Suggestions needed for engineering project
 

Look, before anything, I'm not trying to be a leach and steal anyone's ideas, Im plainly asking for genuine suggestions for me to use in order to make a cannon thingy that will be able to launch a marble, accurately at distances over 3metres. Now, I'm a bit clueless how do I even start to construct this thing, so I'll appreciate everyone's input.

Here's my current thought - Use a small tube, with a spring in it, and then just push the marble into it, and use some thingy to hold the spring in a compressed position, and when its set, push some other thingy as a trigger, decompressing the spring and launching the marble. At the moment, I haven't come up with any diagrams yet, but thats roughly what Im looking to construct...if any of you guys have some spare diagrams to share, then god bless u.

I'll update on the progress, until then, chiow.

Sounds like you're taking and introduction to engineering class.

I'm thinking compressed air-- you could do a lot better than 3m.

Just kidding. You could poke an eye out.

The spring idea seems good. Not sure one would really need diagrams for something like that. Measure the marble diameter, find a tube with a slightly larger diameter, go buy a bunch of springs, figure out the trigger mechanism...

Good luck.

How accurately? Also, accurately as in you're lobbing it, or accurately as in you're shooting a target? If you're shooting a target, compressed air is definitely where it's at.

What's your budget? For probably $20 I can help you build what amounts to a mini potato gun that will put a marble through a piece of plywood at 3m.

If you have to lob it, I'd say make a trebuchet. It's easier to calibrate and more consistent than springs.

I don't have to necessarily lob it nor shoot it, the marble just have to hit the target http://www.caamuseum.org/images/Target_05_75_PMS186.jpg

Budgetwise, I'd say I'm willing to spend to 200 bucks if that would make me the perfect marble launcer.

And thanks twisted for the trebechut suggestion, I'll look into it.

How many shots do you need to be able to fire?
What is your desired rate of fire?
Is this for a class or just for fun?
How much prefab equipment are you allowed?
Is this freestanding or can you hold it and aim it like a gun? Any triggering requirements?
Also, I'm still unclear...target on the floor, target on the wall, or 3d target?

$200 is way way too much for this project, but glad to know we've got a budget.

So you want to build a gun? What kind of limitations are you up against?

1. how many shots? as many as I want, i guess, but one at a time.
2. well, one at a time
3. For class, and stands for 50% for the final grade in the whole subject.
4.What's prefab? Donno, and the teacher won't care, as long as it works as it should.
5.Should be on the floor, and I'm still clueless about the trigger mechanism, that's what I need help the most on.
6.Target is on the floor, on a paper with the circles like in the pic, never seen or heard of a 3d target.

Thanks:)

The trigger mechanism is the simplest aspect of the problem.

For a floor target, a trebuchet or similar device is likely the best option. Are you being graded on accuracy, precision, both or neither?

So you're trying to land the marble as close to the center of the target as possible? Does it have to stay there? How big is the target? How many shots are you allowed?

The mechanism I was going to suggest involved a high pressure air tank, a breech barrel, a large magazine with 10-15 shots, and a quick flow switch. This would have been capable of punching a marble through a car door, though, and is totally inappropriate for your application. Specificity is your friend!

For you, though, I'd suggest buying a $4 nerf pistol called a NiteFinder, tearing it down, analyzing how it works, and duplicating many of the concepts in it.

yep, i would say trebuchet or catapult.

accuracy...look, I really need a plan to look at, cause at the moment, I just can't relate anything you guys are saying, I mean..what should i get, and how do I asssemble them?

I know I sound embarrasingly pathetic, but I just can't be bothered to think all this stuff up by myself...I'm a bit retarded.:)

I just got my degree in engineering. Engineering is all about using your imagination and knowledge to create things that serve a purpose.

I recall making something like this in boy scouts. It's a mousetrap with a spoon attached.
epj.k12.sd.us/Photographs/2005-06/High-School/Catapult-Web/DSC_0150.JPG

This url or a trebuchet shows how you can use gravity
users.hubwest.com/gordo/trebuchet.JPG

I could be wrong, but I think that's when the faucet got turned off....

Really? Cuz, I stopped providing explicit plans when he said

Do your own homework! If you can't put something together with $200 and all of the great suggestions and ideas in this thread, you deserve to fail.

awww, its not like Im asking someone else to construct the thing for me, I'm just asking for the plan, surely the construction won't be easier than the planning itself, would it?

Depends...you want to be an engineer, or not? If you don't like design, you might want to reconsider your choice of careers. Design, planning, calculation is pretty much what we do. What is the roadblock you're running into? Analysis paralysis, time, or procrastination?

Seriously now. Engineering is about design, not construction. I would charactize my knowledge of the subject as 'informed amateur.' I've never sat through a formal engineering class in my life, but I could design what you're looking for. Actual qualified engineers build things like this for fun.

The terminology used in this thread is basic. If you're not able to follow our discussion, perhaps it's time to rethink your field. Why are you getting into engineering if you're not interested in it?

It'd be one thing if you came to us with a specific conceptual problem, ie 'this is my design but this is where I'm getting stuck,' or 'when I test this I run into this problem.' It's another thing entirely to tell us that you can't be arsed to do your own homework and then expect us to do it for you.

With a proper design, the construction should be simple enough that your dear old auntie could do it. Without a proper design, it'll be a nightmare. The design is the key part of the project here, which is why you should really be doing that part for yourself.

If the classs was a construction challenge they would have given you plans. Do you want to be an engineer or a technician?

particularly given that a 5 minute google search will yield some pretty exact plans on how to build any of these devices. you've got to get moving and do some research, or else you won't learn anything.

I concur...

And I'd say the trebuchet would be the best bet. I was looking at making one for fun a little while ago.

And I'd add that one knows your true geeky engineer side by how much FEA you do before you make it.