Pop-Pop Boats Are Weirder Than You Think

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I got a glass pop-pop boat made (or putt-putt boat, or a Ponyo boat!) to see once and for all what's going on inside!
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[@SteveMould]

If you're wondering why the boat never cracked under thermal stress, it's because they made it out of quartz glass! How cool is that! You can also discuss this video on REDDIT: stvmld.com/xf-isn5j Check out Anker 521 Portable Power Station: ankerfast.club/3vq4RRe (#ad)

[@sixtenwidlund4258]

Nice video!

[@robertschnobert9090]

I love you, Steve! 🌈

[@khadimhusen]

Great video, I wonder what would happened if heat is given from the top side.

[@littlebacchus216]

How much did custom made quartz glassware cost? When I was at uni we had to sign glassware in and out and pay if we broke it... I broke so many Graham condensers.

[@nobody-ek5bx]

but what happens if you make a T sektion with the pipes unter the boat and use 4 one way valve to use the sucktion at the front and the push at the back of the boat? is it better or more eficient now?

[@arbitraryconfusion]

Those glassmakers did an incredible job.

[@reidflemingworldstoughestm1394]

probably the most notoriety they've ever had

[@pleasedontwatchthese9593]

i would like a video seeing how they made it

[@schnizzyfizz7832]

@@pleasedontwatchthese9593 Gas torches (maybe oxygen/acetylene to get extra high temp, idk what quartz glass needs to melt), bending tools and various diameter glass tubes. I saw a video from a university where they made custom lab glassware. Also proper cooling to avoid cracking as with all glass. So prob some oven to let it gradually cool. Idk what that is called, but I am very sure there is all kinds of glass making terms. Glass is a fascinating material.

[@anthonynelson6671]

Knowing just a little of how tricky glass can be I was wondering how much that little glass boat costs. I've seen how expensive high precision lab glass can be. It's an interesting yet different world of things.

[@comradegarrett1202]

@@schnizzyfizz7832 the oven is called a kiln and the process of putting glass in a kiln to keep it from cracking is called annealing.

[@PhantomSavage]

Excellent. If I ever find myself on a deserted island with an oil drum, a couple of pipes, and enough wood to make a raft and bonfire, I know how to escape.

[@JD2jr.]

Now I want to see somebody build a human-size one of these...

[@blackmber]

That’s right, put your signal fire to _work._

[@flagmichael]

@@blackmber "I don't know, Captain. The signal fire seems to be moving!"

[@besquareorbethere8093]

Hopefully you can keep that fire going long enough to cross the 7 seas.

[@mucia55]

Just tell me the exact max d of the pipes to maintain the capillary effect of water preventing the vapor to move over inside it and I'm building it.

[@matthewbarncord3984]

for forward motion, the shape of the boat also acts as a latching/winching mechanism. It glides forward in the water easier than it glides backwards, due to the hull shape.

[@craigcole9337]

This is correct. You put a corner in the front of the boat, so it sluces easier. In the back of the boat is a wall, which absorbs energy. The greater area of the wall blocks the boat going backwards. It’s the same reason a man in a rowboat will expend WAY more energy rowing it backwards, rather than forwards.

[@matthewbarncord3984]

@@craigcole9337 on the other hand, I've seen these boats made out of plain sardine cans, so there must be some net forward gain.

[@DeanTheDoctor]

Well said guys! 😊🌎💖

[@marcopruscini1603]

Water on speed wants to stay in direction, here to the back, as long as it moves fast. Sucked water (or any other medium) tries to get the easiest and shortest way and that is every possible direction. That means, the reaktion force of the pressure water is forward and of the sucked water is in almost every direction and eleminates most of it by it self. May be the physical terms are not correct because of my non Oxford english...😉

[@germanvtg]

That is correct but as he said, when the water is coming in the tube it has less velocity than when is going outside. If you answer me I can give you the fluid dynamic formula which models this phenomenon. You can see it when an octopus is running away, it takes water with its siphon wide open and then it makes his siphon smaller to take the water away and gain velocity.

[@kenbobca]

I am 69 years old, when I was a child my father brought home a metal Pop-Pop boat. I now have one to amaze my Grandchildren. Thank you for your video explaining how they work.

[@blaisebaileyfinnegan8202]

I'm 200 hundred years old, when I was a child my father was a mercenary returning from the Java War fighting for the Dutch and he brought home a metal pop-pop boat. I now have one to amaze my great-great-great-great-great-great grand children.

[@buckfizzard291]

@@blaisebaileyfinnegan8202 why would you disrespect the man like that

[@blaisebaileyfinnegan8202]

@@buckfizzard291 Because I can, homeboy.

[@buckfizzard291]

@@blaisebaileyfinnegan8202 well that's immature

[@amarnamarpan]

Your grandchildren are so lucky. ☺️☺️👍🏼

[@Eidolon1andOnly]

I'd assume that the shape of the boat also plays a factor in its forward trajectory as the bow of the boat is more streamlined for less resistance while the stern of the boat is not.

[@khalilahd.]

Yeah I definitely agree

[@Lezenda]

oh well, there I go with my comment (17 min after you), thinking that I am the smartest :)

[@archbox8593]

In that case it would be interesting to put the tube openings in the front and see if this would make it still move forward?🤔

[@chorusofoddities]

He cut the bit where he mentioned that from the video, thinking it wouldn't interesting anyone, he said in another comment

[@bbugl]

making a symmetrical boat would be interesting.

[@chorusofoddities]

No-one could be disappointed with any good visual explanation - even if it makes your channel a 'transparent version' channel!

[@khalilahd.]

Always the best content 💛

[@desu38]

Right? It's like those cg graphics, but better.

[@amicloud_yt]

Better than "pour things out of jars" channel

[@sethgwiyo2250]

kzbin.info/www/bejne/oaLVgmWqnZx4gKs

[@desu38]

@@amicloud_yt Well, I like NileRed

[@MaxineInYourWifi]

i have only seen this toy from Ponyo and it has been in the back of my mind. thank you for the name of it, and explanation of how it works.

