So he gradually increases the energy transfer from the weight to the arm over the course of the drop. But that arm swinging around must have a lot of energy loss due to friction and air resistance.
This loss will rise exponentially with the speed increase right? So in a sense he is holding his energy budget in a very inefficient phase, with high losses.
Two things support this. A) he spent a lot of time trying to make the arm more arodynamic. B) The spool widening at the end, which is essentially changing back down gears, applying more torque, right at the end when you want speed.
An alternative would be to drop the weight, and let it fall unrestricted until it gets to it's highest speed (this would minimise friction and air resistance) and only at the end of its fall, transfer the energy into the arm.
In this case the arm would only need to rotate 180 degrees or whatever, and not waste energy rotating right?
And then, to take this a step further to make this work there would need to be some flexibility or elasticity in the system to take energy from the high speed falling weight to the arm.
And what you have ended up with is something that looks like.... A whip!
Aerodynamic drag on the kinds of things that are involved in trebuchets is always quadratic with velocity.
I think your assessment is correct about the energy losses. I'm just not sure about the fix.
If you want to accelerate a weight quickly in a single swipe, (simplified) gradually reducing the mass along the length of the whip imparts more kenetic energy at the end (the whip crack).
So the arm would no longer be rigid, although you can see in the OPs video it isn't actually fully rigid.
To make things easier, start with an "integrated sling ballistic" (ie: a piece of thread between two lego pieces). Sling release is actually fairly complicated so chop it out!
The arm is generally a rigid lever, and the sling acts exactly as your "gradually reducing mass". In his design you can see the kindof bike gear shape at the axle and eventually coming like an "A" towards the tip (and reducing to "infinite thin-ness" via the string/sling).
After you've built one simple (small) trebuchet, test to failure! How much weight can you stack on it before a component breaks (bucket? arm? axle? sling? frame?). How heavy of an object can you throw before "everything starts messing up"?
My recommendation for ballistics is mini-marshmallow (desktop), regular marshmallow, mega-marshmallow, then switch to "hard" ballistics, eg: mini candy pumpkin (the connoisseurs choice), tennis ball, basket ball, etc.
Once you start throwing dense, solid objects (marbles, golf balls, baseballs) your risk of property damage and injury goes up fairly exponentially, so stick to marshmallows and tennis balls until you feel more comfortable.
Spend lots of time figuring out safe/reliable trigger mechanisms, WITH A SAFETY! For my tennis-ball treb, I did three eyebolts with a dumb screwdriver on a string, and a vise-grip (clamping) on the far side. Eventually, you're trying to safely "release" 100's of pounds that is being held in tension, and if you have a misfire (fail to release trigger) you're potentially approaching a "loaded" machine which is demonstrably "not working right". Lifting/loading 100's of pounds and then having an unlocked trigger (which _also_ may fail) is not safe for anyone.
You're going to transfer the energy quickly, you'll just break any "arm" that's light enough to accelerate with the energy available.
You could maybe use an 'already broken' arm (rope, like a whip) but then it's not a trebuchet.
Not saying its impossible to create a successful system like that, in fact it sounds sort of a natural/organic design that potential could be closer to the optimal design, but it would be more difficult to accomplish and probably need more testing and design iterations. So I think OPs strategy is more simple and pragmatic in this case.
The big issue in your proposed version is building an arm that is light enough to not absorb a lot of energy (it still needs to be rotating at the same speed as the progressive version in the video) but rigid enough to survive that sudden acceleration. My bet is you'd lose way more to the arm flexing and the added weight than you would the benefit of not dealing with aerodynamic losses.
Had a similar feeling come to me as I watched this video a few weeks ago. It made me really want to see someone make a whip-based trebuchet that uses a big spring like https://www.youtube.com/watch?v=PkQZU-CBwhk
Either way, the weight of the whip is hardly important right, as you are just doing an energy transfer from the falling weight into the small ball, the lighter the whip the better, as long as it doesn't break. If the whip is heavier, it will soak up the energy budget in momentum
He has some great videos. I watched this one and was impressed at the calculations, the transparency and the celebration at the end when he reached supersonic speeds.
A thing that I completely don't care about: Supporting some YouTube guys.
YouTube "creators", even if they are not basically "influencers" (a.k.a. advertizing), even in the best case, a YouTube guy is for me the same as someone at RTL, DMAX, Fox, or any other random TV station. It might even be that I watch their show every now and then... But I'm not constantly thinking about how I can support these guys. And IF they actually disappear tomorrow, there will be other ones coming up.
There is DEFINITELY no scarcity in YouTube guys...
