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Message started by Matthias on Oct 28th, 2004 at 2:33pm

Title: Significant projectiles
Post by Matthias on Oct 28th, 2004 at 2:33pm
Ok, I'm currently working on a little program that I hope does a better job of simulating sling ballistics than what we've been able to find on the web. It takes into account fluid drag at varying Reynold no, density, size, surface roughness, wind speed, shape (sphere/ellipsoids only), height above ground at launch, angle.

I currently have dropdown menus allowing you to quickly select materials of various densities (lead,steel,concrete,stone,rubber) and properties of a few commonly slung balls (golf,base,tennis,soft)

I'd also like to add a list of "significant projectiles". I've been thinking along the lines of a few artifacts (roman lead glans etc) as well as modern one like Larry Bray's rock.

I think maybe forum favourites deserve a shot too - things like David's concrete tennisballs and Techstuf's 1" lead spheres spring to mind.

You guys want to help me fill out these categories? Bonus points if you include vitals (weight/dimensions etc) with your nominations!

Matthias

Title: Re: Significant projectiles
Post by KnollSlinger on Oct 28th, 2004 at 7:33pm
Be sure to include a section for projectile orientation.

I learned in my last outing that when my bullets go thru plywood, the long side goes thru.  This is not like a bullet, where the point goes thru first.

Ie, the long axis of the eslipsoid is verticle.

This is because I use a sidearm technique, and the pocket holds the stone in verticle position, as  it is also released.

Title: Re: Significant projectiles
Post by Almulek on Oct 29th, 2004 at 2:57am
Matthias,

Your program sounds great!  You are very ambitious.  Are you going to make it available?

Title: Re: Significant projectiles
Post by Matthias on Oct 29th, 2004 at 12:04pm
Of course! That was mostly the point. Still working on a few interface bugs, but you guys will be the first to know when it's ready for play...

No attitude control for the short term at least... Same with spin. I agree that they would both be useful additions but things start to get complicated with lift forces. It will be there eventually, particularly because I don't like the approximation that the glans flies point first for the entire trip. If it is thrown point first at 40deg, with spin, it is going to be 40 degrees "nose up" (almost 70 relative to flow) be the time it lands. In between we've had regions of zero lift, "gliding" flight (big range boost here) and stall. Doing the calculations for _one_ projectile is pretty "easy" but doing a 6 dimensional fit so that any input value are accepted takes more work!

I'm serious about the call for projectile though guys! Let the suggestions fly!

Matthias

Title: Re: Significant projectiles
Post by Hobb on Oct 29th, 2004 at 4:26pm
I'm in awe of your programming abilities...  Not to mention your grasp of physics!  

As for projectiles -- I vote for snowballs!  Tennis balls would also be good to include, since many of us city slickers are restricted to those (they keep fencing in all my best slingin' spots!)  

Truly and amazing project.  Good luck!

Title: Re: Significant projectiles
Post by Gun on Oct 30th, 2004 at 11:39am
My modifyed golf ball. It is 4 oz and is just a hollowed out golf ball.

Title: Re: Significant projectiles
Post by Matthias on Oct 30th, 2004 at 11:46am
Nah, that is an easy one to for a user to enter as everything but the weight is the same as a regular golfball, so you just choose the gb from the menu then change the material...

Snow is a great idea for a material (you choose the size), though as one whose been hit by my fair share of slushballs (nice wet snow here on the coast) I'm not sure about what to pick as a "standard" for density...

I just remembered eggs, so that one is going on, and I have tennis balls already. Interestingly, the sim throws a tennis ball further than I would have thought possible. I'm pretty sure that my real world trouble with those things is lack of initial speed... something to check out. Maybe a weighted pouch would help get them up to full velocity?

Matthias

Title: Re: Significant projectiles
Post by Novice on Oct 30th, 2004 at 12:37pm
how about mouse balls?

Title: Re: Significant projectiles
Post by Yurek on Oct 30th, 2004 at 3:07pm
Yeah. It's very difficult to simulate tennis balls or similar ammo. Due to their small desity, the ranges strongly depend on the spin and "shaggines". I see the clear difference beetwen new tennis balls and those tousled by my dog. The wet ones also fly further, and give a nice aerosol tail. Moreover, if I use the tennis balls wraped tight and smoothly with duct tape, I can even surpass the 100 m (110 yards) distance with them and my short 27" sling, what is absolutely impossible for me with naked ones. The wraped tennis balls look pretty nice, like silvery cannon balls.

Matthias, what about ice-balls formed inside dimidated broken tennis balls? Something like these David's concrete balls but made of water. Their density would be pernament.

Jurek

Title: Re: Significant projectiles
Post by Matthias on Oct 30th, 2004 at 4:55pm
Duct tape has to be cheating ;D as it changes the weight significantly... wet balls too. How about burning the "fuzz" off with a torch?

