It turns out the launch site at Cliffe Fort is a 40 minute walk from the nearest road. And we chose the windiest day of the year to make the journey. It's a miracle that we got any usable audio at all! Th sponsor is Odoo: try it out today: www.odoo.com/r/Si6
@@mikethewhizz5085 Where are you going after you die? What happens next? Have you ever thought about that? Repent today and give your life to Jesus Christ to obtain eternal salvation. Tomorrow may be too late my brethen😢. Hebrews 9:27 says "And as it is appointed unto man once to die, but after that the judgement
Step back to 1877 when Louis Brennan invented this. From Wiki: The Brennan torpedo was a torpedo patented by Irish-born Australian inventor Louis Brennan in 1877. It was propelled by two contra-rotating propellers that were spun by rapidly pulling out wires from drums wound inside the torpedo. Differential speed on the wires connected to the shore station allowed the torpedo to be guided to its target, up to 2,000 yards (1,800 m) away. Amazing.
I wonder why they did not use a steam pressure vessel inside the torpedo as an energy source. Maybe the aspect that it was remote controlled was more important than just propelling it forward 🤔
Steve had to build FULL 3D version because he could not figure out how to simplify it into a 2D cross sectional model. I also love the fact that we saw over a dozen prop prototypes too. Thanks, Steve.
@@DhruvGN8 You are right! I stand corrected. I actually meant it as a bit of a joke how he always simplifies to a 2D model, but I didn't think of the mass model. So I have to laugh at myself for not seeing it. Thanks.
There is a much easier way to experience it. Consider a typical wire spool with plates at its ends. You put it on the table with the wire coming out at the bottom and pull back on the wire. If plates at the end have the diameter of the spool, it will stand still unless you overcome friction. If the plates are larger (as you see on typical spools) the spool will start rolling towards you, while upping the wire (that's the "mechanical disadvantage" situation). If the plates are smaller (e.g. they are just an axle) an running on rails, the spool will roll away from you. That's the "mechanical advantage" situation)
Something that you guys missed it that there were two contra rotating propellers. It was also spun up to speed out of the water as it slid down the ramp, meaning much less force would need to be applied to keep the torpedo up to speed
And also to school Derek in front of us all. I think Derek has a very superficial understanding of most of the concepts he tries to explain. Even with multiple researchers and writers, he can not compete.
@@amosbackstrom5366 I feel like it's the difference between a generalist that sometimes goes into a deep dive versus a specialist that occasionally explores outside their realm of expertise. Derek tends to cover large amounts of ground (be it subject matter, historical time, or just multiple related concepts) in his videos so there's often not a lot of space to go into deep explainers. At least not without making even longer videos. Derek also seems more interested in the relationship between pieces of knowledge - his recent video talking about how the Principle of Least Action is a different form of Newton's F=MA is a good example. And, he tends to be a bit more of a storyteller - his more recent videos are often about HOW something was discovered and not so much the theoretical implications or the practical followups. Steve focuses on one thing for his videos and if something like Bernoulli's Principle comes up, he'll explain what it means and how it's used and why it's relevant but he's not likely to explain the story about it and start talking about Bernoulli. His videos aren't structured as stories about the origins of a principle or mechanic he's talking about. Rather, his stories are the story of his specific experience with the specific experiment he's working on. Slice of life, scientifically speaking. I don't think there's anything wrong with each approach. It just depends on which kind of knowledge you need at the time. Ultimately, both are important.
I thought he was going to go with what I think is a neater example - a spool that's placed on a flat plank that's the width of the spool's centre cylinder, so it can roll back and forth along it, with one of the side discs of the spool made extra thick so that string can be spooled around *it* as opposed to around the centre piece. Pulling the string would make the spool roll away from you along the plank. The mechanical advantage comes from the then obvious fact that the string is spooled around a larger radius than the part of the spool that is in contact with the plank.
Your non-propeller mechanical advantage explanation was a great way to break it down. I’m a turbomachinery aerodynamicist, and my initial thought was that this would work with a sufficiently large drum. While the fluid dynamics of a propeller are complicated, the macroscopic performance parameters are fairly simple: the propeller will create a thrust T at an RPM n, and will require a shaft torque of Q = r*f, where r is the radius of the drum and f is the force of the wire on the drum, which equals the force of the wire on the torpedo. It is then just a matter of choosing r such that f < T, as you mentioned. Not surprising to hear that it took so many propeller iterations to get this to work, the system as a whole would need to be pretty well matched to get it to work. Very cool showcase of a really unique application
"turbomachinery aerodynamicist" is quite a job title "so what do you do for a living?" "me? oh I work on the aerodynamics of turbomachinery, ya know, normal stuff."
It is worth noting that it is fortunate that M. Mould was looking at the revised RE design in the museum. The original actual Brennan design had transverse drums and a whole load of gears. The advantage of it being immediately apparent from the existence of wheel ratios that there was mechanical advantage involved is outweighed by the fussiness of the original transmission.
@@JdeBP I wonder if anyone contemplated constructing and using torpeoes based on the simpler design? I would think that torpedoes which used a pair of propellers and steered via differential thrust could be built so much more cheaply and quickly than one with an integrated power source that they'd be used in any situations where where targets would be within cable range.
@@chrisakaschulbus4903 given the number of propellers I ended up making, it felt like it was black magic. Though I think the problem was made a lot harder as the propeller is too close to the surface and there were lots of surface effects on the propeller which were adding drag.
Louis Brennan was an absolute genius, He also invented a Gyro-Monorail in 1903, the prototype was built in Gillingham, Kent in 1909, then in 1910 he built a 1 Mile circuit at the Japan-British Exhibition at White City, London where Winston Churchill reportedly drove it for 1 circuit, In 1916 he patented a Helicopter design and it had it's first tethered flight was in 1921, If you go to 'Sappers Walk, Gillingham, Kent, UK' on Google maps you can see some bronze plaques commemorating his work, The last remaining Torpedo is at the Royal Engineers Museum in Gillingham (well worth a visit!) the archive for his personal papers is at Gillingham Library
I think a simpler explanation would come from the bicycle paradox (which you also did a video on IIRC). Attaching a rope to the pedal and pulling backwards causes the bike to roll forwards - which again is due to mechanical advantage.
I kept thinking that there were similarities between this and another video. The thought experiment was so similar, but I couldn't recall the actual experiment. Thank you
Not sure if were talking about the same thing, but I was thinking the spool experiment, where pulling the cord made the spool roll away from the pull. But yes, it is all about mechanical advantage. Not about forces pulling in different directions.
Pretty classic physics demonstration. The bobbin pull. A string wound to the smaller diameter section is pulled in the same direction of the wind, and the larger diameter resting on a surface is pulled in the same direction as the pulling force faster than the rate of pull.
I was thinking this the whole video, waiting for him to show it! I suppose some demonstrations will always be forgotten, but to me it seems the most tangible way to show that pulling something backwards can make it move forwards (as you're pulling the cable backwards and not the thing!)
My mind went to a yoyo or a spool. You can make it go forward or backwards or no where depending on what angle you pull the string on. Generally if the spool is below the string it pullw forward. Has to do with torque. Is that what you mean when you say bobbin? The thing with my spool or yoyo explanation is obviously this uses a propeller. I bet a bigger spool helps.
Yeah was not impressed. If you attach the power source, say a drill with a spool to the actual body of the device and get the drill to pull it. You just created a cable driven motor. I think the illusion of wonder comes from not being able to understand you're not putting on the device. You're putting on the engine of the device. You're the power source. There's no reason it wouldn't go forward. We use the same thing for spinning tops, yoyos and a whole other manor of toys. Steve's mind just gets lost in the wonder and can't figure it out a lot of the time. He needs it be more than it is. Which is a lot of the reason I don't respect him.
Great to see this collaboration (I'm slightly jealous). I had half expected the drums in the torpedo to be heavy and spun like flywheels and then the torpedo to shoot off unattached to the cables. That would obviate the pulleys and lower friction, but the torpedo would be heavier.
1:21 "Cliffe has the dubious distinction of being the only known Brennan Torpedo Station to sink a ship, albeit in error: in August 1901 a Ketch, WS Flower, was struck by a torpedo on trials. The torpedo, containing a full charge but no detonator, made a large hole below the ship's waterline and it sank quickly. Fortunately, no one was injured and the vessel was recovered (R E Museum)." From the Historic England report on Cliffe station.
There was in Finland in 70's under ice torpedoes that worked by pulling from a line. They had claws and levers, often two lines, one for propulsion and one for release. Now they make still those torpedoes, but they have rechargeable batteries and motor. It's even quite simple to guide the torpedo following an electric cable pair from one hole in ice to another. Some have also a strong light to show where to drill the other hole. The two hole system doesn't need the torpedo to stay underwater or pull the net, it's e enough to pull only a line. The original version worked, but it's pretty slow and cumbersome, if one has 25m net, and the torpedo moves 5 to 10 cm each 50 cm pull and gets stuck on uneven ice surface.
