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Message started by mgreenfield on Jan 1st, 2004 at 5:11pm

Title: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 1st, 2004 at 5:11pm
Fellow slingsters, ....if we ignore air drag, and assume launch point and impact point are at the same elevation, calculation of range needs just two inputs:

*Projectile initial velocity
*Projectile launch angle above horizontal

Note that projectile weight isn't a factor.

For a quick calculator of range see:

http://id.mind.net/~zona/mstm/physics/mechanics/curvedMotion/projectile/Motion/commonQuestionsCalculator.html

Just for fun, I assumed a sling with 1meter long cords, swung at an rate equal to 10rps for a projectile initial velocity of 63meters/sec.   I assumed a launch angle of 45deg above horizontal, and the calculator gave me an effective range of just over 400meters.

1meter long cords are certainly realistic, ...and I didnt add in any shoulder-to-fist swing length for the slingster.  The 10rps rate might be a little faster than normally possible.

Interesting, huh!        mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 1st, 2004 at 8:42pm
.....and according to the calculator, everytime you double your launch speed, you QUADRUPLE your range.  Just no substitute for launch speed!    mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Whipartist on Jan 2nd, 2004 at 11:25pm
Pretty cool.  Too bad the real world's so complex.  Nah that makes it more fun huh.

                      Ben

Title: Re: Calculating Theoretical Sling Range
Post by JeffH on Jan 3rd, 2004 at 10:43am
One must not leave out air drag, however.  No matter what size or shape or material your stone is made from, it does not go through the air without resistance.

This is interesting:  two bullets with congruent shapes but of considerably different size have considerably different ballistic coefficients (the amount of "air drag", that is).  The larger bullet will have a better coefficient.  The same holds true for stones we sling.  The larger ones have LESS resistance to the air than smaller ones of similar shape.

As discussed before in another thread, the slinger has a maximum weight of stone he can sling before it is so heavy he can't get up the rotational velocity to make a good throw.  This is different with every slinger, tho most of us are of similar strength. ( Except for Jurek, who is much stronger than most!)  What is needed at this point is to discover the coefficients of spheres of a given sizes and weights (spherical is best here I believe.)  

Also what is needed if for David T to get those velocities from the State Trooper.  Did I miss the thread where he posted them?

Once we get real numbers on these things, we can help Jurek break the world record!!!!!!!!!!!!!!!!!  Well, maybe we can say we encouraged him even if we didn't actually help.

jeff <><

Title: Re: Calculating Theoretical Sling Range
Post by David_T on Jan 3rd, 2004 at 5:54pm
Jeff,

You didn't miss my post--the trooper had to take his car to the shop for repairs the day we were to meet, and we have not yet gotten together. We shall see about next week. :-/

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 4th, 2004 at 10:30pm

Quote:
Once we get real numbers on these things, we can help Jurek break the world record!!!!!!!!!!!!!!!!!  Well, maybe we can say we encouraged him even if we didn't actually help.


I see that I have no way of a retreat alredy :'( I may not fall short of your guys expectations. It would be better if I didn't vanut ;) But seriously I'm glad that you are supporting me. Now I really think about the attempt. Probably I haven't get this idea alone.  Just Ben has suggested it. Now I believe I can do it.

If I have time I will test the spherical projectiles and compare with the glandes. It is not easy to find the best weight because it require a lot of testings with a lot variables. It is true the bigger lead ball flies better than smaller one started with the same velocity, because the relation of mass to the cross-section surface is bigger (R^3/R^2, R-radius). But we need more power of a body to accelerate it. It makes the limit. Finding this one is a serious scientific problem. So we should believe own feeling and intuition.

Jurek

Title: Re: Calculating Theoretical Sling Range
Post by Hondero on Jan 5th, 2004 at 3:11pm
Hi Yurek, I see that it has been created a group of support in your fight for the Guiness, so as you seem determined  I´d like also to collaborate in the team.
With respect to the weight of the projectiles, I think that with heavy projectiles  the range is shorter. Let us suppose that the maximum muscular power that we can develop is transformed in the kinetic energy of the projectile:

Speeds of launching:
For an optimal mass M:  ½ MV^2
For a double mass: ½(2M)V^2,,   V = V/1.2 (approx.)

