How Do These Fireworks Fly?

[@Nighthawkinlight]

This video may be an example of my ability to make a simple concept complicated, but I'm sure if that's the case you'll set me straight in the comments. It took longer for me to finish with this video than it should have. Hopefully it's entertaining and gives you something to think about even if my own conclusions are less than decisive. I'm excited about other projects I have coming up, so stay tuned.

[@ibuildthings6576]

👀 👄

[@SuperMegaCoffeeGuru]

It looks to me like the firework fuse feeds in not just into the side but is also following the curve at a slight angle, maybe due to being wrapped into the paper or cardboard housing. This would give it enough thrust in that direction to effect the top-like spin that causes it to right itself before the main rocket fires. Then the spin acts as a crude rifling, giving it a stable line upward. It would also answer why the first is offset instead of centered; a middle mass burst would not allow for stability on an end and it would likely fire off randomly in one direction once the secondary kicked in.

[@joeydubbs763]

2 things. 1 - it looks as though they're also weighted heavier towards the 'nozzle' end via a thicker clay wad & 2 - I further suspect you'll never truly understand how they work until you 1st build one & then improve on the design of them..... ..challenge extended?..😉

[@MrAndrew535]

This question has literally kept me awake at night. I do appreciate the difficulty in saying that without sounding sarcastic.

[@al-aurum2457]

making your own versions of it will prove your theory

[@USWaterRockets]

The way it appears to me is that the hole in the side of the tube is not at a normal to the side but angled slightly, It is also not centered on the length. This gives the tube a spin along two axes, but it will preferentially spin faster about the axial center (think about the famous example of the ice skater spinning and bringing their arms in to spin faster because the mass is closer to the axis of rotation). The offset nozzle along the side gives thrust that also tries to rotate the tube somewhat perpendicular to this, but the tube is spinning axially so much faster that the radial thrust is only going to wobble it since the radial thrust will be rotating about the axial rotation and cancelling itself out since the thrust vector is constantly sweeping around the tube. However, the "ground effect" will tend to provide a larger radial thrust whenever the nozzle is pointing to the ground, so this will cause the radial thrust to be imbalanced when it is pointing down. The imbalance causes the lengthwise offset nozzle end to lift until the tube is closer to vertical and the ground effect cannot cause the imbalanced thrust. The tube at this point is nearly vertical but wobbling as the radial thrust is more or less the same as it rotates around the axial center. Now the bottom nozzle fires and shoots the whole thing up at a somewhat vertical angle. I hope I explained that well enough.

[@hellishgrin4604]

Do they spin in the same direction every time? That would be a good indicator of factory design rather than crude (albeit effective) construction. Seems like they did for the most part, but I might rewatch to check.

[@EzriAran]

I had the same thoughts with the 2 axis offset on the thrust. the hole, and fuse, is notably drilled to one side of the tube, not dead center. and the ground-effect for righting the spinner. Of course once its spun up and upright it likely takes advantage of the gyroscopic effect to stablize it. especially since its spinning much faster on the narrow axis, than the wide one when its laying down. Which is also different from the ground spinners.

[@tbac2432]

What I would like to see is placing the firework into a wheel bearing. Get a wheel bearing that has the same or almost the same ID as the OD of the firework. Lite the firework and film from the top. This will let you know if the burn is on a slight angle for the spin. If it is my guess is your guess could be confirmed.

[@woodandwheelz]

I think I was thinking similar to what you explained but thinking of the firework as more of a gyro. As it spins on the axis you described, like a qyro, it will want to upright itself and stay on the center of the length. As it stands up, the wobble becomes less and less and by the time the bottom ignites it's almost standing straight up and down. With the continued spinning from the initial stream the tube will stay perpendicular to the ground (or flat surface) and the second blast sends it straight up. Just my thought.

[@AzurusNova]

I would also think to look at the firework head on to get a look at how far off the first initial jet is from 90 of the center axis of the firework itself, so even a small degree one way or the other would help the effect of getting it to spin, the ground effect helping to push it up on its tail end and start to spin like a top, and by that time it is pointing up and the secondary rocket kicks in, launching it into the sky.

[@TheBackyardScientist]

those are so fun! I always buy a few a few packs every chance I get. Ive wanted to slowmotion these for awhile but never got around to it. Im glad you did because you did it better than I would have :P Ive always thrown them when the fuse is almost done. they take off in very unpredictable way and its always a mini heart attack when they zip past your head.

[@ComradePhoenix]

3:03 Awfully considerate of that glass to wait until the test was finished to crack. Honestly, though, I think you've hit the nail on the head with your revised hypothesis (not so sure about the tippy top one). Don't sell yourself short, either.

[@yeet1337]

You can really see heat conduction with the glass. It takes some time and that's really wonderful somehow

[@brapamaldi7666]

its the cooling of the glass that causes it to crack, not so much the heating. hence why glassmakers have to anneal their glass and cool it slowly over several hours in order for it not to crack / shatter.