@@olliefoxx7165 pulling fishing net guide rope under ice. The old torpedos pulled themselves forward with claws gripping underside of ice on a lake/sea. I saw a version that had lever that you just tugged to make the device to kick few cm/inch forward. With lots of tuggin you got enough distance. Other version had spiked wheels and small spool and you just pull lots of rope (or yarn) to make it drive under ice just like this torpedo or that bicycle paradox.
While I was already convinced by the blackbird videos, I think this video will help a lot of people grasp it better. In addition to being a terrific video in it's own right
@@hogandromgool2062 Remember: There's a big difference in submitting a response from a smartphone and from a computer. You've got to account for difficulty in handling predictive spelling. And you can't do this: t̶o̶ (strike through) or this §
Love it. I visited the Brennan torpedo tracks (at Cliffe Fort) with my son a couple of years ago. How the torpedo actually works is a conversation we keep coming back to. It is an absolute work of genius. There is a Brennan torpedo on display at the Royal Engineers Museum in Brompton (not far from Chatham Dockyard). My son is keen on physics and has been a longtime fan of Veritasium. So this video has serendipitous qualities for us both. Another connection is that my son is studying engineering at Medway Campus. This is where the Royal Engineers officers were trained and where Brennan himself may have given talks.
I think the torpedo would get its blade spinning from its weight tugging on the rope while it was going down the slide , and then they would release some kind of clutch on an working engine and would start pulling the rope once it reached the end of the slide , it would give a extra boost and it would remove the initial enertia needed to get the blade spinning
It's like that trick with the rolling spool; it just gets more confusing to think about because instead of just friction you're dealing with hydrodynamics.
yep, this didn't feel all that unintuitive after having seen the spool thing before. I just took one look at it and was like, nah that's probably doable with gear ratios, which is essentially what was explained with the levers.
15:20 this whole conversation reminds me of the techniques my college Computer Graphics professor had for visualizing things: "make it big. be there." When you imagine something, imagine it so huge you are a part of it. and look around it at all the parts. That's exactly what Derick was doing. He was making the system huge, and putting himself in it, holding part of it. Really cool.
"The Way Things Work" is the best illustrated example of this concept. Turns various tools, devices, and instruments into fantastical structures powered by harnessing small mammoths.
Identification of the root “problem” and then visualization of how that problem works at its fundamental level is so critical to rendering and general problem solving. Should be required education instead of the combinatorics class every CS major takes
It's easy to forget that propellers are functionally a lot like "gearboxes" and "wheels" all-in-one for wheeled vehicles, and various boats/planes have varying propeller designs to change and optimize the ratios of rotating input torque to linear output force at different speeds. It's entirely impractical to couple a combustion motor directly to the wheels in a car, but for boats and planes this is almost always exactly what we do because of the flexibility offered by varying the propeller design.
occasionally with reduction gears, usually at a fixed ratio, though a lot of modern diesels are just designed to operate at the right power ratio not to need it
Wow, this reminds me of a cool childhood memory! You know how when we pull a string tied to a spool on the ground, the spool rolls forward? It's such a simple yet fascinating physics principle! Turns out, the Brennan Torpedo worked on a similar idea! The torpedo used wires to create tension, propelling it forward in water and controlling its direction. It's crazy how a playful childhood trick connects to historical military tech. Physics is awesome!
@@m4rcyonstation93It's a phenomenon where someone spends a long while putting together a science video, only to have Derek put out a better video on the topic right before their video drops. That dang veritassium and his video quality!
@@m4rcyonstation93 Matt Parker talks about him and Steve Mould getting Derek'd in this video about him getting reverse-Derek'd. th-cam.com/video/gusXBTyg1O4/w-d-xo.htmlsi=MJAg16dFJWdRzIpF
@@MSheepdog it has nothing to do with your opinion of the quality of the videos, the issue is entirely unrelated to your opinions and instead related to upload dates and behind the scenes communications. It's not some horrible crime he's been caught doing, I don't get why it's so hard for people to accept criticism that is not even addressed to them but instead addressed to someone who is literally a stranger that they've just seen on a screen before.
The lever analogy (and especially the 'what if the mass was fixed' bit) are really clever. It makes it clear that mechanical advantage *could* make this work, therefore a version with a propeller is plausible. It honestly actually improves on the understanding of Veritasium's video too.
Always found Derek’s video a bit frustrating, I haven’t watched it in a while but I remember is explanation not really helping me to understand the idea. The lever analogy is great
As an electrician this torpedo made perfect sense to me in the first few seconds of the video. I didn’t even have to watch how it worked. Its the counterintuitive action of unrolling cable by rolling the drum along the ground. If you pull on the cable, the drum will stop and then come back to you. It’s two separate torque arms.
Hey Steve, Off road enthusiats know about this well. While using a winch to affect a self recovery, you can use pullies to have the cable/rope go under the vehicle and atttach to the back of the vehilce via pullies in the back. When using this you can change the direction you want to go merely by changin the pully setup. love the videos keep them coming.
TH-cam stopped recommending your videos to me 6 months ago. I was a loyal watcher up until that point. They just recommended this video to me and I was like STEVE MOULD!! So glad to be watching your videos again
@@Hermanos22 Imagine reading that comment... and the comment you make is an insult. Your life must be... well, I don't know you, and I'm not arrogant enough to make a statement about your life.
@@Hermanos22 Your response to someone excited to be introduced to Steve Mould's cat is far worse. The fact that you needed to comment on it is pathetic. Maybe some day you'll get a human interaction firmware update. Until then you should consider keeping your thoughts to yourself. Shout out to Steve Mould's cat. I hope to see it featured in more of his future videos.
Well, I know it too, but i honestly didn't even think about the torque because I imagined the drawing just as an abstract schematic, so I didn't think about the exact positioning of it's components
As usual Steve puts a lot of work and effort to explain real life things. Having Derek side by side was like watching two David Suzukis in one episode! They should have a science TV show!
@@electrodacusNo, it does. The cable/road is moving backwards at a certain speed relative to the water/air, and the power of that relative motion is used to propel the craft forwards through the water/air even though there is no net force in that direction except between the propeller and the water/air. It's the exact same setup. (edit: and of course now I unpause and see Steve mention the treadmill example in Derek's video. Glad to see he made the comparison clear.)
@@charltonrodda Steve video explanation is incorrect and so is Derek's explanation of direct downwind faster than wind. My last video debunked Derek's claims and proved clearly how those type of vehicle work. In this torpedo example input is the cable/string and it is the equivalent of air/wind in the case of wind powered carts. The water is the road equivalent. You can not just chose what the input is. Energy at the output (propeller) will always be lower than energy provided at input cable/string. You can not make the claim that propeller in Steve torpedo example is the input as it is very clearly the output. So no matter what reference frame you want to use the output will remain the propeller.
@@electrodacus But you *can* choose what the input is. That's one of the fundamental principles in physics, you can choose whatever inertial reference frame you want and the system will still behave the same. From the wind vehicle's frame of reference, a moving treadmill with still air is identical to a stationary surface with moving air. The only difference with the torpedo is that you have to attach the rope to the front, and change the spool's winding direction. You can't push on a rope, after all.
@@areadenial2343 No you can not chose the input. Yes you can change the frame of reference to whatever you like but the result will be the same in all reference frames if you did not made any mistakes. Unless you change the gear ratio (this includes the propeller pitch) the input will always be at the string for this torpedo and the output will be at the propeller. You can build a torpedo where propeller is the input but that requires a differently build torpedo same as the direct upwind and direct downwind carts are not the same device they are constructed differently. So the torpedo shown in this video is designed with input at the string and output at propeller. You can look at the experiment from any reference frame that you prefer or fine more intuitive but the result will always be the same.
Those early torpedo designs were incredibly fascinating. But then I'm still fascinated by the much later ones of WWII and all their mechanical systems as well.
If your are interested, there's a video showing how this torpedo works. th-cam.com/video/sQJCOnyUvfU/w-d-xo.html They've also done videos on ww2 torpedoes as well.
It's amazing to see your creativity and how clear it can become 🎉 lovely to see Derek on your channel as well 💪👏 You are doing such a great job at explaining ☺️
You're absolutely right, it's a lot like the one Veritasium and Xyla Foxlin tried out. I'm 58 and in my mid 20's I reinvented the principle and made a toy yacht that went straight up wind. Very big low pitch under water prop and very high pitched wind mill direct coupled above deck. Worked first time! I then researched prior art and found someone had made a wind powered bicycle that went down wind faster than the wind. Nice to know there were humans playing with this stuff long ago! In my 20's one of the other ideas I had was effectively a corrolis force earth motor using earth's spin to generate power with reference to latitude line gyroscopes.