Maximum reaches in vacuum:
D = V^2/10 (approx),,  D = D/1.4 (approx)

Air drag  for spherical projectiles):
F = K(S x V^2),,   F = F/2.25 (approx)

For the optimal speed that we are considering, the air drag could be translated in a reduccion of the reach of 30 % aprox., reason why its diminution when using great projectiles affects less to the range than the increase of it by diminution of the weight of the projectile

Ranges in the air:
D = (1- 0.3) x V^2/10 = 0,7 x V^2 /10
D = (1- 0.21) x V^2/10 = 0,54 V^2/10,,    
D= 1,3 D
The range with the optimal projectile is a 30% greater than the one of double weight.

(I call optimal mass or projectil, the one of less weight that can  get all the muscular power in the launching. Projectiles very small can´t do it).

Any way, an important aspect in the fight for the Guiness is to consider the relative influence of the different factors in play. To the optimization of the sling and the projectile I would give an importance of 15 % each and to the optimization of the technique of launching and to the muscular training  30 % each. I think  that in general the muscular training is the main factor to develop. Gym, launching with great weights, etc. I think you have to publish in the forum your body measures for consideration of the support team, and evaluate your possibilities... It´s a joke.

Saludos


Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 6th, 2004 at 10:10am
Hi Hondero,

Thank you very much. The Interesting post. I have read this through and this gives me a lot thinking. I understand the nitty-gritty. Your calculations drive to conclusion that we should try to find the minimal weight of the projectile, what we are able to control and what doesn't cause a idle run, with the specific sling (lengh, air drag of the sling etc.). Because of the adventage of a velocity is bigger than the adventage of the bigger relation "weight/fece" (R^3/R^2) of a more heavy projectile.

My idea have been different until now: just to determine the maximal weight of a projectile, what will not slow down me perceptable, so I will still have the adventage of the "weight/fece" (in simple words "a heavier projectile can overcome its own air drag easier than a lighter one, therefore doesn't lose a velocity so quickly").

I have used 100 g glandes for last testings. So it would make sense to try with 50-70g and with the reduced sling design of course. The lighter projectiles, the sling must be more aerodynamic. The Jeff has the good balistic software and if it can consider a size and mass of a ball, it would be good to plan the simulation for the sling velolocities range. Real testings are difficult due to a shortage of good amo and very incovenient measurements of ranges.

Anyway, first, the most important thing is a power delivery, as you mentioned, then next, don't waste it. So I must practise... and practise, but the winter so cold as I must use the hammer for tearing frigit stones out from the frozen ground. Brrr! The pretender's life is so hard ;)

Jurek

Title: Re: Calculating Theoretical Sling Range
Post by Chris on Jan 6th, 2004 at 5:38pm

Quote:
The larger ones have LESS resistance to the air than smaller ones of similar shape.


I think it's less resistance compared to change in volume or weight.  A Mac Truck has a lot more air resistance than a bullet, but volume wise, the ratio is less.  I think that is what it means.  

However, this property can be exploited, and is why super dense projectiles (like lead) have such good range.  Their weight to size ratio (which determines how much drag they have) is much much better than just stone.  

What is another material, like lead, but denser that doesn't cost a fortune.  Things like gold and uranium might not be so easy to get hold of. :)

Chris

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 21st, 2004 at 12:05pm
I've found the calculator site hard to return to using the whole address.   But this works:

Go to -  
http://id.mind.net/~zona/mstm/physics/mechanics/curvedMotion

Select - projectileMotion/

Select - commonQuestionsCalcul..

Again Select - commonQuestionsCalcul..

FYI     mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 21st, 2004 at 3:40pm
I have played with this simulator a bit. Here is one of the results:

Original velocity:  80.00 m/s
30.00 degrees N of E

x-component:  69.28 m/s
y-component:  39.99 m/s

Basic information about the trajectory:

Time till at top:  4.08 s
Total time:  8.16 s
Maximum height:  81.63 m
Range:  565.56 m

It is interesting but that one works as well for lead projectiles as for feathers bacause simulates the motion in the total vacum. So we know only the velocity may not be smaller than 80 m/s in real conditions for that range an angle.

