Trebuchet Project (picture intensive)

[Brain]

Well my senior year in high school a friend of mine and I decided to build a trebuchet. The location was his cabin in a tiny town in the mountains called Monarch, MT. The first prototype was about a foot tall, and we just nailed a folded over lead rectangle to the swing arm for weight. We launched golf balls about 20 feet with this one, and we knew we could do more and do it better.


The second one we made was contructed mainly from 2x4's, for the base we used floor joists(?). This one was about 8 feet tall, for the cross beam we used 3/4" rebar affixed to the angled beams. For ease of rotation we added a 1.5" pipe to the middle of the 2x4 swing arm, so the metal on metal contact would decrease friction. For weight we used an affixed door weight (~50lbs) and some pipe flanges, which added about another 25lbs. We launched 2L bottles full of water about 30 yards with this one. This was in the early fall of 2006.

http://i257.photobucket.com/albums/hh208/brainanator/campinpics010.jpg
http://www.youtube.com/watch?v=Ip6iffCZB7k
http://www.youtube.com/watch?v=G3ivI1xR5Xg
http://www.youtube.com/watch?v=JgNnDUxxASQ



Then we decided to go bigger, we actually drew up some rough sketches, and went to Home Depo to buy the main swing arm, which was a 15' pressure treated 4x6. First we built the main frame, based on a hospital door, which I think measured 10'x6'. The main supports are pine 4x4s (his dad let us "borrow" them, and all the wood but the swing arm, his dad rocks). We used single 6" lag bolts to hold them together, and made bolts to hold the frame to the door/base.

http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS016.jpg
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS024.jpg
About the purple sweater, we didn't bring coats, and it was like 35F out, that is my buddy Ed.
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS059.jpg
Drilling and fitting the holes for the bolts to hold the upright support
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS046.jpg
He is about 5'09"
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS068.jpg
This is the medium one in the frame of the big one.


Next was to build the weight basket to....well, to hold all the weight.

http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS071.jpg
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS072.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture005.jpg
Nearly finished, need to add the holding beams in the middle.


We decided to carpet the main beam with some scrap squares to reduce splinters going into the operators' hands.

http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS078.jpg

Disassemble able for transport and storage.

http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS090.jpg

To strengthen the 4x6 swing arm we added some metal plates to each side, these also gave a great place to bolt the bearings that we bolted to the arm. The bearings were given to us from his dad (who is the head engineer at the hospital in Great Falls). They are bearing from the huge air conditioning units on the roof, each set retails new for about $500, ours were used. We used some simple pins to hold the bar laterally in the bearings.

http://i257.photobucket.com/albums/hh208/brainanator/Picture010.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture014-1.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture084.jpg

At this point we are nearly done, but the hardest part is yet to come: devising a way to consistently release the item being thrown. But first it is time to do some proper testing, and looking over it some more.


http://i257.photobucket.com/albums/hh208/brainanator/Picture053.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture076.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture061.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture064-1.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture068.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture060-1.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture050.jpg
http://i257.photobucket.com/albums/hh208/brainanator/Picture105.jpg
That night tending the fire.

After testing (and failing) many different sling release mechanisms we decided to revert back to the way we attached the projectiles to the first trebuchets: a curved nail and a rope. We just slip the rope over the curved nail (curve points forward), and adjust either the rope length or nail curvature to dial in the release point. With this method the rope stays attached to the projectile. With the project complete we made some crappy videos with the only camera we had at the time.
Construction was finished probably in mid November of 2006. We hauled it into town in the middle of May, and did a demonstration for many science classes at both the high school and middle school. I would say about 500 students got to watch it in action, probably like 40 students from a high school physics class, and then the morning of our high school graduation we demonstrated it for the middle school, where many science classes came out all through the morning.
On average I'd would guess that we loaded the weight basket with 300-400 lbs, our main weight came from a cinder block that we filled completely with molten lead, and let cool. This alone could have easily weighed 150-200 lbs, the rest of the weight was large metal pieces and large stones.
The trebuchet could throw a full 2L bottle of water about 90 yards, depending on weight. With more weight we could have thrown farther, but we just enjoyed the huge *cathunk* sounds it made while launching.

