This instructable will teach you how to construct a large, almost authentic looking knex trebuchet. This trebuchet can launch marbles about 25 feet with a good launch. I had built this about a year ago, and just took it out of the basement. Loaded it with a marble, pulled the launch pin, and to my surprise, almost broke a window. Later, i loaded it up with airsoft pellets, and launched it at my sisters door. The trebuchet stands about 2 feet, 4 inches tall. It is very simple to construct, and takes about 30 min. The movie should show you a short clip of the trebuchet launching.


I am not liable for anything stupid you may do with this trebuchet....If you injure or kill anybody with it, don't come crying to me. Just be smart

PS: this is my first instructable, so tell me if it is good, and what improvements i could make to it.

PSS: sorry about the low quality pictures, But you should still be able to get information from them.

UPDATE: i just built a duplicate at my friends house using this instructable...I think i miscounted a few pieces, but if you have your knex bucket near you, this shouldn't be a problem. Also, you may need to tinker with the string length, counterweight weight, and other small stuff...It still works fine though!

Step 1: Materials List

Knex stuff:

(all measurements may not be accurate)


Blue x 50
Yellow x 24
Orange/red x 6
Grey x 1


Yellow x 9
White x 12
Light Grey x 2
Dark Grey x 2
Red x 18
Blue x !0
Purple x 10

PS: Red can be used in place of orange, and the other way around

Other stuff:

Some sort of tape ( I used scotch tape..the clear stuff...because i was sort of in a pinch...works fine!)
two D cell batteries
a bit of spare cloth
I need to adjust the sling. ammo falls out almost every time. the one that did go went quite far though.
<p>I thought this only uses K'nex!!!!!!!!!!!!!!!!!</p>
<p>AMAZING!!!!!LOVE the idea!!!</p>
cooool! <br>do u know how to make one with a rector set? im trying to do so now but not finished yet
oh yeah second comment
Hi there. does anyone know what i could use for a weight for a trebuchet that stands about 5ft high? i previously use 1.5 kg of lead, but because i have moved house recently the tebuchet had to be dismantled and the lead has gone missing. please reply if you have any suggestions.
if you can find big rocks you could use those
I made a trebuchet for a school project and it was 12ft tall, and we used about 225 lbs worth of rocks and patio blocks&nbsp;(the patio blocks are about 20 lbs. each) and we broke the school record for distance. So maybe scale that down a bit and you should be good.<br />
well u can use the wheels for a counter weight. i used them once and they work rather well. also you could try to use same smaller batteries.
save up your money and buy 1.5 kg of silver. that way you have a good investment worth about 960 USD right now ( about 500 british pounds) that you can use as a weight for your trebuchet.
good idea, lol
Me and my friend built one a couple years ago ours wasnt as big as yours but it was close. To get a tennis ball to go a meter we used a brick.
i made and it it so cool! i cut my old 3 year old shirt dident fit my mom almost threw out but i took it i used a rock for weight
it looks good! I have a question:is there an alternative for the counterweight and the piece of cloth?
u can use smaller batteries for the weight, but u need cloth for the sling
flio191 you dope it says that you need 50 blues!!!
I have already corrected that
ok i hadn't realized that
i had a lot of trouble with your trebuchet because when i would fire it would just swing the cloth cause the marble fell out right behind the thing
so i decided to mod it to prevent that from happening (but i think i got a "little" carried away because i ended up with a prototype of a catapult) now i guess the problem can't be mine unless i rebuild the trebuchet. ehehehehe :D please tell me should i post it (here's some pics)
lol! that's awesome! how far does it launch? Yours looks really cool :) If you do post it ( I hope you do) I will definitely build it. It looks like you are using rubber bands for propulsion, am I right?
i need either more rubber bands, newer ones, or the wide, blue ones like you find in the store. because im using rubber bands that i just find on the ground, theyre not in very good condition. right now it only shoots about 2 1/2 feet.
my prototype trebuchetshoots about 10 feet
wow dude that's so cool
that looks awesome! put it on so i can build it plz.
sorry dude, thats a negative. I would post it but two hours after I posted my last comment, I put too many rubber bands on it and it broke. oh sorry, I meant that there were pieces flying everywhere!!!!!!!! I just gave up.
isn't it more of a catapault?
post it!!
make it again and post it!!!!
i built it from your pics its good +1
can u post it den?
i like it very much. i thought about it to make a trebuchet 2, but i dindnt know how. thanks for the ideas
this sucks balls it does not work at all it sucks
i put 2 d's and 2 c's and a rubberband on the arm doubled it up and it works great. i couldnt get it to work but then i put 1 marble in and it went a good 20 feet
hey how many blues u need 4 dis ps looks great dooo
I think you should post it.
it is posted nooblet
I think it is a great idea!!!!!!!!!!!!!!!!!!!1
I think it is a great idea!!!!!!!!!!!!!!!!!!!!!!!!
can you make a mini version of the catapult you posted?
check out this beast!!!!<br/><a href="https://www.instructables.com/community/knex-trebuchet/">https://www.instructables.com/community/knex-trebuchet/</a><br/>
i like the idea, i may try an make one as well.
it only needs 46 or something blues
nice job but i had a little trouble firing b/c the marble fell out.lol
the frame is a bit to week it snaped on me but good 1+
Nice Machine. I've never played with knex. People make some impressive projects with it. I had an erector set as a kid. I wish I still had it.<br/><br/>I made a quick, easy, no tools, no cutting, no drilling, no lumber, no hardware, no measuring, no plans, super easy Trebuchet. <br/><br/><a rel="nofollow" href="https://www.instructables.com/id/ELS7AFBF5R8MQQU/">Quick-n-Dirty Trebuchet</a><br/><br/>I published it last night but it isn't showing up yet. Maybe it isn't accessible yet, but check it out when it shows up. Here are the video links from Google, they are up and running now. <br/><br/><a rel="nofollow" href="http://video.google.com/videoplay?docid=7177348096653267453&pr=goog-sl">Trebuchet Video 1</a><br/> <a rel="nofollow" href="http://video.google.com/videoplay?docid=-3765857587744240299&pr=goog-sl">Trebuchet Video 2</a><br/><br/>Shot with my still camera so the quality isn't that good. The first one shows a close shot of the machine firing. Second video shows the view of the projectiles hitting about 14 feet away. It throws 12-15 feet consistently. <br/><br/>I tried a heavier weight and my projectile hit the wall 20' away. It's my biggest room, so I can't test the full range here.<br/><br/>It's not pretty but it's sure easy. It's also one of those projects a 10 year old can make without wasting their allowance. It's made out of 9 chopsticks, 2 toothpicks, 2 rubber bands, 3 paper clips, a weight, and masking tape. (I know 10 year olds aren't supposed to join but they can still read - I would have been all over this site when I was 10). <br/><br/><a rel="nofollow" href="https://www.instructables.com/id/ELS7AFBF5R8MQQU/">Quick-n-Dirty Trebuchet</a><br/>

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