I have found some free balistic software but it usually works corectly for the gun ammo velocities and for the much more flat shots :(

Here is one of them which would be pretty good, but works with velocities at least 500 ft/s. Does know anybody a more proper one?

http://www.eskimo.com/~jbm/ballistics/maxdist/maxdist.html

Jurek



Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 21st, 2004 at 6:27pm
Yeah, Jurek, the assumption of vacuum conditions is a drawback, but I suspect the estimates might be pretty close for lead glades.    But it does give us a comparative idea what different launch velocities and angles do for range.   And it lets us use relatively slow launch velocities.    Neat thing is that is shows us shots of 1/2 kilometer AND longer are certainly possible.    Now THAT will be the day for me, .....especially if I can come close to a target at that distance!     Happy rockchucking!   mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 21st, 2004 at 8:34pm
mgreenfield,

In vacum the best angle is exactly 45 degrees, but in air the optimal angle is usualy between 30 and 40 degs. It depends on a few main factors: size and shape of projectile, mass, velocity and weather conditions. I'm afraid we can't determine this angle precisely. Anyway we wouldn't be able to get this angle with the sling. So we should shot at angle of 30-40 degs at a guess. It will be close to the best angle.

To see what different angles do for range, play with this base-ball simulator, try find the best angle. You may experiment with the wind and Mangus effect too. Have a fun.

http://www.scri.fsu.edu/~jac/Java/baseball4.html

Jurek


Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 21st, 2004 at 8:57pm
Jurek, ....that baseball hit simulator is VERY! slick.   Our guys should be all over it.   Tnx!   Where do you suppose the drag should be set to approximate a spherical lead glande??    Also, it shows the importance of reducing drag.   Launching the same mass w 1/2 the drag makes a huge difference, ....and again takes us to the importance of launching "almond" glandes point first w stabilizing spin if at all possible.   For sure, you dont want to launch them crosswise to the wind!  mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Hondero on Jan 22nd, 2004 at 11:43am
Very nice simulator this of baseball. I know some others for pinball, trebuchet, etc. The problem with all them is the air drag calculation, that must be an input in the simulator . It´s a difficult problem that calculus, that in fire gun is foccused by means of tables as there aren´t precise formules to represent it. Unfortunatly I think there are not tables for the margin of sling velocities and ammo, or at least I don´t know them.
Would the slinging group be able to make an approach to the problem? It´ll be a rewarding task... may be exploring the net we can find some interesting approach  ::).

Hondero, just feeling lazy today

Title: Re: Calculating Theoretical Sling Range
Post by David_T on Jan 22nd, 2004 at 2:12pm
I once read an accout of a Roman slinger as to projectile speed.
He observed that if you saw an ememy slinger release his stone at the same time you did and his stone hit you before you saw him fall---you were slower than he was. ;D ;D
Its my lunch break what can I saw ::)

Title: Re: Calculating Theoretical Sling Range
Post by David_T on Jan 22nd, 2004 at 2:15pm
I meant: ...what can I say

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 22nd, 2004 at 4:34pm
David,

Just the great idea of the projectile velocity measurement! We must try it! It is just absolute measurment! LOL

Jurek


Title: Re: Calculating Theoretical Sling Range
Post by Hondero on Jan 22nd, 2004 at 4:50pm
Humm, to be exacts I think the David method has some deficiency as it dont´consider the velocity of the light. So, the slinger that see the enemy falling when he is struck has thrown to higher speed than him  :o  ;D

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 22nd, 2004 at 5:09pm
Hondero,

Probably David assumed that a velocity of the missle is greater than the light velocity  ;D

Jurek

Title: Re: Calculating Theoretical Sling Range
Post by Ulrica on Jan 22nd, 2004 at 5:18pm
Hi...

I´m totally green in this subject, but I just got an idea...
( maybe it was the Champange??)

Well, is there somewhere, something you can throw that can measure the speed in the air when it´s flying?
I mean like a watch but something that measure the stream of air???
I don´t know if such thing really exciced...  But maybe there is??

Just an idea.....

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 22nd, 2004 at 5:23pm
He he

That thing is an anemometer, so just we must throw the one ;)

Jurek

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 25th, 2004 at 1:45am
Jurek, .....I went to your www.scri.fsu.edu/~jac/Java/baseball4.html site & tried a little "experiment".    

I launched a baseball in the simulator at 93mph, an angle of 35deg.  It "flew" 330ft.

I assumed the baseball sphere had a volume of 8 cubic units.

I found the circular area a flying sphere of 8 cubic units presents to the oncoming wind.  It is 4.75 square units.

I "rearranged" these 8 units into an almond shaped glande that flying point-first would present just 2 units to the oncoming wind.

The same almond glande flying edge-first would present 4 to the oncoming wind.

The same almond glande flying top first would present all 8 units to the oncoming wind.