Ice is a good addition.

What's a mouse ball? - oh, think I just figured it out. Nice ammo to be sure, though maybe a little delinquent.

Matthias

Title: Re: Significant projectiles
Post by lobohunter on Oct 31st, 2004 at 1:26pm
so how about six ounce lead egg sinkers at 25 yards

Title: Re: Significant projectiles
Post by Hondero on Nov 1st, 2004 at 3:28am
Hmmm... may I suggest to restrict the calculator to proper slings projectiles? ;D  Are we playing golf, tennis or throwing eggs to a bad speaker? Of course all this is very funny and every body has done it sometimes, but to simulate it as if it was a proper slinging modality is too much in my opinion  :P
What about to consider these sort of materials: common stones (limestone, granite, basalt, etc), clay, cement or concrete, lead, metals(iron, bronce, etc).
And about the shape: spherical, ellipsoide(various ratios), irregular(typical stones from railways).

And like significant projectiles  I think historical ones are are the best samples:  average Roman glans, Balearic stone (1 mina), Neolithic clay proyectil, Medieval stone projectil, etc.

Well, is only an idea. All depends of what we want to make, a professional calculator or an internet game  ;D  

Title: Re: Significant projectiles
Post by Matthias on Nov 1st, 2004 at 2:21pm

wrote on Nov 1st, 2004 at 3:28am:
Hmmm... may I suggest to restrict the calculator to proper slings projectiles? ;D  ........
......common stones (limestone, granite, basalt, etc), clay, cement or concrete, lead, metals(iron, bronce, etc)......
spherical, ellipsoide(various ratios), irregular(typical stones from railways).

And like significant projectiles  I think historical ones are are the best samples:  average Roman glans, Balearic stone (1 mina), Neolithic clay proyectil, Medieval stone projectil, etc.


I'd have to argue that golf balls are a proper sling projectile for a lot of people! Particularily for those in the city. The calculator is quite flexible, and you can input any value you want. The idea of the library is to store some presets for people to work with. I'd like for someone to be able to take a few "standard" ammo types out to a field and measure their range, working back to launch velocity - then use the sim to check out what their "potential" is with true-slinger glandes! I bet we'd see a spike in glans casting posts! ;)

I have a materials list that includes most of the ones in your suggestion. I'll expand the stone category to include more types.

The sim is restricted to spherical/ellipsoidal projectiles (on axis) for the time being :(

I completely agree about the value of the "historical projectiles" category! Are you able to post some characteristic properties?

Matthias

Title: Re: Significant projectiles
Post by KnollSlinger on Nov 1st, 2004 at 6:10pm

wrote on Oct 30th, 2004 at 3:07pm:
Yeah. It's very difficult to simulate tennis balls or similar ammo. Due to their small desity, the ranges strongly depend on the spin and "shaggines". I see the clear difference beetwen new tennis balls and those tousled by my dog. The wet ones also fly further, and give a nice aerosol tail. Moreover, if I use the tennis balls wraped tight and smoothly with duct tape, I can even surpass the 100 m (110 yards) distance with them and my short 27" sling, what is absolutely impossible for me with naked ones. The wraped tennis balls look pretty nice, like silvery cannon balls.

Matthias, what about ice-balls formed inside dimidated broken tennis balls? Something like these David's concrete balls but made of water. Their density would be pernament.

Jurek

how about tennis balls soaked in gasoline and thrown thru a flaming hoop, thus setting them alight at the start of their journey?

Title: Re: Significant projectiles
Post by Yurek on Nov 3rd, 2004 at 7:38am

Quote:
how about tennis balls soaked in gasoline and thrown thru a flaming hoop, thus setting them alight at the start of their journey?


We would get pretty nice comets. A haystack behind would be a nice addition ;D

Title: Re: Significant projectiles
Post by Hondero on Nov 3rd, 2004 at 12:41pm
Matthias wrote:
" I'd have to argue that golf balls are a proper sling projectile for a lot of people! Particularily for those in the city"

Well, I agree golf balls are good sling projectiles, though a little light. In Australia they play a golf modality called cross-golf, or something so, and they use elliptic golf balls that are better for the sling. The versatility of the sling allows to use any kind of projectiles, and along the history they have been used many types according the circunstances or the availability of materials, being the most common the stones, and the best one the lead glandes.
If the sling were a modern sport it woul have an exclusive projectile, like in golf, baseball or tennis, and I wonder whow woul be such a projectile. Maybe the standard would be a cheap, heavy concrete ellipsoide, and of course another special for range made of lead. Then nobody would be trying tennis balls or golf balls, in the same way golf or tennis players donīt try stones or lead glandes :P. That doesnīt means that there is not a lot of fun throwing such funny things like eggs, potatoes, bottles or cats and dogs ;D... but to simulate it in a calculator or to train usually with them I think is to be a little  disorientated about what a sling is. Only in a first learning it would be excusable to use soft projectiles like tennis balls, etc.

