs, so maybe this is due to the smaller sig - like a glande.  Sad

There's also the Speed Chex:http://www.astroproducts.net/speedchek2.htm
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Chris
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Re: Velocity and Penetration
Reply #25 - Apr 10th, 2004 at 1:34am
 
363 FPS = 206 MPH.  Nice slinging techstuff.  How long was your leather sling?

Chris
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Re: Velocity and Penetration
Reply #26 - Apr 10th, 2004 at 3:23am
 
Hi Chris,


I believe that was my 49 inch model.  Very light and fast with extremely thin kevlar cord and small star shaped pocket which wraps around the lead ball ammo securely for a great release each and every time.  I will be posting some more pics as I dig through my ancient relics!   When I get some time,  I will be duplicating some performances of old, with more advanced equipment and will get some video uploaded that should prove impressive......I went to the lake awhile back to fart around and quickly found how rusty I've become.  I hadn't been slinging in a coon's age and it showed.  Also,  I had gained a considerable amount of muscle mass from weight lifting as part of a recuperative regimen to realign my upper spine and I can tell you that the increased muscle mass of the forearm is a 'speed slinger's worst enemy.  I no longer can sling the light stuff (>4oz.) to hyper velocities like I did in the late eighties.  The resulting blood rush to my hand and lower forearm is an agonizing experience.  Like you,  I had mastered the 'loose wrist/wrist curl combo' and achieved amazing results but am currently no longer able to duplicate some of my earlier performances largely due to the increased forearm mass...... So,  I am relegated, for now, to slinging at more moderate speeds with heavier ammo.    Angry Sad Cry
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Douglas
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Re: Velocity and Penetration
Reply #27 - Apr 11th, 2004 at 12:23pm
 
Since a sling and its common ammo are dirt cheap, I'm sure we can afford a $150 radar gun. Think of handgunners and other sportsmen who can't even look at their primary weapon for that price.  Roll Eyes

On that note, I can't really see a Slinging magazine coming up, since most of the trade glossies depend on advertisers and aside from nice braided slings, we don't have much product to sell. So I guess we're safe from the ravages of Madison avenue... Smiley
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english
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Re: Velocity and Penetration
Reply #28 - Apr 11th, 2004 at 1:18pm
 
A slinging magazine would be unfeasible, but it would certainly broaden appreciation of the weapon.  I think that a newsletter style thing would be better, but what information could it contain that isn't already on this website?
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Chris
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Re: Velocity and Penetration
Reply #29 - Apr 11th, 2004 at 11:31pm
 
Yeah, I think there isn't enough people to warrant a slinging magazine.  This site is the first step.  People spreading the word about this site to friends, or at renaissance fairs, or with stickers on their cars, will gain momentum and hopefully earn some much needed respect for this truly great weapon.

Chris
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