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Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

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Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#51

Post by magicalhippo »

throw310822 wrote: post #48
adlpz wrote: post #44

Earlier quoted context omitted.

You sound fun... This is HN. The trip is the destination, bla bla.

No, I understand, it's the claim from the very first sentence that "gravity itself seemed to forbid" (reiterated later in the text) that annoyed me. It's just making up a non-existent obstacle to hype up the result.

It's a bit clumsily written, but I'm pretty sure that's a reference to what Tom mentions in his video, that since g = 9.81m/s^2 you're not getting close to the speed of sound just from falling from a reasonable height, even ignoring air resistance.

Thus a traditional trebuchet design cannot reach that speed.

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#52

Post by throw310822 »

magicalhippo wrote: post #51
throw310822 wrote: post #48

Earlier quoted context omitted.

No, I understand, it's the claim from the very first sentence that "gravity itself seemed to forbid" (reiterated later in the text) that annoyed me. It's just making up a non-existent obstacle to hype up the result.

It's a bit clumsily written, but I'm pretty sure that's a reference to what Tom mentions in his video, that since g = 9.81m/s^2 you're not getting close to the speed of sound just from falling from a reasonable height, even ignoring air resistance. Thus a traditional trebuchet design cannot reach that speed.

But since potential energy from gravity is mgh and kinetic energy of a projectile is 1/2 mv^2, calculating height and mass of a weight to power the projectile is absolutely straightforward. The terminal velocity of a falling weight has nothing to do with it (even historical trebuchets used a leveraged system in any case).

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#53

Post by bethekidyouwant »

jijijijij wrote: post #38
daemonologist wrote: post #3

Also (mentioned by Tom), this elastic-powered supersonic trebuchet is an excellent video: https://www.youtube.com/watch?v=gdXOS-B0Bus

That device is so much more scary! Both really demonstrate the ridiculous amount of energy stored in a pinch of gun powder. And I presume gun powder is quite inefficient at driving the projectile, too.

I’m not sure dropping 50 kg 4 feet… is my idea of demonstrating the ridiculous amount of energy stored in something…

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#54

Post by krisoft »

red_admiral wrote: post #37
MomsAVoxell wrote: post #2

Seems like such an advance in this ancient technology. It would be really cool to see it applied in interesting ways. I really wonder just how effective this could be as a defense system .. the mind wanders with every update Tom makes .. I imagine an aiming/targetting system would make this an effective, easily replenished, low-resource weapon system for some applications. Attacking feral animals, perhaps? How could…

> deal with avalanche conditions Swiss solution: chuck some explosives out of a helicopter https://www.youtube.com/watch?v=H519qhLnRtM (start at 1:20) (In the image at https://swisshelicopter.ch/de/aktuelles/721-lawinensprengen-... the explosive pack says "do not eat". I'm not reassured that we need this warning for people allowed to handle that.

> I'm not reassured that we need this warning for people allowed to handle that.

Not sure what type of explosive that is but the rumour is that C4 when ingested gives a high similar to alcohol. Or at least that is what some troops believe.

“Amongst field troops in Vietnam it became common knowledge that ingestion of a small amount of C-4 would produce a ‘high’ similar to that of ethanol, and it is possible that this was the reason for this episode.” From the clinical description of a c4 poisoning case.

https://pmc.ncbi.nlm.nih.gov/articles/PMC1279680/

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#55

Post by cricalix »

genewitch wrote: post #13
daemonologist wrote: post #3

Also (mentioned by Tom), this elastic-powered supersonic trebuchet is an excellent video: https://www.youtube.com/watch?v=gdXOS-B0Bus

the "shot you've been waiting for" was sort of anticlimactic, but the two plywood arm shots after show what it actually sounds like. I think the grass and tree dulled the sound a lot on the metal arm. I actually have a camera that can shoot that at high speed (1200fps), but i'm sure other people have better cameras these days, mine has very low resolution.

Slow Mo Guys have a Phantom that rocks up around 1.5 million FPS. They've used it to show how glass cracks etc. when you get to that speed though, you need a LOT of light, and a very low resolution.

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#56

Post by Mashimo »

throw310822 wrote: post #49
Mashimo wrote: post #47

Earlier quoted context omitted.

Mate, you are on HACKERnews. We are all about this.

Of course, but there is a continuum between "I spent years tackling this complicated problem and the solution will benefit us all" and "I've entered the same McDonald's drive-through 1000 times in one day to order always the same thing". Some achievements are closer to the first end, others lie more somewhere in between.

You will hate his stirling bike.

I love his entusiasmen for engineering and having the drive for a multi year project, even when the result is just another trebuchet. All while teaching physic in an entertaining way.

I don't get how this is close to driving through a drive through.

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#57

Post by fc417fc802 »

gcanyon wrote: post #35
gattr wrote: post #9

Earlier quoted context omitted.

I also loved the video. But I'd think if one wanted to deploy "simple" mechanical projectile weapons at scale, pneumatic launchers would be easier, more compact and more reliable (way less cool-looking and operating, though!).

I think the cycle time on this would be far superior to a pneumatic system: cycling this system effectively means lifting ~100 pounds ~8 feet, which a reasonably fit person (who could reach that high) could do several times a minute for extended periods. He got an efficiency over 40% (if memory serves, I watched this video yesterday) -- I wonder between pumping and discharge how efficient a pneumatic system would be,…

If the pump were operated by a bicyclist and the projectile feed automated I imagine the pneumatic system would win out by a very wide margin regardless of any reduction in overall efficiency.

Re: Tom Stanton's supersonic trebuchet breaks sound barrier with gravity alone

#60

Post by itronitron »

27183 wrote: post #42

It would be interesting to scale this design up. Not necessarily in terms of velocity--supersonic velocity for a large trebuchet munition isn't necessarily desirable. What I mean specifically is scaling up the multi-revolution arm and sling release technology to be capable of launching a ~1 ton projectile. Could it be done reliably with traditional construction techniques (wood, treenails, lashings, minimal metal har…

The spiral drivetrain seems like the most innovative, and elegant, technology that could be built with old tech. It requires some very strong rope though, so if you went back in time you'd need to really focus on that.
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