I think the lever explanation still gives a much more mathematically complete understanding of what's happening, and you might not have completely realised how important that extra analysis is. The fact that "It's just a pulley system" doesn't automatically tell you that it'll be pulled in the direction you're hoping for, as evidenced by the three examples of mechanical advantage and disadvantage at 11:35-12:05, (as well as, to a lesser extent, the more extreme version of the first example where he holds down the counter-weight completely). Without simplifying the details of the system, you wouldn't be able to figure out the fundamentals of how your pulley-powered propeller can receive enough energy to counteract the acceleration in the wrong direction that your pulley system receives from you pulling the rope.
@@TheHadMatters It's not so different from a pulley system installed in a cart that moves forward as you pull on the rope. One pulley takes the rope into the cart and then it goes around a flywheel on the axle. With the right gearing you can gain a torque advantage at the sacrifice of needing to use higher speed pulling the rope. For me when I see it work I can intuit how it is working. His explanation helps people too.
I'm sure someone will mention this, but we STILL have wire-guided projectiles. The GM-71 TOW (Tube-launched, Optically tracked, Wire-guided) is an anti-tank missile and the U.S. Mark 48 Advanced Capability (ADCAP) torpedo are both "current" technologies. Of course they just use the wires, as you mention at the end of your video, for steering. It seems crazy that they still use them. Hopefully no fishies get tangled up in these filaments...
13:21 That is a revised design done in Chatham, based upon Brennan's, in the RE museum. The original actual Brennan design had transverse drums and a whole load of gears. There are detailed plans of both in old history books. This is second system effect in action, and there is probably scope for some enterprising TH-camr to replicate the original design and field test it, to show why they had to redesign it.
For such people: Read chapter 5 of Charles William Sleeman's 1889 edition (since some of this dates from the middle 1880s) of _Torpedoes And Torpedo Warfare_ if you want to see detailed diagrams of two "Brennan"s and the 2-wire flavour of the "Maxim".
Thank you very much. It seems the Royal Navy at the time would have worked through and documented the Newtonians of the system in their designs, no? Can you shed you shed light on that?
I remember, when I was a kid, my mother handed me a spool of thread and showed me that by changing the angle (and nothing else) of thread as I pulled it that it could be made to roll away, stay still, or even come back towards me. I love these kind of creations because they showcase incredibly simple mechanisms that do absurdly counterintuitive things. Well done and marvelously explained.
@stevemould I saw you at the RI for the Night of Unnecessary Detail. We really enjoyed your presentation on this torpedo during the live event and the other presenters as well. The map showing the 1.5 day trip to this launch location was such a fun addition to that presentation.
Another simple example is taking a spool of thread or a wide spool of fishing line, then pulling on the line with it coming from the bottom makes it want to roll away.
I never heard of this torpedo before but as soon as you showed the 1st illustration, I understood how it worked. Nothing impossible about it. Range would be a liming factor but we use wire guidance today, so face those same limitations. The mechanics are straight forward. Speed would be another factor & is probably a bigger factor into why it was not explored further, given that the trigger mechanism of the time required the torpedo to slam hard into its target requiring high speed.
It took a minute of explanation to realize that when you pull the string backwards you're not pulling the torpedo backwards, you are turning the spool. There is some parasitic resistance in the system that will cause a fractional tug backwards on the structure, but most of the force is going into rotating the spool. Seems fairly intuitively obvious?
Remember the inertial loading of the spool/propeller system will be transferred to the pulley brackets which will result in rearward motion. Only if the cable was being pulled perpendicularly to the direction of motion would this be avoided.
?? He doesn't even say that. He just says the successor to the Brandon torpedo still had a cable to direct itself for where it was launched. That is not a statement about modern torpedoes.
You could not understand because Veritasium explanation was wrong. Steve's explanations is also wrong tho this is a different problem as it is the equivalent of direct upwind propeller cart not the direct downwind one. I made a video correctly explaining the direct downwind version and when I get the time I will do the same for the direct upwind version (the equivalent of this torpedo).
There were two cables being pulled by steam engines on shore. They each drove one of two counter rotating propellers for propulsion. They also used differential speed between the two cables to enact, through a series of mechanisms within the torpedo, a steering force on the rudder. Speed up one cable and the torpedo turned left. Speed up the other and it turned right. Equal speed and it went straight. There's a very good TH-cam video that details the whole thing. . . . th-cam.com/video/sQJCOnyUvfU/w-d-xo.htmlsi=l7FKEd2srrL945nx
@@40-forty-plus There was one engine and one winding drum the two wires were attached to. The wires went through an S shaped path, the length of which was varied by moving pulleys, shortening one path and lengthening the other. This activated the steering mechanism in the torpedo which is presumed to be a differential that, in turn, operated the rudder.
Great explanation. The same is true for the propeller with the wind coming from behind. Since the blades move at an angle against the wind (mechanical advantage) the cart can move faster than the wind.
Before watching, this already makes sense. It's just like pulling a yoyo towards yourself to make it roll away. If you get the tension just right, I bet it can roll 50 times the string's length on a smooth surface. A paddle boat version of this would also work well, though not as cool as a torpedo.
I felt like Terence Tao watching these two being confused by this "paradoxon" But then i realized, that maybe they did not study physics, while i do. I was very confused on how they are confused by mechanical advantage, just because of the extra step of a propeller.
For some reason this just makes perfect sense to me, if no one had called it impossible or a paradox I wouldn't have even doubted it. I don't know if my thinking is actually correct but I think about it in a much simpler way. When you pull on the cable you're producing a backwards force but pulling on the cable turns the propeller which generates a forward force, as long as the latter is greater than the former then the torpedo goes forwards. And with gearing, or mechanical advantage, then you can always reduce the force required (the rearwards force) in exchange for having to pull the cable a greater distance (or at a faster rate than the forwards movement of the torpedo). Just think if you decreased the mechanical advantage so much that the mechanism was effectively stuck solid (like how if you try starting from a stop with a bicycle in its highest gear, there's a lot of resistance at the pedals), you're not going to generate any thrust at the propeller and just pull the torpedo backwards as if the cable was tied to the rear. And taking things to the opposite extreme you could increase the mechanical advantage such that there would be very little resistance to pulling the cable, you'd just need to use a top fuel dragster to pull it fast enough to spin the propeller.
@@HORNOMINATOR There's a backwards force because by pulling the cable you're doing work (spinning the propeller), there needs to be an opposite reaction (resistance) to that. If instead you were just unravelling the cable from a frictionless and weightless drum then yes there wouldn't really be any backwards force. If you've ever used a Beyblade or similar spinning top then you'll know that with the hand that holds the launcher you need to provide a force opposite to the hand pulling the ripcord, spinning up the weight of the top produces a resistance in the mechanism. Likewise using the launcher without a top attached produces less resistance.
one of the main things i've learned from you is that discretizing things helps to understand them. here you replaced the propeller with a lever and a single mass; in the ball-under-the-table video, you made it easier to understand the golf ball paradox by turning the cylinder into a shape with a small finite number of sides.
Wasn't there a manufactured toy like that? I have the vaguest memory of it, it's rather madenning. I think the body was made of metal, the grips out of latex rubber, so it was made a long time ago.
I remember having a toy car when I was a child that worked the same way: You pulled a string out the back and the car drove forward. My 10 year old brain couldn't wrap my head around it and I took the car apart, and discovered the exact same thing: Between the spool and the gearing connecting the spool to the axle there was some mechanical advantage. It was one of the early moments in my life that tickled the engineering side of my brain, because I didn't understand the physics at that age, but once I saw the parts my brain intuitively understood the concept. The part that made the most sense for me was that the length of string that came out the back was _more_ than the distance that the wheel turned; I had to pull the string faster than the car moved forward, and so in my head the car was "taking" some of the "pull" I was applying.
The acknowledgement at the end, if the possibility of getting Dereked every now and then is so awesome. I love the relationship among science communicators
I"m at 2:15 now and just recording my thoughts: the spool inside the torpedo is rotating, so some, maybe even most, of the force applied by the cable being pulled is used for that spool rotation. So, yes, it seems plausible that the torpedo could go forward. And I would think that especially once the spool is rotating at a stable speed, the rotational momentum of the spool makes it easy to be kept rotating.
I believe he missed a critical part of the design, that being one or more flywheels. A flywheel could have been spun up before launch much like how Gyroscopes are used to stabilize and balance rockets. It could have been used to help with the steering as well as provide some force to the spool to offset the resistance of the cable in propelling the torpedo.
The problem is you need really high rpms or a very heavy flywheel. Heavier flywheels means more mass, which is harder to make neutrally buoyant. And there is a lot of friction in water. It's hard to store that much energy in a flywheel.
@@RCAvhstape @benphartine Yes. It was the Howell Torpedo (1896) It worked like a toy flywheel car. On the ship, a steam turbine would spin a flywheel up to high speed. then when launched, the inertia would spin the props, propelling it through the water. Here's an animation showing how it works. th-cam.com/video/xTRBbFX7AxA/w-d-xo.html
Great video. There is also an analogy to one of Derek's videos where you pull backwards on a bike's pedal and ask which way the bike will go. Turns out it theoretically depends on the gear but no bike ever has a gear small enough to make the bike move forward. I remember one commenter modified their bike to make it move forward when the pedal is pulled backwards.
