Support the GITP forums on Patreon
Help support GITP's forums (and ongoing server maintenance) via Patreon
Results 1 to 24 of 24
  1. - Top - End - #1
    Orc in the Playground
    Join Date
    Jan 2011

    Default Making A Vehicle That Moves Faster Than The Tailwind

    I really don't have much to say . I'll just let the video speaks for itself:

    Last edited by Nourjan; 2021-05-29 at 08:24 PM.
    Quote Originally Posted by Nourjan
    Only a truly egotistical narcissist would ever quote himself

  2. - Top - End - #2
    Troll in the Playground
     
    Lord Torath's Avatar

    Join Date
    Aug 2011
    Location
    Sharangar's Revenge
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by bettJones View Post
    The car is very cute and strange at the same time. But it's hard for me to imagine that this can be of practical use.
    My first thought is ocean shipping. Ships are already starting to use rotating vertical cylinders to generate 'lift' in the direction of their heading to decrease their fuel costs per mile (Norsepower Rotor Sail - I am not affiliated with Norsepower). I cold see this being used for something similar.

    I will say that "risking my life" seems a bit overblown. He was doing 15 mph max, not exactly life-threatening speeds.
    Last edited by Lord Torath; 2021-06-02 at 08:49 AM.
    Warhammer 40,000 Campaign Skirmish Game: Warpstrike
    My Spelljammer stuff (including an orbit tracker), 2E AD&D spreadsheet, and Vault of the Drow maps are available in my Dropbox. Feel free to use or not use it as you see fit!
    Thri-Kreen Ranger/Psionicist by me, based off of Rich's A Monster for Every Season

  3. - Top - End - #3
    Dwarf in the Playground
     
    Kobold

    Join Date
    Aug 2019

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Lord Torath View Post
    My first thought is ocean shipping. Ships are already starting to use rotating vertical cylinders to generate 'lift' in the direction of their heading to decrease their fuel costs per mile (Norsepower Rotor Sail - I am not affiliated with Norsepower). I cold see this being used for something similar.
    There are probably Engineering and efficiency issues here. The vehicle derives energy from diminishing the speed gradient between the ground (wheels) and the wind (rotor). For a ship you'd need a sail or a turbine in the water. Sails are a well understood technology (thus you assume good reason why they arent used). Turbines can be tricky because they increase drag. Notice how even on land they required perfect wind conditions to make it work. Probably really hard to get any advantage for a container ship with route and time restraints.

  4. - Top - End - #4
    Orc in the Playground
     
    GnomePirate

    Join Date
    Apr 2020
    Location
    United States
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Sailboats that compete in the America's Cup can go like 1.8 times the speed of the wind.

    "Sure, Philosophers can say 'But how do we know the sun will rise tomorrow?' to which the correct response is 'Shut up nerd! Stop playing 3D chess against your own brain and find something real to worry about'."

    -ContraPoints

  5. - Top - End - #5
    Ogre in the Playground
     
    ElfPirate

    Join Date
    Aug 2013

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Lord Torath View Post
    My first thought is ocean shipping. Ships are already starting to use rotating vertical cylinders to generate 'lift' in the direction of their heading to decrease their fuel costs per mile (Norsepower Rotor Sail - I am not affiliated with Norsepower). I cold see this being used for something similar.
    Quote Originally Posted by Rydiro View Post
    There are probably Engineering and efficiency issues here. The vehicle derives energy from diminishing the speed gradient between the ground (wheels) and the wind (rotor). For a ship you'd need a sail or a turbine in the water. Sails are a well understood technology (thus you assume good reason why they arent used). Turbines can be tricky because they increase drag. Notice how even on land they required perfect wind conditions to make it work. Probably really hard to get any advantage for a container ship with route and time restraints.
    One of our local cruiseliners had one of those as a test run at fullscale, and space planned for a second. Exactly from Norsepower I think (looks exactly like the illustration and it was from some Norwegian company). They recently removed it after a few years' testing as it just didn't provide enough whatever it provides to be worth the bother.

  6. - Top - End - #6
    Troll in the Playground
    Join Date
    Jun 2011

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Trafalgar View Post
    Sailboats that compete in the America's Cup can go like 1.8 times the speed of the wind.

    But not in the direction of the wind (not when accelerating, anyway), they get their speed boost when moving across the wind.

