pic: "You should never go against a robotics kid"
 

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"You'll shoot your eye out, kid!"

(yes I watched A Christmas Story recently)

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That thing make the most awesome swishing noise when it fires. It was like a knife through air, and was one of the quietest catapult there, though it went the furthest.

It uses a 25/32 inch steel axle and car bearings.

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yeah there a big spread in most tech class projects from robotics kids a not yet robotics kids

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A video would be awesome (if possible)

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I've died and gone to surgical tubing heaven.

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I have a few videos from testing, but i need to get them on my computer, so i will problably upload them to youtube by the end of the week.

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Not to be stickler... ok, yeah, I am:) . That thing looks a lot more like a trebuchet than a catapult. Remember, engineers must always be precise in communication.
:rolleyes:
Anyway, awesome job! The physics classes at my kids' school also have a project to build a "device" to launch a tennis ball and hit a target 20 feet away (30 for honors, variable distance for AP, accuracy counts) Requirements were 2' x 2' base, no part may extend above 1 meter at any time. last year, one of the classes put a spin on the project and said shoot as far as you can, bonus for more than the minimum distance. One of the robotics kids built a monster device that fired a tennis ball well over 250 feet (tennis balls don't fly as well as baseballs). Kids are still talking about that catapult.

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If you don't want it banned, you should have the project changed so that the students not only have to go 40-50m but also have to hit a target at that distance. That way the hard physics of calculating and attaining the necessary final speed and launch angle is thrown into the mix while also keeping such a valuable learning project in the curriculum.

This begs the question, 'Is it better to be famous, or infamous?'

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It's not really a true trebuchet either. Trebuchets use counterweights to throw their payload, this uses surgical tubing. This does appear to use a sling however, which is a staple of trebuchets. IMHO, it still qualifies as a catapult.

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http://en.wikipedia.org/wiki/Catapult

Nope, its a catapult but at the same time it is a trebuchet as well. Think quadrilateral -> square. Catapult is the generic term.

I would argue it is a trebuchet because it is essentially using the tubing to act as a weight.

Also, very slick, makes me wish I had known how to do that sort of thing during high school.

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I would suggest to the administration to simply change the projectile. Tennis balls, oranges, and racquetballs are a bit softer. How many projects do schools offer that teaches THIS much and is also fun to do?

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OK if we go with the Webster definition of catapult "an ancient military device for hurling missiles", then yes all trebuchets are catapults (but obviously not all catapults are trebuchets). That would then mean that all missile throwers are catapults, including ballistae, onangers, mangonels, and even more modern weapons like howitzers, cannons, rifles, pistols, magnetic rail guns, FA/18 jet fighter...... All of these devices hurl missiiles. (though not all could be classified as ancient).

But if we look at Webster's definition of Trebuchet "a medieval military engine for hurling heavy missiles (as rocks)" there is little difference. It would appear as though the two devices are the same. I attribute this discrepancy to laziness on the part of Webster. I still think a catapult refers to the traditional definition of on arm with a basket on the end that rotates about a pivot until it hits a stop, thereby propelling a projectile forward.

But I have been told to sit down and shut up before, I expect I will be again.;)

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I wouldn't tell you to sit down or shut up, clear concise communication is important and using the correct word can often make things much easier. :)

Though, I think your definition of a catapult is more accurately a Mangonel or an Onager. I believe the typical view of a catapult is one of those two. From some quick reading I think the main difference between the various catapults was the trajectory they launch their projectiles at. A trebuchet had a very high trajectory whereas a Mangonel had a low trajectory.

Sorry to be getting so off topic. Im a huge history nut.

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I just got done with one of those....we were outside in the rain, then later snow, at midnight the night before, changing the entire throwing arm,trying to figure out how to attach the weights, and how to trigger it with a mousetrap. We had to shoot a golfball, and we had to shoot it 4 meters or more to get the full points, and we had to trigger it with a moustrap.

I like building things, but this was terrible!!!! We actually got our total grade back today, and we had a C- overall, out of the 200 points. It was 10%of our grade, too. I was kind of upset, and our technical report is actually where we lost most of our points...