[@Sanjay-eb6fe]

I've played with a dozen of these when I was little. They used to keep me entertained for hours. I have forever been wondering exactly how these boats worked. At last your glass boat has put an end to that. High five !

[@ezioboiz-ieatchildren-]

You should already know this because this is taught in physics 💀

[@DemoniteBL]

@@ezioboiz-ieatchildren- Not everyone learns the same things in school 💀

[@ezioboiz-ieatchildren-]

@@DemoniteBL wait so you're 9 year old?

[@DemoniteBL]

@@ezioboiz-ieatchildren- ?

[@ezioboiz-ieatchildren-]

@@DemoniteBL i mean the physics taught in this video is basic physics you're taught.

[@v_Shami]

I remember seeing one of these in ponyo when I was little, I thought it was so cool. Still do actually, would love to have a little boat like that big enough for me to actually fit in

[@Laurpud]

OMG, right? That would be so cool to putter around in!

[@rachelcookie321]

Wait, they have one of these in ponyo? I only watched the movie a couple years ago and don’t remember seeing this!

[@v_Shami]

@@rachelcookie321 yeah, it's how sosuke and ponyo go around to look for his mom once the water rises

[@rachelcookie321]

@@v_Shami oh, I thought that was just a regular toy boat. I didn’t realise it was one of these.

[@korwynze6288]

same i thought of Ponyo right away! ahh what nostalgia

[@AndrewSmithThomas]

"The batteries are just there for weight" - exactly what someone would say to hide their perpetual motion machine. You can't fool us!

[@truongnguyenhongnhat6590]

ok

[@leyrua]

😆

[@truthbetold1855]

Haha yes, the ONLY thing he could find.. HAPPENED to be two AA batteries.. SUUUURRREEE LOL I think they call this hiding it in plain sight 🤣 kidding.

[@hankholschuh7987]

@@truongnguyenhongnhat6590 it was a joke genius

[@bstikkel]

If you do not believe the batteries really are only there for counterweight, have a look at the metal version. We had several of those and it really works the way it is demonstrated.

[@tombig4011]

My dad and I built one of these for a science fair in 2nd grade. Won the fair and blew the teachers and judge away. We used coiled copper wire instead of a tank.

[@mr_dillus]

Lies

[@liahansen6896]

huh, do you remember how that worked with the wire? Like did you use the wire to essentially make a tank, or something else?

[@tombig4011]

@@liahansen6896 sorry, it was small copper tube the we bent into a coil that the flame heated. Not wire.

[@ShadowsOfTheSky]

I always like to put my guess for the big question on these types of videos… I’m at 7:30 and we’re about to figure it out. Basically, even though water is going in and out, theoretically putting the same force on the boat each time in opposite directions, we should stay still or perhaps shift back and forth slightly. However, because of the shape of the hull, there is very little resistance when moving forwards, and a large drag resistance when moving backwards. So even though the same force is imparted on the boat, the boat slides forwards easily, but doesn’t ever want to slide backwards.

[@bencejoful]

That was my guess as well

[@Games_and_Music]

And funnily he didn't even mention it. Although it's not the main reason, but it's definitely a big part of hydrodynamics overall. Now it might be kinda "interesting" to see a pop-pop installed backwards and see which force wins. Will the 'engine' win, or will it slowly wander backwards or sideways because of the reverse installment and contra hydrodynamics. And how much is needed to turn that result around.

[@plaguepotato6624]

I was introduced to the Pop-pop boat from Ponyo and always wondered how it worked. Amazing video, thanks for the explanation!

[@Mattguy-lg3nr]

yea

[@spunkyspaz]

Ponyo brought me here too. :)

[@fotiacruz3911]

W movie

[@kennethsizer6217]

Same!! 👍

[@its_aj251]

Same

[@Nighthawkinlight]

I saw a clip or two in this video with the engine running with asymmetric amounts of water in each tube (3:35). That's very strange. Other thermoacoustic engines require pretty precise resonance matching between the engine cavity and the load to get any work done. In this case you've got two mismatched loads with competing resonances somehow popping at the same frequency. I'm guessing the mismatch must be minor enough to force synchronization but would like to see further tests. Does the amount of water in the tubes effect the frequency of the popinating? If you make one tube a little longer than the other so it contains more water by default will it still run?

[@SteveMould]

That's a really good point. Happy to send you the boat if you want to run some test. Drop me an email if you're interested [e-mail]

[@littlejackalo5326]

How does this comment not have a single like? Why was it buried? Nighthawk in light is a huge KZbinr who does similar videos and this comment should have way more likes..

[@Lets-Talk-Law]

@@littlejackalo5326 The bot presence is strong on youtube

[@Resonanttheme]

That brought to mind a clip "Stirling Twins Pogo Engine", two syringes driven from a common chamber, one deciding to bounce higher then the other adjusting displacement.

[@Resonanttheme]

@@MadScientist267 And the heat transfer properties of quartz is different. Ideally, if you could maintain a steam hammer effect, you'd get a lot of thrust.

[@davesunhammer4218]

The drawings you refer to with the metal tank show a tank that is very flat with a height that is very similar to the tubing (~1D in height and only a few tubing diameters in width), and is slanted down towards the tubing. Your glass tank is several times the tubing diameter in both height and width, and doesn't have the same fluid dynamics as the metal tank. The tubing in the glass system are perpendicular and not tangental to the tank, again causing different dynamics. These changes might acount for the tank not cycing like the metal system. However, the end result is "the same" type of oscilation but different efficiencies occuring in different locations.

[@harrymoyes5069]

I think the top of the metal tank is also part of the resonant system, adding another enhancement to the system, missing from the glass boat. I'm guessing that it helps to contribute the pop-pop resonance notable in the tin boat, and absent in the glass version.

[@collomps]

I think the boat has a shape that helps forward movement and not bacwards, so it will tend to go forward even if you apply the same force in both directions.

[@Layarion]

easy to test, just put this in a box and see if it still moves

[@beaconblaster33]

@@Layarion one annoying thing is the word is "help" not "essential"

[@Games_and_Music]

@@Layarion Yeah, the box will still move forwards, but probably less fast, or less 'guided'. The point about the directional flow of water is still true, so, like beaconblaster said, not essential, but definitely beneficial.