[@yeet1337]

@@brapamaldi7666 Oh, I didn't know that! Is it because some parts cool down faster than others and the slight contractions cause it to crack?

[@brapamaldi7666]

@@yeet1337 i think so. im not 100% on all the details, but when I was at uni doing glass work they had big ovens that you put your work into so they didnt cool too fast and crack. with the heat being so focused on the glass pane and the rest of the pane being cool id say there would be a high amount of internal stress in that glass and even just a small temperature change would possibly causes the cracks to happen. im not an expert on it tho, just something I learned when I took glass as an elective at art school.

[@reggiep75]

The glass is like ta-dah and then starts shaking it's jazz hands awaiting the applause!

[@arthurabraham3271]

Admitting that you may be wrong, and others correct, is itself a sign of being smart :-)

[@MarkJones-zk1sj]

So now that you understand the physics, it is safe to assume your next video will be a DIY giant speed ball? PLEASE! PLEASE! PLEASE!

[@Volvary]

You made me realize that we haven't had a DIY firework video from NightHawk in a long time.

[@vbkfivn]

@Zephyr Haven Rocket candy would be very nice.

[@AmorDeae]

First a diy ball mill for making the BP.

[@carsonhunt4642]

Volvary because KZbin turned pc and deranks and demonetizes those types of videos:/

[@SoulDelSol]

Speed ball? No cocaine and heroin does not a good video make

[@c4715]

I'm a physicist, you're correct in your assumption with the spinning top. Horizontal rotation isn't energetically favourable, so that's why it eventually rights itself to vertical. But it's a very chaotic system so there will be a lot more things going on, but the angular momentum component will be the main explanation.

[@zicada7661]

Great idea cutting them in half and gluing them to a pane of glass! You got some really good shots. Well done mate.

[@BillDWP]

Yeah, that had me mesmerized.

[@d6wave]

true ..true .

[@TheRealIHP]

Especially seeing a glass shattering.

[@mat100ca]

@@TheRealIHP i saw that and now have to test if i can use these to cut irregular holes in glass. welp guess its time to buy some glass and fireworks

[@amarug]

As a mechanical engineer, I am in love with this design. It uses friction, the asymmetry of floor/sky + actio/reactio ("groundeffect"), conservation of angular momentum... all in a beautiful ballet with redunancies that lasts just a tic longer than a blink of an eye.

[@rustlebruxz0013]

I think the secret is the hole formed by the fuse, and later the side exhaust, is not bored straight into the center of the tube. It is angled off to one side. This causes the exhaust to start a twisting motion which forces the tube to start rolling on the surface. When the exhaust starts firing down into the surface, that forces the tube to stand up. Now that it is in a vertical position the exhaust from the hole on the bottom of the tube launches it upward. Also, twisting motion from the side exhaust also has a rifling effect which will try to stabilize the upward direction of the tube.

[@DarkDragonEgg]

Yeah same thought, also when looking at the slow motion i think there is a small time where the side thrust is pointing down(to the longer side of the tube. I think that is based on the positioning of the material with is around the fuse hole and above it. ) maybe this also brings a bit more of the tiny stand up force. To test it you should stick it again on wood and see from top perspective where the bust comes from.

[@JR-nw4to]

could the "bottom" of the rocket have a higher weight distribution also? the side nozzle then pushing it up vertical on to its "base"

[@ESSBrew]

Yeah, he never mentioned that at all. Need more info.

[@AtomicShrimp]

I enjoyed thinking about this along with you in the video - the thought process journey is as enjoyable as any conclusion we may eventually reach. As a further experimental idea, I suggest trying to spin small cylinders on a flat surface, with no rocket thrust - I feel like there is something about the geometry of the contact point with the ground vs the rotation of the object that tends to drag the cylinder into an upright position

[@alexanderwatson9845]

Same with a hard boiled egg- spin one flat and it will stand up!

[@charlesenfield2192]

Clearly the alignment of the side nozzle provides a significant thrust vector tangential to the circumference of the cylinder. Combined with it's orientation relative to the CG, that's going to tend to make it stand up. If the thrust was also angled axially toward the CG, ti would make the object want to take off, without any help from the jet on the end. That said, it would require much more thrust, and it wouldn;t be as fast or impressive. This configuration would be much cheaper and much more exciting, which, after all, is the point.

[@rebelfanatic93]

As a kid I used to play with empty soda cans. When you lay one down on its side and place your fingeron one ends and press until it slides out from under it, it will start to to spin and it it will lift axially sometimes even standing straight up. I think this is a similar effect.

[@SteveReynold]

Jackson Cunningham I think you should’ve drink less soda

[@kNasty_]

I would do this in elementary school with crayola marker caps. press down on one side, it would shoot out some distance while spinning rapidly. Usually would lift one side into the air and sometimes finish standing on end..

[@Videoswithsoarin]

Jackson Cunningham i cant figure out how this is supposed to work.

[@savage6394]

As a kid, My parents bought me toys.... Only kidding Jackson.

[@christian.tisdale]

You can also do this with chapstick! I immediately thought of doing that as a kid when I saw this video.