  7. - Top - End - #7
    Orc in the Playground
     
    OldWizardGuy

    Join Date
    Jul 2015

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Lord Torath View Post
    I will say that "risking my life" seems a bit overblown. He was doing 15 mph max, not exactly life-threatening speeds.
    My understanding is that the serious injury/death concerns had little to do with the vehicle's forward speed, but instead were centered on the rapidly spinning propeller and the dubious nature of whatever was preventing it from crashing down onto the car (or generally becoming a massive, fast moving projectile in an unpredictable fashion).

  8. - Top - End - #8
    Orc in the Playground
     
    GnomePirate

    Join Date
    Apr 2020
    Location
    United States
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Rakaydos View Post
    But not in the direction of the wind (not when accelerating, anyway), they get their speed boost when moving across the wind.
    These boats can go 1.2 windspeed INTO the wind. They have been clocked at over twice windspeed cutting across or going downwind. They are a gigantic vertical aerofoil on a wing in ground hull (so very little displacement at speed). They are very different from a traditional sailboat.

    https://www.odt.co.nz/sport/yachting...-cup-yachts-go
    "Sure, Philosophers can say 'But how do we know the sun will rise tomorrow?' to which the correct response is 'Shut up nerd! Stop playing 3D chess against your own brain and find something real to worry about'."

    -ContraPoints

  9. - Top - End - #9
    Titan in the Playground
     
    Yora's Avatar

    Join Date
    Apr 2009
    Location
    Germany

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    25 knots is damn fast in a little air powered boat. Upwind that's pretty crazy.
    We are not standing on the shoulders of giants, but on very tall tower of other dwarves.

    Spriggan's Den Heroic Fantasy Roleplaying

  10. - Top - End - #10
    Orc in the Playground
     
    GnomePirate

    Join Date
    Apr 2020
    Location
    United States
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Yora View Post
    25 knots is damn fast in a little air powered boat. Upwind that's pretty crazy.
    I was in San Francisco in 2013 during that America's Cup. It is really impressive to watch these sailboats zip by escorted by power boats that are going full out and having trouble keeping up.

    I don't think its a practical way to move passengers or cargo because, every now and then, something goes terribly wrong and the boat ends up upside down. If I remember right, two different boats flipped in 2013.
    "Sure, Philosophers can say 'But how do we know the sun will rise tomorrow?' to which the correct response is 'Shut up nerd! Stop playing 3D chess against your own brain and find something real to worry about'."

    -ContraPoints

  11. - Top - End - #11
    Barbarian in the Playground
     
    MindFlayer

    Join Date
    Feb 2015

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Trafalgar View Post
    I don't think its a practical way to move passengers or cargo because, every now and then, something goes terribly wrong and the boat ends up upside down. If I remember right, two different boats flipped in 2013.
    They have to be operating at the edge of possible failure because if they don't and several of their opponents do, one of the opponents might survive and win. This leaves open how fast boats could go if they only accepted 0.1% chance of catastrophic failure.

  12. - Top - End - #12
    Archmage in the Playground Moderator
     
    truemane's Avatar

    Join Date
    Mar 2007
    Location
    Grognardia
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Trafalgar View Post
    I don't think its a practical way to move passengers or cargo because, every now and then, something goes terribly wrong and the boat ends up upside down.
    Part of my real-world job is to manage risk assessment for medical devices and manufacturing processes. I imaged that line at the conclusion of a formal risk assessment and laughed. "In conclusion..."
    Adventures in the Borderlands [5E] - IC-Ch.1 / OC / Info
    Hard Times in Halcyon City [Masks] - IC-Ch.2 / OC

    Tarot-Mage-atar by Cuthalion, may his pixels never die.

  13. - Top - End - #13
    Bugbear in the Playground
    Join Date
    Mar 2007

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    I think one of the reasons for the disbelief in such a thing is that bit about "relative motion" that the maker talked about.

    And it wouldn't work in the physics land of spherical cows. Or most computer simulations. Because it won't work with a wind at a constant speed.

    The force accelerating the vehicle konstant||vwind-vvehicle|*.
    So right as it gets close to wind speed, it will asymptotically stop accelerating and never reach that magic speed.

    But real life isn't like that. Real wind has gusts, and rarely is all that constant. It requires at least one gust to push it enough over average wind speed to the point where it can keep accelerating at "normal" wind speed. And it obviously has to reach that magic number before you run out of straight desert. Note that a lull in the wind might work as well, although I doubt it. It would only work if the vehicle managed to maintain a higher speed that the wind as it picked up: I'm pretty sure the windspeed can increase faster than the vehicle speed, but it is certainly possible with the right wind.