PS: The narration inside the community is fundamentally more romantic. But guess what, I don't care. ;)
PPS: With all my browser addons (incl. "Sponsor Block" - every YouTube consumer should have it!!!), I'd not be so much of a support anyways.
PPPS: The first thing when someone would ask me to consume a YouTube clip would be to ask Claude or whatever service to generate a summary/transcript for me. I reject to constantly burn multiple minutes in order to consume random/funny/pointless content that could be a matter of 10 seconds if provided as text together with four of five images.
The domain of ML-driven design optimization isn't exactly new, is quite specific, and I would need convincing that Claude has anything to contribute to it.
It’s not a problem of the ML model. It’s a problem of the human setting up the description of the problem in such a way that the model can operate. OpenSCAD gets a long way towards that target. Use it with a model thats been trained for the purpose - just the same way that ML has been used to produce optimal rocket engine nozzles and fuel transfer systems.
Not that difficult, really.
> Claude has been trained on high school physics textbooks, yo
The very fact that physics textbooks have little bearing in the real world is the whole damn reason why Mechanical Engineering exists as a separate discipline, yo
> It’s a problem of the human setting up the description of the problem in such a way that the model can operate.
It's a problem of defining the initial state (which is the trivial part that OpenSCAD may be a contributing element of), defining constraints and variables (what is allowed to be changed and not, for what can, in which ways, to what extent, i.e. what is the library of allowed material, fastening, machining, assembling techniques available to your very specific situation), defining evaluation and fitting criteria.
I see very little adequacy of general purpose LLMs in that
> the same way that ML has been used to produce optimal rocket engine nozzles and fuel transfer systems.
Which has nothing to do with "just use Claude, yo"
- text description to 3D geometry gap: you can't easily describe complex geometry in a language that's common and convenient to both humans and machines
- 3D geometry to physical model gap: material , geometrical constraints induced by manufacturing (machines, tools, costs, …)
- physical model to model fit for simulation gap: meshing, constraints, stress modelling, …
- simulation outcome to fitness assessment gap: now you have a high-dimensional and numerically heavy simulation to weigh against a non-rigorously defined acceptance criteria
- simulation outcome to geometry profiling gap: how do you even start to guide the LLM into the vast space of possible changes to apply to the 3D geometry and reboot that loop?
LLMs don't strike me as a particularly relevant technique to apply here, to be honest.
I say, put your money where your mouth is and prove you can double the efficiency.
Both of those can be modelled - rather precisely if you have the compute power. By modelling the derivative of all of those things with respect to every parameter of a parametric design, losses can be minimised with gradient descent and a huge Jacobian matrix.
A few parameters are obvious (string length, arm length, etc), but there is no need to keep the set small - you could model the exact shape of the projectile latch as a spline with 100 parameters for example, and let gradient descent find the best shape to minimize losses.
AI can set up and run all those simulations, and all you have to do is pay the AWS bill for all the open foam instances you'll be running.
Other trebuchet fans who dream of building one some day may be interested in googling "walking trebuchet" for a surprisingly high complexity/results ratio.
Just for the fun of it. Pure whimsy.
- structural: There are height and size limits on things you can build without a permit
- trespassing: flinging objects onto others people property is illegal
- endangerment: any activity that can endanger other people is illegal
All of these three depend on how rural you live I guess. So in a suburban neighborhood I would assume they get involved very quickly.
I would think you want it decreasing to near zero to extract all the kinetic energy from the mass, leaving the mass stationary as it hits the ground.
But seriously, it's one of those things we had preciously little of before online video became a thing.
It just seems like such an obvious tool, rather than a weapon.
Honestly, what the hell. Where do you think gunpowder comes from, thin air? Oh, is gravity a subscription service in your country?
Come on, try to at least be sensible about your response.
And yes, people who do avalanche control typically fire explosives out of a cannon or drop them from a helicopter. Getting a machine supply all the energy is the whole idea instead of climbing mountains yourself.
The point is to avoid that entirely and harvest gravity.
Re-wilding teams already climb far and wide, and this would extend their reach without increasing their dependencies.
Ammo is a dependency.
And if you INSIST on making everything completely low-tech and renewable, build a potato gun and use high-proof alcohol as fuel. It'll weigh less and last longer than whatever rube-Goldberg trebuchet design you have.
It's not obvious whether a trebuchet is better than compressed air, like a BB gun.
All harvesting requires some secondary-energy source.
Gravity is a resource, it takes effort to convert it to a form that can be applied - just like wheat, photons, air guns, etc.
> It's not obvious whether a trebuchet is better than compressed air, like a BB gun.