[@michealpettitt9246]

This is great! This effect is basically the reverse of spinning a AA battery like a spinning top! While the rpm of the battery is high it will stand on end but as it slows down the battery becomes less stable and tilts until spinning to slow and lays on its side and stops, a combination of centrifugal and gyroscopic force

[@TheGuruNetOn]

Weight distribution changes with fuel exhaustion. The firework is exhausting it's fuel from one end. So the heavy end is the opposite end. The rotation makes the firework spin like a top. By the time the rocket stands on the heavy end the firework starts jet from the heavy end changing from a top to a rocket.

[@christhebirb]

Exactly what came to my mind when I saw the fuse burning through the glass.

[@king4aday4aday]

Pretty much this. Also the rotation plays a non-negligible factor, but other comments sum that up pretty well

[@arthurmcconnell7483]

it is weighted heavy at the start I have ariel that is heavy at 1 end with side exit turns vertical then blades turning cause flight

[@maxximumb]

This is what I was thinking too. Is the firework bottom heavy to start with? As the spin fuel is burnt, the centre of mass changes and the lighter end would lift. To demonstrate the effect spin a cylinder full of clay and it will stay rotating on the same plane. Then spin a cylinder that has only been half filled with clay at one end and the cylinder and the lighter end should lift up if the rotational speed is high enough. The thrust from the fuse hole being offset from both the radial axis and the initial centre of mass gives the tube enough momentum to spin. As the fuel is depleted the centre of mass moves away from the fuse hole thrust causing the tube to lift at the lighter end because as the centre of mass moves, the rotational axis moves with it. At some point the two axes of rotation meet and the tube is now aligned for the lifting charge to ignite.

[@TechyBen]

@@maxximumb Oh of cause! Nice spot!

[@Liam_Patton]

My favorite firework I've ever seen used was dark turquoise blue and said SHAZAM in bright turquoise on the side. Its size was about halfway between one of these and a stick of dynamite, and it was completely nuts. In a crowd of people who loved fireworks and in North Dakota where the 4th of july is world war 3 every year, not a single person there had seen anything like it. Somebody lit it, threw it out in the street, and it spun for a second before it sounded like a jet flew overhead and it shot straight up into the stratosphere and disappeared forever. I've never been able to find one for sale or even in a youtube video ever since, and out of everyone there that day, we all only had the one. A single firework that just totally bamboozled everybody and vanished from our lives forever.

[@msmeyersmd8]

The Coanda Effect from the off center axis side exhaust causes the exhaust flow to adhere to the side of the cylinder in an angular 2-D fashion. Primarily circumferential but including an axial component pointing to the shorter end. This resulting lower pressure areas combined with the flat surface high pressures in the 2 axes and rapidly accelerating spinning gradually cause the erection of the cylinder. The secondary gyroscopic effect providing basic but wobbly vertical stability. Ultimately the end exhaust nozzle ejection gases erupt providing powerful vertical forces and the firework shoots upward until the fuel is exhausted. I am being semi-serious about this. But, even to me, it smacks of over analysis. Great video. No. A Fantastic Video. This should be shown to anyone with an aptitude and interest in science and critical thinking. One of the best I’ve seen in a while. With no preference of gender, racial or any other category. You either love this stuff or you don’t. You can teach it (force it down their throats) to people who are indifferent but that will be wasted effort. I’m 60 years old and I was glued to the screen to see the slo-mo video and hear your analysis. Unfortunately, that is not what Public and most Private schools are promoting and teaching today. Sorry for preaching but this is a great video. Keep up the great work.

[@hisoka44444444]

teachers should reference this video when teaching about forces, rotations, center of mass and so on in physics. Cool video indeed

[@nraynaud]

What's crazy, is that they are quite a complicated mechanism, but they are reliable albeit being made of crappy cardboard and clay. It should be an inspiration for rocket designers :p

[@Videoswithsoarin]

nraynaud1 i wouldnt call it complicated, its a tube with a hole in the side and a plugged end full of black powder

[@JoshB_TheTower]

@@Videoswithsoarin there is a *LOT* of physics and chemistry at work when it comes to fireworks. even the very simple ones like firecrackers.

[@crfsikness]

Imagine how dizzy the astronauts would get..........

[@sigmamale4147]

Most rocket motors are already made out of cardboard and clay

[@sharpsteels4635]

Rather it's itself an inspiration from rocket science buddy ✌🏻

[@deedeegreen300]

“That was a mouth full of words and every one of them might be wrong.” 😅 First time watching your videos and I am subscribing bc of that line. Doing the work to test the science and still admitting possibility of error! 👍

[@hardwirecars]

nighthawk does not put out a ton of videos but i believe he is one of the smartest people on the planet.

[@CanIHasThisName]

Watched the slow-mo footage and turns out I was right. It's all magic.

[@allentremper8243]

To be honest, I think you hit the nail right on the head with that"really long mouthful of words...", That the friction from touching the ground, with the spinning motion creates a simple spinning top type effect, then a short burst from the tiny rocket engine that by necessity is pointing straight down and spinning, no tail needed. Thanks for the video, very interesting.