I think it makes more sense to think of it in power (watts) instead of force (newtons). Knowing that the cable got pulled 4x the distance as the torpedo moved it should be obvious that the extra power was going somewhere (into the water to move the torpedo)
@@renedekker9806 This problem in Steve video is the equivalent of direct upwind vehicle and I did not made a video about that (maybe will do when I get some free time). But I made a video about the direct down wind version and properly explained how it works looking at power and energy. Spoiler it is not working the way Derek thinks as his explanation was incorrect (he even made up equations :))
@@electrodacus I would love to see that. But you cannot base the explanation on power and energy alone, because they don't have a direction. At some point you will have to discuss the forces and their direction.
@@renedekker9806 There is an input and an output power so yes you can know direction based on the relation between the two but I included forces also in the explanation. Is just a 10 minute video.
Interesting concept ... imagine having a drone like this, but with a looped string (on one side the line goes in and on another side it goes out) might make it possible to make it fly indefinitely. But I guess the only advantage over an electric cable would be the reduced thickness of the string/wire.
That won't work. The energy to drive this is coming from pulling the cable out. So the cable needs to be connected to something else which provides the energy. If you just connect it to itself, there's no energy source, and it won't go anywhere. Basically, everything inside the torpedo is just an elaborate mechanism to turn the pull force of the cable, into a push force on the torpedo. If the cable isn't pulled from outside, there's no push on the torpedo.
to explain it better: if you would not have a looped string, the drone will stop to fly once all of the string was used and you reach the end.(thats why a looped string with that goes in and out)
I must admit, I don't find this hard to comprehend. It's just a matter of the propeller exerting more force when rotating than the force pulling the wire backwards. There is only one logical result of this: the torpedo should move forward.
@@lukasg4807 When he won $10K from the UCLA physics professor the first thing he did was to have a little contest for people to make 1 minute videos, and gave the money away.
I love that the actual Brennan torpedo includes two spools. Each rotating the opposite direction of the other. I kept asking myself why not introduce two wires/spools and use the other to work as a gyroscope. Countacting the turning of the propeller and first spool. However I see the original inventor thought further than that. Using said mechanism for steering. Brilliant!
how nice to see you both together - it just had to happen some day. It is moderately hard to beat formalism, but beating intuition is the true master discipline.
V nice explaination. I had a similar thought along Derek's lines: replace the water with an immovable wall and the propeller by scissor legs attached via a screw mechanism to the drum, therefore opening when you pull the cable. Clearly in this case, the torpedo moves forward. If the scissor legs were attached to a large flat plane and the wall replaced by extremely viscous liquid (thick very cold thick syrup), then you would still expect the torpedo to move forward. As the syrup got thinner, at some point, it would no longer move forward. Your explaination with the lever for mechanical advantage really shows that process - it is just not obvious how one gets mechanical advantage from a propeller without going into the fluid dynamics.
In terms of leverage, I think this analogy also works in a case I have seen somewhere on the internet: there was a fixed axle going through a wheel (The wheel having the bigger diameter) but only the axle was contacting the ground either side of the wheel. The wheel was then spooled with rope/string and once you pulled backwards on the string, the axle would move the contraption forward. (I tested this home with a few toilet paper rolls myself and it works! Fancy that.)
I think a line thrown in at the end really helped - the idea of the mass being thrown out (the mortar and pestle) being infinite. That helped me understand.
These counterintuitive demonstrations are always fascinating, if only by the care required to build the demonstrators - though I find a difference almost in essence between the "solid" versions (e.g. cable propelled with a solid ground anchored point to impulse some force) vs. the "fluid" air/water "free" moving versions, where as you mentionned fluid dynamics and drag is more tricky to grasp and optimize (e.g. competition sailboats going faster at an angle with the wind while exerting pression to the water)
It turns out the launch site at Cliffe Fort is a 40 minute walk from the nearest road. And we chose the windiest day of the year to make the journey. It's a miracle that we got any usable audio at all!
Th sponsor is Odoo: try it out today: www.odoo.com/r/Si6
you wrote "Th" rather then "the" :)
There is no audio in basing sei
@@TheGahta Fire nation isn't at war with anyone.
great video
@@DeconvertedMan they sponsored thorium and were very confused when they ended up on this channel.
Talking about selling designs to a torpedo while stroking a cat? Steve has entered his bond villain era
No context, no mention of it, just kitty scritch
When I thought that, I thought "Dave McKeegan, but with a cat" 😊
Came to say the same thing! 😂
@@mikethewhizz5085
Where are you going after you die?
What happens next? Have you ever thought about that?
Repent today and give your life to Jesus Christ to obtain eternal salvation. Tomorrow may be too late my brethen😢.
Hebrews 9:27 says "And as it is appointed unto man once to die, but after that the judgement
I said he's the best teacher I've ever seen. And I just read your quote. And you're the funniest dude I've ever heard. That was brilliant.!😂😂
that's the most steampunk thing - mechanical torpedoes powered by steam engines located in a brick building, launched by rails
I Like Watermelons Too 🍉😋
@@goldenegg1063huh?
Step back to 1877 when Louis Brennan invented this. From Wiki: The Brennan torpedo was a torpedo patented by Irish-born Australian inventor Louis Brennan in 1877. It was propelled by two contra-rotating propellers that were spun by rapidly pulling out wires from drums wound inside the torpedo. Differential speed on the wires connected to the shore station allowed the torpedo to be guided to its target, up to 2,000 yards (1,800 m) away. Amazing.
Industrial revolution was basically steampunk
I wonder why they did not use a steam pressure vessel inside the torpedo as an energy source.
Maybe the aspect that it was remote controlled was more important than just propelling it forward 🤔
Steve had to build FULL 3D version because he could not figure out how to simplify it into a 2D cross sectional model. I also love the fact that we saw over a dozen prop prototypes too. Thanks, Steve.
Oh no he did simplify it, that's what the lever and mass model was. Steve can make anything 2D
He probably had to do a portion in 3D anyway to design the propeller
Thanks, Intel.
@@DhruvGN8 You are right! I stand corrected. I actually meant it as a bit of a joke how he always simplifies to a 2D model, but I didn't think of the mass model. So I have to laugh at myself for not seeing it. Thanks.
@@DhruvGN8 there's more simple and better model - a spool on shaft on rails, you pull the thread backwards - spool unrolls forwards
Well done, master! That's a strange mechanical voodoo shown very easily!
It's missing high voltage capacitors!
I love you
This is so cool. Can you make one that lights on fire and explodes?
There is a much easier way to experience it. Consider a typical wire spool with plates at its ends. You put it on the table with the wire coming out at the bottom and pull back on the wire. If plates at the end have the diameter of the spool, it will stand still unless you overcome friction.
If the plates are larger (as you see on typical spools) the spool will start rolling towards you, while upping the wire (that's the "mechanical disadvantage" situation).
If the plates are smaller (e.g. they are just an axle) an running on rails, the spool will roll away from you. That's the "mechanical advantage" situation)
Something that you guys missed it that there were two contra rotating propellers. It was also spun up to speed out of the water as it slid down the ramp, meaning much less force would need to be applied to keep the torpedo up to speed
They kind of did when Steve was talking about the force to get the spool to spin is greater the force needed to keep it spinning.
Excellent point.
The primary reason Steve invited Derek to do this video was to prevent Derek from making his own video on this subject.
And also to school Derek in front of us all.
I think Derek has a very superficial understanding of most of the concepts he tries to explain. Even with multiple researchers and writers, he can not compete.
@@amosbackstrom5366 100%
@@amosbackstrom5366 Ok, so it's not just me. :)
300 IQ move
@@amosbackstrom5366 I feel like it's the difference between a generalist that sometimes goes into a deep dive versus a specialist that occasionally explores outside their realm of expertise.
Derek tends to cover large amounts of ground (be it subject matter, historical time, or just multiple related concepts) in his videos so there's often not a lot of space to go into deep explainers. At least not without making even longer videos. Derek also seems more interested in the relationship between pieces of knowledge - his recent video talking about how the Principle of Least Action is a different form of Newton's F=MA is a good example. And, he tends to be a bit more of a storyteller - his more recent videos are often about HOW something was discovered and not so much the theoretical implications or the practical followups.
Steve focuses on one thing for his videos and if something like Bernoulli's Principle comes up, he'll explain what it means and how it's used and why it's relevant but he's not likely to explain the story about it and start talking about Bernoulli. His videos aren't structured as stories about the origins of a principle or mechanic he's talking about. Rather, his stories are the story of his specific experience with the specific experiment he's working on. Slice of life, scientifically speaking.
I don't think there's anything wrong with each approach. It just depends on which kind of knowledge you need at the time. Ultimately, both are important.
Steven's ability to find a fundamental model to explain complex counterintuitive problems is unparalleled. Building the models is the cherry on top.