    * Presumably k1(vwind-vvehicle)+k2|vwind-vvehicle| would be a little more accurate, with the overall aero drag being k1 and the force on the propeller being k2.
    Last edited by wumpus; 2021-06-04 at 02:36 PM. Reason: close parenthesis. Change parens to absolute value.

  14. - Top - End - #14
    Orc in the Playground
     
    GnomePirate

    Join Date
    Apr 2020
    Location
    United States
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by DavidSh View Post
    They have to be operating at the edge of possible failure because if they don't and several of their opponents do, one of the opponents might survive and win. This leaves open how fast boats could go if they only accepted 0.1% chance of catastrophic failure.
    As I recall, there were 2 or 3 times the boats capsized or pitchpoled during the 2013 Americas Cup. In a quite spectacular way. I don't think they work well in any kind of a rough sea.
    Last edited by Trafalgar; 2021-06-05 at 07:14 AM. Reason: Added a link
    "Sure, Philosophers can say 'But how do we know the sun will rise tomorrow?' to which the correct response is 'Shut up nerd! Stop playing 3D chess against your own brain and find something real to worry about'."

    -ContraPoints

  15. - Top - End - #15
    Troll in the Playground
    Join Date
    Jan 2007

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by wumpus View Post
    I think one of the reasons for the disbelief in such a thing is that bit about "relative motion" that the maker talked about.

    And it wouldn't work in the physics land of spherical cows. Or most computer simulations. Because it won't work with a wind at a constant speed.

    The force accelerating the vehicle konstant||vwind-vvehicle|*.
    So right as it gets close to wind speed, it will asymptotically stop accelerating and never reach that magic speed.

    But real life isn't like that. Real wind has gusts, and rarely is all that constant. It requires at least one gust to push it enough over average wind speed to the point where it can keep accelerating at "normal" wind speed. And it obviously has to reach that magic number before you run out of straight desert. Note that a lull in the wind might work as well, although I doubt it. It would only work if the vehicle managed to maintain a higher speed that the wind as it picked up: I'm pretty sure the windspeed can increase faster than the vehicle speed, but it is certainly possible with the right wind.

    * Presumably k1(vwind-vvehicle)+k2|vwind-vvehicle| would be a little more accurate, with the overall aero drag being k1 and the force on the propeller being k2.
    I do not think this is the case. The threadmill test of a small concept machine was taken under far more stable conditions.

    The whole trick lies in how the the propeller is linked with the wheels. It rotates in the same direction as a motor-powered propeller would. This means when the car has the speed equal to the wind, the propeller is still pushing the air back. It obviously sounds crazy and requires additional thought on what actually pushes the car? It is important to note that this whole faster-than-wind travel works only for cars and boats - it is all about exploiting the velocity difference between air and ground (or water). So the wind pushes the car, the wheels spin due to the ground not moving along with the wind, which spins the propeller giving that extra edge needed to go faster than expected.
    In a war it doesn't matter who's right, only who's left.

  16. - Top - End - #16
    Dwarf in the Playground
     
    Imp

    Join Date
    Jan 2019

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by wumpus View Post
    I think one of the reasons for the disbelief in such a thing is that bit about "relative motion" that the maker talked about.

    And it wouldn't work in the physics land of spherical cows. Or most computer simulations. Because it won't work with a wind at a constant speed.

    The force accelerating the vehicle konstant||vwind-vvehicle|*.
    So right as it gets close to wind speed, it will asymptotically stop accelerating and never reach that magic speed.

    But real life isn't like that. Real wind has gusts, and rarely is all that constant. It requires at least one gust to push it enough over average wind speed to the point where it can keep accelerating at "normal" wind speed. And it obviously has to reach that magic number before you run out of straight desert. Note that a lull in the wind might work as well, although I doubt it. It would only work if the vehicle managed to maintain a higher speed that the wind as it picked up: I'm pretty sure the windspeed can increase faster than the vehicle speed, but it is certainly possible with the right wind.

