I saw on the news where a couple of guys, in England I believe, built themselves a catapult that can throw a person about a hundred feet and land them in a big net. They were saying it will be the new "bungee jump" for people who feel the urge to piss their pants.

I want one, and will have one, probably at the compound.

The trouble is they only showed the entire thing for a few seconds, mostly the camera focused on the guy getting thrown, numerous times.

What I need to know is: Is there anyone on totse who has the brain power to do the math that needs to be done to figure out how long the catapult arm needs to be and how much counterweight will be necessary to throw a 200 pound man 100 to 150 feet?

Maybe catapult is the wrong word, it was more like a French trebuchet, it consists of a long arm with an axle/fulcrum about a third of the length from the bottom. There is a bar/hook at the top end to drop the looped end of a rope over and the other end of the rope is a harness that the tossee wears. On the very bottom is the counterweight, then there are two more posts sunk into the ground and the axle/fulcrum rests on those. Easiest way to think of it is to hold a spoonful of something in one hand and hook your finger over the end and let fly.

So who can do the equation?

You gotta give a few more statistics then just the description

1. Distance of net from catapult/trebuchet
2. Directions (Is it behind/close to a wall for reduced wind friction)
3. Are you shot in some kind of protective ball (Thus a constant wind surface area not your body flailing)
4. Area of the net

I dont know how to figure this kind of stuff out but thats the sort of stuff you'd need to know..

BTW. I suggest against making this. I know you probably want to and if you screw one thing up... your landing on the pavement... head first.

quote:

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Originally posted by C4era:
You gotta give a few more statistics then just the description

1. Distance of net from catapult/trebuchet
2. Directions (Is it behind/close to a wall for reduced wind friction)
3. Are you shot in some kind of protective ball (Thus a constant wind surface area not your body flailing)
4. Area of the net

I dont know how to figure this kind of stuff out but thats the sort of stuff you'd need to know..

BTW. I suggest against making this. I know you probably want to and if you screw one thing up... your landing on the pavement... head first.

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Uh....thanks for your help?

You must have missed the part about how the catapult was going to be used for a 100 to 150 foot throw.

Unless you were going to throw the wall too, what effect would it have on wind resistance? Unless we were throwing people inside a building?

And I would love to hear how the area of the net has something to do with the length of the arm and mass of the counterweight.

But again, thanks for all your help....I think?

It's all a matter of torque, isn't it? A 450 N (about 100 lbs) weight on a 2 m arm gives you 900 Nm of torque. If your load is placed 3 m from the fulcrum, then you've got 1350 N of force exerted on your load.

At approximately what angle were you planning on throwing things?

I'm thinking the hook end of the arm would be in the 8 o'clock position for firing. It should release the sling at about the 1 o'clock position. The actual ballistic arc of the throw would be more of a high lob (like an elliptic) but I'll know more after I've made a scale model. The thing I was really interested in learning you have already told me.

Thank you.

the attemps and failiure method migth help also

You offering to be the first tossee?

Bah! Its just that the description that its only 100-150 feet long is sort of not enough. Alotta factors affect the person being shot. As for the net catching you. Well think of it... when the people were doing there tests they didnt fire just once on a still (no wind) day. they fired multiple times and made an area of where the object would fall!! You make a small net and you eject someone thinking they'll land on that small net is just thinking like a stupid moron that doesn't think of the risks or lawsuits. What if they hit the pavement? What if the net breaks on contact? What is they land neck first and become paralyzed (Sueing the makers ass)

Bah.. its a thread, I had an opinion, I said it!

C4era You are taking the wrong things into account here.

Basically assume a 85kg particle. Calculations should be done for a wider range to determine landing recovery requirements. But lets just start with 85kg.

The first thing one needs to know is the release angle. Knowing this one can determine how much momentum must be imparted to our particle.

This would never pass as a commercial venture over here so lets also assume that it doesn't need to be lawsuit proof.

Also the best way would be to start small and go from there. Build a toilet flinging catapult with a range of 20 meters and a trajectory angle of 50-60 degrees. I suggest an angle like this to allow for a smaller safety net initially. Then drop in a larger weight that will fling a dummy this short distance. Get this perfect and go from there.

This really is a cheaper version of human cannonballs. No expensive compressed air equipment. I like it, I'd even strap myself into one.

He just obviously doesn't get the physics of the thing. If you throw a 150 pound item from the trebuchet, barring a heavy wind (above 10 mph) it should land within a 3 foot circle just about every time. If your catch net is 30 feet wide by 50 feet long the chances of missing the net are astronomical. Only if you alter the equation will the impact area change. If you make the arm longer, add or subtract weight from the counterbalance, try to throw a heavier or lighter person, etc.

Naturally if there was a high wind you wouldn't throw. Same if it was raining, storming or there was a tornado coming, just common sense.

Now if your tossee is lighter or heavier the only thing that changes is throwing distance so you will need a longer net and it will have to begin closer to the trebuchet. So you go with a 100 foot long by 30 foot wide net. No matter what, you cannot argue with physics, they do not change.

I believe I shall start with one that will throw a 25 pound rock at least 150 feet (which is 50 yards by the way, if you think that isn't far enough for you have someone toss you that far), then I will increase the weight from there. Pictures will be on my website.

quote:

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Originally posted by Global Dominator:
He just obviously doesn't get the physics of the thing.

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*Shows his physics 30 report card*

65%!

*Walks off in other direction kicking a can wondering why it doesnt float into outer space*

okay kiddies, listen up. you can fuck around with the physics all you want, or you can look for a handly little program called wintreb. does it all. saves effort, and has a little animation of it throwing the stone with a little castle and everything. its the coolest. i would provide a link, but, a) i don't want to and, b) its a bit hard to find (it may require google.)

just remember, wintreb.

wintreb


wintreb

Careful Global Dominator, on the first fireing the bloke lofted his girlfriend high into the air, she landed about 2 metres too short of the net and spent the next 3 months in a body cast. It was on the local news early this year.

Chunkmiester

Now that girlfriend is a good sport. If she could balance a Foster's Lager on her head she would be marrying material.

ROTFLMAO!! Oooh I like her already! I wish mine was like that!!

why dont u set up this catapult in front of a lake or some big watery surface... it would be safer to test

the word catapult is used in genral the more specific term would be trebuchet i have built a few of these for class projects and self amusment .. the largest one i have made was 7 feet tall it had a counter weight of 250 pounds and a sling of about 6 feet and had a leather pouch the design is very simple you need to make two "A" frame and a sqaure base then you need to have in the top of the two A frames a berring (sp?) then you have to have an axle i find that the arm should be about 1 inch clear of the ground when it swings with its counter weights the throwing arms should be about double the lenghth the of the side with the weight on it the hook should have about a 15 degree angle upwards you should build in some sort of locking mech me i hade a eye hook in the end of my throwing arm and it had two hooks on the base then all it did was go in the middle when the arm was broght back and you just had to have a pin in there attached to a rope it isn't to hard to make one i made one when i was 8 for a school project that throws 5 pound lead fishing weights across the room ... lol i put two holes in the wall

here is a very good site that i think you may enjoy that will help you alot
http://www.ripcord.ws/