Will this toy engine work at full size? (yes)

But what was that giant duck doing there?
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There's a society somewhere in our galaxy where pop-pop boats are the most advanced form of propulsion

Thought they really had built a life-size pop pop boat for Steve to ride but then I saw the rubber ducky for scale and realised they'd simply shrunk Steve down enough to fit in a toy boat...

Now I know why USS Enterprise has it's shape 🙂 It'a an interstellar pop-pop boat!

when I watched the movie ponyo, I was fascinated with their pop boat. id never seen even a toy of one before the movie, and i wanted one so bad after seeing them driving around their city in one with just a candle powering it. incredible that this works at this scale. so cool

An anecdote from the UK. In 1946, I had a tinplate boat about the size of a slipper. In the centre was a small container into which one poured about 20ml of methylated spirits. Around the rim of the container were two layers of smallbore pipe. The two pipetails were soldered either side of the rudder, one being 10mm above the other. One lit the meths ,waited for a few minutes for the water to heat and expand in the top pipe before watching the boat cross the pond in silence. I still have it in my nostalgia box.

I would love to see a pop pop boat with many many smaller engines. Like your eight cubes separately, the surface area would scale with the volume. But maybe the medium engine, so you wouldn’t need 1 million of the mini ones.

There's two ways to make a human sized put-out boat.
I feel like this one is the "one horse sized duck" strategy. But I think I'd like to see the "100 duck sizes horses" strategy too

My Father and I crafted and sold handmade pop pop boats on a website 20 yrs ago. The boats were called “featherlite steam boats” because they were press formed from aluminum sheets and we included certificates with serial numbers for each one. These were the only pop pop boats with small rudder on the rear. Fun times !
Although my Father has passed away some time ago I still have the press forms to create the boat hull and top and all parts to braze the engine parts.

it is a bit strange at parts, but it is incredibly how the audio while on the boat would have been unusable and probably require a voiceover even just a year ago
but now we can noise-cancel and reconstruct dialogue pretty well given how I imagine the original audio is

It's cool that it works scaled up! At the sacrifice of 1:1 modeling after the source material, I bet this would get better performance in terms of speed if done in parallel with a specific size. If the reservoir size that provides the most propulsion that also has the least amount of weight / water can be worked out, I bet it might be able to go a lot faster. I'm no expert but a V8 pop-pop boat sounds pretty cool.

"We're very much on the cutting edge of life-sized pop-pop boat technology." I totally guffawed at that.

A lot of great theory here. I'm wondering about multiple tanks feeding to single or dual outlook with check valves. Honestly my mind is running wild with multiple ideas. Thanks for the content!

Yeah, square-cube law really defines the size of some things when it comes to engineering. You can't scale things up too much, and also can't scale things down too much. Some engineering solutions just work best at certain scales. And also various material properties come into play.

The spring and weight model was such an elegant way to visualize a complex concept. Thank you for such wonderful videos.

Great video Steve! Very Interesting.
I have been thinking about the analogy you´ve made with the cubes, and it make sense (yeah physics =D ) but what if you used 1000 pop pop boats in a larger one.
Would you get a better propulsion efficiency, or the result would be the same?
Thank you.

I wonder if the "pop pop" action would oscillate faster if you were in cooler water? Could be cool to try in the winter!

With an inlet and outlet check valve I think you could make it a steam pulse jet. Would need a serious amount of heat input.

Had a bit of a fascination with these boats and this video was fun to watch with a great educational piece on how scaling up works, doesn't work. Brilliant work and great to see those guys where happy to have you come and test their boat.

my childhood dreams after watching ponyo have been made real

I was thinking about the inverse square law, and I am glad you brought up the square cube law. I think the two laws are related.

Several smaller pipes seems like a logical improvement.
Another thing would be a bit more bracing over the main tank, that likely also don't have to be that dish shape, perhaps something more sturdy could be more efficient.
I would have gone for a section of pipe with added support rings on its outside. Then added some sheet metal outside it to funnel the flame up around the whole tank, as to provide more efficient heating of the whole thing. And of course clad the outside of the sheet metal in some degree of thermal insulation, as to waste less heat. Then perhaps it could even become a bit more fuel efficient.

If the heated surface of the larger boat had ripples on it there may be a way to compensate for the square cube law. Subsequently to help the steam cooling pipe function more efficiently it could be oval shaped and have a series of heat sinking fins on it as well these can also help it steer better as well as help the steam cool faster. Finally fins or channels in side the steam cooling pipes can help them collect and diffuse the hear faster as well.