Yes,very underrated. He is epically good at it
I thought he was going to go with what I think is a neater example - a spool that's placed on a flat plank that's the width of the spool's centre cylinder, so it can roll back and forth along it, with one of the side discs of the spool made extra thick so that string can be spooled around *it* as opposed to around the centre piece. Pulling the string would make the spool roll away from you along the plank.
The mechanical advantage comes from the then obvious fact that the string is spooled around a larger radius than the part of the spool that is in contact with the plank.
Your non-propeller mechanical advantage explanation was a great way to break it down. I’m a turbomachinery aerodynamicist, and my initial thought was that this would work with a sufficiently large drum. While the fluid dynamics of a propeller are complicated, the macroscopic performance parameters are fairly simple: the propeller will create a thrust T at an RPM n, and will require a shaft torque of Q = r*f, where r is the radius of the drum and f is the force of the wire on the drum, which equals the force of the wire on the torpedo. It is then just a matter of choosing r such that f < T, as you mentioned. Not surprising to hear that it took so many propeller iterations to get this to work, the system as a whole would need to be pretty well matched to get it to work. Very cool showcase of a really unique application
So magic and wizardry are at play to make it work.
"turbomachinery aerodynamicist" is quite a job title
"so what do you do for a living?"
"me? oh I work on the aerodynamics of turbomachinery, ya know, normal stuff."
It is worth noting that it is fortunate that M. Mould was looking at the revised RE design in the museum. The original actual Brennan design had transverse drums and a whole load of gears. The advantage of it being immediately apparent from the existence of wheel ratios that there was mechanical advantage involved is outweighed by the fussiness of the original transmission.
@@JdeBP I wonder if anyone contemplated constructing and using torpeoes based on the simpler design? I would think that torpedoes which used a pair of propellers and steered via differential thrust could be built so much more cheaply and quickly than one with an integrated power source that they'd be used in any situations where where targets would be within cable range.
@@chrisakaschulbus4903 given the number of propellers I ended up making, it felt like it was black magic. Though I think the problem was made a lot harder as the propeller is too close to the surface and there were lots of surface effects on the propeller which were adding drag.
It’s great that Steve helps up and coming TH-camrs get going….
Derek sitting there like, "this could've been a Zoom meeting. I do those all the time."
badabing badaboom
More like he gets a business write off for the flight and so travelled to the UK for free
He he was already in London for another reason which is the most likely reason
@jmi967 that's not how write offs work. You cant write of things for personal use, you can only write off the % that was for strictly buisness work.
@ There’s no rule that says that you can’t take a day off while on a business trip. The flight has to be for business, but 100% of your time does not.
Louis Brennan was an absolute genius,
He also invented a Gyro-Monorail in 1903, the prototype was built in Gillingham, Kent in 1909, then in 1910 he built a 1 Mile circuit at the Japan-British Exhibition at White City, London where Winston Churchill reportedly drove it for 1 circuit,
In 1916 he patented a Helicopter design and it had it's first tethered flight was in 1921,
If you go to 'Sappers Walk, Gillingham, Kent, UK' on Google maps you can see some bronze plaques commemorating his work,
The last remaining Torpedo is at the Royal Engineers Museum in Gillingham (well worth a visit!) the archive for his personal papers is at Gillingham Library
I think a simpler explanation would come from the bicycle paradox (which you also did a video on IIRC). Attaching a rope to the pedal and pulling backwards causes the bike to roll forwards - which again is due to mechanical advantage.
I kept thinking that there were similarities between this and another video. The thought experiment was so similar, but I couldn't recall the actual experiment. Thank you
Not sure if were talking about the same thing, but I was thinking the spool experiment, where pulling the cord made the spool roll away from the pull. But yes, it is all about mechanical advantage. Not about forces pulling in different directions.
@@anteshell That's not what I had in mind but is a GREAT example, about as simple as it gets!
Exactly.
Yeah, I'm surprised that and/or the spool experiment weren't mentioned.
Pretty classic physics demonstration. The bobbin pull. A string wound to the smaller diameter section is pulled in the same direction of the wind, and the larger diameter resting on a surface is pulled in the same direction as the pulling force faster than the rate of pull.
I was thinking this the whole video, waiting for him to show it! I suppose some demonstrations will always be forgotten, but to me it seems the most tangible way to show that pulling something backwards can make it move forwards (as you're pulling the cable backwards and not the thing!)
Same with a yo-yo.
My mind went to a yoyo or a spool. You can make it go forward or backwards or no where depending on what angle you pull the string on. Generally if the spool is below the string it pullw forward.
Has to do with torque.
Is that what you mean when you say bobbin? The thing with my spool or yoyo explanation is obviously this uses a propeller.
I bet a bigger spool helps.
Yeah was not impressed. If you attach the power source, say a drill with a spool to the actual body of the device and get the drill to pull it. You just created a cable driven motor. I think the illusion of wonder comes from not being able to understand you're not putting on the device. You're putting on the engine of the device. You're the power source. There's no reason it wouldn't go forward.
We use the same thing for spinning tops, yoyos and a whole other manor of toys. Steve's mind just gets lost in the wonder and can't figure it out a lot of the time. He needs it be more than it is. Which is a lot of the reason I don't respect him.
@@dianapennepacker6854 a bobbin is a type of spool, as used for sewing.
Great to see this collaboration (I'm slightly jealous). I had half expected the drums in the torpedo to be heavy and spun like flywheels and then the torpedo to shoot off unattached to the cables. That would obviate the pulleys and lower friction, but the torpedo would be heavier.
Hey! I know you. I didn't expect to find Lindy Beige on Steve Mould's comment section. What a joy! 😁
Flywheels would have to go very fast and we all know the gyro effect would be making it impossible to steer it
1:21 "Cliffe has the dubious distinction of being the only known Brennan Torpedo Station to sink a ship, albeit in error: in August 1901 a Ketch, WS Flower, was struck by a torpedo on trials. The torpedo, containing a full charge but no detonator, made a large hole below the ship's waterline and it sank quickly. Fortunately, no one was injured and the vessel was recovered (R E Museum)." From the Historic England report on Cliffe station.
Finally, the Beyblade Torpedo
Let er rip
This was my first thought. Unintuitive? fella clearly never let er' rip.
Let it rip!
gyroscope, toy top, beyblade...? this seemed pretty intuitive to me. my only hangup was how to run the wire *through* the axle
There was in Finland in 70's under ice torpedoes that worked by pulling from a line. They had claws and levers, often two lines, one for propulsion and one for release. Now they make still those torpedoes, but they have rechargeable batteries and motor. It's even quite simple to guide the torpedo following an electric cable pair from one hole in ice to another. Some have also a strong light to show where to drill the other hole. The two hole system doesn't need the torpedo to stay underwater or pull the net, it's e enough to pull only a line. The original version worked, but it's pretty slow and cumbersome, if one has 25m net, and the torpedo moves 5 to 10 cm each 50 cm pull and gets stuck on uneven ice surface.
What were the torpedoes used to do? Why did they have claws? This is intriguing.
@@olliefoxx7165 pulling fishing net guide rope under ice. The old torpedos pulled themselves forward with claws gripping underside of ice on a lake/sea. I saw a version that had lever that you just tugged to make the device to kick few cm/inch forward. With lots of tuggin you got enough distance. Other version had spiked wheels and small spool and you just pull lots of rope (or yarn) to make it drive under ice just like this torpedo or that bicycle paradox.
These devices are used to lay out nets under the ice for fishing. Still used today. But a very different kind of "torpedo"
While I was already convinced by the blackbird videos, I think this video will help a lot of people grasp it better. In addition to being a terrific video in it's own right
*its
@@Gehr96 ^ billy no mates
@@von1477 While I agree the comment was likely unneeded. you're way worse for personally attacking someone.
@@hogandromgool2062 Remember: There's a big difference in submitting a response from a smartphone and from a computer.
You've got to account for difficulty in handling predictive spelling. And you can't do this: t̶o̶ (strike through) or this §
@hogandromgool2062 ^ billy no mates
Love it.
I visited the Brennan torpedo tracks (at Cliffe Fort) with my son a couple of years ago.
How the torpedo actually works is a conversation we keep coming back to. It is an absolute work of genius.
There is a Brennan torpedo on display at the Royal Engineers Museum in Brompton (not far from Chatham Dockyard).
My son is keen on physics and has been a longtime fan of Veritasium. So this video has serendipitous qualities for us both.
Another connection is that my son is studying engineering at Medway Campus. This is where the Royal Engineers officers were trained and where Brennan himself may have given talks.
I think the torpedo would get its blade spinning from its weight tugging on the rope while it was going down the slide , and then they would release some kind of clutch on an working engine and would start pulling the rope once it reached the end of the slide , it would give a extra boost and it would remove the initial enertia needed to get the blade spinning
It's like that trick with the rolling spool; it just gets more confusing to think about because instead of just friction you're dealing with hydrodynamics.
I was thinking the same thing
Me too
yep, this didn't feel all that unintuitive after having seen the spool thing before. I just took one look at it and was like, nah that's probably doable with gear ratios, which is essentially what was explained with the levers.