[@intothecalm420]

Flying fireworks were illegal where I grew up. We found a way around that as children that I never understood. We found that if you lit then threw one of the "ground bloom" fireworks into the lake about 50% of the time they would fly out of the water similarly to these fireworks being demonstrated. I would love to see a slow motion video of this phenomenon.

[@mentalunicorn9567]

Doesn't matter how long it took you to figure it out be proud you think like that how the art works rather than just being simple and enjoying it

[@simonjelley]

Interesting... I might know but am equally unsure... I remember being taught that objects only stably spin around axes of maximum and minimum moments of inertia. Books can spin flat like a frisbee about an axis perpendicular to the pages or side ways around an axis parallel to the spine (assuming portrait format) but cannot be stable end over end. This firework will only be stable spinning on its end as the maximum inertia is shared by two axes sideways through the cylinder. The off-centre thrust especially with ground effect can kick it to transition, as can friction at the bottom like the tippee-top. That’s my guess anyway:) great video

[@brandonfowlkes4406]

I was thinking the same thing and you explained it perfectly!

[@StrokeMahEgo]

As the fuel burns away, the center of mass changes. Based on your cutaway, it would result in more mass towards the bottom/nozzle. This probably helps the tube right itself along with the effects you've mentioned.

[@siscanumihail7501]

Maybe the bottom is heavier, that's why it aligns vertically?

[@aravindmj920]

an object, if allowed to rotate freely, will do so in the axis of least moment of inertia. MI directly propotional to radius. You are right, in this case keeping jet one eccentric to one side makes the other side heavier, which makes spinning on that side more stable (stable equilibrium) long enough for the second jet to fire.

[@sidjindal]

Yeah but maybe like tippy top. It had its heavy side up!

[@Slowly_Going_Mad]

It's a variety of effects that give it it's properties like you said. The main one though is the gyroscopic precession like Euler's disk. And thank you for the slow motion on those, I wondered these things too.

[@kengamble8595]

Slow motion cameras, Essential need for curious minds ! 😊 Thanks for sharing and take care. 👍

[@htmagic]

NightHawkInLight, I saw this before and fell upon this video again. This time I had a fresh look and studied your slow motion videos. One thing I noticed is that the fireworks burns at the top, making the unburned powder below. This heavier weight would tend to be at the bottom and the burning section at the top, like a plumb bob. Then the powder continues to burn and the flame hits the open core which exhausts out the bottom.

[@jayytee8062]

I think it tends to stand upright because the propellant burns from the fused end making it lighter in weight. The bottom end must be where it is because it has still unburned propellant making it heavier. But of course I'm only taking a guess......

[@SylasTheGreat]

@David Barr They aren't right though... There's a giant tunnel in the bottom half... That's way less material then a tiny fuse. Idk how you thought they could be right lmao

[@totally_not_a_bot]

Torque. Torque points toward the fuse end. If the fuse was flipped around, it would point away.

[@brapamaldi7666]

@@SylasTheGreat a giant tunnel... through a piece of clay at the base. if you pause it at 3.00 and have a look at the clay on the top part of the bottom section (above the 'tunnel') you can see it angles towards the fuse hole ever so slightly, which I bet changes the centre of balance and spin axis ever so slightly, but probably just enough.

[@SylasTheGreat]

@@brapamaldi7666 it's still lighter on the bottom so it still doesn't work

[@jayytee8062]

@@SylasTheGreat How is it lighter on the bottom when ignition starts from the top where the fuse is? The other thing to consider is centrifugal force and motion added to the mix.

[@rbivgq1734]

Love how you have your own disc golf cage in your back yard great way to practice the short game.

[@7171997007]

try it again on surfaces of varying friction coefficients!

[@xpumpkins8951]

When the firework's initial exhaust is pointed upwards or anywhere pointing up, it pushes the firework to the ground, but there's no downward movement due to the ground blocking it, but when it's pointing down, there's nothing holding against the firework on the upper part, therefore it's pushed upwards. When the firework is lifted up, the gyroscopic precession and other things play their part.

[@qvatch]

if this were kerbal space program I'd say it was gyroscopically stabilized. Spinning stuff goes straighter because it averages out. Handy in flight.

[@arnomaas6452]

theory : the cylinder is initially bottom heavy because of quantity or/and type of the second stage propellant.So, while the first stage burns and the stabilizing spin initiates even more propellant is burnt from the first stage /top and therefore when the time comes for the second ,still heavy ,stage to ignite the whole thing has balanced/righted itself on the vertical axis and off it goes . Nice videos as always !

[@Advoko]

I felt like a kid again! ))) p.s. Ben, if you want your brain to explode try to figure out a "Spinning T-handle in zero gravity" effect. There are videos on youtube showing this amazing effect (of t-handle spinning in the air and flipping back and forth at the same time).

