Picture of Giant Trebuchet
Make a giant trebuchet in less than a day with a couple of trees, some rope and a few other easily found parts.  

Best made in a paddock with plenty of room for hurling and a tractor with a loader will make it easy to get the throwing arm onto the support frame.
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Step 1: Prepare Materials

Picture of Prepare Materials
Actions required for step 1 are:
  Select tree
  Detatch roots from trunk
  Remove branches

We used a couple of blue gums, a fast growing eucalyptus (Eucalyptus globulus) approx 10 years old.

We cut the following:
Main arm 10.5m long
Legs 2 x 3m long
          2 x 3.5m long
cross arm (pivot) 2m long

For cross bracing we used 1 by 5m length and 2 x 2.5m lengths.

     (multiply by 3 for approx lengths in ft)

(note the chaps, face mask and safety helmet used when felling tree are omitted by model pretending to fell tree)

After cutting timber to length, find a good location for building the treb and set out timbers.  Starting with legs, lash the tops of each 3m leg to a 3.5m leg leaving enough overhang at the top for the cross arm (pivot) to sit in.   I had some help from my kids who had practised lashing at scouts with this step.

Step 2: Set up Frame

Picture of Set up Frame
Stand up the legs and hold in place with temporary bracing while you attach cross braces.   We originally put permanent cross braces between the legs as this was easy to do.  This was not a good move as you want the arm to swing freely without hitting the cross bracing.  Yes seems obvious in hind sight.  The mannequin in the second photo is demonstrating where not to stand when there is only temporary bracing in place.
Outrigger style cross bracing is a better solution.  Lay a long pole (approx 5m) on the ground in front of the legs  and fix to legs by lashing or heavy duty coach bolt.  Then lash or bolt cross braces between the pole and the legs.  

urtlesquirt2 years ago
The pouch is person size. *evil grin*
flamesami2 years ago
what was your maximum throw?
Ganhaar (author)  flamesami2 years ago
About 40 yards. It really needs a much heavier counterweight to get good distance, but at the moment one person can pull the throwing arm back down, if I increased it significantly it would need a different arrangement to pull the arm down.
BrandonF2 Ganhaar3 months ago

Have you thought of using a boat winch (see )? It would give you a mechanical advantage in pulling the arm back into battery.

Ganhaar (author) 10 months ago
I think the counterweight made a big difference here because the blue gum log I was using for a throwing arm was quite heavy and had lots of inertia so just didn't pick up speed fast enough with the smaller counterweight. Probably could have got similar results with a light weight arm too. No problems with the arm breaking on this one. I've got some big bamboos growing so maybe theses would be good for next time.
50cal2daHead10 months ago

I made one of these a while back. Smaller mind you, but just as fun. It flicked a soccer ball about 20 metres using about 25-30kg barbell weights. Regarding your comment with the 25% increase in counterweight weight leading to 100%+ increase in distance, I found that there is a critical ratio of sling length to counterweight weight. If the sling is too short for a given weight (i.e. the weight is too heavy for a given sling length), or vice versa it will release the :insert projectile type here: at the wrong time. Simply adding more weight will not necessarily lead to a further throw. I can't quite remember straight, as it's been a while since I tuned my treb, but I think the heavier the weight, the longer the sling needs to be to be "tuned". If the projectile is going high but not far, make the sling longer, or alternatively, remove some weight (having too much weight can result in snapped cross-members – I was using bamboo and snapped several). If it is hitting the ground early and at a shallow angle, shorten the sling, or add weight.

claramecium2 years ago
COOL! who doesn't love an admittedly lethal giant trebuchet?
Wow this looks amazing, does it is ilegal?
Ganhaar (author)  Austin Rampt2 years ago
I can't see how a few sticks lashed together in the paddock would be illegal, but I would expect that there would be some laws that would bring you unstuck if pumpkins were in invading your neighbours airspace.
Then can you believe that a pair of sticks tied together by a rope/chain IS illegal? Also known as nunchucks. Taken from wikipedia:
Possession of nunchaku is illegal or nunchaku is defined as weapon in a number of countries including Norway, Canada,[21][22] Russia, Poland, Chile and Spain. In Germany, nunchaku have been illegal since April 2006, when they were declared a strangling weapon.[23][24]
Ganhaar (author)  Antzy Carmasaic2 years ago
I'll have to rule out how to make giant nunchucks for my next instructable.