Yours looks pretty good. We had to have a theme, too. Ours was "Jankapoult";we had caution tape all around it, too, partly as a joke, but partly because we really didn't know how safe it was and our teacher is 8 months pregenat!

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...3 kids from 1501 (non-school sponsored team) were finally allowed to be in a group together in our schools engineering class. It was the first time the teacher let us choose our own groups. It was 1 mechanical, 1 electrical (me), and 1 design student. The task was to demonstrate a usage of pneumatics. We could recreate something using paper, or any other building material. So while most kids used the manual valves, Our group was the first in the classes history to actually use the solenoids in the kit. We did not have a programmer, but i managed to figure it out in a couple of minutes...:D
Anyways, while most people made something simple like the outriggers on a bulldozer, our group made a pneumatic claw! It was massive compared to all the other projects, used more solenoids than our last 3 bots combined...and used 2 controllers because the schools could only handle 4 motors/solenoids a piece. It could pinch. move outward/inward, and tilt up and down. I will try to remember to snap a pic of it tomorrow... If you can see it lol, its made out of awesome clear plexiglass:rolleyes:

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Technically the lack of a counterweight does not disqualify this as being a trebuchet... rather it puts it in to the category of the traction trebuchet. http://members.iinet.net.au/~rmine/htt/htt02.html

Jason

Re: pic: "You should never go against a robotics kid"
 

First, however we define what this creation is, it is wickedly cool. I wish I had a class like the one you built that in... and team members to build it with.

I believe these definitions are far too vague to get a good definition (just as I would never define "justice" by a Webster definition; it's good for a quick reference, but for anything remotely technical, it is lacking). For the sake of rapid research, I'm going to use Wikipedia's definitions:

Catapult is defined as "any one of a number of non-handheld mechanical devices used to throw a projectile a great distance without the aid of an explosive substance;" this invalidates the examples of Howitzers and does include ballistae; originally, catapults referred to "ballistae" and ballistae referred to "catapults;" the definitions switched, but it can apply to either as long as it does not use explosives.
This is an example of a catapult.

Trebuchet includes the following: "trebuchet is often confused with the earlier and less powerful torsion engines. The main difference is that a torsion engine [ie mangonel or ballista] uses a twisted rope or twine to provide power, whereas a trebuchet uses a counterweight" and it continues to state "A trebuchet also has a sling holding the projectile, and a means for releasing it at the right moment for maximum range." and "Both trebuchets and torsion engines are classified under the generic term 'catapult,'."
This would appear to be a torsion engine, or a "torsion trebuchet;" however, that is not the normal context of the term "trebuchet."

I would argue that this is a torsion engine but not a trebuchet, for a trebuchet uses a counterweight, whereas the surgical tubing more closely matches the twisted rope used to power many catapults, such as mangonels and onagers.

I apologize for the length of this post, but I love both debate and medieval weaponry... This is not a confrontational post, it is just my viewpoint on it.

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You're fighting over whether this is a catapult or a trebuchet? I feel you time and effort is being used as well as if it went towards the game hint.

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Game hint? you mean the picture of a fish? The one that has a topic with over 700 posts discussing a picture of a fish? what else can be said about a picture of a fish that hasn't already been said? This catpult / traction trebuchet is a whole lot cooler, and is much more interesting.

Re: pic: "You should never go against a robotics kid"
 

the trebuchet is probably also more relevant to the game then the fish also:rolleyes:

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It's a trebuchet with a twist

;)

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A torsion engine stores energy through torsion or twisting of something (usually ropes). The catapult pictured stores energy through the stretching of the surgical tubing, not twisting.

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I agree Barry! I think, however, before the decision is made extensive testing is needed. I propose setting up a "splatter wall" and flinging all kinds of fruits at it to see which one makes the prettiest pattern. (oh yeah, and safest).

Dave, can you spare a banana or two? :D

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Catapult/trebuchet/launcher throws the fish across how far???

Hey, could you guys find an opah and launch it, just to relieve everyone's stress around here (and discussion of the game hint)?

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how did you make it realease on end of the sling at the right time? or was it just try-bend?