    * Presumably k1(vwind-vvehicle)+k2|vwind-vvehicle| would be a little more accurate, with the overall aero drag being k1 and the force on the propeller being k2.
    No, it still works with a constant wind speed. All you need are two mediums moving relative to each other that you are able to 'grip' onto somehow and you can move in any direction relative to both of them with no additional energy input. If you are pushing on something efficiently you require power proportional to the force times the speed you are moving relative to it in the direction of the force. This works because you are moving faster with regards to the ground than the air*. Lets say you are moving at 2m/s relative to the air, and you are harvesting energy by applying a braking force of 1N. That gets you 2W of power to work with. If you are only moving 1m/s relative to the air, that 2W can get you 2N of force, if you push efficiently (props are pretty efficient if trimmed right, which was why it was so important to get that right). If you are not moving at all relative to the wind then the prop is only fighting it's own inefficiencies, as static forces don't inherently need power.

    *Usually we leverage that we are moving faster with regard to the air than the ground, but there is nothing magical about ground and air, they are just 'things' we apply forces to (with the ground much easier to grip onto). We can reverse them with an appropriate design.

    Where it confuses people is that they assume that the energy is being taking from the air, and applied to the ground (or water), where it doesn't have to happen that way around. You can perfectly well take energy from the ground and apply it to the air instead, and because the air is moving slower you don't need as much energy to apply the same or greater force.

    It does amuse me that people who can accept that a sailboat can sail into the wind can be so adamant that it is impossible to sail 'into the current' so to speak. You are using the difference in velocity between two fluids, and it really doesn't matter which is supporting you. Air and water have quite different properties, but nothing fundamentally different, so it would be extremely odd if there was some sort of asymmetry in how you could move relative to each of them. It might be harder to build something that can sail downwind, but it should not be impossible for symmetry reasons.

  17. - Top - End - #17
    Bugbear in the Playground
    Join Date
    Mar 2007

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Fat Rooster View Post
    No, it still works with a constant wind speed. All you need are two mediums moving relative to each other that you are able to 'grip' onto somehow and you can move in any direction relative to both of them with no additional energy input. If you are pushing on something efficiently you require power proportional to the force times the speed you are moving relative to it in the direction of the force. This works because you are moving faster with regards to the ground than the air*. Lets say you are moving at 2m/s relative to the air, and you are harvesting energy by applying a braking force of 1N. That gets you 2W of power to work with. If you are only moving 1m/s relative to the air, that 2W can get you 2N of force, if you push efficiently (props are pretty efficient if trimmed right, which was why it was so important to get that right). If you are not moving at all relative to the wind then the prop is only fighting it's own inefficiencies, as static forces don't inherently need power.
    So that's the reason for the treadmills. I couldn't figure out the point (they only introduced the wheels driven by the fan later).

    Still, while I concede the treadmill experiment might have proved the point, I have to wonder why it failed so many times to break "the windspeed barrier" and suspect that it didn't have enough of a runway to get there in a steady wind.

  18. - Top - End - #18
    Troll in the Playground
    Join Date
    Jan 2007

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by wumpus View Post
    So that's the reason for the treadmills. I couldn't figure out the point (they only introduced the wheels driven by the fan later).

    Still, while I concede the treadmill experiment might have proved the point, I have to wonder why it failed so many times to break "the windspeed barrier" and suspect that it didn't have enough of a runway to get there in a steady wind.
    I think this was mostly connected to the fact that the prototype was made on a shoestring budget and the construction needs quite a lot of mechanical durability and precision to work. This is also why it can be only driven in fairly narrow wind conditions.
    In a war it doesn't matter who's right, only who's left.

  19. - Top - End - #19
    Troll in the Playground
     
    georgie_leech's Avatar

    Join Date
    Sep 2011
    Location
    Calgary, AB
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Radar View Post
    I think this was mostly connected to the fact that the prototype was made on a shoestring budget* and the construction needs quite a lot of mechanical durability and precision to work. This is also why it can be only driven in fairly narrow wind conditions.
    See Also: Why Kitty Hawk planes* kept crashing.

    *In materials and design know-how if not in willingness to fund the venture.
    Last edited by georgie_leech; 2021-06-07 at 10:13 PM.
    Quote Originally Posted by Grod_The_Giant View Post
    We should try to make that a thing; I think it might help civility. Hey, GitP, let's try to make this a thing: when you're arguing optimization strategies, RAW-logic, and similar such things that you'd never actually use in a game, tag your post [THEORETICAL] and/or use green text
    Quote Originally Posted by Lvl 2 Expert View Post
    So a ranger is like a Bachelor of Applied Druidology.
    Quote Originally Posted by Kid Jake View Post
    What's the word for 'fear of being eaten by a mounted bear in half-plate' again? Because that's the one I have.