[@clearlakerain]

Yes! 3 axes of rotation with different center of mass. It's cool & must see.

[@marc-andreservant201]

It's called the intermediate axis theorem, and the reason it wants to spin on its longitudinal axis is because this is the axis with the least moment of inertia compared to the second principal axis (spinning on its side) and the third principal axis (cartwheeling off the table). This does NOT work with a uniform cylinder as it only has one well-defined principal axis. However, there is a brief moment where the firework has a light spot on the side with the fuse hole, making that direction of rotation unstable compared to spinning like a top. By the time the weight becomes uniform, it becomes spin-stabilized. Try spinning a deck of cards in the air on its width axis. It wants to spin on its length axis instead.

[@LogicBob]

I think if you watch regular ground bloom fireworks AND the helicopter version in slow motion, you'll be surprised! 😉

[@Landogarner83]

Yep i think so too

[@your_dude]

Keeping the glass crack in the slow mo shot excited me way too much 😂

[@dananorth895]

I burned some magnesium in a glass ashtray once and it cracked/exploded.

[@potato4dawin1]

take the spinning top and record it. now play the footage backwards. that's how the rocket stands upright except rather than normal force it uses a pressurized jet of burning fuel decelerating spinning top versus accelerating spinning rocket both changing angular momentum, transitioning from upright and spinning to laying down and not spinning or vice versa tippy tops work on the same principle but are a different application of it.

[@Bombskwad92]

That half firework was pretty dope. First time I've seen that

[@c4715]

The cut away of the firework is amazing, it's so similar to solid rocket boosters used for spaceflight!

[@IngeniousOutdoors]

I think you're on the right track with the friction idea. I used to take batteries and marker lids and such and spin them on the table. What you do is lay ir flat on the table and put your finger on one of the ends. Then you press down hard until it pops out from under your finger with a great deal of spin. It will shoot out and away until you perfect the pulldown and back method. but you'll see it does the exact same thing as these fireworks. It shoots out spinning on its long axis and quickly stands up but then drops back to riding on just the bottom edge of the battery until it loses all of its momentum and stops. Try it yourself. Film it in highspeed even. You'll see it spins up and stands up just like your fireworks only with no thrust from black powder.

[@jeansiggy470]

pls do a collaboration with the slow mo guys or smarter everyday to film even more impressif firework ignition from the inside with your glasplatt technic, it was awesome

[@NatCo-Supremacist]

god yes this

[@cobraman90]

That cut in half firework was oddly satisfying to watch in slow mo

[@askquestionstrythings]

This is very cool slow motion. (sad no ending bird clip)

[@blackturbine]

The top of the firework that produces side thrust lifts the top with side nozzle off the ground and at the same time pushing the top with lift nozzle down increasing it's fricton causing it to always correct to the right top Using math and stuff this firework is really simple but ingenious in it's construction

[@user-fm2bh2qd4i]

I found it by looking at Ben on a Japanese TV show! Please do your best to make fireworks!

[@rerere284]

This brought to mind two old youtube videos: "Spinning Tube Trick Explained" by Veratasium, and "Strange Spinning Tubes - Numberphile" by Numberphile. In that situation, the tube, despite not having a rocket on it, still lifts up a little off of the surface.

[@Coltrabagar]

It would be really great (technically difficult to achieve, of course) to see them go off in free air rather than close to the ground. I bet that would help unlock the effect of having that solid plane of the ground causing them to go up. Another idea is to set them off inside a half sphere and see if they tend to go up or more perpendicular to the surface of the bowl. The fact that the flat surface is perpendicular to gravity may be significant. Being able to observe them in freefall reduces or eliminates gravity. Angular momentum is definitely a factor. Changing center of gravity. Air resistance, perhaps even magnus effect to some degree. Probably even The Dzhanibekov Effect.

[@ersanseer3078]

Good theories in these comments. I think it comes down to a combination of a) the rotational axis will always shift from propeller-ish to bullet, b) during the axis shift the fuse end always becomes "front" of the rocket, unsure why though, c) the fuse end technically has two choices during the axis transfer: point down or point up. But since the ground is in the way of down, it inevitably finds itself pointing up.

[@sketchyAnalogies]

“Which you should not do.” *nearly gets hit by firework* Well then, he made that point well.

[@2007Aman1947]

From what I can gather, and also my playing with things, it is the rotation that makes the other end of the cylinder behave like a wheel's contact point and it rotates like a turning wheel which tilts it like the bikes do while turning and the wheel's axis starts to go towards being vertical. So the faster it spins, the straighter up it gets. Try spinning a small but long cylinder like thing like an empty lipstick, a plastic tumbler or something on its axis and let it go to the ground sideways, not perfectly horizontal though, and the faster you have spun it, the straighter it will start to stand while spinning. And it wouldn't matter which direction/side you spin it from and which side touches ground. BTW, I saw this firework for the first time and it amazed me how a simple effect was used to create such a nice little mystery.