True, it’s not obvious yet, but it sure is fun following along and imagining the final, highly optimal version making its way through the process. I’d use it for some seed bombing hijinks, anyway. Green up the place, I would.
Problem is the muzzle velocity is pretty paltry right now. I think we are stuck behind the energy density of the power source
Is gravity a subscription service in your world?
One launch location or multiple?
What frequency of launch?
How heavy are the payloads?
How good accuracy?
What transport methods are available?
How long should it operate without maintenance?
Is solar an option if we go electric?
Etc.
I guess a couple hundred launches a day would be useful for seed-bombing/re-wilding, especially on rugged terrain.
Seed-bomb weight: I’d say anywhere from 1-10 grams, maybe?
Accuracy - it’s a seed bomb, you want dispersal to happen, so maybe the more interesting question is, how would you design a seed bomb to survive the trebuchet speeds and g-forces while also allowing for directed dispersal in the intended area. Seed-bomb design for impact conditions is also something of interest - some seeds need to be embedded in a layer of soil, some don’t. There are many parameters to optimize in the seed-bomb side of things, too.
Transport method: backpack-friendly, I think. I’d hike to an area, set up the trebuchet, and spend the day dispersing in a wide circle around the base. If the terrain is rugged, portability is especially important.
Operational time - one thing I think is important is that the trebuchet be resilient for long term use. If Toms’ engineering efforts prove fruitful, I’m sure the material construction will get some optimization such that, perhaps, the only thing that would need to be maintained would be the line - however, this is a known science, see for example the sailing industry, rappel lines, etc.
Solar/electric? I think a wind attachment for rewinding might be a bit more productive.
The scenario: a team of 5 is off for a month in rugged terrain, with the intent of dispersing targeted seed packages over a wide region. The seed bombs are designed to protect the seeds, the trebuchet is designed to deposit them sufficiently well that they remain viable in their final destination. We hike out there for a couple weeks, do a mass trebuchet dispersal, we come back a year later and observe the results.
Your biggest problem here isn't the launcher, it's the projectile. It's going to be damn near impossible to get a 1 gram projectile more than a couple hundred yards unless it's a dense metal. Doesn't matter how fast it's going, drag always wins here.
10 grams is more plausible, but then you're looking at ~1000ft-lbs cranking energy to get 10g supersonic (@ 40% efficiency) It's doable and you'll only be burning an extra ~100 calories per day for 200 shots. You might get bored though. An airgun will have far worse efficiency most of the time, though it can launch dart-shape things which can go much further for the material density.
You mentioned a bow, which is probably the tradeoff point of everything discussed so far. Flight bows are designed for distance shooting, are lightweight and can go 500 yards easily. The downside is you'll need to make the arrows yourself, cause there ain't no supply chain to sell hundreds at a time cheaply.
For the "jUsT uSe a hElIcOpTer lol" comment;
No, that's not practical, but you CAN get an RC plane that will carry a couple pounds for a tiny fraction of the cost. In terms of how much area it can cover vs supplies needed, that plane is going to be the least thirsty thing on the mountain, assuming you even need to climb it then.
Seriously, rich people, get out of your own bubble heads now and then.
A low-tech, low-resource-intensive, no-dependency application of this technology has huge applications around the world.
Do you know how much it costs to operate a helicopter per hour? Now scale it to month-long efforts to turn desert into forests. Scale it to a thousand villagers. Scale it to ten thousand villages.
>Why the need to have people hike out just to launch the seed bombs.
Because re-wilding requires a hands-on approach to be very effective. Just look at what China has done with the Great Green Wall - this was a labor intensive mega-project. Low-tech, highly effective solutions for seed distribution could be of great benefit in that context - without a bit of fancy speculation on our part, we'd still just have deserts and nothing to eat.
YES, you could 'just use a helicopter'. You could just sit back on your deck chair and be served mocktails, too.
Sometimes, kids, you need to do a bit of hard work.
Do you know how easy and cheap it is to make gunpowder?
I was making black powder rockets from grocery store ingredients when I was 12.
Also pretty sure several parts of the mechanism would need to be considered consumable if operating over a long period.
>Also pretty sure several parts of the mechanism would need to be considered consumable if operating over a long period.
Well, that remains to be seen after the optimization steps complete. Fine with me if it takes a year before I have to replace a string.
Meanwhile, I'm guessing you are suggesting the "ma' gunpowder" deliveries happen via drone, or helicopter, or methane-powered rocket ship or some such nonsense, lol ..
Seeds do.
Bread is consumed - it does not self-multiply.