This is a catapult (ala torsion style) I built inspired from the video a contributor named schoondogs posted. His catapult looked simple enough so I thought I'd make a step-by-step with some improvements (that's the American way right? - and the Japanese way for that matter). I am not a master craftsman, just trying to be a Hero Dad* for my boys so look past the low grade finishing and more so on the end result. The design is not pretty but it is very functional and that's really all a 5 year old cares about anyway. It took about three hours to build (not counting the trips to Home Depot) and does not include any difficult cuts (all straight cuts) or elaborate tools.
2 - 8' 2x4s
25 or so 3" brass wood screws
24" 1/2 PVC pipe (SCH40)
6 feet of paracord cord
2 small wood dowels (I used a old drum stick)
some type of cup to hold ammo (with hardware for attaching to arm)
Approx 10 big nails (2 1/2 inch honkers)
Power drill
9" Japanese pull saw (this is great for silent late night projects)
7/64 drill bit
1" drill bit
tape measure (or yard stick)
hammer
Range: after all modifications this baby can chuck a tennis ball easily 60 feet
*Hero Dad - any dad trying to impress his kids with some type of act or service - in this case (in the steps of my dad) it's building something really cool
2 - 8' 2x4s
25 or so 3" brass wood screws
24" 1/2 PVC pipe (SCH40)
6 feet of paracord cord
2 small wood dowels (I used a old drum stick)
some type of cup to hold ammo (with hardware for attaching to arm)
Approx 10 big nails (2 1/2 inch honkers)
Power drill
9" Japanese pull saw (this is great for silent late night projects)
7/64 drill bit
1" drill bit
tape measure (or yard stick)
hammer
Range: after all modifications this baby can chuck a tennis ball easily 60 feet
*Hero Dad - any dad trying to impress his kids with some type of act or service - in this case (in the steps of my dad) it's building something really cool
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Signing UpStep 1: Building the base
Cut the 2x4s into 14" and 30" lengths. Drill the 3" screws into each end to create a base for the catapult
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(please reply)
- So you pass the paracord only once through the throwing arm and then just alternate between the two sides correct?
-There should be 2 dowels and you ended up using twice as much paracord to up the power (8 yards)?
- Once you crank it up the pegs snug up and hold themselves flush against the wood?
Thank you in advance, appologize to all for my ignorance in catapult matters. My daughter is going to love it.
Look at my last step on this project. I highly recommend getting some type of elastic to add power to the throwing arm. I hope this helps.
It is commonly available at Mil-Surplus stores or online.
actually my wife is a good sport about this kinda stuff. she knows boys will be boys. I am a lucky dad.
Good choice of power lever for a kids machine, enough to be interesting, but not enough to do serious injury. You should be able to skip drilling the holes in the throwing arm, the bundle will hold the arm just fine.
If you are building this for a "big kid" (one of beer drinking age) you will naturally want more power. Power comes from the size of the bundle. Add strands, till you get something where the length is 8-10 times the diameter. You will need to add a brace near the bundle to keep the frame from crushing inwards. You would also need a more durable material in the arm, and some sturdier material for the bits at the ends of the bundles (the greeks called them "epizigus", Mista Ballista uses steel 5 inches thick on its bundles)
Twisted rope can exert tremendous force, so if you scale things up, do your research first. The machines you see on the Punkin Chunkin show, with their bundles a foot in diameter, exert as much as 100 tons of crushing force just from the pre-tension. Our machine has bent heavy steel structure, sheared off 1 inch steel pins, and crushes the 2x6" joists that we use as "padding" on the arm stops.
Oh yea, the most difficult bit when you start to scale things up is the trigger.
But seriously, just remember this a WEAPON and even a model can accelerate a projectile to an alarming velocity.
http://www.instructables.com/id/Make-a-Mid-sized-disassemblable-Steel-Trebuchet/
It could throw a 1 pound water-washed pebble around 300 feet in a low trajectory. Or an egg around 400 feet in a high arc.
The axles - for the throwing arm and the counterweight, were 1 inch solid steel bar. On the rear pair of struts I built a winch going across, with a handle for winding the arm down. It worked a treat. The hook was adjustable in angle using a quadrant mechanism. I ended up selling it to the historian and author, Daniel Diehle. What HE did with it, I've no idea. Maybe he is still playing with it !
Only difference was that one was hydraulic powered. It was bizarrely accurate tho! Have contests! Have fun!
Bizarrely Accurate (or do you mean precise).
We need an Instructable on that.
And yes, accurate is precise. :P
I made a trebuchet a few years ago for a physics project and it was quite a fun experience, especially with all of the moving parts and the way the sling works. It's definitely a thing of beauty when you get it calibrated.
Quick history:
They started throwing rocks with things that looked (and functioned) like an ordinary crossbow. (ca:8-500 BC) There is only so big you can build a wooden bow, so ca: 400 BC they invented the torsion ballista, with rigid arms, and rope springs for power. Around 100BC they discovered that if the turned it inside out, (springs on the outside, arms sticking inward) they worked better (one example, found near Hatra in Persia) because you wound the springs further.
By 100 AD, they invented the Onager, (the machine described here), which only needed one bundle, and one arm, but performed at least as well. They stopped making ballista.
Around 1000 AD, somewhere in Asia, the Trebuchet was developed, and it spread to Europe within 200 years. They had fewer parts than an Onager, and required fewer special parts get hauled around. They stopped building Onagers.
Eventually gunpowder ended the use of mechanical artillery.
Oh yea, for the most part catapults were built as/where needed. The engineer would show up with a cartload of the special bits, and some stonemasons, The grunts would be sent out to cut down and drag the nearest forest to just outside of bowshot. The engineer would direct the grunts to get things built, the masons would make ammo, and then the castle would suffer granite rain.
Treb's were faster to build, and since they didn't need a lot of expensive and bulky to transport rope, won the logistical battle.
You a Scadian or Scouter?
Ever year we have a catupult contest at our scout camp, they lauch flour filled paper bags at each other.
It is a site to see. Look up Rovent Camp OPE
As for range, that varies with the size of the throwing arm, the amount of weight, the release angle, etc. A good sight to go to for that kind of information is THIS LINK. He even has a link near the top of the page to a trebuchet calculator that will calculate the range, but it requires quite a bit of information. Anyway, with a trebuchet, it is less about the distance and more about how it all works together. I made one and enjoyed messing around with it, I would post pictures of it but I'm in a dorm and not at the house.
this is a hoot, use water balloons. I will see if my son still has his where I can find it and post a picture. But sadly mine is rubber powered!
Try to do with him and a catapult to storm the sand castle.
To adjust the range to add a movable plank-limiter at the top.
But don't fool us : we're all pretty sure you made this catapult not only for "father image" purposes but also to (re)enact a pleasure you had when you were a kid !!!…
:D :D :D
I'm pretty sure your son, while getting his kick out of "playing catapult", will agree with this. But that will mean no harm : you're a hero anyway.
We call for other brilliantly executed ideas.
Best wishes.