[@JimC]

As you've probably already been told, the "water flowing into the pipes from all directions" explanation that you rejected is the same reason Feynman gave as to why his s-shaped water sprinkler wouldn't work backwards. So it might be interesting to run that experiment in a clear box, like Hero's engine in reverse.

[@anotheral]

YES SOLVE THE FEYNMAN SPRINKLER PROBLEM FINALLY!

[@Lastielion]

Any excuse for a clear box :D We all love that sweet, sweet visible physics

[@jeeeeeeeeeeezus]

You'd see nothing illuminating doing the feyman sprinkler transparently.

[@resintom852]

@@jeeeeeeeeeeezus you’re fun at parties I bet.

[@shawniscoolerthanyou]

@@jeeeeeeeeeeezus adding dyes to the water could give a qualitative feel to the asymmetric flow between in and out.

[@coryman125]

Reminds me a bit of a pulsejet engine, the way it oscillates to produce a net force. Obviously it's very different in a lot of (very big) ways but I can see some similarities in how they work

[@reubeng2110]

my favorite was in the 50s and 60s scientist wanted to launch huge payloads into space using pulsed thermo nuclear explosions Kennedy shut that program down they did nuke testing and it works just like a nuclear powered missle

[@ruskiwaffle1991]

@@reubeng2110 orion right?

[@Nikarus2370]

@@ruskiwaffle1991 Well Orion IIRC was having a rocket in space propelled by dropping nuclear bombs behind it. There was another project exploring nuclear salt water rockets. Basically a nuclear reactive uranium (or plutonium or other) salt would be dissolved into water and stored in tanks with a lot of boron or other material to lower reactivity. Basically would work by spraying the fuel out the back through a nozzle lined with a moderator (like graphite) to cause a constant flow nuclear reaction out the back of the rocket. Scott Manley has a good video about it IIRC. A 3rd, (more feasible, and tested, adn I think Space X was makign some noise about bringing it back up) option is Nuclear Thermal. Instead of mixing fuel and oxidizer to burn (to make heat) to propel the rocket. You use the heat of a nuclear reactor (one running in a controlled fasion, and not actively exploding) to heat up your propellant.

[@JohnDoe-rx3vn]

i think there's plenty of reason to call it a pulsejet

[@Sacred_l0g1x]

STIRLING ENGINE 😆

[@LiquidAudio]

Fascinating, I was scratching my head pondering the dilemma of how it moved forward vs just back and forth. Very cool!

[@abhishekgnadkarni]

Played with this boat since my childhood. Always wondered how it actually works. Thanks a lot for this beautiful explanation!!

[@jacoblawrence9145]

Another possible reason for the oscillating motion moving the boat forward: the shape of the boat generates much more drag being pulled backwards than it does being pushed forward, so the net effect over a full cycle is in the positive direction.

[@233kosta]

It's not really going fast enough for pressure drag to be significant, at that point it's mostly viscous drag which is symmetrical. Even if that wasn't the case, the boat would have to stop and reverse direction for the drag bias to have any effect at all, and it doesn't. It just keeps going.

[@fireballxl-5748]

@@233kosta Disagree. Simply disagree and would have to see empirical evidence.

[@233kosta]

@@fireballxl-5748 If you want "empirical" evidence, go run an experiment. I'm not paying for all that instrumentation just to prove a point to some rando on the internet who doesn't know what a Reynolds number is. Your choices are to either learn fluid dynamics and kinematics, or pay for an experiment everyone in the industry sees as a complete waste of effort. I suggest you start at Anderson's Fundamentals of Aerodynamics.

[@fireballxl-5748]

@@233kosta What "experiment"? Suggestion? You're the self called expert.

[@233kosta]

@@fireballxl-5748 You asked for empirical evidence, that is how you get empirical evidence.

[@pyrotas]

Actually more than resonance I think this is a nice example of limit-cycle oscillation, where a steady supply of energy (from the candle) produces an oscilatory motion.

[@sethgwiyo2250]

kzbin.info/www/bejne/oaLVgmWqnZx4gKs

[@velbythorngage]

Yeah I wish he'd gone into more detail there, I still don't get how a constant force from the candle results in oscillation, I'd expect the expanding gas to reach equilibrium (kind of like applying a candle to that syringe, it would expand but wouldn't oscillate)

[@acters124]

​@@velbythorngage Candle does not provide a true constant energy to the glass and gas inside. it is providing an oscillating energy to the glass and inside gas that you can visibly see. It would be great if there is a way to pinpoint heat transfer to a single point without it leaking to the surrounding environment. however, entropy will exist in any lab environment. This whole boat is a practice in how imperfections provide a oscillation in energy levels in the system. How one uses the oscillating energy is a mystery, in this example it is used to drive a boat forward. Another example of using oscillating energy sources is in an AC system. In an ac system, an oscillating energy source changes pressure from one side to another in a continuous motion.

[@sumdumbmick]

@@velbythorngage he'd have to know wtf he was talking about to go into more detail, though.

[@lucasbiaggini]

@@acters124 wouldn't a resonating frequency be constant, while random oscillations would be random? I think simply measuring the frequency of the popping sound in one of this boats could pretty much settle it.

[@Soporbum42]

Most honest sponsorship/review out there. Love your videos and appreciate your approach to this. Cheers!

[@jele38]

Now imagine doing this with a full scale boat

[@FrogEmpress]

Just like in ponyo!

[@TTHJJD100]

Well the issue here with the pop pop boat is you still need heat that causes this process. Thus you still need a fuel like coal, gas, or wood. So we're back at the problem of needing a finite resource.

[@JustRememberWhoYoureWorkingFor]

It would be a very slow and inefficient boat

[@michaeldougherty6036]

@@JustRememberWhoYoureWorkingFor But at least you wouldn't be slap-chopping manatees and whales with a propeller. I wonder how well a solar powered heating filament could work, in place of a flame. I'm sure there could be a market for an environmental and sealife friendly put-put boat.