[@Ramius117]

I’m refraining from reading the comments just to keep my thoughts trained on what my intuition was telling me, and I didn’t pick up on you mentioning anything about it: mass! Or rather, center of mass. I’m not a rocket expert, but a center of mass is crucial in getting right in rocketeering (thanks Destin!). I’m wondering if the burned fuel from the spinner nozzle end of the firework causes a shift in mass in such a way to force the firework upright while spinning. My guess is this would cause the center of mass more towards the large nozzle. I also think that there probably is some gyroscopic procession or however it’s spelled that helps exploit the shifting in weight to cause it to be upright. Maybe you could do an experiment that shows a spinning rod (with unsymmetrical distribution of weight to one side) while prone/horizontal, will want to stand up straight with heaviest part on the ground, and lighter upwards. Thanks for the video and for sharing the unsolved problem with others :)

[@NormReitzel]

You should refer to some of the (many) videos on the "Intermediate Axis Theorem" This is why the thing stands up and spins. The math is a pita, but it boils down to having a positive feedback whenever there is a deviation on the less-stable axis.

[@rustlebruxz0013]

note, patreon email telling me about this video had a bad link to the video. i had to go to patreon and then click on the video link there to get here.

[@nonothebot]

I think high speed cameras were invented to frame fireworks, and I love it ! I played with this kind of firework when younger, I had some with two holes on either side of the cylinder, one up and one facing down. The firecrackers flew systematically but only by rotation, it was not a propulsion. I never found them again later.

[@Willj461]

Could try and make one of these for yourself? That would be something I would like to see.

[@twdodd439]

ok, my guess is..... the exit hole is not only tangential to it length but as you also pointed out tangentially to its axis. this creates a spin in 2 axis. one of those spins is high energy, axially, and one of those spins, along its length, is low energy and used to help start a gyroscopic procession so that the point of contact will shift as friction grabs hold. because of the spin tangential to the axis it also rotates and when the jet is blowing into air it only has so much mass to push against (and/or is just pushing down in with gravity) but when it rotates about and faces down it has the "ground effect" or something to push against (and/or is blowing in a direction not forcing the body against a solid surface) which starts to stand it up. when it stands up you develop the friction point along its annular face which combines the low energy spin and high energy spin combine to finish standing it up. think 'spins faster, when the procession wants to bring the axis of rotation over the friction point as the friction point is brought under the axis of rotation. because the speed of rotation is increasing as force is continued to be exerted you see the gyroscopic procession work backwards then you are used to seeing (as it gets slower it processes more is now happening in reverse. gyroscopic recession?) this brings the body to line up in a direction mostly up when the launch charge ignites, and, as its still spinning while being launched you now have a rifling effect to stabilize it in flight and through doppler effects and hiding or exposing the noise source on the front or rear side of the body as you view it you get the warbling effect in the sound.

[@russelltalker]

Me: Sis what do you think? You figured it out? Sis: It flies straight up because it does that's why.

[@danielconway7190]

Dude that shot of the motor cut in half was SO COOL

[@extremeanglersgr455]

I thought exactly that this was going to happen no joke

[@teeshark6584]

Luv those little guys. We used to light flares the same way, lay down on the street in our hood, light and run for your lives. Hahaha DO NOT TRY THIS AS ITS EXTREMELY DANGEROUS AND A FOOLISH THING TO DO. But when your best friend's family owned a pawn shop so at 13yrs old we got into anything you could imagine growing up. Amazing we all survived it. Lol.

[@electronicsNmore]

Excellent video as usual. :-) Check out the desalinator I told you about, I just uploaded it.

[@sharpsteels4635]

Okay Believe this or not, but I got this one right. I love physics. The theory I had before you showed the footage was that the upper exhaust generates a rotational motion in the cylindrical firework along the revolution axis and that's because of the ground effect. I honestly didn't knew that the effect had a name and is justified before you explained it, but I had this effect known to me long before as I have observed it many times, it can be easily observed when you totally seize a tap's mouth with your palm, it will show exceptional resistance to your palm even if it has very low pressure. So I knew that instead of rotating along the axis perpendicular to the flat table, the firework would rotate along the axis with the least moment of inertia. Now once it starts rotating rapidly, it creates the gyroscopic effect and tries to balance the subject along the axis of rotation which is also the axis with least moment of inertia, in a perpendicular position to the force of gravity. Now because the side exhaust is not located in the exact centre but the upper side of the cylinder, the weight of the lower part of the cylinder will make the bottom part of the cylinder face the ground while rotating (which in this case, the lower face of the cylinder has the main exhaust). After this it's obvious that as soon as the fire reaches the main exhaust, which is already facing the flat ground, it will thrust the cylinder up in the perpendicular direction of the flat ground. And this is not the end, when there is a single source of uncontrolled thrust, then the body doesn't go straight up, it needs stability. But if we recall the start, the cylinder is already rotating, creating a gyroscopic stability, and also has the rotating exhaust which adds on to the stability of the rotation. I hope you like my version of the theory, and I swear it's mine and I had it before watching the slow mo clip and your explanation. Surely though the slow Mo footage helped build the theory in a refined structure.