I am extremely grateful for all your uploads! Thank you for sharing to the world!

Muy buen video !!!! Yo tengo una lancha que era de mi padre ( año 1950 aprox ) . Yo creo que en el modelo que probaste Puede ser que al expandirse las chapas del tanque , hagan perder presión, y por eso ande mas lento ?? Saludos desde Argentina ,

a system of check valves to allow it to pull water from the front and expell out the back would probably be another improvement to the design.

Would be intriguing to see whether solar heating in a hot location would be enough to drive the engine.

This was something i had always wondered. Thank you for saving me from making a massive mess that wouldn't work.

What if you used a radiator instead of the big tank to get more surface area for the heat to soak through?

I was skeptical that these guys were up to the challenge….but then I saw the giant rubber ducky and there was no doubt these guys came to play.

Would love to see if a V8 pop pop engine could be made to overcome the up-sizing issues 😂

In chemical engineering, there are concepts to overcome the square-cube law. Instead of a scale-up of a reactor (bigger tank), you can do scale-out (more reactors). In extremis, this results in chip-size reactors with lots of surface area. To bring this into the context of the video, just use 10,000 of the minisized pop pop boats :)

This is a very interesting and fun experiment.
In Japan, it is called a pom pom boat.
It is fresh in my mind that it appeared in the anime "Ponyo".
I thought it would not work with a scaled-up model, but was a bit surprised to find out that it could work with low efficiency.
The biggest surprise, however, was their attempt at a full model.
It's fantastic.👏👏👏

Interesting, Steve… A point missed by yourself and the others is that a pulsating water engine (PWE) or 'pop pop', 'Tok Tok' etc., doesn't have to have the flat plate. Toy ones only had a flat diaphragm to make an engine noise.
A simple coil of tubing over the flame works better as the flash boiler, and was used in larger model boats like the beautiful, pressed aluminium 'Miss England' by Victory Industries, sold just after WW2, as well as in many kit and scratch built models.
The PWE engine works by rapidly boiling the water in the flash boiler, which turns to steam and forces the water in the tail pipes out quickly. As the steam hits the cold pipes, it condenses, while the exiting water providing the thrust carries on moving down the long tail pipes under its own inertia (some small toy 'pop pops' only had a single tail pipe). The moving slug of water's inertia then creates a vacuum after the pressure of the steam bubble disappears, which eventually pulls in water, increasing the cooling of the condensing steam and refilling the tube, and 'boiler' section, with liquid. The coil (or chamber/boiler) over the heat source gets rapidly boiled again to send another pulse of steam down the system as it overcomes the back pressure from the now condensed previous bubble of steam and the drawn in water, which is pushed out to provide thrust (but not a lot).
A 'full size' PWE powered boat was actually built before WW2, though only a dinghy in size and very slow, it was virtually silent and used to stalk and net waterfowl on a calm pond.
My late father had a huge collection of old steam powered toys, including a lot of PWEs. Most of the PWEs were small candle or spirit heated 'pop pops', but some commercially sold ones, usually methylated spirit fired, were as big as half a metre long or more.

This is the most satisfying followup video I was never even expecting!!

I would think the simplest thing would be having rows of standard toy motors with a common burner. Lots of small high frequency engines that are already tuned.
P.S. after your first video I bought these in bulk for Christmas presents (1 for me 😁) they were the most played toy by all, my friends spa-bath had a Navy 🤣

I would like to see this powered by a TLUD filled with wood pellets.
I also wonder if you could put the intake up front for better performance.

I love the whole sequence in Ponyo when she enlarges the little pop pop boat and I’m so glad to know it would actually work for real!

Adorable. Yeah. Tactile physics museums are awesome. I remember going to one is Boston as a kid and had a blast. Wonder if it's still there and you're still able to run around doing real life counter intuitive experiments.

In the museum there was a tap in mid air pouring out water. I remember seeing this in 1964 at Bingley Hall in Birmingham UK. A lot smaller but to a 5 year old this was real magic !

I just had an Idea, what would happen if you had saucer/plate sized version of this in multiple ( more than one) doing this all at once or in consecutive intervals similar to a piston engine?

I made one of these little boats as a kid. it was literally just a thin copper tube coiled around a few times and the two ends stuck through two holes in a block of wood that was roughly cut into a boat shape, and a little tea light candle sitting underneath the coils. It was completely silent when operating since there was no reservoir to make noise like yours does.
I wish I knew what happened to it, but I suspect it probably got thrown away years ago.