Sounds similar to slingshots here. Again a simple piece of rubber tied to a stick and it is a prohibited weapon. It's regulated differently in different states of Australia, in WA where I live you can get a license to have a gun and is possible to obtain a permit to have a cross bow which is also a prohibited weapon, but there is no avenue for a license or permit to have a slingshot.
So obviously government thinks it's far easier to kill using nunchucks and slingshot than with a gun. I'll leave the gun and take these whenever I go hunting :P
Next thing we know, fishing pole will also be illegal.
Dude, this Is epic. I've made one before but not on this scale ,keep up the good work
criggie2 years ago
From memory there's all sorts of ratios and tuning that can increase your range dramatically. Things like ratio of end/pivot/weight on the main arm, length of throwing rope etc.

The bugger is that all the numbers are interrelated, so fiddling one messes with others.

It even makes a difference to the calculations if the weight is fixed or free-swinging from the end of the main boom, or if the whole thing is fixed to the ground like yours vs on wheels that allow it to roll forwards and backwards.

Try some of the calculators like or theres some excellent software at

Mine's made from an old bicycle front fork, just haven't got enough lead for a decent counterweight yet. Should sling a pebble 50 metres when complete, if I get 10 KG of mass in the counterweight
Ganhaar (author)  criggie2 years ago
I started out looking for some software to refine the concept before building, there were a few links on the Grey Company trebuchet web site, but could find anything that was compatible with the mac, so just went with trial and error, which was not difficult and kind of more fun as it gives a reason to keep firing it. The distance ranged from going backwards if the sling was too short to around 40m which I don't think is very far for this sized machine. I've spoken to a guy who said he had one that actually fired a lot further with a smaller arm, which I guess is because the counterweight is not big enough to get a large arm moving quickly enough. I have commented previously that to increase the size of the counterweight significantly would create a new challenge on how to load the device as at the moment, a (full sized) person can haul it down with a rope.
criggie Ganhaar2 years ago has a macintosh version.
Ganhaar (author)  criggie2 years ago
Cool, works well, but the numbers don't fit in the fields very well, obviously designed for small devices. I have some fine tuning to do and I have to find some bathroom scales to weigh the counterweight.

From the first few runs, it demonstrates that a heavy throwing arm needs a big counterweight. Even with my approx 100kg counterweight, the inertia of the throwing arm takes a lot to overcome.
Great job. Have you dialed in the optimum projectile size yet? That's my favorite part, though I've never made one that big before. Wow. I hope you have an ample supply of the severed heads of your foes to fling about.
Ganhaar (author)  donedirtcheap2 years ago
In absence of severed heads, melons or plastic milk bottles filled with water are good. The milk bottles explode on impact, soft drink bottles not so good as they tend to bounce rather than smash.
I've also had a recommendation to use a bag of flour to "print" the impacts of testing on the ground.
alzie2 years ago
Wow, nice job.
I remember seeing these on tv.
Theres a guy that likes to hurl old pianos.
Gets em going like 500 ft!
That's an awesome project, I take it next door will keep the noise down in future? lol
billbillt2 years ago
Please take care with this! Trebuchets store large amounts of energy and can do a great deal of damage, both to property and people.

This trebuchet is quite large for modern versions, but small historically.

The history of trebuchets is long, IIRC, they began in China and came to the West via the middle-East. There are trebuchet simulators to aid their design and papers of mathematical analysis, plus a lot of historical research.

Trebuchet related deaths Someone catapulted from a trebuchet died.
A historical trebuchet death: In 1218 Simon De Montfort, while besieging Toulouse in Southern France was hit on the head and killed by a trebuchet stone, shot by the city's inhabitants. Given De Montfort's behaviour, I believe this was a very fortunate shot.
What if all the other trebuchets are small, and this one is normal-sized?
Ganhaar (author)  MoustacheCat2 years ago
Or if this one is small and no-one has ever built a giant one? It sounded better calling it a Giant Trebuchet, hope you weren't too disappointed - it did seem to be a lot bigger than the average treb on instructables.
I really liked your build, I just thought it was funny that an actual sized trebuchet is called large, because all the others on the webs are so small.
A guy in England has a permanently set up trebuchet that launches cars, pianos, and other large objects across his property. It's rather awesome to watch it be fired.
This looks amazing! I hope to build something like this at Scout camp in the summer.
Ganhaar (author)  purpAl-chAos2 years ago
I'm hoping my young fellow likes it when he gets back from scout camp, he's at the Australian Jamboree but his brother did help me building and was a good test of lashing skills learned at scouts.