[@bconroy328]

Ponyo!!!!!!!

[@colincenge]

You glossed over the flexing metal making a popping sound, but that compliance is actually another spring in the system. I believe this added spring sort of amplifies the steam effect which is what makes the metal boat faster than the glass one.

[@DJZofPCB]

On the head of the nail.

[@SebastianWoodard]

man I love KZbin. you can learn so much stuff just by reading the comments

[@SebastianWoodard]

but I assume because of the motion, it creates a bit of a vaccumn to assist th oscelation?

[@DavidMartin-jr8nd]

I bet the glass boat is also much heavier. It might have worse fluid dynamics as well.

[@altruismfirst6489]

It is a basic version of a Sterling engine with the metal acting as a piston . This flex is vital as is the cooling properties were and metal pop is a frequency with some other non audible frequencies that are yet to be observed in the overall propulsion total percentages. A glass version defeats many observations and in fact indoctrinates the real working aspects of the metal original. An infrared camera using a metal unit will be interesting.

[@harryf9885]

This is very interesting, reminds me of a pulse jet, both initially seem like the forces should be balanced and no thrust should be produced, and both essentially consist of just a cleverly engineered tube.

[@jeanpaulceulemans9973]

pulse jets expell more gas mass than it takes in because the burnt fuel components are also going through the tube unlike this construction which has external combustion. That said, I still think he's wrong and the asymmetry of omnidirectional intake versus directed expulsion generates the thrust This also applies to a closed pulse jet as part of its thrust generation imo

[@Jasonrotfl]

I built one when I was a kid out of thin galanized steel and a coil of thin copper tube I got at a hobby store. Was really heavy but worked suprisingly well with a sterno can heating the coil.

[@TimeBucks]

Very interesting & well made as usual

[@Fuddleton]

There is a very critical part you're missing. The resonance is controlled by the bulk modulus of the fluid. In a glass chamber, you purely have the bulk modulus of the gas in the chamber. The metal pop boat has a variable stiffness based on the size of the diaphram, which tunes the resonance to that of the heat input of the system.

[@the-real-zpero]

Interesting 🤔 Explain it again, but pretend I'm 15 😁

[@caseclosed9612]

I second ZPERO's motion for elaboration, but like a layman version please lol.

[@unfa00]

What is a bulk modulus?

[@hjertrudfiddlecock4394]

@@caseclosed9612 explain it to us like we're a slow cousin! please Fuddleton

[@The_Rising_Dragon]

@@the-real-zpero So oonga bunga explanation is, that different material sound different when you hit them. Water if flow at certain speed, within certain vessel, it makes same vibration as material. Glass is not same material as plastic, so different shape required, or water need flow to be faster or slower! Capiche? EDIT: Also heat be important for good popping!

[@danielescobar7618]

Never have even heard of pop pop boats. Amazing

[@prateeksharma1981]

Intresting video ! I used to play with this boat in my childhood during rainny day's.

[@trstmeimadctr]

I would be incredibly interested to see someone make a full-size version of this propulsion method

[@icouldntthinkofagoodname7216]

I was thinking of a remote controlled rudder boat toy scale at first because the bigger it is, the cost also goes exponential.

[@educationalpurposesmostly]

came here to say this

[@TheCookiePup]

I'm worried that you would need a huge fire and/or the oscillation would be very slow, but I imagine you'd still get some forward motion.

[@pleasedontwatchthese9593]

@@TheCookiePup maybe a lot of small engines

[@SharpAssKnittingNeedles]

@@pleasedontwatchthese9593 Great idea!

[@ransapar2259]

Oh I've always wanted one of these after watching Ponyo when they turn one giant and use it as a real boat! I wondered how well it would work if a large version was made

[@groggers]

That's where I first saw these too! Led me to buy one on a trip to Berlin, but regrettably I've not yet tried it after 4 years... I think it's about time

[@Gammix]

If it weren't for watching that movie, I probably wouldn't have clicked on this video

[@Book_Thoughts]

I found you guys! I was looking for anyone who had watched Ponyo. I want a giant one two.

[@ArunNalluri]

i had this when i was a small child here in India, i always thought it pulled water in from one tube and pushed it out of the other, great video!

[@kylemiller6765]

The shape of the boat will influence it's motion as well. For a typical V shaped haul, it's much easier to push the boat forward, as apposed to reverse.

[@marthabenner6528]

I've always wondered (like since I was three) if one could make a person's size pop boat. In Hayao Miyazaki's "Ponyo" the little boy has a person size pop boat, my dad thought it was the cutest thing.

[@zonesproductions]

It was the cutest thing 😄

[@JimmyZeng]

To be precise he had a regular sized pop boat, Ponyo used her magic.

[@joecool4656]

Oh you definitely could make a human sized version of this. It would work

[@BierBart12]

Imagine having a nice wood campfire in a little metal stove under the tank

[@DyersEve726]

@@BierBart12 roasting marshmallows while taking a boat ride. Brilliant, lol.

[@OntologicalQuandry]

Just a small note that the natural frequency of a system is not the same as the resonant frequency. They may be close, but they are not the same and can be calculated depending on the energy source driving.

[@SteveMould]

Good point

[@kain0m]

Also, the initial phase shift doesn't matter. If you have a energy supply coming in near the resonant frequency of the system, it will align it's phase _very_ quickly.

[@Lillith8810]

Ah I love these. My dad had some vintage ones from his childhood we got to play around with when I was a kid.

[@bernieshort6311]

This was an interesting video for sure, one which I would never have believed had you not produced the glass model. From model engineer books I read as a child, some 55 years ago, I was led to believe that one tube was fixed into the cylinder at a slightly higher elevation, just a tiny amount and this in turn caused one tube to suck in water and the other to expel the water and vapour causing the forward momentum. So, I thank you for clarifying a miss held perception I have had for about 55 years or so. I am a marine engineer retired, yet I still held this belief to this day. Amazing really. Thank you for this video.

[@viliemtoth6387]

Collision and momentum. Fascinating!