  20. - Top - End - #20
    Bugbear in the Playground
    Join Date
    Jul 2010
    Location
    Togliatti, Russia
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by wumpus View Post
    I have to wonder why it failed so many times to break "the windspeed barrier"
    To put simply, because it's not a magical machine.
    It's still subject to many energy losses, and it has mass and drag of its own. In order to start accelerating, the thrust generated by the propeller needs to exceed the dynamic resistance of the machine. As the machine nears windspeed, the energy it receives from the wind drops off sharply, and it needs to be going at sufficient velocity for the fixed-gear-ratio link between the wheels and the propeller to spin the latter quickly enough to generate enough thrust to keep accelerating against the mechanical resistances of the vehicle.

    If you've ever tried building dual-mode spaceplanes in KSP, you may have sometimes faced a similar issue. In order to give you thrust, your Turbojets need enough air hitting your intakes, but as you climb the air thins, so in order to keep accelerating you need to hit the high altitudes at the right speed, or you end up setting into a 'lull' - with your engines unable to generate enough thrust to push you faster because you're going too slow. If you use a rocket motor for a bit at that point to increase your speed a little, you will get get more air into your intakes, which then allows your turbojets to keep accelerating you.
    Bearer of the Psionic Flame
    ---------------------
    Current occupation: Considering drawing a better Psionic Flame avatar.
    ---------------------
    Skills: Competent Modder, Proficient Programmer, Accomplished RTD Game Master, Adequate Artist, Dabbling Writer
    ---------------------
    Join Dropbox! It's free! And useful!

  21. - Top - End - #21
    Bugbear in the Playground
    Join Date
    Mar 2007

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Sean Mirrsen View Post
    To put simply, because it's not a magical machine.
    It's still subject to many energy losses, and it has mass and drag of its own. In order to start accelerating, the thrust generated by the propeller needs to exceed the dynamic resistance of the machine. As the machine nears windspeed, the energy it receives from the wind drops off sharply, and it needs to be going at sufficient velocity for the fixed-gear-ratio link between the wheels and the propeller to spin the latter quickly enough to generate enough thrust to keep accelerating against the mechanical resistances of the vehicle.

    If you've ever tried building dual-mode spaceplanes in KSP, you may have sometimes faced a similar issue. In order to give you thrust, your Turbojets need enough air hitting your intakes, but as you climb the air thins, so in order to keep accelerating you need to hit the high altitudes at the right speed, or you end up setting into a 'lull' - with your engines unable to generate enough thrust to push you faster because you're going too slow. If you use a rocket motor for a bit at that point to increase your speed a little, you will get get more air into your intakes, which then allows your turbojets to keep accelerating you.
    True, but my point was that "if it had enough losses so that ideal conditions were needed to work" implies that "ideal conditions" aren't just a fast wind, but a wind that gusts in just the right time. If you have to argue "just the right conditions" it hardly implies that "just the right conditions" *include* a "steady wind" when it likely works better without one.

    Also KSP spaceplanes are a bad example, largely because the trick beginner KSP players into thinking that spaceplanes might somehow be viable on Earth. Kerbol (the planet that you start on in KSP) has an orbital velocity of ~3km/s. Earth has an orbital velocity of ~9km/s (Kerbol and Earth each have 1g of gravity, but Kerbol is much smaller and has something like the density three times uranium). This helps make rockets more easy to design and much quicker to get into space. Unfortunately, 3km/s is something like "mach 8" on Earth, and they don't scale speed of turbojets down to match, so turbojets get nearly to orbital speed in KSP.

    On Earth, the record for jet powered propulsion (the X-43) is something like mach 6.8, with a similar craft "barely maintaining (i.e. the center of the error bars was just above zero)" mach 10. The test vehicle was unmanned, almost entirely engine and fuel tanks, and accelerated up to operation speed by a rocket 10 times its own size. Spaceplanes won't be a reality on Earth anytime soon.

  22. - Top - End - #22
    Bugbear in the Playground
    Join Date
    Jul 2010
    Location
    Togliatti, Russia
    Gender
    Male

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by wumpus View Post
    True, but my point was that "if it had enough losses so that ideal conditions were needed to work" implies that "ideal conditions" aren't just a fast wind, but a wind that gusts in just the right time. If you have to argue "just the right conditions" it hardly implies that "just the right conditions" *include* a "steady wind" when it likely works better without one.