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



I'm sure there are many spelling errors in this, I wrote it without a proof read, hope you enjoyed it.

[EvilChicken!]

Awesome!

Thanks for the read. :D

[Wizzup?]

Ok, that was damn awesome. :)

[Orbital]

Reminds me of age of empires... That was pretty awesome I have to say...

[Dan Cardin]

A winch and release would have been cool, but pretty much unnecessary if you can do it by hand with no trouble. Nifty beyond belief

[noidea]

Thats pretty cool :D I dont think many people have the initiative to do something like that :p

[Torrent of Flame]

Dat Beard ;)

Awesome. I'd love to see it in action IRL.

[3Garrett3]

I think the only reason you didn't need a big sweater was because of the beard. :)

You were in high school with that? I'm accusing you of failing multiple times :p

[rogeruk]

Very interesting read.

What an awsome project.

[XcanadamanX]

being in engineering, that makes me giddy :P

[Dan Cardin]

Thats pretty cool :D I dont think many people have the resources/money to do something like that :pyes, true.

[Ruroken]

Go Beard man go!

[Brain]

A winch and release would have been cool, but pretty much unnecessary if you can do it by hand with no trouble. Nifty beyond belief

It is actually pretty hard to bring it down by hand, someone has to climb up one of the supports, grab the swing arm as high as possible, and pretty much jump off while throwing their weight trying to bring it down. Another person needs to be on the bottom ready to help catch it, or it will pick up the person trying to bring it down....It sucks, happened to me once, lol. Cut up my shin on the basket a little


being in engineering, that makes me giddy :P
Yeah, we're both going into engineering too. :D

Go Beard man go!
I will.


Ad for total cost to use, we paid $18 for the swing arm, and about $5 on all the fasteners we used. The cabin up there is always under construction, his dad likes to build, so he has lots of wood around. He was generous enough to donate most of the other wood. I would guess if he didn't we would have used plywood for the base, and still used 4x4's for the supports, and all that would have cost about $20.


edit:
Oh yeah, in case you missed it, one of the pictures has all 3 trebs in it, I've helped you by circling them, see if you can find the third:
http://i257.photobucket.com/albums/hh208/brainanator/VIDDDSSS046-1.jpg

[RAM]

Those are awesome, I built a small catapult for school when I was younger, but never had the ambition to build something this big, Good Job !

~RAM

[Cartmann]

Could be cool if you placed it near the beach, and vidded while you threw each other in the sea.

[Dan Cardin]

Unless im seriously overestimating the price of wood, i think it would have cost a bit more than $20 for all that wood + other stuff.

[Awkwardsaw]

Could be cool if you placed it near the beach, and vidded while you threw each other in the sea.

agreed :D

[Brain]

nope, guess wood is pretty cheap around here, also, it was 3 years ago.

edit: well of course I could be wrong, It was just a rough estimate, it would not have been very expensive regardless. (except for the bearings....but we would have used some other method)

[R0b0t1]

You had problems aiming it? You aren't supposed to aim...

[Main]

Lol
No calculation Madness.
We had to calculate the Fapplied from it and estimate with projectile motion and crap like that.
Ours were MINI thou, and we had like 2 month to built it.

[marpis]

Wow that's amazing dude!
What's the range? :)

[anonymity]

On average I'd would guess that we loaded the weight basket with 300-400 lbs, our main weight came from a cinder block that we filled completely with molten lead, and let cool. This alone could have easily weighed 150-200 lbs, the rest of the weight was large metal pieces and large stones.
The trebuchet could throw a full 2L bottle of water about 90 yards, depending on weight. With more weight we could have thrown farther, but we just enjoyed the huge *cathunk* sounds it made while launching.


Wow that's amazing dude!
What's the range? :)

@ marpis =] there you go....

@ Brian, nice beard. Great job with the trebuchet!! That's pretty neat.