[@niteshpant1974]

Since childhood I have the pop pop boat but the only forward motion complexity cleared now after watching your great video ❤❤❤❤❤ thumbs up for the great explore with glasstube boat which is state of art 😀😀😀😀😀😀❤️❤️❤️

[@dpidcoe]

I feel like this explanation was lacking the usual rigor of explanations in previous videos, and it raised more questions than it answered: - What about a symmetrical boat with the same amount of water resistance forward as backward? - What if you pointed the tubes forwards? - What if the underwater portion of the tube had a T-junction with a one-way valve so that it would suck water in from the front and push water out the back?

[@NareshSinghOctagon]

Time to hire more glass boat makers,eh?

[@prophetsspaceengineering2913]

Agreed. I could definitely see asymmetric resistance being a significant factor. Hard to tell how much of the motion can be attributed to it.

[@enaudeni]

Symmetry of the boat aids the forwards motion but to a minor degree, if the boat was square it would still move in the opposite direction of the tubes. It comes down to the characteristics of the suction vs expulsion of liquid from those tubes. On the suction of the liquid, it sucks water in from an omnidirectional area. Yet when it expels the water it is in a directional / concentrated stream, like when you squirt water from a syringe it is in a long directional stream. So the expulsion of the water has a greater directional force than the suction so will always move in one direction far more than the other.

[@andrewfleenor7459]

I like the one way valve idea. Maybe a Tesla valve or two.

[@dave7038]

Explanations like in the video are pointless without experimental proof clearly demonstrating in isolation a 'wrong' explanation failing while the 'right' explanation succeeds. Otherwise the explainer could equally well describe a mechanism involving magical fairies that just like it when the boat moves 'forward'. That's why the ball-chain fountain series was interesting and educational. This was half-assed (maybe because Steve wants some other KZbinrs to call him out on it so they can do some response videos that get more engagement, much like Derek's recent electricity video (which IMO was specifically designed to be 'wrong' in ways that generate responses (see his other videos on clickbait and experiments with video titles that maximize engagement) that generated a great deal of traffic and engagement across several channels, much more than if they just posted a single correct, well-researched video).

[@gaminawulfsdottir3253]

9:41 It would be interesting to see this done with the tubes closed off by a flexible membrane, to preclude any possibility of water being sucked into the tubes any appreciable distance.

[@charlieevergreen3514]

I’m wondering if dampening the oscillation would nullify the thrust. I’m guessing it would but I’m not certain.

[@thebonedawg2808]

@@charlieevergreen3514 I'm not up on my physics but I think due to the inverse square law as soon as you close that thing the valve pressure would be so high It just blows back open, but at half pressure.

[@greenaum]

Doesn't using red water demonstrate that? You can see that most of the water in the tubes remains the same water, once it's up and going. You can see that none of the water from the tank it's floating in gets in there.

[@gaminawulfsdottir3253]

@@charlieevergreen3514 That's what I was curious about.

[@gaminawulfsdottir3253]

@@greenaum No, I really can't tell from the dye whether outside water is diluting it, or if so, how much. Mainly I'm interested in how much of the motive force is generated by allowing water into and out of the pipes, or whether it's more of a vibratory function that can just as easily be performed by a membrane.

[@T-RexRita]

Thank You. You explained that very well. I like to learn new things every day!

[@arvind7820]

Great Explanation sir. Glad to learn the working of this toy. 🎉🎉

[@Fernando_S]

I still have my dad's pop pop boat from the 1950's. It was his toy as a child. And it still works very well. Nowadays, my two 5 year old boys are the ones that play with it.

[@infpail7232]

I bet the shape of the boat helps too. Since there’s more drag when the boat is accelerated backwards, it will have a slight preference to move forwards with the periodic motion from the tubes. Could be worth building a setup where the tubes are mounted in reverse to see if the drag being different is dominant over the argument you made for the collision between water and air. Great Job on the video! Edit: I said it was the first video I’ve seen on this channel. Turns out that was a lie. You got a new sub today

[@quartercast]

I agree. Movement is due to the streamlined shape of the boat. Same as the biased shape of the toothbrush bristles leading to forward motion of the bristlebot. I'm also not convinced with his first argument that jetting does not have an effect, I believe it would have an effect, regardless of conservation of mass in the reciprocating volume of water.

[@Dino14345]

If you move side to side on a small sailboat, you will go forward

[@mmmdananananone]

I'm watching this on a Sunday morning with a stinking cold, and it reminds me exactly of watching Open University as a kid, except now it's less dry and I more or less understand it! Thank you.

[@sukyoungkwon5784]

재밌게 상세한 설명 감사합니다.(62년생인데...어렸을때 마당에다 큰고무통에 물에띄어 신기해하며 놀랐던 추억이 생각나요)

[@borincod]

There is a similar "cancellation" effect during expulsion phase as well as during the "suction" phase. At the final point of the expulsion phase, there is negative pressure difference in the chamber, that will later suck the water in the tube. While negative pressure difference holds in the chamber, the vapor/air inside it "sucks" boat backwards (or in other words, stronger atmospheric pressure pushes the boat backwards). So, the given explanation of the boat propulsion is not complete.

[@tau9632]

Came to the comments to say exactly this!

[@johnineson]

My gut feeling was that that explanation was wrong. For me, a more logical explanation for forward motion is the asymmetrical hydrodynamics of the boat. Going forwards, you're pushing the streamlined prow through the water, whereas backwards is is trying to force the flat stern against it. Even with exactly equal forwards and backwards impulses, I would expect net forward motion. The toothbrush is a good analogue. The bristles are sloped backwards, making the friction asymmetrical. Push backwards and they will tend to grip; forwards they will tend to glide.

[@hanvyj2]

@@johnineson a good test of that theory would be to have the tube exit the front of the boat. It should still go "forwards" if that was the case, and it was the hydrodynamics, whereas it would reverse the direction of the video exposition is correct.

[@enderyu]

Of course there is no total cancelation! The water being spat out will inevitably mix with the surroundings. Its not like it is sucking in the same water it just ejected out

[@ewicky]

I also came to the comments to see if anyone else was totally thrown off by his explanation of "only a cancellation in one of the two phases of the cycle". Like, huh?!?