Yeah, that'd be the go-to. Maybe missed it on purpose to make us feel smart / clickbait.
Sometimes you are too smart to figure out how to simplify things
15:20 this whole conversation reminds me of the techniques my college Computer Graphics professor had for visualizing things: "make it big. be there."
When you imagine something, imagine it so huge you are a part of it. and look around it at all the parts.
That's exactly what Derick was doing. He was making the system huge, and putting himself in it, holding part of it. Really cool.
I’ve never heard this technique. Sounds cool.
"The Way Things Work" is the best illustrated example of this concept. Turns various tools, devices, and instruments into fantastical structures powered by harnessing small mammoths.
Identification of the root “problem” and then visualization of how that problem works at its fundamental level is so critical to rendering and general problem solving. Should be required education instead of the combinatorics class every CS major takes
@@Rapt0rham what a lovely book! I adored my copy as a kid.
It's easy to forget that propellers are functionally a lot like "gearboxes" and "wheels" all-in-one for wheeled vehicles, and various boats/planes have varying propeller designs to change and optimize the ratios of rotating input torque to linear output force at different speeds. It's entirely impractical to couple a combustion motor directly to the wheels in a car, but for boats and planes this is almost always exactly what we do because of the flexibility offered by varying the propeller design.
occasionally with reduction gears, usually at a fixed ratio, though a lot of modern diesels are just designed to operate at the right power ratio not to need it
@@pizzaivlife i would think the prop is designed to the engine since the engine would also have an optimum rpm for efficinecy.
15:45 "Beyond the scope of this [blank]". Every PhD student' favourite phrase.
Wow, this reminds me of a cool childhood memory! You know how when we pull a string tied to a spool on the ground, the spool rolls forward? It's such a simple yet fascinating physics principle! Turns out, the Brennan Torpedo worked on a similar idea! The torpedo used wires to create tension, propelling it forward in water and controlling its direction. It's crazy how a playful childhood trick connects to historical military tech. Physics is awesome!
Can't get Derek'd if you include him on the idea & video hahaha. Genius
What does Derek'd mean?
@@m4rcyonstation93It's a phenomenon where someone spends a long while putting together a science video, only to have Derek put out a better video on the topic right before their video drops.
That dang veritassium and his video quality!
@MSheepdog oh lmao that's funny. Do u have examples of this
@@m4rcyonstation93 Matt Parker talks about him and Steve Mould getting Derek'd in this video about him getting reverse-Derek'd. th-cam.com/video/gusXBTyg1O4/w-d-xo.htmlsi=MJAg16dFJWdRzIpF
@@MSheepdog it has nothing to do with your opinion of the quality of the videos, the issue is entirely unrelated to your opinions and instead related to upload dates and behind the scenes communications.
It's not some horrible crime he's been caught doing, I don't get why it's so hard for people to accept criticism that is not even addressed to them but instead addressed to someone who is literally a stranger that they've just seen on a screen before.
The lever analogy (and especially the 'what if the mass was fixed' bit) are really clever. It makes it clear that mechanical advantage *could* make this work, therefore a version with a propeller is plausible. It honestly actually improves on the understanding of Veritasium's video too.
Always found Derek’s video a bit frustrating, I haven’t watched it in a while but I remember is explanation not really helping me to understand the idea. The lever analogy is great
As an electrician this torpedo made perfect sense to me in the first few seconds of the video. I didn’t even have to watch how it worked. Its the counterintuitive action of unrolling cable by rolling the drum along the ground. If you pull on the cable, the drum will stop and then come back to you. It’s two separate torque arms.
Hey Steve, Off road enthusiats know about this well. While using a winch to affect a self recovery, you can use pullies to have the cable/rope go under the vehicle and atttach to the back of the vehilce via pullies in the back. When using this you can change the direction you want to go merely by changin the pully setup.
love the videos keep them coming.
TH-cam stopped recommending your videos to me 6 months ago. I was a loyal watcher up until that point. They just recommended this video to me and I was like STEVE MOULD!! So glad to be watching your videos again
That is why subscription exists 😅
2:56 HIS CAT IS SOOOO CUTEEEEEEE ❤❤❤❤
Imagine watching this video.. and the comment you make is a teenage scream in all caps about a cat. Your life must be sadness.
@@Hermanos22 Imagine reading that comment... and the comment you make is an insult. Your life must be... well, I don't know you, and I'm not arrogant enough to make a statement about your life.
@@Hermanos22 Your response to someone excited to be introduced to Steve Mould's cat is far worse. The fact that you needed to comment on it is pathetic. Maybe some day you'll get a human interaction firmware update. Until then you should consider keeping your thoughts to yourself.
Shout out to Steve Mould's cat. I hope to see it featured in more of his future videos.
@@Hermanos22You've been on youtube for 18 years and the best you can manage is "teenage scream"??
It really is!! 😸😸
Since I learned the trick with pulling the spool to make it go forward or backward 30+ years ago I'm willing to absolutely believe this worked :D
Yes, I prefer the spool analog.
My thought exactly.
9:47 I'm one of those people who knows what they're torquing about
Well, I know it too, but i honestly didn't even think about the torque because I imagined the drawing just as an abstract schematic, so I didn't think about the exact positioning of it's components
It's not that hard, you learn this in middleschool
@@RaVen99991 I learned how to make bad puns before middle school.
As usual Steve puts a lot of work and effort to explain real life things. Having Derek side by side was like watching two David Suzukis in one episode! They should have a science TV show!
I love the conversation style of this video. Feeding off one another is a tremendous learning method.
We could think of that lever being an oar, or rather a pair of oars to move the torpedo forward.
And then the propeller is really a "continous oar"
To compare this to the downwind-faster-than-the-wind craft, the cable takes the role of the road and the water takes the role of the air.
This has nothing to do with that. It is the equivalent of the direct upwind cart.
@@electrodacusNo, it does. The cable/road is moving backwards at a certain speed relative to the water/air, and the power of that relative motion is used to propel the craft forwards through the water/air even though there is no net force in that direction except between the propeller and the water/air. It's the exact same setup.
(edit: and of course now I unpause and see Steve mention the treadmill example in Derek's video. Glad to see he made the comparison clear.)
@@charltonrodda Steve video explanation is incorrect and so is Derek's explanation of direct downwind faster than wind. My last video debunked Derek's claims and proved clearly how those type of vehicle work.
In this torpedo example input is the cable/string and it is the equivalent of air/wind in the case of wind powered carts. The water is the road equivalent. You can not just chose what the input is.
Energy at the output (propeller) will always be lower than energy provided at input cable/string. You can not make the claim that propeller in Steve torpedo example is the input as it is very clearly the output. So no matter what reference frame you want to use the output will remain the propeller.
@@electrodacus But you *can* choose what the input is. That's one of the fundamental principles in physics, you can choose whatever inertial reference frame you want and the system will still behave the same. From the wind vehicle's frame of reference, a moving treadmill with still air is identical to a stationary surface with moving air. The only difference with the torpedo is that you have to attach the rope to the front, and change the spool's winding direction. You can't push on a rope, after all.
@@areadenial2343 No you can not chose the input. Yes you can change the frame of reference to whatever you like but the result will be the same in all reference frames if you did not made any mistakes.
Unless you change the gear ratio (this includes the propeller pitch) the input will always be at the string for this torpedo and the output will be at the propeller.
You can build a torpedo where propeller is the input but that requires a differently build torpedo same as the direct upwind and direct downwind carts are not the same device they are constructed differently.
So the torpedo shown in this video is designed with input at the string and output at propeller. You can look at the experiment from any reference frame that you prefer or fine more intuitive but the result will always be the same.
Those early torpedo designs were incredibly fascinating. But then I'm still fascinated by the much later ones of WWII and all their mechanical systems as well.
If your are interested, there's a video showing how this torpedo works.
th-cam.com/video/sQJCOnyUvfU/w-d-xo.html
They've also done videos on ww2 torpedoes as well.
It's amazing to see your creativity and how clear it can become 🎉 lovely to see Derek on your channel as well 💪👏 You are doing such a great job at explaining ☺️
You're absolutely right, it's a lot like the one Veritasium and Xyla Foxlin tried out.
I'm 58 and in my mid 20's I reinvented the principle and made a toy yacht that went straight up wind. Very big low pitch under water prop and very high pitched wind mill direct coupled above deck. Worked first time!
I then researched prior art and found someone had made a wind powered bicycle that went down wind faster than the wind. Nice to know there were humans playing with this stuff long ago! In my 20's one of the other ideas I had was effectively a corrolis force earth motor using earth's spin to generate power with reference to latitude line gyroscopes.
It clicked at 2:36 for me. In my head it's nothing more than a pulley system. But the viscosity of the water allows it to work.
