krwlz

Research time again. For those interested, the mousetrap car went well, didnt win, but definatly did well.

New project though. Design and build a mechanical (read:no compressed gasses/explosives) device to throw an egg (raw) 60 ft, into a bucket.

Any ideas?

Lotsa trebuchete ideas floating around my class, im thinking more of a spring loaded "cannon". Would be fairly simple to construct and design. Physics calculations would be simple. Easily adjustable.

Lets hear what you all think... Probably be narrowing it down to a few ideas at the end of the week.

jbrooks544

I would think that you would want to spread the g forces out over time - g forces involved in the acceleration of the egg. A cannon would accelerate the egg over a very short period of time and you would have a g-force spike. I don't know how you could protect the egg from these forces.

I would create a spinning arm with the egg on one end. The longer the arm and the faster the spin, then the further the egg would go. I would have the other end of the arm, past the pivot/motor weighted so that the whole spinning mass is balanced. The tricky part is "how do you hold the egg?" and "how do you release it at the right moment and at the right angle?" The only thing I can think of is to have a bucket at the end of the arm with the end being a trap door. The trap door has a release mechanism that can be tripped via a string that goes back along the arm, near the axis of revolution. When the arm is spinning fast enough then a pin could be inserted into a bracket that would "catch" the string at the right position of the arm, tripping the trap door. Have fun. Do a google search for

"Bad to the Bone" pumpkin

and you will see how well this concept can work.

MSD

This has been tackled time and time again. The trebuchet is the most easily adjustable and fine-tunable way to do it.

krwlz

how does the side to side accuracy prevail with the trebuchet? gotta hit a 5 gallon bucket, 60 ft away.

theguyondacouch

For the most part, the trebuche is easy to tune, but there are several variables, including but not limited to too: weight of counterweight, lenght of sling, and angle of sling release hook(not sure of exact term). provided there is no wind, the egg should fly relatively straight, but it may curve if it starts to spin. If you have time to test it, it should'nt be a big problem.

__________________
"Lick my frozen metal ass!"

krwlz

We have a program downloaded that simulates a trebuchet, so the physics of making it do what we want should be reletivly easy.

theguyondacouch

Does it simulate friction? wind? If not you could use it as a ballpark guess, but it would need some tuning. Also, are you allowed to hardboil the egg? If so do it.

__________________
"Lick my frozen metal ass!"

Daval

what about a crossbow type deal?

I would use some 3" PVC to form a nice straigh barrel and some medical rubber elastics to launch with.

Or do you think the g-forces would destroy the egg every time?

__________________
"It is impossible to obtain a conviction for sodomy from an English jury. Half of them don't believe that it can physically be done, and the other half are doing it."
Winston Churchill

krwlz

Cant hardboil the egg. THe program is used to simulate friction and wind yes, but you would have to know what the friction and wind were. We are also considering a more traditional, spring loaded catapult device. Spring being attached to a threaded rod, which is easily adjusted. I think this might take care of the lateral stability.

Redjake

I know this is unrelated, but it's too badass to let go.

In high school, the guys one class in front of us (they were seniors, we were juniors) built a potato-gun for Technological Studies (senior-only class you can take, self-motivated class).

You are probably thinking of the kind where pressure is used by forcing a ram stick down into the back of the barrel to force the potato out.

They used ignition. Seriously.

They filled the "chamber" with hair spray (a shitload) and they had an ignition spark switch at the beginning of the rifle. You hit the switch, it ignites the hairspray, and good God almighty did that potato fly like a bitch. It was awesome. We're talking launching a potato chunk hundreds of yards. Crazy.

__________________
Off the record, on the q.t., and very hush-hush.

dumbnutofak

hmmm, used one of those to launch a roll of toilet paper friday night... of course it the flame caught it on fire... so that was way sweet....til we remembered it was 4am, in the city, in a neighborhood... im glad we have lots of snow handy.


Back to the topic at hand. How many shots will u get with the egg? I think a trebushe(i know spelling is off) would be good except for the wind factor and all that. I mean ur trying to hit a 5 gallon bucket 60 ft away with a object that is 2.5 - 3 inches in diameter.

anything u use will be tough to make it happen. good luck and happy building.

__________________
If a little knowledge is dangerous, where is a man who has so much as to be out of danger?

krwlz

4 shots... Less points if any of the shots fail to make it in the bucket.

Dil

This sounds awesome,

WarWagon

The trickiest part of the trebuchet would be the release. Ask my friends, who accidentally put a watermelon through the roof of my old high school's equipment shed.

I would still consider something along the lines of a spring loaded catapult though. Calculations should be simple enough with the spring constants, and it may be easier to fine tune than using weights. An egg is a very strong little thing, and a properly designed "seat" should prevent any breakage. I think the problem with a cannon would be any shifting of the egg during acceleration, since its not perfectly round. It could bind up against the wall and be crushed before its being launched.

krwlz

Looks like we are going with the spring loaded catapult. Easy release, no binding, and easily adjustable.

krazykemist

For the release mechanism you might look into archery releases for drawing back the string of a bow. The only thing I see with the catapult over the trebuchet is that the catapult has the potential to put more force on the egg upon release.

__________________
"Everyone thinks of changing the world, but no one thinks of changing himself." -- Tolstoy

Giltwist

Wanna go for the gusto? How about a maglev launcher? You can contol the distance launched by angle of elevation and frequency of pole oscilation.

amonkie

I had the same assignment for my physics class, and we used a trebuchet design and had no problems getting distance once we had established baseline counterweight distances. PM me if you want to see the plans we used- it might give you some ideas.

__________________
Calling from deep in the heart, from where the eyes can't see and the ears can't hear, from where the mountain trails end and only love can go... ~~~ Three Rivers Hare Krishna

krwlz

We used our spring loaded catapult... Only team ever to make it into the bucket for a score. Did really well on our other 3 shots as well, one came down right on the edge of the bucket, and 2 in the inside circle.

Ill post a picture of it later.

Crunchy Nipple

I had to make one of these in a science class in middle school. All I ended up using was a rat trap with a spoon epoxyed to the arm of the trap. To control the arc of the throw I had thick twine tied to the swinging arm of the trap, was very easy to adust, longer string made for straighter throw but less distance, shorter string made for a nice arc that went quite far. Make sure it is stablized well though as the force of the spoon swinging makes the whole thing flip over and a nice mess if you are using eggs. Hope this helps any.