Well, I think this opinion will have many objections, so Iīll stay on waiting some tennis and others softballs thrown against me ;D

About historical projectiles Iīll try to define and average  for each one, though they have been used differents designs and weights and itīs not an easy task  ::)

Title: Re: Significant projectiles
Post by Hobb on Nov 4th, 2004 at 4:22pm
I agree that historically accurate projectiles and rounded stones are the best ammo, and should be thought of as the 'proper' ammo for slings, but there are other considerations.  Slinging as a modern sport is still in it's infancy.  Heck, it's still in the fetal stage.  Lots of folks don't have access to areas where the 'real' ammo is safe to use.  Others live in areas with odd or irregular-shaped rocks and don't have the skills or resources to start making their own lead glandes.  It's a little like skating in America.  At first, skaters had to use parking lots and sidewalks, which served as the basis for lots of the tricks the professional skaters use today (hopping up stairs or curbs, sliding down rails, etc.)  There were no 'proper' places to skate, so they had to contend with rough terrain, security guards, traffic, etc.  Now their are skate parks springing up everywhere.  With slings, I think we have to sling whatever and wherever we can until we get some recognition, which comes from encouraging others to sling whatever and wherever they can.  Besides, if the only place you can sling is the city park, and so the only ammo you can use is tennis balls or snowballs, it's still nice to have some kind of guide to tell you about how far you can expect your shots to go.  I think this is an outstanding project!

Title: Re: Significant projectiles
Post by Hondero on Nov 4th, 2004 at 6:08pm
Hobb,
of course that one can sling whatever and wherever he wants and especially when he have problems to find the proper ammo and place, as being the sling an incipient sport there are not  specific courts and standardized ammo avalaible, as you say. Itīs just that Iīve practise many years with the sling and sometimes forget that it is not comparable with golf or baseball, and I would like to use a simulator like those of them that not include anything but its proper balls. But about our incipient sling sport welcome then all the help the beginners can have.

Matthias,
here is an approach to the historical projectiles, that must be understood only like "typical" ones better than averages, what is very difficult to calculate without a extensive data collection and otherwise has no much sense as there are many shapes and measures for each type.

NEOLITHIC:
Shape: ellipsoidal 2:1 or biconical.
Material: Clay
Measure: 5.4 x 2.7 cm.
Weight: 35 gr.

BALEARIC:
Shape and Material: natural stones, spherical or ellipsoidal low ratio.
Measure: 7 cm aprox.
Weight: 436 gr. (1 mina)

ROMAN GLANS:
Shape: pointed ellipsoide 2:1
Material: lead
Measure: 3.4 x 1.7
Weight: 60 gr

MEDIEVAL:
Shape: spherical or ellipsoidal low ratio.
Material: smooth stones
Measure: 5.5 cm
Weight: 225 gr

PACIFIC ISLANDS:
Shape: pointed ellipsoide  1.75:1 (lemon shape)
Material: basalt
Measure : 5.5 x 3.15
Weight: 115 gr


Hope it will help :)

Title: Re: Significant projectiles
Post by Matthias on Nov 4th, 2004 at 11:33pm
Thanks Hondero! Now I'll have someone to pin the err.. uhm..

"But Hondero said that such and such was shaped such a way!"

;D

That's a good list though. I'm thinking I might need to include a picture of the representative glans in the menu or at very least a short description for future users who might not be familiar with the different types. I'm trying to keep this uncluttered - maybe I can have "mouseover hover" stats for the different glandes.

More work this weekend - updates promised.

Matthias

Title: Re: Significant projectiles
Post by Hondero on Nov 5th, 2004 at 4:05pm

wrote on Nov 4th, 2004 at 11:33pm:
Thanks Hondero! Now I'll have someone to pin the err.. uhm..
Matthias


Yeah... well, one must accept his own responsabilities  :-/

Itīs a good idea to include a picture of each projectile type. About Balearic one, Vicente posted good pictures of the local stones they use, one of them was around 400 gr and match quite well the ancient projectiles of one "mina".
The Pacific projectiles are all very similar and you have one in the Home page and others at the end of the Gallery, I think. As for Roman glandes, there are lots of pictures, I can send you hundreds, mainly this typical I said. Clay glandes pictures are also available, Iīll look for someone. And about medieval smooth stones nobody could diferenciate a modern one  ;D. When I have the time Iīll try to make a "collage" with all the types in an only picture to compare the sizes and shapes.

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