I think the lever explanation still gives a much more mathematically complete understanding of what's happening, and you might not have completely realised how important that extra analysis is. The fact that "It's just a pulley system" doesn't automatically tell you that it'll be pulled in the direction you're hoping for, as evidenced by the three examples of mechanical advantage and disadvantage at 11:35-12:05, (as well as, to a lesser extent, the more extreme version of the first example where he holds down the counter-weight completely). Without simplifying the details of the system, you wouldn't be able to figure out the fundamentals of how your pulley-powered propeller can receive enough energy to counteract the acceleration in the wrong direction that your pulley system receives from you pulling the rope.
@@TheHadMatters It's not so different from a pulley system installed in a cart that moves forward as you pull on the rope. One pulley takes the rope into the cart and then it goes around a flywheel on the axle. With the right gearing you can gain a torque advantage at the sacrifice of needing to use higher speed pulling the rope. For me when I see it work I can intuit how it is working. His explanation helps people too.
I'm sure someone will mention this, but we STILL have wire-guided projectiles. The GM-71 TOW (Tube-launched, Optically tracked, Wire-guided) is an anti-tank missile and the U.S. Mark 48 Advanced Capability (ADCAP) torpedo are both "current" technologies. Of course they just use the wires, as you mention at the end of your video, for steering. It seems crazy that they still use them. Hopefully no fishies get tangled up in these filaments...
Signal transmission wires are effectively immune to most forms of counter measures that don't physically sever them.
13:21 That is a revised design done in Chatham, based upon Brennan's, in the RE museum. The original actual Brennan design had transverse drums and a whole load of gears. There are detailed plans of both in old history books. This is second system effect in action, and there is probably scope for some enterprising TH-camr to replicate the original design and field test it, to show why they had to redesign it.
For such people: Read chapter 5 of Charles William Sleeman's 1889 edition (since some of this dates from the middle 1880s) of _Torpedoes And Torpedo Warfare_ if you want to see detailed diagrams of two "Brennan"s and the 2-wire flavour of the "Maxim".
Thank you very much. It seems the Royal Navy at the time would have worked through and documented the Newtonians of the system in their designs, no? Can you shed you shed light on that?
I remember, when I was a kid, my mother handed me a spool of thread and showed me that by changing the angle (and nothing else) of thread as I pulled it that it could be made to roll away, stay still, or even come back towards me.
I love these kind of creations because they showcase incredibly simple mechanisms that do absurdly counterintuitive things.
Well done and marvelously explained.
@stevemould I saw you at the RI for the Night of Unnecessary Detail. We really enjoyed your presentation on this torpedo during the live event and the other presenters as well. The map showing the 1.5 day trip to this launch location was such a fun addition to that presentation.
If you get the spindle moving fast enough, and it’s heavy enough, you also get the added benefit of a slight gyroscopic stabilizing effect…
That's true however unnecessary as in real life they could steer the torpedo from land (this things were so cool)
Another simple example is taking a spool of thread or a wide spool of fishing line, then pulling on the line with it coming from the bottom makes it want to roll away.
Different idea.
@vbbsmyt produced beautiful animations of the brennan torpedo several years ago. His channel is dedicated to victorian military tech and worth a view.
I love their videos. Such exquisite animations.
Here's the video they did on this torpedo.
th-cam.com/video/sQJCOnyUvfU/w-d-xo.html
Perhaps xe should do one for the original Brennan design as well. (That video shows the Chatham RE redesign.) It is somewhat fussier.
I love the lever explanation, that's so clever! As soon as you mentioned it, it clicked in my head and made intuitive sense
I never heard of this torpedo before but as soon as you showed the 1st illustration, I understood how it worked. Nothing impossible about it. Range would be a liming factor but we use wire guidance today, so face those same limitations. The mechanics are straight forward. Speed would be another factor & is probably a bigger factor into why it was not explored further, given that the trigger mechanism of the time required the torpedo to slam hard into its target requiring high speed.
It took a minute of explanation to realize that when you pull the string backwards you're not pulling the torpedo backwards, you are turning the spool. There is some parasitic resistance in the system that will cause a fractional tug backwards on the structure, but most of the force is going into rotating the spool. Seems fairly intuitively obvious?
He explains the "issue" at 2:30ish. The force you are apply backwards is the source of the energy to move forward. It can't exceed the amount.
Remember the inertial loading of the spool/propeller system will be transferred to the pulley brackets which will result in rearward motion.
Only if the cable was being pulled perpendicularly to the direction of motion would this be avoided.
rctestflight channel's recent experiments with propeller efficiency might give you some ideas for a more efficient propeller.
I thought of that too. A lot depends on the power and rotation speed I think though.
16:02 to this day, Torpedoes still have cables trailing out the back to send commands. Not those dropped from aircraft though.
?? He doesn't even say that.
He just says the successor to the Brandon torpedo still had a cable to direct itself for where it was launched. That is not a statement about modern torpedoes.
@@abcoi123That’s why there’s a comment. To say a thing the video didn’t say.
@DanKaschel and...
Well...
The comments I responded to acts like it is quoting the video, then correcting it. The video made no such claim.
@@abcoi123 no, i don't see any indication of of being a quote. where did you get that from?
@@abcoi123 I think you just misunderstood the comment. It happens.
I'm glad I'm not the only one having sleepless night thinking about these videos. Steve must of been thinking about Derek's video for a long time. 😊
I never could wrap my head around Veritasium's video. Thank you Steve!!
You could not understand because Veritasium explanation was wrong. Steve's explanations is also wrong tho this is a different problem as it is the equivalent of direct upwind propeller cart not the direct downwind one. I made a video correctly explaining the direct downwind version and when I get the time I will do the same for the direct upwind version (the equivalent of this torpedo).
it might be beyond the scope of this video, but you have to do a follow up explaining how it was steered
I'm guessing by the gyroscopic effect of the spools
I agree. The obvious solution would be to have separate left and right spools/propellers, but maybe the designers found some even better idea?
There were two cables being pulled by steam engines on shore. They each drove one of two counter rotating propellers for propulsion. They also used differential speed between the two cables to enact, through a series of mechanisms within the torpedo, a steering force on the rudder. Speed up one cable and the torpedo turned left. Speed up the other and it turned right. Equal speed and it went straight. There's a very good TH-cam video that details the whole thing. . . . th-cam.com/video/sQJCOnyUvfU/w-d-xo.htmlsi=l7FKEd2srrL945nx
th-cam.com/video/sQJCOnyUvfU/w-d-xo.htmlsi=p8BrKPyl2O26iK0a
@@40-forty-plus There was one engine and one winding drum the two wires were attached to. The wires went through an S shaped path, the length of which was varied by moving pulleys, shortening one path and lengthening the other. This activated the steering mechanism in the torpedo which is presumed to be a differential that, in turn, operated the rudder.
14:40 Steve = 😍
I'm straight as Indian hair, but I look at Derek like that every time he posts a video.
A much better idea is to throw a line to the enemy ship, and get them to winch the torpedo towards themselves.
I had my issues understanding Veritasiums video back then. But you did so great with those levers and masses. Thanks a lot!
Great explanation. The same is true for the propeller with the wind coming from behind. Since the blades move at an angle against the wind (mechanical advantage) the cart can move faster than the wind.
Designing a unique style of torpedo and offering it online while petting a cat.....you are now a bond villian lol
Before watching, this already makes sense. It's just like pulling a yoyo towards yourself to make it roll away. If you get the tension just right, I bet it can roll 50 times the string's length on a smooth surface.
A paddle boat version of this would also work well, though not as cool as a torpedo.
I felt like Terence Tao watching these two being confused by this "paradoxon"
But then i realized, that maybe they did not study physics, while i do.
I was very confused on how they are confused by mechanical advantage, just because of the extra step of a propeller.
For some reason this just makes perfect sense to me, if no one had called it impossible or a paradox I wouldn't have even doubted it. I don't know if my thinking is actually correct but I think about it in a much simpler way. When you pull on the cable you're producing a backwards force but pulling on the cable turns the propeller which generates a forward force, as long as the latter is greater than the former then the torpedo goes forwards. And with gearing, or mechanical advantage, then you can always reduce the force required (the rearwards force) in exchange for having to pull the cable a greater distance (or at a faster rate than the forwards movement of the torpedo). Just think if you decreased the mechanical advantage so much that the mechanism was effectively stuck solid (like how if you try starting from a stop with a bicycle in its highest gear, there's a lot of resistance at the pedals), you're not going to generate any thrust at the propeller and just pull the torpedo backwards as if the cable was tied to the rear. And taking things to the opposite extreme you could increase the mechanical advantage such that there would be very little resistance to pulling the cable, you'd just need to use a top fuel dragster to pull it fast enough to spin the propeller.
i dont see any backward force (besides some friction), all you do is making the propeller spin by pulling it with a rope
@@HORNOMINATOR There's a backwards force because by pulling the cable you're doing work (spinning the propeller), there needs to be an opposite reaction (resistance) to that. If instead you were just unravelling the cable from a frictionless and weightless drum then yes there wouldn't really be any backwards force. If you've ever used a Beyblade or similar spinning top then you'll know that with the hand that holds the launcher you need to provide a force opposite to the hand pulling the ripcord, spinning up the weight of the top produces a resistance in the mechanism. Likewise using the launcher without a top attached produces less resistance.