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If you look closely at the picture on the right (the CAD does not have it) there is a piece of 1/4" aluminum coplanar to the main arm that has a slight V shape cut out. The release angle wasn't perfect (was about 35 degrees I think) but it was good enough. And since it was luck that it went at that angle on the first try, the group decided to just keep it that way.

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First of all, I don't think anyone is "fighting" over anything. There is a polite, rational discussion going on as to the appropriate terminology to use when referring to this design. Precision with words is equally as important as precision in drawings, or in machining. Often it is more important!

But I do appreciate the humour in the statement.

Jason

Re: pic: "You should never go against a robotics kid"
 

I think we decided to call it a "Catachet"

Sounds French...

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Or a "CAD-achet."

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my school security guards flipped out when we were test firing our robotic t-shirt cannon because they thought it was a weapon so we arent aloud to make stuff like that anymore lol. great job by the way... i sure wish i had one;)

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Lol, that's why you should usually let school admin know what you're up to with stuff like that :p

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Our school actually asked us to build a t-shirt cannon for rallies, and they actually reimbursed us on the cost of the parts, so that was pretty cool.

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RE: What it's called?

First of all, I call it "cool"! :)

Trebuchets were the ultimate development of the stationary flinging-arm military weapon, but by the 14th century they were being overtaken by early cannon. Since no one alive now speaks a 14th century dialect, we are unlikely to be using the proper name in 21st century English, especially since I doubt medieval siege engines used in probably dozens of different kingdoms, duchies, and counties were all called the same thing. I believe were are applying our modern passion for rigid definitions to devices created in a time where no such cladistic hegemony existed.

Re: pic: "You should never go against a robotics kid"
 

Not entirely sure but i believe the term was changed during the Mongolian rule of Central Asia... or at least the Khan or Seljuk Turks created a different type and changed the terms..:confused:

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doesn't a trebuchet have a mass one one side of its arm instead of surgical tubing?

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Well, what people have been saying is that a trebuchet uses a weight and not a spring, so it sholud be called a catapult, but a catapult doesn't have a sling, so it should be a trebuchet.

let's just call it a "Catachet"

And the video should come soon, Bannanakin is (attempting to) upload it to Youtube.

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I really hope that that CAD was not made in Inventor provided for FIRST....
(That may violate the EULA! Oh Noes!)
Sweet "Catachet" though!
Maybe our team should make an pneumatic catapult...

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I don't believe that would violate the EULA for the FIRST provided inventor. I haven't used it in a few years, but IIRC it's simply the educational version which means that the only restriction is that you are not allowed to use it for any commercial products (ie anything you would be making money off of). This is clearly a non-commercial product.

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The CAD was made using a student edition of SolidWorks.

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The video has been uploaded to YouTube!

http://www.youtube.com/watch?v=p0vZhZob9lk

We will probably take some better videos (ones where you can actually see the ball) over winter break. Also, we'll try to take some at 240 fps (the max my camera can handle, though I think we need a higher frame rate) and slow it down.

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Based on the testing data, you logically now need to put an infinite number of loops of tubing on it.

Re: pic: "You should never go against a robotics kid"
 

building on that, you may want to replace at least some of the wood with metal for durability reasons. (eventually, the wood or the metal will fail)

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call discovery channel and get the guys at time warp

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seconded

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I've never heard of that show before and I just watch a bit of it at discovery.com. It's really cool. We'll see if we can get this on, and see how inefficient our release angle is!

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Awesome. That definitely puts my Vex ping-pong ball launcher (but actually robot altitudinal booster :ahh: ) to shame. I wish we did stuff like that in my physics class. I third the recommendation to get it on Time Warp, that's exactly the kind of thing they'd do. And you know you've done a good job on something when you're the reason administrators try to ban it.

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Haha, yeah. I head the teacher talking today, and he said that he wasn't worried about safety with this particular catapult or the safety practices of the group, but in the future, who knows what dangerous contraptions less experienced groups would make, without proper safety training?

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Any chance you would release the SolidWorks File

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My Gift to u

yes i am trying to make it

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Nice work on the CAD so far.

