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Discussion Starter · #1 ·
Hello guys,

i am really new to all of this, i have a project to make a slingshot or catapult to launch a small ball (like a tennis ball) about 200 yards (or even more if possible) , the ball weight is 1lbs, i would really appreciate some help with the physics of this project as i have no idea about slingshots, which are the best bands to use and their ideal length and width for this kind of purpose.

i am trying to make a smaller version of this:


the device doesn't have to be exactly like that, any kind of device will do, Many thanks for your help and time
 

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I don't think you scared anyone at all. I just haven't seen anyone trying to build
something where they shoot big ammo at 2 football fields length.
I personally like to see my target and try to hit it.
 

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Discussion Starter · #5 ·
lbojoe lol, i guess the 1lbs weight will be a challenge, but the soccer ball in the video example that i posed is 1lbs too.

Devils son in law, i am actually not trying to shoot anything, the purpose is to get maximum range for a 1lbs ball like a soccer ball, i am sure the guy who built it in the video knows less about bands and the physics of slingshooting that you guys here, i am looking for some guidance so that i don't waste time and money on the wrong bands/dimensions.

thank.
 

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Id like to help but i really have no idea if the bands that i use for the ammo that i like to shoot (.177 bbs and clay shot) would scale appropriately or effectively, rubber is kinda funny. Rolls of latex flat band material can be had for like $10-15 now a days. Maybe just bite the bullet and get some and start tinkering?
 

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Hi slingdude, thanks for your reply, yea i am definitely going to start experimenting soon, just thought i'd get some input from the pros before, i was thinking about buying a roll of those latex band things, there is another video with a double band setup that really seems to launch a soccer ball easily more than a 100 yards:


are those bands also something to consider or are the latex band the way to go to get more speed/force ?
 

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Hello guys,

i am really new to all of this, i have a project to make a slingshot or catapult to launch a small ball (like a tennis ball) about 200 yards (or even more if possible) , the ball weight is 1lbs, i would really appreciate some help with the physics of this project as i have no idea about slingshots, which are the best bands to use and their ideal length and width for this kind of purpose.

i am trying to make a smaller version of this:


the device doesn't have to be exactly like that, any kind of device will do, Many thanks for your help and time
The rubber used in the video is full width old formula theraband gold. I'd estimate the length at 24 inches. The theraband looks to be two layers thick too. Joerg Sprave makes some interesting projects. Hope this helps. :)
 

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The largest ammo I ever sent flying fast with a homemade contraption was 20 mm steel ammo, and that required fairly stout bands:


Hypothetically (I've never shot with XXX-L ammo) what works for fairly standard 9 mm (38 cal.) steel ammo in terms of a straight trajectory over, say, 10 yards could be used as a viable basis to calculate the draw weight required for a tennis ball by multiplying the draw weight used for the 9 mm ammo according to the actual weight of the tennis ball. You will of course need to take into account the thickness and length of the rubber flat bands, bearing in mind that more band thickness (layers) will require more band length for the specific draw length required to optimize ballistics. Unknown territory...

Your pouch would of course have to be of a material and thickness to resist the somewhat high draw weight, and the overall design of the XL-sized slingshot for the job will need to be structurally sound to avoid catastrophic failure :hmm: . Trial and error is fine of you have a basic understanding of what wood and metal does when subjected to stress: basically, you want to make something that is stronger than it needs to be, unless of course you can get some relevant advice from an engineer. If not, maybe hide behind a tree when you try out your future device for the first time :panic:.

If ever, this is what it takes to shoot 80 mm diameter steel balls (oh, don't do this at home):

Last, but certainly not least, you may find that achieving a range of 200 yards will be challenging in view of the projectile weight (tennis balls are relatively light) and aerodynamic considerations: round ammo does not do very well here, and "hop-up" (backspin or "Magnus effect) might be difficult to achieve. A look at a top notch player like Roger Federer with his tennis racket in full swing should give you a rough idea whether a 200 yard range is feasible.

Intrigued by that last aspect, I had a look at how far tennis balls had ever been sent flying with a tennis racket:

https://www.menstennisforums.com/threads/how-high-how-far-can-you-hit-a-tennis-ball-with-a-racquet.953520/

(Quote) "the fastest official shot was 157mph by Isner. Assuming a tennis ball weight of 57 grams, a 1G drag function, a 0.56 Newton of G force, and normal atmospheric and altitude conditions, that ball would have travelled 134 yards horizontally and 91 yards vertically."