@@HORNOMINATOR The force is generated via the pulleys that are anchored in the torpedo.
one of the main things i've learned from you is that discretizing things helps to understand them. here you replaced the propeller with a lever and a single mass; in the ball-under-the-table video, you made it easier to understand the golf ball paradox by turning the cylinder into a shape with a small finite number of sides.
Very elegant design and very elegant explanation, the level analogy really works well.
The lever arm is the radius of the drum.
I love the cat at 2:49
There's a cool lizard 3D print that works on same principle. Pull the string down and the lizard climbs the string up
Wasn't there a manufactured toy like that? I have the vaguest memory of it, it's rather madenning. I think the body was made of metal, the grips out of latex rubber, so it was made a long time ago.
I remember having a toy car when I was a child that worked the same way: You pulled a string out the back and the car drove forward. My 10 year old brain couldn't wrap my head around it and I took the car apart, and discovered the exact same thing: Between the spool and the gearing connecting the spool to the axle there was some mechanical advantage. It was one of the early moments in my life that tickled the engineering side of my brain, because I didn't understand the physics at that age, but once I saw the parts my brain intuitively understood the concept. The part that made the most sense for me was that the length of string that came out the back was _more_ than the distance that the wheel turned; I had to pull the string faster than the car moved forward, and so in my head the car was "taking" some of the "pull" I was applying.
The acknowledgement at the end, if the possibility of getting Dereked every now and then is so awesome. I love the relationship among science communicators
11:14 Theorhetorical Torque :3
I"m at 2:15 now and just recording my thoughts: the spool inside the torpedo is rotating, so some, maybe even most, of the force applied by the cable being pulled is used for that spool rotation. So, yes, it seems plausible that the torpedo could go forward. And I would think that especially once the spool is rotating at a stable speed, the rotational momentum of the spool makes it easy to be kept rotating.
These prediction comments are best made to good company watching alongside you
I believe he missed a critical part of the design, that being one or more flywheels. A flywheel could have been spun up before launch much like how Gyroscopes are used to stabilize and balance rockets. It could have been used to help with the steering as well as provide some force to the spool to offset the resistance of the cable in propelling the torpedo.
At least one early torpedo design used energy stored in spinning flywheels for propulsion.
The problem is you need really high rpms or a very heavy flywheel. Heavier flywheels means more mass, which is harder to make neutrally buoyant. And there is a lot of friction in water. It's hard to store that much energy in a flywheel.
@@RCAvhstape @benphartine
Yes. It was the Howell Torpedo (1896) It worked like a toy flywheel car. On the ship, a steam turbine would spin a flywheel up to high speed. then when launched, the inertia would spin the props, propelling it through the water. Here's an animation showing how it works.
th-cam.com/video/xTRBbFX7AxA/w-d-xo.html
M. Mould did not miss it. It is not there in the first place. There are no flywheels in either design of these torpedoes.
Love to see Derek and Steve in one video. Legends who make us happy.
Great video. There is also an analogy to one of Derek's videos where you pull backwards on a bike's pedal and ask which way the bike will go.
Turns out it theoretically depends on the gear but no bike ever has a gear small enough to make the bike move forward.
I remember one commenter modified their bike to make it move forward when the pedal is pulled backwards.
Of course everything starts with British military
Except that Brennan was Australian. (-:
I think it makes more sense to think of it in power (watts) instead of force (newtons). Knowing that the cable got pulled 4x the distance as the torpedo moved it should be obvious that the extra power was going somewhere (into the water to move the torpedo)
The power does not explain why it goes forward, and not backwards. Power does not have a direction.
@@renedekker9806 This problem in Steve video is the equivalent of direct upwind vehicle and I did not made a video about that (maybe will do when I get some free time). But I made a video about the direct down wind version and properly explained how it works looking at power and energy. Spoiler it is not working the way Derek thinks as his explanation was incorrect (he even made up equations :))
@@electrodacus I would love to see that. But you cannot base the explanation on power and energy alone, because they don't have a direction. At some point you will have to discuss the forces and their direction.
@@renedekker9806 There is an input and an output power so yes you can know direction based on the relation between the two but I included forces also in the explanation. Is just a 10 minute video.
Interesting concept ... imagine having a drone like this, but with a looped string (on one side the line goes in and on another side it goes out) might make it possible to make it fly indefinitely. But I guess the only advantage over an electric cable would be the reduced thickness of the string/wire.
That won't work. The energy to drive this is coming from pulling the cable out. So the cable needs to be connected to something else which provides the energy. If you just connect it to itself, there's no energy source, and it won't go anywhere.
Basically, everything inside the torpedo is just an elaborate mechanism to turn the pull force of the cable, into a push force on the torpedo. If the cable isn't pulled from outside, there's no push on the torpedo.
You're describing perpetual motion. Which, is not a thing.
@@THE-X-Force nope I don't ... the motor is just not inside the drone but at the other end of the looped string.
to explain it better: if you would not have a looped string, the drone will stop to fly once all of the string was used and you reach the end.(thats why a looped string with that goes in and out)
@@solandri69 you misunderstood me ... read my other comments ... I never said that it would fly indefinitely without energy beeing used.
Sweet Guest :D Veritasium feat. towards the 2nd half :o Awesome!
This is a video that makes you feel smart when you see it. Absolutely brilliant and enjoyable.
I must admit, I don't find this hard to comprehend.
It's just a matter of the propeller exerting more force when rotating than the force pulling the wire backwards.
There is only one logical result of this: the torpedo should move forward.
god damn, Derek really rubs me the wrong way. DO NOT like that guy.
Great video regardless!
Same, no idea why though. He mostly seems great
I thought I'm the only one
It's hard to imagine what you dislike so much about Derek. In my experience, he's a great guy.
@@Rick_Cavallaro I love veritasium, but best I can guess he comes off smug to these guys? Or he uses personal anecdotes too much?
@@lukasg4807 When he won $10K from the UCLA physics professor the first thing he did was to have a little contest for people to make 1 minute videos, and gave the money away.
Yes!! Finally you two came together to make a video!!
I love that the actual Brennan torpedo includes two spools. Each rotating the opposite direction of the other.
I kept asking myself why not introduce two wires/spools and use the other to work as a gyroscope. Countacting the turning of the propeller and first spool.
However I see the original inventor thought further than that. Using said mechanism for steering. Brilliant!
Brilliant video! you've managed to make the counterintuitive quite intuitive 👍 Thank you very much!
Mark Rober is for kids and teens. These two are for adults. I love this collab. Please give us more! ❤
that analogy with holding onto the moving cable at 14:08 is EXCELLENT !
Can you explain in details. It was bit confusing to me
Great to see the amazing engineer Xyla Foxlin, who actually did the hard work of coming up with a working model of the wind vehicle.
how nice to see you both together - it just had to happen some day. It is moderately hard to beat formalism, but beating intuition is the true master discipline.
Great job weeding through the confusion as always!
I adore how fluid dynamics unites everyone in terms of how much of a headache it causes.
I never understood the Blackbird, and now I finally feel like I sort of get it!! Thank you so much, Steve!
V nice explaination. I had a similar thought along Derek's lines: replace the water with an immovable wall and the propeller by scissor legs attached via a screw mechanism to the drum, therefore opening when you pull the cable. Clearly in this case, the torpedo moves forward. If the scissor legs were attached to a large flat plane and the wall replaced by extremely viscous liquid (thick very cold thick syrup), then you would still expect the torpedo to move forward. As the syrup got thinner, at some point, it would no longer move forward. Your explaination with the lever for mechanical advantage really shows that process - it is just not obvious how one gets mechanical advantage from a propeller without going into the fluid dynamics.
In terms of leverage, I think this analogy also works in a case I have seen somewhere on the internet: there was a fixed axle going through a wheel (The wheel having the bigger diameter) but only the axle was contacting the ground either side of the wheel. The wheel was then spooled with rope/string and once you pulled backwards on the string, the axle would move the contraption forward. (I tested this home with a few toilet paper rolls myself and it works! Fancy that.)
I love this one a lot because the physics is so accessible when you’re just summing up forces like that.
The physical demonstration of the lever-cart really shows that Steve is one of the best physics/engineering communicators we've got
I think a line thrown in at the end really helped - the idea of the mass being thrown out (the mortar and pestle) being infinite. That helped me understand.
These counterintuitive demonstrations are always fascinating, if only by the care required to build the demonstrators - though I find a difference almost in essence between the "solid" versions (e.g. cable propelled with a solid ground anchored point to impulse some force) vs. the "fluid" air/water "free" moving versions, where as you mentionned fluid dynamics and drag is more tricky to grasp and optimize (e.g. competition sailboats going faster at an angle with the wind while exerting pression to the water)
Very interesting video, I really liked how you used the soda bottle as part of the build.