[@thundernargundkar9618]

I remember when me and my dad would make these out of old soda cans. We would have to buy pre-made tubes and tanks but it was still fun. He said that these were a very common toy in India and other places in Asia

[@ApoorvPadhye]

This video unlocked a core memory for me as a child. I remember my dad bringing such boats from a regional fair nearby the city and showing me how it works. I wasn't allowed to touch it as I was very small and the boat used to be hot from recent usage. They went away as I grew up and I subsequently forgot about them until now.

[@Carlofer7]

I had a little boat of this type, at the beginning of the 60s. It was made of a tin and with a cotton ball and alcohol, it sailed through the waters of the bathtub. Very clever toy.

[@WillFox-js2hu]

In my teaching days we use to make these with the kids but the 'engine' was just a length of copper brake tube formed into a coil for the boiler with the ends soldered into the back of the tin boat. Without the flexible tin on top of the boiler they didn't pop so audibly but still worked. Also we didn't fill the tubes with water, just tilted the hull slightly so one exhaust was under water and the other not so a few drops of water entered one end, that was enough to set them off.

[@timus545]

Love the "transparent version" of everything. Understood engine working from transparent engine from SmarterEveryDay channel. It's make me understand concept, always knew how engine works but never felt from inside. This is also very beautiful.

[@piconano]

I love how they reused a tin can to make the hull. Clever recycling. The glass boiler made of chemistry test tube didn't do it justice, since glass is a good insulator. It brought back memories from when I was 6-7

[@hwgusn]

The glass one is cool, but I also like the little flutter of the metal one on the top.

[@Skarry]

Fascinating. One thing that I didn't hear you mention was that water doesn't compress, air does. You can put pressure on water but not compress it like air can. So, the air on the suction cycle acts like a pillow.

[@arktom7335]

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[@Richardson238]

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[@betheluktu7647]

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[@philip1258]

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[@Tim.Reader]

This reminds me of Feynman’s thought experiment of what would happen to the motion of the arms of one of those rotating (“helicopter”) sprinklers if it were placed underwater and sucked water in instead of expelling it out. Would it rotate in the same direction as the expulsion case, the opposite direction, or not at all?

[@hollt693]

I wouldn't think the spring loaded diverter arm that drives the rotation would move much (if at all) if water was being sucked into the spray aperture, but I can't say that I have anything more than intuition to base that on. Am I close?

[@charlieangkor8649]

It could also sometimes rotate this way sometimes that way or not at all. If we do a similar experiment - drain a sink and ask "will the water rotate or not and which way?", it may rotate every time a different way or not at all.

[@samroyston7281]

@@charlieangkor8649 that's the opposite of a scientific answer, congratulations. Feynman's ghost is probably doing backflips and it's not even true, water drains in a remarkablely consistent direction based on your hemisphere, an observation that has helped us deduce things about gravity and fluid dynamics. If we had just said "sometimes it does one thing and sometimes it does another", we havent observed anything, we've ignored reality

[@Mister_Brown]

not at all by my account for two reasons, one the force of the water coming in at a right angle hitting the back of the tube would cancel the suction "force" (i know, i know) but the main reason is those sprinklers use hydrodynamic bearings that float on a film of water provided by the hose pressure and seize up if you don't have pressure pushing up on the arms, even worse in suction

[@bobafettjr85]

@@hollt693 I think you're thinking of a different type of sprinkler. The helicopter type doesn't have a spring.

[@spddiesel]

The original boat tank is very thin, about the same thickness as the pipe, compared to your glass one. This may make it easier to push out more air, especially if one tube extended all the way to the back of the tank.

[@agniveshF]

Also something as simple as the shape of the boat where the front allows for less water resistance vs the back of the boat would contribute to the impulse (change in momentum) to forward motion, even in the hypothetical condition that the forces cancelled each other out

[@DJTI99]

Theoretically, how large could you make a pop-pop boat and still have it work?

[@DragonFiesta]

this is what I want to know aswell

[@_Matchu]

as big as my p... house

[@thomasbarlow4223]

Here come the new latest and greatest winter boats all over Wisconsin

[@ChickenDeranged]

ha ha, the answer to this is in a movie called Ponyo... lol

[@Aquanorte]

At least as big as titanic .. it had a similar working principle

[@caesertullo1824]

Fluid-dynamics is always so interesting.

[@Dr.Mrugendra]

A simple explanation by me🙃🙃🙃: it produces just back and forwards oscillations, and the main reason which pushes the boat forwards is ---> 1) the watter coming out of the end of both tubes goes straight direction i.e. 180⁰ angle only (becauseof momentumof water) , so it creates the much pressure which propells the boat forwards, but 2) while the contraction cycle the water gets sucked in but this water comes in not in straight direction, it comes from all direction of the both ends of the tubes , (in least resistant way) so the pullback force is less for 180⁰ angle as the force is diveded on other angles i.e. sideways. that difference between forward and backward pull forces makes boat to travel in forward direction. its like vacuum cleaner motor needs more energy to suck 1kg mass from a large distance. but blower motor consuming same energy can propell the same 1kg weight from same larger distance easily.

[@marcfruchtman9473]

Thank you for the transparent view. I found it to be very helpful in explaining the oscillation of the liquid and how far the liquid actually travels back toward the tank. (As others have mentioned, the dye was also very helpful!)

[@AG-pm3tc]

I never heard of scientific glass blowing team, that sounds like the strangest hobby ever, but the really made something pretty

[@explosiverift2037]

Labs have them sometimes.

[@DocBree13]

It’s also a career, for some

[@johnmf6096]

My BIL is a scientific glassblower by trade and it IS in fact a career.

[@AG-pm3tc]

@@johnmf6096 can you tell us a bit more? what use cases employ your ability? how you got into it?