    Also KSP spaceplanes are a bad example, largely because the trick beginner KSP players into thinking that spaceplanes might somehow be viable on Earth. Kerbol (the planet that you start on in KSP) has an orbital velocity of ~3km/s. Earth has an orbital velocity of ~9km/s (Kerbol and Earth each have 1g of gravity, but Kerbol is much smaller and has something like the density three times uranium). This helps make rockets more easy to design and much quicker to get into space. Unfortunately, 3km/s is something like "mach 8" on Earth, and they don't scale speed of turbojets down to match, so turbojets get nearly to orbital speed in KSP.

    On Earth, the record for jet powered propulsion (the X-43) is something like mach 6.8, with a similar craft "barely maintaining (i.e. the center of the error bars was just above zero)" mach 10. The test vehicle was unmanned, almost entirely engine and fuel tanks, and accelerated up to operation speed by a rocket 10 times its own size. Spaceplanes won't be a reality on Earth anytime soon.
    KSP actually works well as an example here because it doesn't rely on how practical spaceplanes are on Earth. :P
    It's a very simply modeled simulation of aerodynamics and turbojet performance, so it's closer to "the land of spherical sheep", as it were. I used it as an example of a performance lull where there is a definite capacity for continuous acceleration, but a particular state of balance prevents that acceleration, until and unless a particular threshold is reached.

    Same effect, broadly, applies here. In this case, is the wind pressure on the propeller is the main driving force on the vehicle. Wind pressure increases with relative windspeed, and, thanks to the drivetrain, also with landspeed. So as your landspeed increases, the wind pressure decreases (as you catch up to the wind), but also increases. The threshold for acceleration continuing, is when the delta between those two is higher than the sum of resistance forces from the vehicle, be they inertia, friction, air resistance, etc. Air resistance decreases to zero as relative windspeed approaches zero, but so does the wind pressure from windspeed. Inertia ceases to matter soon after the vehicle sets in motion. Therefore in order to keep accelerating, at some point prior to matching the windspeed, the vehicle has to move fast enough where its spinning propeller creates enough thrust to overcome its friction forces and increase the vehicle's velocity by itself. Wind, at that point, serves essentially to nullify the vehicle's own mass and air resistance, allowing the usually impossible maneuver of propelling a car with a propeller linked to its wheels to work.

    I'd actually be quite interested in some more in-depth testing of the phenomenon. Maybe it really can't work as a static-performance machine, and requires the adjustable prop blades featured in the machine in the video, to increase and decrease the prop's resistance and thrust during the run. Or maybe it indeed only requires a windspeed of particular magnitude and a machine well made enough to withstand the dynamic forces. Maybe it could work with a more aerodynamic machine, and ducted fans with rear-facing funnels to collect wind?
    Bearer of the Psionic Flame
    ---------------------
    Current occupation: Considering drawing a better Psionic Flame avatar.
    ---------------------
    Skills: Competent Modder, Proficient Programmer, Accomplished RTD Game Master, Adequate Artist, Dabbling Writer
    ---------------------
    Join Dropbox! It's free! And useful!

  23. - Top - End - #23
    Orc in the Playground
     
    OldWizardGuy

    Join Date
    Jul 2015

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    There's now a followup vid that goes into more depth and more detail about what's going on with this car:

  24. - Top - End - #24
    Ettin in the Playground
     
    Bohandas's Avatar

    Join Date
    Feb 2016

    Default Re: Making A Vehicle That Moves Faster Than The Tailwind

    Quote Originally Posted by Trafalgar View Post
    I don't think its a practical way to move passengers or cargo because, every now and then, something goes terribly wrong and the boat ends up upside down.
    What if they marketed it to fans of The Poseidon Adventure?
    Omegaupdate Forum

    WoTC Forums Archive + Indexing Projext

    PostImage, a free and sensible alternative to Photobucket

    Temple+ Modding Project for Atari's Temple of Elemental Evil

    Morrus' RPG Forum (EN World v2)

    If we shadows have offended, think but this, and all is mended. That you have but slumbered here, while these visions did appear, and this weak and idle theme, no more yielding but a dream. -Midsummer Night's Dream, Act 5, Scene 1

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •