I’m looking to enter a trebuchet in a (raw) egg throwing competition, rules state “A team of players construct a gravity powered machine based upon the ancient trebuchet design. The base of the legs is restricted to 2 square metres (outriggers may protrude beyond this). The power source must be contained within a 9 litre container.
I have a few weeks to do this and I have a decent amount of space to test, looking for ideas as to how I can calibrate it to fire set distances, do I just have various marked start heights for the counterweight or would I need to adjust the sling length?
Any design ideas would be welcome but looking to keep it as simple as possible for reliability.
>>992350
I've built smaller trebuchets before. There are rules of thumb that you can look up for proportions that should get you in the ballpark. You should probably use a pullcord trigger, which would be easy to rig for specific spots for set distances.
Some fiddly stuff you should be prepared for: For best performance, a trebuchet should be "tuned". This means that the payload, counterweight, arm lengths, and sling are all working optimally together, and virtually all of the counterweight's gravitationally energy goes into the projectile. The arm of a perfectly tuned trebuchet will stop in a vertical position as it releases the projectile, with no swinging. The angle of the pin is what determines when the sling is released (which is generally the best way to set distance, since the right sling length depends on the arm.). Make sure you can adjust it to dial it in, but once set it won't budge. For consistency, make sure the sliding surfaces are smooth and clean. Trebuchets aren't exactly precision weapons, but attention to detail can make a big difference here.
If you're going for max range, you'll want all the weight you can fit in 9L, which means solid metal counterweights. Steel or iron would be decent (70kg). Lead would be better (100kg). Tungsten or depleted uranium would be much better (170kg). For an egg, this is a vastly disproportionate weight, and engineering the arm for that will produce some odd proportions.
170kg of tungsten is around 20 000 dollars.... steel and lead are more feasible. The sling pouch design will the most critical part as it needs to distribute the acceleration forces evenly on the egg and release the egg cleanly so it doesn't break up at that point. Its definitely going to take some time to optimize the machine for maximum range.
>>992375
>170kg of tungsten is around 20 000 dollars
You didn't give a budget. Some people spend lots of money on competitions like this.
>The sling pouch design will the most critical
Probably not. I've never had any issues with any slings. Most any soft material will not break the egg (trebuchet accelerations are very gentle as catapults go), and unless the sling grips the egg like a glove (it shouldn't - cup it just enough so the egg doesn't roll out the sides), there shouldn't be any problems with release (with the sling at least - as I mentioned, the hook can be tricky.) Maybe thin leather with cord sewn into the edges. I usually cup my slings by using two pieces of material, slightly wider in the middle, and baseball-stitching them together.
Awesome thread Anons. You just reminded me why this board is worth looking at.
For small size and overall performance you might look into a guillotine style trebuchet, though more mechanically complex they are more efficient.
>>992375
The depleted uranium didn't phase you?