I watched this Video not only because of the quality content you always deliver, but also specifically because of the non clickbait title. Thank you

As an estonian, seeing such a big content creator visit the small country and seeing a physics youtuber go to ahhaa is really exciting :D

At that scale you should try one directional valve. To make one pipe as intake and other one as outlet. Plus, yes. Camera with better stiffness.

A mnemonic for remembering which side of the boat is the port side: "There is no PORT LEFT in the bottle". Port is also red which is used to light the ports side of a boat in the dark and in Europe at least red bouys indicate the left side of a shipping channel into a harbour or estuary as you are entering it.

I'm impressed that the thing works at all. Life-sized pop-pop boat races should be a thing!

Thats crazy! I was just asking about this possibility 5 to 6 months ago. Only replies I got was that it was impossible for that scale. Thanks for posting this! Really interesting

I think several smaller units operating at higher cycles would be more efficient. Might even be able to connect multiple units to one outlet and tune the pipe or even reduce the outlet to increase pressure.

I wonder what the speed would APPEAR to be if you sped up the speed of a video of the full sized boat to the point where the frequency of the popper pan matched that of the toy's.

Id imagine if surface area of pipe is issue, perhaps having a hollow shelled pipe might be the "ideal" solution, or as mentioned multiple thinner onez

Hats off to the Estonian Science guys! Love your work.

👍 ♥ I love that idea! You guys are awesome! 🤘😁

Looks like a big success, fuel-efficient too.

Would it work better if they used much thicker gauge sheet steel for the diaphragm? Or if they used several smaller diameter motors (3 or 4) if the surface area to mass ratio is a factor?

To somewhat counteract the square cube law, we could use fins to increase the surface area of the water tank, maybe an idea for a future video?

@SteveMould what would happen if you superheated the steam through a series of smaller tubes? Would this increase the thermal efficiency of the life-size boat therefore increasing the speed of the boat?

What if you made several small engines that feed into a central pipe? Would that increase efficiency?

It was my imagination when I was a child to see a full scaled Pop-pop boat.

So the logical solution would be to make multiple pop-pop engines on a slightly smaller scale, say 1/2 or even 1/8 the size in this video and have them each linked together through an unequal length header so there is always propulsion 🙂
Good luck with timing tho, haha!

I think 1 thing that wasn't taken into account was the simple fact that area that is heated on the pop pop boat os greater than the area being heated on the larger version. One way to increase hp I think would be use a smaller diameter pipe to increase force coming out

I want a full pop-pop boat engine optimization series. I'm interested in seeing what can be achieved with them

Have you considered using Duck-Bill Valves. Light, Durable, efficient at keeping water moving in one direction without back-flow or mixing. Love the videos!

I'd like to see what would happen if you scaled the engine size down, and placed multiple in its place. A 4 (cylinder?) pop-pop engine would be an interesting concept

If one is not in a hurry, a slow boat like a pop up boat could be provide a very relaxing, romantic and nostalgic sense with classical theme environment in a man made lake or river area.

After seeing the original video I was rewatching the movie "Ponyo" with my kids when I realized that they made (through magic) a human-sized pop pop boat in the movie. Ever since then I've though, "Man, it'd be cool to see one of those in real life!" so this video is really cool

So, as per your explanation about the square cube law with the blocks, where there are surface area missing after it goes inside the bigger cube:
Does that mean that if the big human boat (or even the teddy bear boat) is propelled by 20 or 50 small pop pop boat engine, the boat will run faster?
(theoretically, we will have 8 small cubes without the surface area diminished caused by the combination into a bigger cube).

2:25 Honestly kind of surprised no one there put an RC rudder on the teddy bear boat. Or even a fixed/adjustable rudder to make it just go in circles and not straight out on the lake

I never knew of it in this form, but I used to make little tiny jet boats out of a coil of aluminum tubing that didn't need any special setup to fill all you did was pump water in one and until it came out on the other side without needing a container in the middle. Then you just heated the end of the loop and the water vaporizing expanding, cooling and collapsing was mostly silent. The way i look at it is if your engine is making noise, then that is energy not moving you foreward.

I wonder if reducing the diamter of the outlet pipes would help increase the speed.

