# Forget planes on treadmills, here's a sail-cart out-sailing the wind! **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [November 7, 2010, 8:17am UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778 "2010-11-07T08:17:09Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 12, 2010, 8:32am UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/81 "2010-11-12T08:32:20Z")
> [@GargoyleWB](#): > > That’s right. I certainly believe that it is possible to exploit mechanical advantage to drive yourself faster than the wind _for a non-sustainable period of time_, but I interpret their claim as being able to do so perpetually given a long enough road. Also, did you look at my Lego model? It moves _ **faster than it is pushed** _, for as long as it is pushed. (sustainability in this case being limited solely by the length of the toothed rack pushing it, which is analogous to the length of time the wind keeps blowing) ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 12, 2010, 9:37am UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/82 "2010-11-12T09:37:59Z")
> [@ThinAirDesigns](#): > > Let me point something very important here – the ratchet has absolutely _nothing_ to do with normal operation of this craft. The ratchet has _not once_ released and gone ‘click, click, click’ during the running of the vehicle. > > Here’s the purpose for the ratchet on the prop shaft – if the driver of the Blackbird has to make a panic stop, the spinning mass of the propeller would try to keep it spinning while the brakes (on the drive axle) try to bring it to an immediate stop. For safety reasons, the brakes are much more powerful than the propulsion system (just as on any car). We wanted strong brakes (for obvious reasons), but we don’t want our transmission to break just because the driver had to slam on the brakes. > > Without the ratchet, the mass of the prop would backdrive the transmission and overload it. With the ratchet, in a panic stop the vehicle can be brought to zero quickly, while propeller can at its own pace coast to a stop independent of the vehicle movement, just going ‘click, click, click’ until it RPMs are zero. > > As an additional plus, the ratchet allows us to tie the prop down and push the vehicle around by hand (backwards) without the prop spinning and getting in our way or hitting something. > > Again, since under normal operation the torque on the shaft is always in the same direction, the ratchet remains engaged the entire time during and run. We’ve never had to make a panic stop so it’s never even been used for it’s primary purpose. > > JB Thank you - I misunderstood something I’d read earlier in the discussion. 🙂 ---
**Author:** ![hdc\_bst](https://avatars.discourse-cdn.com/v4/letter/h/9f8e36/32.png) [@hdc\_bst](https://boards.straightdope.com/u/hdc_bst)\ **Post date:** [November 12, 2010, 2:37pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/83 "2010-11-12T14:37:52Z")
> [@Mangetout](#): > > OK, here’s the video of my little Lego car that moves much faster than you push it: > > [http://www.youtube.com/watch?v=pELVCP\_anKY](http://www.youtube.com/watch?v=pELVCP_anKY) Very nice demo, thanks for making it. ---
**Author:** ![ThinAirDesigns](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@ThinAirDesigns](https://boards.straightdope.com/u/ThinAirDesigns)\ **Post date:** [November 12, 2010, 3:48pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/84 "2010-11-12T15:48:06Z")
> [@Mangetout](#): > > OK, here’s the video of my little Lego car that moves much faster than you push it: > > [http://www.youtube.com/watch?v=pELVCP\_anKY](http://www.youtube.com/watch?v=pELVCP_anKY) Impressive fraud. 😉 JB ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 12, 2010, 3:53pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/85 "2010-11-12T15:53:43Z")
> [@ThinAirDesigns](#): > > Impressive fraud. > > 😉 > > JB C’mon, there is totally a hidden electric motor in there. 😛 ---
**Author:** ![ThinAirDesigns](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@ThinAirDesigns](https://boards.straightdope.com/u/ThinAirDesigns)\ **Post date:** [November 12, 2010, 3:58pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/86 "2010-11-12T15:58:25Z")
> [@Malacandra](#): > > C’mon, there is totally a hidden electric motor in there. 😛 And those giant tires are excellent flywheels. JB ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [November 12, 2010, 4:22pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/87 "2010-11-12T16:22:03Z")
> [@ThinAirDesigns](#): > > And those giant tires are excellent flywheels. Naw, any fool can see it’s powered by thermite. ---
**Author:** ![MaxTheVool](https://avatars.discourse-cdn.com/v4/letter/m/9fc29f/32.png) [@MaxTheVool](https://boards.straightdope.com/u/MaxTheVool)\ **Post date:** [November 12, 2010, 5:45pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/88 "2010-11-12T17:45:38Z")
> [@GargoyleWB](#): > > The rub with this is that everytime you pick up your generator, you have to accelerate its mass to the velocity of your car, slowing your car each time you do so. This could never be an ideal massless generator either, because if it is storing any energy at all it necessarily possesses mass when you again pick it up due to mass/energy equivalency. At best, your thought experiment could give my “Case 1” pulsed system as result. Except that whatever energy it takes to pick the generators back up and move them and so forth is NOT in any way linked to how fast the wind is blowing. So double the wind speed in the hypothetical. Now they’re generating twice as much energy. Heck, increase the speed of the wind by 100. The point is that there is no violation of some magical principle of physics going on. Nothing in physics says (as others have pointed out) that “the amount of energy it takes to make a cart move 90 mph” is the same as “the amount of energy you can extract from a system with a certain volume of air moving at 90 mph with respect to the ground”. In fact, the second one is constant and large, and the first one is, with a sufficiently well-designed cart, much smaller. ---