Ouch, my physics is a bit rusty these days...but OK, 134 yards. Not bad.

My 2 cents worth...but by all means, give it a try, and let us know what you come up with. Good fun...
 

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Thank you all the valuable info.

Grumblecakes: i knew about those balloon launchers but they will won't fly a ball 300 yards, i considered them too, but most people in the reviews say that the most they get is 50-100 yards, also i would like to build something portable that doesn't require a huge base to launch.

Neophyte: thanks for the info, yea Joerg Sprave makes a lot of interesting stuff, one of my favorite youtubers, he also made this:


This device is very portable, those are ideal dimensions for me, and it launches a 1.75 lbs javelin 190 yards, which means that launching a 1 lbs ball 200 yards away should be possibly in theory, but maybe the shape of the javelin is helping against air resistance too

Pebble shooter, many thanks for all the info and the links, i will try to make it as solid as possible, i think i will try flat bands first, i am thinking about buying those:

https://simple-shot.com/diy/simpleshot-premium-latex-sheet#trustspot-widget-wrapper

i am thinking about ordering the 0.8mm roll, is that a good choice or should i just get the theraband gold bands ?
 

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I have to ask: "WHY?!?!? What's the point?!?!?"

I doubt you will get a tennis ball to travel 200 yards, even if shot from a cannon, (ok, it might go that far shot from a cannon.)

A light weight projectile, especially a round ball, is limited in range by our "good friend", Physics. (He no friend of mine, that I can tell)

A light projectile loses its velocity very quickly. (have a look at some ballistics tables to confirm this)

You might have better luck with a golf ball, instead of a tennis ball or volley ball, I think they are going close to 200 yards, depending on what club hits/launches it.

Due to the draw length needed, it will not be a handheld thing, no matter what you do. It may take more than one person (or a winch) to reach full draw, too.

I can tell you this: Even back \in the days when a war crossbow had a draw weight of 1400 or 1500 pounds, unless the shooter arched his shot, it did not send the bolt/arrow even 75 yards. That bolt/arrow weighed considerably more than a tennis ball, by the way, maybe 700 grains. (there is 7000 grains to/in a pound)

Personally, I doubt what you want to do is possible,

Even the trebuchets of old did not send a dead livestock or boulders over the walls from 300 yards out. They were a lot closer than that.

Once you start scaling things up, you may find it difficult or impossible to even lift the bands, let alone stretch them...
 

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Discussion Starter · #18 ·
Hi afishhunter,

When i said size of a tennis ball, i didn't mean the weight, as i said it will wait 1lbs that's 450grams, so what i want to launch is no as light as a tennis ball, in the video i posted in my last example, the guy throws a 1.75lbs javelin close to 200 yards from a hand held one person slingshot.

as for the purpose of the project, it juts a fun project but I will also use it as a bait launcher to throw baits 200 yards in the beach, some people use compressed air cannons to achieve the same thing, but I would like to do it with a big slingshot instead.
 

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Hi Cosmo,

My calculations show that in order to shoot a ball of 6.7 cm (average of a tennis ball) whose weight is 1lbs (some 453 grams) to a range of 200 yards you might need the following:

- 58 cm of TBG active band length stretched to 2.9 meters total draw length whose total width (width of bands on both forks added) of some 43.4 cm and whose draw power in that case might be 50.7 kg.

(This is done under given air temperature, humidity and pressure and for a given power of Gravity but it is not crucial here).

The same result can be achieved by extending the length of the total draw, lets say to 3, 4 or so meters and diminishing the power (and in that regard width of the bands in the same percentage, I believe.)

These are somewhat extreme values and I am not completely sure in my calculations but I believe that they are in some credible range.

cheers,

jazz
 

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Honestly, to get a ball going out as far as you want, you might want to consider a spud gun instead of a giant slingshot. I once built a potato cannon with some college buddies and we would routinely launch golf balls (or golf ball sized veggies) several hundred yards easily with just some hairspray as the propellant fuel. Would be more compact than a big slingshot.
 
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