# Oversized slingshot questions...



## Nanno

I hope this is the right forum for this...

I recently lost a tree to pine beetles, and it's forked very nicely to turn it into a slingshot. The fork starts about 5 feet above the ground and the forks are about six or seven feet long now that I've cut them down to size. I want to launch pumpkins and rotten melons into our horse pasture with this thing. I'm thinking we'll need a couple of people to pull it back properly.

So... what should I use for the pouch? And what should I use for the rubber band?

Do you think a slingshot that has to be pulled back manually will be strong enough to fling something as heavy as a pumpkin? I can't use the tractor because the lay of the land prevents getting one up there.

If you don't think that 2 people pulling would be strong enough to launch the pumpkins very far, is there a safe way to rig up a kind of winch or come-along to pull the thing back? How would we build a trigger?

Thanks for reading. I hope ya'll can help, cause I think this thing is gonna be a blast if we can make it work! =)


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## treefork

Be careful. A return to sender could be dangerous


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## Sunchierefram

Well, I don't really have any tips but good luck on this!


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## Nanno

Nice video! I shall endeavor not to backfire my slingshot and whack myself in the face with a rotten melon! However, it looks like she survived the experience and now has a fantastic video to show for it. :rofl:


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## Sunchierefram

There are topics on this forum about how to not get RTS shots. You'll probably find them pretty useful.


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## BlackBob

I think for Pumkins I would have to use something like this and not a fork.


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## Nanno

Yeah, but I don't have something like that growing in my yard.


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## mastersedge

check out jeorg sprave videos on youtube, might get some good ideas there.


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## Imperial

make a 3 person water balloon style slingshot . attach tubing to the fork and make a pouch out of a welders bib or of the same type of material that is used to make the slingking water balloon launchers. if you make one similar, once attached to the fork it will be easy to pull by yourself, as long as the fork is securely anchored. just think- angry birds style.


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## Sunchierefram

Imperial said:


> make a 3 person water balloon style slingshot . attach tubing to the fork and make a pouch out of a welders bib or of the same type of material that is used to make the slingking water balloon launchers. if you make one similar, once attached to the fork it will be easy to pull by yourself, as long as the fork is securely anchored. just think- angry birds style.


One of my friends got a rock to the eye using one of those. He said that he and his friends were using a water balloon slingshot, but they ran out of water balloons, so they started using rocks. Which he said worked pretty well until one got caught in the pouch and swung back, hitting him in the eye. Luckily for him, all he got from it was a black eye and a good story to tell from summer vacation.


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## Imperial

Sunchierefram said:


> One of my friends got a rock to the eye using one of those. He said that he and his friends were using a water balloon slingshot, but they ran out of water balloons, so they started using rocks. Which he said worked pretty well until one got caught in the pouch and swung back, hitting him in the eye. Luckily for him, all he got from it was a black eye and a good story to tell from summer vacation.


i hope he was using safety glasses. ive put rocks in mine also. ive always wanted to put a molotav cocktail in one . :devil:


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## Nanno

Welders bib... that's a good idea. Yeah, the fork is anchored very well... it grew out of the ground and has excellent roots. 

We'll probably avoid things like water balloons and definitely won't be launching rocks. I'm doing this over a horse/goat pasture, so I want anything I launch to be edible and not spark if I hit it while mowing with my bush hog.


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## gbeauvin

We need pics of this fork! Sounds like fun .

-GB


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## Sunchierefram

Imperial said:


> Sunchierefram said:
> 
> 
> 
> One of my friends got a rock to the eye using one of those. He said that he and his friends were using a water balloon slingshot, but they ran out of water balloons, so they started using rocks. Which he said worked pretty well until one got caught in the pouch and swung back, hitting him in the eye. Luckily for him, all he got from it was a black eye and a good story to tell from summer vacation.
> 
> 
> 
> i hope he was using safety glasses. ive put rocks in mine also. ive always wanted to put a molotav cocktail in one . :devil:
Click to expand...

Nope. He wasn't wearing safety glasses. I'm pretty surprised that all he got from it was a black eye. But he did say it was bleeding pretty badly and that he had to go to the hospital. So basically, the moral of the story is: wear your safety glasses when shooting!!!! You have 2 eyes! Keep them!


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## jazz

Hi Nano and all,

What is the average distance you want to reach with the pumpkins/melons?

What is an average of their mass and diameter, or, the most likely range?

How many times a day/week you will do this feeding and what number of projectiles (pumpkins..) you intend to fire on average also?

I aks this because I think that these parameters and the initial speed are basic for the most important estimation in your problem an it is the energy/power needed to fire those things, and for some other considerations.

cheers,

jazz


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## Nanno

Here are some photos of our fork and the pasture.









I had my husband stand next to it for size reference. Phil's pet goat, Cuzco, is helping. He can't wait till we start launching edibles into his pasture!









We probably won't use this very often--mostly at family get-togethers and when we have a group of friends over. I'm guessing not more than about a dozen or so times a year at most. I'll probably remove the rubber when we're not using it so as to make it last longer--we have very intense sun up here--and to keep it from being an animal chew toy or entanglement hazard.

Items would be launched several hundred yards (I think). I haven't officially measured the distance from here to the fence line, but I know it's further than it looks. The tree in the background near the left fork in the first photo is where our fence line is, and that tree is massive. Heck, if it were possible, I don't think our neighbors would mind if we launched rottables/edibles across the fence into their pasture as long as the animals aren't there at the time. We would obviously never risk hitting an animal with this. I don't want anyone to think we're planning to be irresponsible or cruel.