My estimates are these.    If my spherical glande could fly 330feet, my almond glande flying point first (best case) could make 430feet, ....almost 1/3 farther than the sphere.   Worst case is my almond glande flying flat-side first, making just 277feet, ....which is 15% less than the sphere.

Here's the kicker, ....a well thrown (point-first) glande in my "experiment" "flew" 432feet, ....which is over 50% more distance than a poorly thrown (flat-side first) glande at 277feet.

If the above is pretty much right, why would ancient slingsters throw almond glandes if they couldnt control them go point-first?   Distance results and therefore accuracy of "uncontrolled" almond glandes are just too variable.    I say, if they had not means of controlling the almond glandes, they would have thrown spherical glandes.

What do you-all think??    mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 25th, 2004 at 2:05pm
mgreenfield,

Your experiment is interesting. I'm a bit surprised that you have got so big differences between the ranges in the different kinds of fligh. Yesterday I tested a few ball shaped and elongated lead projectiles on the frozen lake. But, alas, I didn't find any of them. All projectiles were lost because there was too much snow and the traces on it, and I hadn't too much time for seeking due to grow dusk. One day I will repeat it.

But, at a guess, the range differences didn't seem so big, although the launch velocities had to be bigger than that one which you tested. The bigger velocity, the bigger shape influence for the range.

Surely, the reason is in a big desity of the lead projectiles relative to the baseball density.

Anyway your tests confirm our common opinion about adventage of the elongated projectiles in the "point-first" flight over other ones. I think you are right about the reason of using the almond shaped glandes by the Romans.

Jurek

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 25th, 2004 at 4:10pm
Yeah, Jurek, I suppose the real-world range and accuracy differences between well thrown & poorly thrown glandes will never be as dramatic as my estimates of best case and worst case.    In real life a well thrown glande is still never "best case" thrown, and a poorly thrown glande is still never "worst case" thrown.    Plus there are a lot of other variables in every throw that hide the effects of glande orientation in flight.    So, it will be tough to tell really how good a job a slingster is doing.  

That aside, I figure no slingster will make it to "world class olympic" status without getting a LOT of glandes off point first.    That will be the difference between a world class slingster and a simple rock-chucker like me.

I have cast some 80gram plaster of paris eggs, which I will paint one side white and one side red.  I plan to sling them "softly", and watch them closely to see if I can learn a technique that puts point-first NFL football spins on them most of the time.

But it's gotta get warmer outside!!    Last week or so it has been -20 to -3 Celcius all the time here in Wisconsin USA.

Happy potato chucking!        mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by JeffH on Jan 25th, 2004 at 4:44pm
I have slung a stones of varying size, weight and shape.  I have achieved 400 feet or so with these widely varying stones.  I am not, therefore, convinced, that the difference in shape is going to have as much affect on the distance as the baseball program suggested.

Certainly some elements of the stones shape and weight will affect distance.  But without good experiments, I distrust the software.

jeff <><

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 26th, 2004 at 9:38am
Right you are, Jeff.   Looks to me like we have guys doing pretty consistent long-range rock-chucking.   I'm concerned about possibilities of putting (say) 4 out of 5 rocks in a washtub at (say) 400yards.   Ancient writings are full of tales of hair-splitting sling accuracy, ...makes 'em sound even better than bow & arrow.    How DID they do that??    Or is much of this writing hot air, .....my army slingsters can beat your army slingsters, etc.    Further, if slingsters were known to be such crack shots, why didnt Goliath just throw down his spear & run when David showed up??  Inquiring minds want to know!   :)  mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by David_T on Jan 26th, 2004 at 12:31pm
If we lived in the Belaric Islands off Spain we would not doubt the accuracy that the sling is capable of in the right hands. I'm really hoping Hondero can get videos of some of the competitions they have over there. It would help us non-experts see exactly how they sling and how good they are.