I think you’d find the boats with multiple pipes interesting

I remember making thse little boats for a science fair in year 5 lol. I didn't have the resevoir part though, it was just a full on looped pipe. Worked great too. I don't remember them being slow, so I think it'd solve that pop pop issue? I also didn't have the noise coming off the boat, since no flex. Maybe next one you could try it with just a looped pipe? Less internal volume to move around cuz well, less area to move in the first place.

I think increasing the frequency would be the best way to scale the large version, how to do that is a bit tricky.. perhaps you would need many 1000x of the small pop pop engines ?

I wonder if making a Multi-motor pop pop would work better. With more smaller motors you would get faster cycles and hopefully scale that speed up.

Always wanted to do this as a full boat just so other people would laugh

thank you so much for this!! I was dreaming for something like that since you uploaded the videos with the pop pop boat

It might work better with a boiler system similar to a steam train, where the surface area contacting the water is much larger.

I feel like having the "pan" or top part that does the popping made of aluminum or even copper would work a lot better, both since it would conduct more heat, but also because as a softer metal it would be more flexible.

I think that some sort of fast non return valve should be used so that the returning water would be sucked from the front, I think that it would increase the efficiency a lot. Second thing is to find a way to increase the frequency of the engine.

great build! I'd love to see a racing league of these (where people compete optimizing them for more 'horsepower')

Steve, try to make the next attempt with one pipe, but with 2 non-return Valves. One at the front of the pipe for water intake & one at the back for propulsion. The 2 NRVs will ensure backward flow of Steam & Water providing impulse during both the intake as well exhaust halves of the cycle.

That's one of the main reasons why shuttles are so hard to get into space because you have to account for the weight of the shuttle itself plus all the stuff inside the shuttle and Rockets.

Imagine a pop-pop boat with a high pressure steam boiler and the exhaust with a turbine, and you'll get a steampunk jet sky !

Put check valves at the back of the propulsion vents so they won’t release until X pressure that way the force of the released water would be greater

The Square-cube law you mentioned is why bigger rounder animals lose less heat, more volume for less surface area.

You pointed out that it could have one pipe, but with 2 pipes it could also have the water inlet pointing forwards to pull the boat when taking water in, like an impeller, both pulling and pushing by drawing water through the system. The inlet drawing straight along the center of boat and a central outlet pipe (used for stearing as it is now) might help to keep it a bit straighter too which will reduce drag/reduce decelertation between cycles.
That would only result in minor speed increases but still ways to achieve more of the potential while understanding how scale (form) impacts operation (function).

I've always loved that kind of boat I had during my childhood.

I think drawing water in from a rear-facing opening slows things down a bit. I'd suggest having one pipe forward with a check valve that only allows water _in_ and the other pipe backward with a check valve that only allows water _out._

I'm curious what would happen if instead you used maybe 6 smaller pops for 1 boat instead of 1 huge one

Can you imagine the efficiency of that contraption

Hence why cars have multiple cylinders, square cube law. If you tried to blow up a three liter bottle the explosion is way slower and takes more rotational mass to keep going as compared to six half liter bottles which explode faster and can keep each other moving. This can be applied to whatever engine size you have.

Nice project!
Looks like a competition - how can you move forward with the worst efficiency 🙂

i wonder if it can be more efficient if they changed the metal plates into a radiator type for more surface area.

I've never heard of this. I'm dying to know what the child's version is! Imagine not knowing and seeing this. 🤣

So if you developed a full sized boat that had a series of small pop-pop engines, each with single pipe setups connected to separate engine chambers that use the same larger heat source? Could you have multiple high frequency propulsion pipes providing more power? Imma have to start making some design sketches.

I am confused! Is there already an efficient propane engine out there?

Would be interesting to see if it would be more effective to use a large number of much smaller engines, instead of one big one.

A most interesting and unique attempt and congratulations to all involved. This type engine will work using a simple flash tube boiler. It is not required that the boiler should be based on the flexing plate boiler used on toy boats. Using a flash tube boiler would also make it possible to arrange an efficient heat transfer system as used in industrial flash tube boilers. During the steam car days, most or perhaps all cars used flash boilers as these are totally safe and do not require to be certified as is required for regular water or fire tube boilers. Perhaps further attempts using a flash tube boiler could result in worthwhile power being developed sufficient to propel a person sized boat. I do hope those interested will proceed further.

Interesting support for scientific reflection.
Obviously for those who, like me, do not have a full understanding of the basics due to limited education😊 (I'm a 76 year old)

Wonder if as you scale up the boat you need to scale up the heat required to produce propulsion 🤔