[@crazyprof5349]

You really dont need to light them with a fricking blowtorch.

[@gabedetter1570]

You sir have clearly never owned a blowtorch.

[@AL_O0]

It's a lot faster and more reliable to use a blowtorch

[@crazyprof5349]

@@gabedetter1570 Did you just assume my gender?

[@rays3761]

Kinda figured the thrust imparted rotation around it's length and it pushes of the ground standing it up then firing it's thrust. Figured it out before seeing slowmo :D. In the end you mentioned how it's not just the ground effect though and I believe you're correct. I think the off entered thrust corrects this. If you think about it the thrust will always have a larger radius when it is spinning at a tilt. Just a junior physics major, hope this helps.

[@user-be4yc2vr5c]

love the way this way shot. really makes viewer think

[@mickmotly4083]

Thank you Ben for always doing a stellar job at explaining what you think is going on and ALWAYS being humble in the process, that alone speaks volumes as to what kind of man you are!👍👍😁😁

I am looking at this as a spin balanced system very much like a spinning top, as you suggested . The side exhaust is pushing in all directions (with a slight angle to incur rotation), preventing it from falling in any one direction (would imagine speed of rotation is a factor) and once it is semi balanced the flame will simply push it up.

[@judyfps5059]

I think it works in a mix of ways. Like the Tippy Top and I also think that the initial 1st stage provides spin and upwards gyroscopic stabilization while also providing some upward lift since it’s on it’s side facing the table while it’s spinning . TSIU the 1st stage provides spin/gyro-stabilization while simultaneously tilting it upwards by the thrust produced by the first stage being in close proximity to the table/flat surface. And when it gets upright gyroscopic stabilization takes over and keeps it upright and spinning while the second stage takes over and provides the more powerful thrust upwards . Hope this makes sense.

[@serisak]

Initially I imagined it similar to a lemon, where you start spinning it on its side and its rotation translates to the adjacent axis and spins on its end. Then when you mentioned the tippe top I was even more convinced I was correct. But seeing it in slo motion, it seems the side vent it slightly off center so it rolls around and is just pushed upright by the jet of exhaust.

[@Langonica]

OK. Your incredibly simple bisected flying ground bloom on a simple plate of glass is a brilliant illustration (pun intended).

[@MeleeTiger]

I've never heard of these things before, but they're freaking amazing, that sound they make is straight out of a cartoon! XD

[@randomnameifyful]

so the first fuse lights, it's positioned to make the tube spin. if the thrust of that gets close to the flat surface, it has something to push against other than the air. so more of the energy emitted is converted into thrust? this then pushes that end of the tube vertically, the spinning creates a gyroscopic effect too, so then it's vertical and semi-stable, it kicks on it's main thrusters! i really love the part when you cut one in half and stuck it on some glass, that looked really cool!

[@MrPs103]

I can tell the internet is wearing down on you. Intelligence doesn't hold a flame to curiosity and willingness to follow the scientific method. I always appreciate watching your videos. You do great work.

[@pattystomper1]

Feathers on the back end of a dart will make the tip point down when you drop it, because the point is weighted. The first sparks make the firework lift up, but since they are on one end of the cylinder, it mostly lifts one end. So now the dead weight of the bottom end makes that side point down. The second release of sparks lifts the whole firework into the air just as you described it.

[@EngineerCatPyro]

This is probably my favorite novelty firework. I just love the sound they make. I'd buy a box of them over ground blooms any day.

[@airplanegeorge]

I think you got it. I just found those things last 4th of july, been trying to figure them out ever since. All I needed was your high speed camera, thanks.

[@Kilbot192]

I always have loved these fireworks. I used to light them and then close them in a plastic water bottle. They get so hot that it shrinks the water bottle practically instantly.

[@ramesha.s1825]

The fuse is placed tangential to the casing in order to turn the body towards the table which helps it to stand up right . As the object is turned upright the thrust from the fuse hole continues to rotate it as the other charge goes off hence lifting it away from the table. Considering the unstable movement during liftoff , it is due to an unbalanced couple ,hance adding another fuse parallel to the first one would help it to (maybe)fly higher and more stable

[@brotherbearalaska7532]

The tippy top and fire work share the same forces generated, off center of gravity. The thrust generated causes rotational spin and also makes contact with the ground generating lift. Once the rpms reach a certain speed, it generates a vortice and partnered with gyroscopic forces allow the thrust to reach position of least resistance. Without ground effect, there will be no particular direction. Basically what you said, thanks for the video, it was entertaining.

[@mikemcdermott7760]

Dude, vid and footage is Amazing. The whole thing fluently speaks to my preferred style of learning. First you present a succinct, pithy hypotheses. Then make verbal statements supporting your hypothesis and then the best for last. You SHOW ME how your idea plays out clearly in slo mo. I love pyro and am grateful to you for sharing how things work. It’s a behind the curtain glimpse of how the wizardry of pyro magic happens. SALUTE

[@theamflitebowler]

Omg thank you so much sir!! Now I understand how & why these little novelty fireworks work!

