True catapult that uses a extremely tightly wound string to power it, it fits in the palm of your hand, it cost under $20. all supplies can be purchased at Michaels. fires small foam objects 40 feet aprox 1053 feet to scale, about 7.5FPS when firing a 14g weight (twice the weight of the catapult its self) (i know cause i did a school project on it. This is my design and i didn't copy it) it can fire other objects farther and faster such as rocks but you can not easily recover them cause they go to far and fast to visually track.
this is for the competition so please comment and rate (this is the 4th catapult i have made they all worked good yours should to)
This is technically an [http://en.wikipedia.org/wiki/Onager_(siege_weapon) onager] but it is still in the catapult family.

this is a rather complicated instructable and is an example on how to build one yours dosent have to be exactly the same i use cm for most measurements but some are in inches ask if you get confused

use safety glasses when drilling cutting wire and when firing
this is safe when fire foam objects when firing rocks never aim at a person animal car personal property it fires hard enough to break a paint ball if used for office war only use foam light weight objects and make sure every one is wearing safety glasses

build this in a room with good ventilation the Ca glue and accelerator smoke when they dry
Ca glue bonds to skin on contact use un-cure do not pull apart. the glue will not separate but the skin on your fingers will.
The accelerator causes chemical heat and you can get a chemical burn from it which hearts so dont touch it

it has a range between 15-50 feet depending on ammunition and angle of trajectory

Other videos on step 4 and 9

I have pics of my 6th grade Sci fair project back when i was 11

Step 1: get your stuff

i went to Michaels and spent a little over 3 on:
wood, midwest 3/18 X 3 X 36100% polyester string 500yds 
you will need other balsa wood i have a huge box of scrap so i didnt need to get any thing else

you could use cotton, or any sting thats not hemp or nylon thats around the same diameter as kite string or you could just use kite string.

you will also need:
wood glue 19 gauge steel wiresawexacto  kniferuler square (a right angle thing)sand paper bamboo skewers Ca glue and accelerator  (with out accelerator its pointless)5min epoxy the kind that you mix two elements together 
you only need epoxy one time the when your gluing the arm, you could use wood glue or hot glue as a substitute but i dont recommend it.
by the way your video on it is listed as private so we CANT watch it!!!! good inst though
abcdefghijklmnopqrstuvwxyz now i know my abc's next time won't you sing with me???
i have a craving for donkey balls.
Nice catapult :D<br>but i can't watch the video it says its on private
&nbsp;nice. very cool attempting on making my own. cant find anyplace but here to find how to build a miniature onager. then ill maybe have an idea on &nbsp;how to build a bigger one on my own. thanks for the great&nbsp;instructable&nbsp;with all the pics and steps.&nbsp;
william gurstelle details how to make one in Backyard Ballistics
the video is private.
Put hooks on it so you can also add rubber bands so you get more power and range.
going to start this project over the weekend as usual my son tell me today he has to build a catapult and that it is due Tuesday, well at least we have the weekend, only he can't use any metal but nails so we figured instead of using the ring we will hold it down with two nails and string will post when we get it done.
well we accomplished it will post a pic later...worked great and it was so solid.&nbsp;When I did the base I put rubber bands around it to hold it tight together. Great Idea thanks...
&nbsp;heyy we made this catapult and it's pretty good, but our arm doesnt tighten that much, so it cant launch anything, it just slowly goes up, any suggestions of what we could do?
Impressive! Much better in design (and range) than mine...still got an A in social studies, though I hit the teacher. :P I hope your instructable wins!
lol, reminds me of the time i made a repeating crossbow for sose
suggestion: the twisty bit u could drill a hole next 2 it and place a pin in the hole 2 hold the torsion<br /> <br /> otherwise, great
is the piece that you used for the 20 cm cross part 1 cm by 1 cm like the 8 cm part? it looks smaller
thanks..<br />
&nbsp;When you make the skien, how do you connect the string in a loop?Could you just tie it?
i love that idea,&nbsp; iv&nbsp; voted for you <br />
Do you think this type of string (or should i day roping) would work on a real catapult, say 15 feet long. I just built one and I wanted to do torsion but I am not exactly sure how yet.
if you were to make a REAL torsion catapult then use wound together horse tail hair
hey pretty cool!
thanks i put a lot of hard work into it (170 pics take forever to download)
ya i know i wish there was a way to upload pics really quickly
Me to.
good concept but i think it could be improved greatly and a better finish could have been achieved but over all not bad i liked it, has given me an idea.... MUHAHAHAHAHA
oh my god... i just realized that i built a ballista for school... i should have entered it in the launch it contest... *whacks self on head*
wow. lotta nivce pics. heh, good job
thnks did you vote?
yuparoo, i did
wats your youtube account i cant view the vids anymore
which vides do you need to see?
all of the youtube ones ithink i might make one of these
most should be up now one or two are gone... sorry for i while iv been wanting to re-edit them and up date and stuff but never gout around to it
P.s please vote for me
ya i voted for you
sweet idea!
I made one of these in middle school, but I made 2, 2x4 "T"s and connected them together with cut aluminum arrow shafts, and like 30 winds of cheap plastic twine. it was VERY powerful. I made a prototype before that one, and the best thing to know is to make the pegs and washers holding the twine as STRONG AS POSSIBLE! if you want to make a strong one, 16 penny nails and big washers won't work, you need HUGE bars, or bolts, and MULTIPLE HUGE washers, You will be clamping onto the bolt with vice grips, or a pipe, and putting your whole weight into it. The pegs will always be your weakest link if you use 2x4s
wow... you must be rich if you're using foam safe that much... that crap is expensive!!! $12.00 for a half ounce!! anyway aesome instructable. i didn't read all the way through it but it's cool none the less.
i had it left over from when i build a warp (its in my group if u wana check it out mine didnt fly i used wrong kind of foam : ( but i scraped the parts and put it in reflection) Btw you dont need foam safe
yeah i figured i wouldn't need foam safe but it's so expensive lol
Very nice !
omg!!! lol when i was reading you statistics on the 16 pictures i saw dog and a couple other things and was like.... "WHAAAAA" and then i red your procedure. very nice job on your presentation i bet you got an A++++

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