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## Imperial

here's one idea. video shows how they went about making theirs. looks like they are using some latex tubing from a local hardware store. i would've used more tubing length, so i wouldn't have to struggle in reaching up to re-load. personally,i wouldn't use duct tape for the pouch. they got some nice distance with theirs. -


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## Individual

Hi there.

First of all i would trim the forks.

The higher the forks the more stress on the forks, and the ground.

Next i would choose your options for rubber, pouch etc etc.

I personally would probably go for drilling 4 holes in the tree and then having 2 sets of looped 1" surgical tubing

As for the pouch thats up to you, but be carfeul

I know especially with bigger projectiles RTS's can be fatal and are more common

I recently saw a episode of mythbusters, in which they launched multiple things.

With bowling balls and such there pouches didnt release correctly and they had bowling balls flying back at them at 40 mph or so.

You should watch the episode as it may give you some pointers.

You could find it online, not that i'm recommending it or linking it due to it being illegal.

You should cut the forks off here(the white dots represent roughly where you should cut the holes for linked tubes, on in each side:










Anyway.

Good luck with your project and be careful with RTS's and such!


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## jazz

Hi Nanno and all,

Thanks for the info, now I understand a little better your intentions although an estimation of average mass and diemater of the projectile - the pumpkin, melon.. - is still not known to me.

Anyway, there is program called Projectile Motion Simulator which you can find here: http://phet.colorado.edu/en/simulation/projectile-motion for downlaod/run.

I entered following parameters just to see some scales of some typical values:

Pumpkin Case:

angle: 45 deg

initial speed: 80 m/s

mass: 3 kg (I suposed this since there is no data in your answer)

diameter: 0.3 m (suposed, same as above)

Air resistance box checked: yes

Drag coefficient: 0.6 (arbitrarily; the round ball's drag coeff is 0.47; i guess that pumpkin is away from it but not that much either..)

The program says that such an object and under such parameters will fly:

distance: 127.1 m

time (of flight): 6.5 s

Now, since I am un-physics guy I must admit that I could not calculate the energy needed for such lounch, but I can point your attention to a more familiar situation to me and it is slingshots and try to find some paralels; so, the same program for somewhat changed parameters to accomodate glass marble looks like this:

Glass Marble Case:

angle: 45 deg
initial speed: 80 m/s
mass: 0.005 kg (5 grams)
diameter: 0.016 m (16 mm)

Air resistance box checked: yes

Drag coefficient: 0.47

Results:

distance: 103.0 m

time (of flight): 6.0 s

Now, I said that I can not calculate the energy needed to launch the pumpkin case, but I estimate that for the glass marble case above I probably stretch the TBG some 3 - 4 kilos, and if that is not true at least is not far from true.

So, if I need some 4 kg to fire a marble at some 100 meters, how much power/energy you need to fire a pumpkin which is some 3000/5 = 1500 times more mass? - I do not even dare to multiply 3.5 kg with 1,500 times because the numbers look scary, and if it is (probably) not the right way to calculate it still does point our attention to the scales involved.

Just to remind you that you want to launch those things at some "several hundred yoards". I am not native English speaker so I never figured out what "several" truly means but I guess it can be 200 to 400 yards, right? Anyway, it is close to 200 - 400 meters..

Now, all this thinking and comparing - I repeat, without formal physics education - still leaves me full of doubts.

My opinion is that you will need lot of rubber and much more people than you originaly estimated (2 times several, at least) to stretch the rubbers needed for the task as we described it above.

As other people alaredy pointed to you in their answers above, the powers involved might be enormous and the fork hits, body slaps (yeah, in normal case you would have hand slap, here you might experience body slap..) and return to senders can be realy dangerous - more probably here than with normal slingshots - because you will never - ever - be able to force a number of people to do one perfectly timed and correct release - not even if you make them some device that they can use to hold onto - all of them.

And I do not even want to think what might happen if a band/tube breaks while they stretch them at those powers: if a normal slingshot band can hurt you seriously, what can happen, then, here?

For these reasons I suggest that you go carefuly with this one, maybe some experimentation on a less dangerous scale first, with some more advice and calculation etc.

Please understand this line of thought as my concerns which are born from my simplistic logic and I place them here only because I wish you well with your project, I wish you as little disapointment as possible and no harfm at all neither to you, to your husband or to your friends.

cheers and good luck,

jazz


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## Rathunter

Sunchierefram said:


> Imperial said:
> 
> 
> 
> 
> 
> Sunchierefram said:
> 
> 
> 
> One of my friends got a rock to the eye using one of those. He said that he and his friends were using a water balloon slingshot, but they ran out of water balloons, so they started using rocks. Which he said worked pretty well until one got caught in the pouch and swung back, hitting him in the eye. Luckily for him, all he got from it was a black eye and a good story to tell from summer vacation.
> 
> 
> 
> i hope he was using safety glasses. ive put rocks in mine also. ive always wanted to put a molotav cocktail in one . :devil:
> 
> Click to expand...
> 
> Nope. He wasn't wearing safety glasses. I'm pretty surprised that all he got from it was a black eye. But he did say it was bleeding pretty badly and that he had to go to the hospital. So basically, the moral of the story is: wear your safety glasses when shooting!!!! You have 2 eyes! Keep them!
Click to expand...

I chuck rocks at roughly 180 miles an hour with a hand sling(NOT A SLINGSHOT) all the time. The two times I have hit myself, at nowhere-near full power, have left grapefruit sized bruises from a 3 oz rock.

wear safety goggles with those big water-balloon throwers, when the tubing breaks it is the world's best whip.


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