[@Mumbungua]

I love that glass crack. Slow-mo of it was beautiful

[@keyabrian7571]

The exhaust from the side is angled at 90 degrees creating a centrifugal force, Now excess force from the side causes it to go vertical then by the time it's vertical the main exhaust has already ignited then it launches into the sky. If you throw it from your hand it doesn't have enough time + force to create the required centrifugal force to create a vertical movement so the main exhaust ends up being ignited then the rocket flares into non predicted directions. The ground effect is really useful in helping the build up of the centrifugal force to create the vertical movement. cheers

[@55Ramius]

Good video. I used to take these things and drop them into a pop can or beer can. They go wild in it and start to burn there way out fairly quick. It is almost like a fire creature is trying to escape. : )

[@verebellus]

before you mentioned the second hole, i had no idea. but when u realized the second hole was at the end. i knew it was gryating stability

[@MrFastFox666]

When I first saw these, the tippy top was the first thing that came to mind. Of course, the tippy top requires some friction with the ground; spin one on ice and it won't flip. I doubt the firework has much friction with the ground (if at all). If you look closely, you can see the side nozzle kinda push the firework into a vertical position when it points at the table, so I think that that is what makes it stand up, and since it's spinning, it resists turning any more and remains at a vertical position.

[@notamouse5630]

Once it starts spinning, the off axis jet applies force so that it keeps spinning and the angular velocity creates centrifugal motion countered by the centripetal force of the rocket. This causes it to nutate around the table normal due to the table spreading the exhaust. In any case, many factors I don't wish to actually do math on.

[@RamLaska]

Ground effect + spin stabilization for the win.

[@billywilliams4396]

I would say ground effect is definitely at play here. In every video we can see the burning end of the firework hop up as the nozzle aligns with the ground. In some of the videos the nozzle passes the ground, the firework hops a little, falls back down, and another pass at the ground kicks it back up (it helps to slow down the video a little more). Once the firework is in that 50ish degree spin, ground effect starts to be less of a factor and the firework spins on an axis orthogonal to the ground as well as in the firework’s lengthwise axis. The firework is unstable while canted and rotating around the orthogonal axis, so it naturally transitions to a vertical position where the orthogonal axis of rotation aligns with the stable lengthwise axis of the firework. Now we have a single axis of rotation that is stable. From here the firework is gyroscopically stabilized until the other nozzle lights and shoots the firework up. That’s what I think is going on anyway. Always something new and interesting in your videos!

[@702pyrotweakin9]

One thing to note is that the fuse hole is not drilled straight through but tangentially to the the tube. It wouldn't spin if this were not the case. I also find it clever that they made the upward thruster a core burner type. I always thought it was just a tube full of BP with two holes. It makes sense though. With how small that device is, you want to get it up in the air as fast as possible using the small amount of powder it contains.

[@JNCressey]

As for it always standing up nozzle down rather than nozzle up, it might be just that the fuse end is the one that's chaotically moving all over the place but the table means it can't go down, so inevitably goes up - then any stabilizing to the vertical possition will end up nozzle down rather than nozzle up.

[@shortystsgp]

I always pondered the physics of these as a kid. But have not thought about this for 15 years. So 15 years ago I would take these fireworks aka "blooms" and have a friend light the fuse as I held it in a sling shot fully pulled back and ready to release as the fuse almost ran out. I would shoot it into the sky and when it would light up it would then rocket spiral its way back to earth and sometimes back towards us like a missile... But most of the time it was short lived and would run out of juice before it would hit us or start a brush fire. But it was in fact really weird because if you just light it on flat ground it would just spin like a top.... aka a flower "bloom". Great 4th of July memories there.

[@piranhabadass1]

The fact you had a Disc Golf basket in the background gave you an automatic like for this Video! :)

[@Goomba_N64]

These fireworks were some of my favorites the speed & sound they make is so cool and they were cheap.

[@nicholasflis]

I believe that the fuse nozzle is set at a slight angle this gives it spin in both x and y axis’s. This is critical because the rolling spin allows for the ground effect to take change more frequently giving it more chance to right its self. Because of its rotation it stabilizes it’s self gyroscopically, and prepares itself for the second nozzle to fire. I believe the ground effect is the major mechanism here. It allows it to correct itself as the force of thrust greatly decreases as it moves to a shallower angle to the ground. This allows for positions with a sharper angle to the ground to push harder and right itself.

[@AB-Prince]

spinning vertically has the smallest moment of inertia, this is the spinning state of least angular momentum. the force of the sideways vent perpendicular to the axis of rotation, causes it to go towards the top because it is in balance with gravity

[@jacktheripper774vods6]

Ahahahaha, i knew it! That slowmo footage got me so excited to see it and confirm my theory. I didnt know how to explain it but i imagined it in my head the same way it was shown, and it made me so happy to see. i love this cannel

[@RaniRani-zt2tr]

this is the first time ever i8 see a video with the person creating difficult words and he is 100% honest