As to Goliath, my theory is that David did not "telegraph" the fact that he had a sling. Scripture says that Goliath was angered and mocked Israel and David for sending a boy with a stick (staves) to fight him (I Samuel 17:42-43) Goliath definately saw the stick David had not the sling.  I believe that Goliath, in his pride and anger, came at David, and amazingly, David ran to meet him. It says that at that point David reached into his shepards bag, got one of the smooth stones and slung it. I believe that Goliath probably did'nt figure out what was happening  until one or two seconds before he went cross-eyed trying to see what was coming at his head. ;D

Title: Re: Calculating Theoretical Sling Range
Post by mgreenfield on Jan 26th, 2004 at 2:34pm
I would love to see the Belaric Is guys do their sling thing.   Maybe we take up a collection to pay Hondero's way there w video equipment, ....full speed & slow-motion to record exactly how the slinging job is done.    I'd sure kick in some decent $$ to see this tape & hear what Hondero said about it.   Maybe we meet someplace in USA to see, hear, discuss, practice.   (Which means also taking up a collection to help Jurek, Ulrica, Hondero, others buy air tickets  ;D)

I figger slinging is like golf, ...get the Form & Technique down, and everything works fine.  Without the F&T, nothing works very well.     I feel like a guy who's been handed a golf club and ball, who's never even seen the game played on TV.   If Hondero goes to the Belaric Is, he gets to be the first modern Internationally Known Sling-Pro.

mgreenfield

Title: Re: Calculating Theoretical Sling Range
Post by Ulrica on Jan 26th, 2004 at 3:05pm
Sounds great to me. I would like to fly to USA and meet you guys! And almost for free... even better :D
But why doesn´t we all go to spain and see it live?  8)

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 26th, 2004 at 6:47pm
I'm sure the ancient or balearic sling masters made no calculations or simulations. So they didn't know that some things are impossible :) I believe that some people could get the amazing skills which are actually impossible for most of us. If we look at the circus artists,  we see they just do "imposible" for us things! Well, it is result of a lot work, passion, talent and inherited experiences.

For me for example it is difficult to belive that someone can constantly hit with the stone into the small pool from 400 yards, as I have read about it on some website. I think that slinger probably did it ones or a few times and people have mythicized it. We love do it. Anyway I said only it is difficult to believe but didn't say it is impossible. I like Hondero's belief that acuraccy has no limit. If we do something well, we always may do it better, great :)

mgreenfield,

He he, I like your idea too :D It would be great to organize The First World Slingers Symposium. Great, I love it!

Jurek


Title: Re: Calculating Theoretical Sling Range
Post by Hondero on Jan 26th, 2004 at 7:18pm
He he, guys... and girl, a meeting of Slinging.org to see videos. It would be nice. Good idea Ulrica, the meeting in the Balearic islands, the best place to spend the summer holydays. Come all to Balearic Is.  next summer to see the honderos live¡¡ I invite you to the welcome dinner¡¡... We of this side of the Ocean we are at least more close... who knows, but already I advance to you that the Balearic ones are a little closed in themselves as good islanders and cultivate the sport of the sling for themselves, like a sign of identity, to half of way between the folklore and the sport. The sling is for them a tradition and do an effort to keep it up with fervour, but does not have the dimension of a sport competicion like athletics championships for example. I mean that the important thing for them is the participation more than quality. Thus, in theirs encounters you can see very good slingers mixed with fat ladies that they do not guess right a shot, or old men who long for their youthful skill. In fact theirs records, even being good, do not correspond to that ability that would have the mythical honderos of the antiquity, and perhaps any of them will snatch to Yurek the next Guiness  ;D. I have a video of one of those competitions from some years ago, but it is of bad quality as it´s a third copy. I live in Madrid and since two years ago haven´t talked with the Balearic people, with which I had much contact others times. I´ll write them to see if they have something new in regard to videos.

Yurek, if the forum continue growing up, may be one year we could organize this International Slinging Competition you say  :D
Adelante Chris¡¡

Title: Re: Calculating Theoretical Sling Range
Post by Chris on Jan 27th, 2004 at 12:32am
I think it would be great fun to have a slinging symposium, perhaps as part of a larger primitive weapons meeting.  It would be nice to put a face to all of your names.  Maybe when Jurek goes for his world record, we can all meet then.  Get Guinness to fly a bunch of us to some field site.   :P

Chris

Title: Re: Calculating Theoretical Sling Range
Post by Yurek on Jan 28th, 2004 at 7:49am

Quote:
...In fact theirs records, even being good, do not correspond to that ability that would have the mythical honderos of the antiquity, and perhaps any of them will snatch to Yurek the next Guiness...


He he. Hondero, I suspect some of them prepare to do it. Anyway if I even can't be the first, then though maybe I will mobilize others to do it. So I will feel my own part in it, or rather our common (some guys from slinging.org) part :D  Because just they have encouraged me and gave some tips (not only for me, of course).

It is good, and maybe brings near the day of the official international slinging competitions :) I would like we meet on such occasion very much :)

Jurek ;)




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