[@5naxalotl]

lab glassware is traditionally hugely expensive and large universities often have a glass blower who can do repairs, when it's not an item that can be mass manufactured in china there are a whole bunch of youtube videos of lab glass blowing. it's exactly as amazing as you'd think it is so you really should check them out

[@joolscornwell1307]

We Love Steve Mould . Fabulous 💪💪😂 keep the momentum.

[@NFMorley]

Really interesting - Thanks Steve. I remember playing with these with my grandpa as a little kid in the park beside their house! I think he did explain to me at the time how it worked, but all I'd ever remembered was that it was a bit similar to a Sterling Engine, so nice to see a clear model in action.

[@jaronjohnson4366]

This is really cool! I just rewatched Ponyo and, towards the end, the main character's little boat (which I now is a poppop boat lol) gets made big enough for him to ride as a method transport. So I wonder how big a poppop boat could actually be 😂

[@sethkeown5965]

i didnt and havent wanted to watch ponyo. can you sell me to watch it?

[@SovietMarmalade]

@@sethkeown5965 what??

[@sethkeown5965]

@@SovietMarmalade ive bot seen ponyo, i want to hear a sells pitch that will get me to watch it.

[@a1esandra]

@@sethkeown5965 underwater town fantasy and the satisfaction of seeing a working Lifesize toy boat :3

[@a1esandra]

Right I've never seen this toy before but when it showed in ponyo I was so fascinated I'm so glad this video conveniently showed up on my feed

[@catnip5315]

This brings a lot of memories. I want to buy one in the future...maybe

[@marcopohl4875]

0:15 thanks for your transparency.

[@matthewbarrowcliffe1091]

I think you missed something… the shape of the boat. I would like to see the test done with a rectangular boat to see if the lack of a bow makes a difference.

[@SteveMould]

I cut that from the video actually! I wasn't sure if it would interest everyone. But yeah, I think it probably enhances the effect.

[@matthewbarrowcliffe1091]

@@SteveMould my curiosity is about whether or not the pipe exiting the bow would allow the effect to be reversed, perhaps not efficiently. I may build myself a couple to experiment.

[@JCisHere778]

I don't think the shape of the boat will have that much of an effect. Most energy will probably not be dissipated through friction but through the surface waves

[@WJS774]

@@SteveMould Cutting that was probably a mistake, I swear like half the comments here are some variation of "you're wrong, it's actually the shape of the boat".

[@1.4142]

The first explanation is somewhat correct. After the first exhaust phase, water is sent backwards while the boat is propelled forwards, conserving momentum. When the boat draws in water a second time, it doesn't come from water used back in the first cycle, but local water ahead of the first cycle. In this sense, it's like climbing a ladder.

[@blackmber]

Ooh nice analogy.

[@megamaser]

Bingo

[@emersonpage5384]

that's interesting, because if true it would mean if he continued running the experiment with colored water inside the tubes, eventually the tubes would be filled with only clear water.

[@DaP84]

It should cancel out the energy/momentum regardless? When you push on something there is an equal and opposite force acting on you = how the boat starts moving. The same, but opposite physics phenomena should happen when the boat pulls water back into the pipe, regardless of which water it sucks in. So why doesn't these two opposite forces cancel out each other? So the analogy of climbing a ladder with your claim of "intake of local water" goes against basic physics. Must be some other factor that does it

[@1.4142]

@@DaP84 The key to the answer is the center of mass of the boat-water system. After the first cycle, if the boat were to draw back in the water expelled from the first propulsion, it would go back to its initial position. But by using local water ahead of the first, the center of mass of the boat-water system has moved forward.

[@SilntObsvr]

I'm thinking this is equivalent in operation to the thermoacoustic engines I've seen -- the extreme form of which is known as a "howler tube" -- a hot mesh inside a tube open on one end, which will oscillate in audio frequencies (depending on the size of the tube). These operate like a Stirling engine without any mechanical displacer mechanism -- which appears to be a similar effect to what's happening in your see-through pop-pop engine.

[@danielgoodman3578]

I did not know these things existed! :) Thank you for explaining why it doesn't just oscillate in place! It makes good enough sense! :)

[@docjackal8511]

Great video. I used to play with them in my childhood and I was pretty intrigued how it worked. Thanks to you now I know. Might get a couple of pop pop boats to play with too 🤪 I also watched your entire advertisement of Anker.

[@JordanSchaeffer]

I used to make bristle bots all the time as a kid and something that is really important is that the bristles are all angled in the same direction. That ensures that it is depressed forward when it vibrates before the bristles spring back to their original position with the brush slightly moved from where it was before

[@The2x4]

Very interesting & well made as usual! I don't quite accept the "collision" on the intake being that important of a factor for moving forward (and having no "anti-collision" on the output.) Just like the oscillating syringe example, the pressure and vacuum forces both slow and stop the motion, then reverse it, with seemingly equal force.

[@tau9632]

Exactly!

[@enderyu]

Why would you assume equal forces? You are grabing mostly still water around the boat and throwing it backwards creating net thrust. The ejected water will inevitably mix with the surroundings, and the still water around it will present less resistance and thus will end up being sucked into the boat, instead of somehow being ignored and forcing the boat to suck the same water it just spat out

[@maxwang956]

"Just like the oscillating syringe example, the pressure and vacuum forces both slow and stop the motion, then reverse it, with seemingly equal force." You're missing one thing: when the vacuum forces stop/slow the outward motion, there is less water in the tubes than during the reverse motion, because some of the water was pushed out!

[@wizardozark2735]

A mechanic you failed to mention about the metal pop pop boat is the top piece of metal in the chamber pops in and out just a little bit. This assists the positive and negative flows of the water. That's one of the reasons the metal one moved faster. Weight is likely a factor as well I'm sure.

[@_..-.._..-.._]

He mentioned that, maybe not that throughly, but it was said.

[@Sam_Chintapalli]

0:14 "this channel is becoming a transparent version of things" lol 🤣🤣🤣😂😂😂

[@AabhasLall]

This was and still is my favourite toy! I always wondered why they don't use this kind of tech to power actual boats. Effeciency, perhaps? I would love to see some madlad making a huge boat which uses spent nuclear fuel to push boats around. Popping sound optional. Or something similarly bonkers yet fun.