Just FYI, the vertical posts that are in the actual picture but not in the CAD is a safety feature added later in the design process. After the arm is pulled back, a bar goes through the two holes in the two upright bars. This is so that so while someone is hooking up the quick release, if the people holding the arm back accidentally let go, it won't do a full swing.

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I have an outdated .stp file. I'll talk to Bannanakin, who has the most recent one.

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Ours where a little bigger...

Great cad, you guys got skills. 500lbs!

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If anyone wants the cad, they can private message me their email, or IM me on aim, and i'll send the cad. I can send any format that solidworks 07 will create. I know it makes .step, .sldasm (of course), and .x_t. Those are the most common formats that I use.

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I did it this is really cool.. the animation of it swinging is spectacular :ahh:

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In my physics class last year we did a similar project, but instead of baseballs we used water balloon. Its almost completely safe in terms of injury from the projectile. I was the only robotics student in the class and my group's sling shot ended up setting the all time school record and put the water balloon around 135 m out.

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Gesundheit!

That name has a certain cachet to it...:P

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I would have to disagree with you on the safety of a water balloon. A friend of mine took a hand thrown water balloon to the eye and, if I remember correctly, ended up with internal bleeding. It was not pretty.

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sorry, idk if anyone actually already said that, but i think the proper term's a trebuchet. lol...still pretty awesome.

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yeah, we had a long discussion about it (see like the first 10 posts) just call it a "catachet"

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Smart school, very smart. They understand partnership, promotion, supporting students interested how things work and like to build them, and fun. They also understand the value of a product. Smart.

Don, I just read your very bad pun. It rocks!

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My family makes puns all of the time, but even by our standards, geez, these are bad! And for reference, the term "almost completely safe" can always be disproven. There's blood on the sidewalk at my middle school from when I did a video project with rubber chickens. If there's enough force to hurl a couple of pounds over a football field's distance, there's enough force to cause damage.

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If these are bad, you haven't been around long enough. (There are some threads that were, for a while, almost solid puns. There are about a half-dozen people that you don't give a punny topic to, because they will go after it to the full extent of the humor.)

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(emphasis mine)

Making a good point, and something we always need to keep in mind, we can think that because the robot is only shooting tennis balls (you never know) that the shooter can't hurt us. If something is moving you need to be alert, and you need to make sure you take all precautions.

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If it doesn't rain tomorrow, we will be shooting some video of the "catachet" in high quality and at 240 fps.

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Hey, everyone!

We shot some slow motion videos (it moves so fast that it's still not that slow...), and we found that the catapult isn't even close to being optimized. We we hope we can push another 50 meters out of it.

See the video here:

http://www.youtube.com/watch?v=XqCeL_rW88M

(you can click "Watch in HD" on the bottom right for better quality)

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sorry to butt in and sound like a nerd, but it's a torsion catapult. if you look at Da Vinci's designs thats how it's labeled, and he's a bigger nerd than i ever will be.

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catapult is a very non-specific term.
there are many different types and forms of catapults:
-Trebuchet:
----Floating arm
----Fixed arm
-Torsion catapult
----Balista, Scorpion, etc. as well as the stereotypical 'catapult'
-Steam catapult
----launch aircraft off short runways
-magnetic catapult
-etc.

all of these fall under the category of "CATAPULT"

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I was watching your slowmo vid and I had a sugestion or two. I built a true trebuchet with a free swinging counterweight of over three hundered lbs. I had some issues with rocking, and seeing as the thing is 16 ft tall I did not want it tipping over. After I added wheels and not only did it stop the treb from rocking it also increased the throwing distance by about 40 ft. Idk if it will increase your throwing distance, but it will stop some of the shaking that you could see in the last frames of the video. By the way I used wheels that were intended to be used on the Regolith, but were damaged while using them on our shop's floor. They come with nice bearings, maybe you have some extras tying around too.

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You mean like this? :P
http://www.chiefdelphi.com/media/photos/32412

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Yup exactly like that. Did it change your throwing distance at all?

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Those wheels aren't actually attached. It was a robot teaser.