[@raghubharadwaj7122]

spent nuclear fuel on regular boats 😂 noice

[@Nineninetails]

I was right there with you until you said spent nuclear fuel. The spent rods dont put out much to any heat. That is why they are considered spent even though they are still radioactive.

[@aquafyre99]

This exact concept was mentioned very briefly in the Harry Harrison Stainless Steel Rat sci-fi series. Not spent fuel, but a small nuclear source, as a simple, reliable backwoods boat engine.

[@AabhasLall]

@@Nineninetails Ah, interesting. I just knew that spent rods are to be placed in cooling ponds for 5-8 years. But nuclear powered popping boats sound nice, both conceptually and literally! :D

[@radadadadee]

Not sure how you can you stop the boat with nuclear rods

[@theNeathBoy]

Nice video. I had never come across these pop-pop boats before. I’ll check out more from your channel.

[@Puppy_Puppington]

It’s cool how sound & like literal energy from heat can create their own frequencies

[@mrmaniac3]

Man, these are giving me visions of full scale, and even giant vehicles operating with these kinds of propulsion systems, perhaps in the style of those in classic Ghibli films. Imagine hopping on the pop-pop boat to be ferried across the channel to the opposite coast, at the edge of the desert where you catch a ride on a bristle bot for the trip to the oasis in the center

[@clownsabound]

there actually was a life sized pop-pop boat in a ghibli film called ponyo! its the reason why i clicked on this video funnily enough 😅

[@coloradolove7957]

Let's keep working on this....

[@ennoshita7495]

@@clownsabound same :)

[@afandianto]

I remember my parent give this at my childhood Btw in indonesia we call it "kapal otok-otok"

[@irchonite1953]

that's so cool! :)

[@doublecritch]

Great job with the commercial! We appreciate the blunt notice. Looks like a good speaker.

[@aristotlespupil136]

I really like these type of engines without moving parts. This one reminds me of the pulse engine of the v1

[@joefish6091]

Pulse jets need flap valves to allow air in, then they are force closed from pressure from the fuel detonation, forming a reaction rocket chamber.

[@zedekiahharris6564]

I had actually wondered how these worked since watching Ponyo. Thank you for answering that question.

[@FogyArts]

I remember seeing this toy in the movie Ponyo and I always wondered how it worked.

[@keepitsimpleideaguy8676]

I would argue the bristle bot is not truly oscillating motion because of the rotary nature of the weight. The weight has a tendency to hop the bristle up and forward then down and backward which has a “hopping forward” effect. You can change the direction it hops by changing the direction of the motor. Great vid. Beautiful glass boat. That visual took so much speculation out of the equation. Two thumbs up

[@VC_27]

As a child, this tinplate toy was a must have every year during my annual vacation to Varanasi, India. I still have a few left, preserved somewhere within my chattel. Thank you for posting this video.

[@RaccoonHenry]

that transparent boat is beautiful! and as a Ponyo fan this might be my favorite of your videos so far!!

[@siriusmywaifu4043]

This does put a smile on my face. 😊

[@Tacospaceman]

I knew it. I’m so glad you’re doing this video rn dude. These were one of my favorite toys to play with. And the movie ponyo really made me love them

[@josephplatania5593]

Very interesting. Simple things can be so complex at the core. Well done. Stay well

[@ianbruce6515]

Thank you! I was always unsatisfied with the standard explanation! I was particularly delighted by the explanation of how the forward motion is caused--a crucial aspect that is totally ignored in the standard explanation.

[@itsawonderfullife4802]

The first explanation of how the propulsion works was actually quite right and also more easily understood using conservation of momentum. He didn't realize it (and was too dismissive of the first explanation) but his own (second) explanation was also a different version of the same first explanation. Remember, the initial momentum of the system (water-tank plus the boat) was zero and so (by conservation of momentum) it must remain zero at all times: 1. During the exhaust phase, collimated water clearly flows backward (along a single direction in 3D) and so the boat must glide forward (to conserve momentum: the two momenta sum to zero) and thus the boat receives a net momentum forward (water-tank plus the boat still has zero momentum). 2. In the suction phase, the inward rushing water comes from all directions and so the boat does not receive a net momentum in any particular direction (various momenta all sum to zero again but because the water on the whole has zero net momentum (rushing in from nearly all directions) the boat does not receive any net momentum either). 3. But it matters not, because the net momentum received during the exhaust phase is enough to propel the boat forward. NOTE much more than the various speeds (magnitude of velocities; Of the water molecules and the boat), it is the direction of various velocities that matters most.

[@jeffreylebowski4927]

But the water rushing in has to ultimatly assume the momentum that the direction of the pipes demand - even if the water is sourced from all around the pipe opening in the beginning, for it to be able to flow into and along the pipe it will need to get collimated anyways... it doesnt really matter how long the column expands outside of the pipes, within the pipes the water is a column and is streamlined.

[@megamaser]

@@jeffreylebowski4927 the water outside the pipe absolutely does matter because it affects the pressure on the boat which is another way to analyze this problem. But conservation of momentum also works. You just have to consider momentum of the entire system including the water outside

[@dominicread797]

Momentum isn't conserved because you are adding energy to the system. Without the candle the momentum would remain at zero.

[@megamaser]

@@dominicread797 Momentum is always conserved! Doing work doesn't change this

[@maxwang956]

@@dominicread797 Momentum is not energy. Momentum is conserved even in situations where energy is not. Backwards momentum generated by the boat is absorbed by the water and it's container, the same way that backwards momentum you generate while walking is absorbed by the earth. The change is negligible because of the difference in mass.

[@MarkStiles]

This seems similar to those u-shaped pulse jet engines, though they typically mount the combuster on one of the pipes and one acts as an intake while the other is the exhaust but the noise produced is effectively the same resonance effect

[@mattiemathis9549]

I’ve never seen one of these before! I know the next project for me and my granddaughter! Super cool!

[@ditship]

When i saw this I had to watch it. Ponyo! Thanks for explaining how it worked. I honestly didn't even know it was a real thing!