**Author:** ![GargoyleWB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gargoylewb/32/199_2.png) [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)\ **Post date:** [November 12, 2010, 7:58pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/89 "2010-11-12T19:58:30Z")
> [@Mangetout](#): > > Also, did you look at my Lego model? It moves _ **faster than it is pushed** _, for as long as it is pushed. > > (sustainability in this case being limited solely by the length of the toothed rack pushing it, which is analogous to the length of time the wind keeps blowing) Very nice, but fundamentally different than what the wind car is talking about. Your Lego car is essentially drawing energy from a “battery”, the battery being the stored potential energy of your finger/hand/arm. The toothed bar is just transfering the mechanical advantage. When your hand travel reaches its limit, where is _that_ energy replenishment coming from? Your lego bar is only as sustainable as the potential m_g_h of your body. To get sustained travel, you would need to suspend a mass infinitely high. Still skeptical 🙂 ---
**Author:** ![GargoyleWB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gargoylewb/32/199_2.png) [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)\ **Post date:** [November 12, 2010, 8:07pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/90 "2010-11-12T20:07:32Z")
> [@MaxTheVool](#): > > …extract from a system with a certain volume of air… Good point, I admit I have been assuming something of an isolated moving air mass. So if you’re talking some sort of theoretical “heat pump” transfer of energy from the much greater external system of air into the car, then I grant you that you’ve put your foot into the door of possibility (though I think it is “moving the goalposts” a bit of the overall claim of the concept validity). But in that case, why not just make an electrically conductive road, tapping into a fixed windmill, and then you can have the “wind car” move as fast as you could want. But that has moved the goal posts, since your external windmill is not being quantified into your overall measurement of the wind car speed. I think a firm concept also requires any “heat pump” equipment to also be traveling with the car faster than the wind speed. Obligiatory skepticon :dubious: ---
**Author:** ![ThinAirDesigns](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@ThinAirDesigns](https://boards.straightdope.com/u/ThinAirDesigns)\ **Post date:** [November 12, 2010, 9:19pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/91 "2010-11-12T21:19:58Z")
> [@GargoyleWB](#): > > Very nice, but fundamentally different than what the wind car is talking about. Nope. > [@](#): > > Your Lego car is essentially drawing energy from a “battery”, the battery being the stored potential energy of your finger/hand/arm. Just as the Blackbird is “essentially drawing energy from a “battery”, the battery being the ‘stored’ potential energy of the moving air.” The analogy is perfectly valid and fair. > [@](#): > > The toothed bar is just transfering the mechanical advantage. When your hand travel reaches its limit, where is _that_ energy replenishment coming from? His hand travel reaching the limit is perfectly analogous to the wind dying off at the end of the day – where does the energy replenishment come from? It doesn’t come from anywhere, the cart rolls to a stop. The claim of “wind powered steady state” does not mean “it goes forever”, it means “as long as the wind blows is powered only by the wind”. JB ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 12, 2010, 9:31pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/92 "2010-11-12T21:31:55Z")
> [@GargoyleWB](#): > > Very nice, but fundamentally different than what the wind car is talking about. It really, really isn’t. It’s almost completely analogous, save for the trivialities of force coupling. > [@](#): > > Your Lego car is essentially drawing energy from a “battery”, the battery being the stored potential energy of your finger/hand/arm. Analogous to the wind > [@](#): > > The toothed bar is just transfering the mechanical advantage. Analogous to the wind transferring to the prop (and vice versa) > [@](#): > > When your hand travel reaches its limit, where is _that_ energy replenishment coming from? When my hand reaches the limit, that’s analogous to the wind stopping from blowing. > [@](#): > > Your lego bar is only as sustainable as the potential m_g_h of your body. Which isn’t relevant at all. _ **For as long as the vehicle is pushed, it moves faster than it is pushed.** _ That’s the bit you need to get your head around. What my arm does to the lego car, the wind can do to the Blackbird. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 12, 2010, 10:20pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/93 "2010-11-12T22:20:52Z")
> [@GargoyleWB](#): > > Good point, I admit I have been assuming something of an isolated moving air mass. So if you’re talking some sort of theoretical “heat pump” transfer of energy from the much greater external system of air into the car, then I grant you that you’ve put your foot into the door of possibility (though I think it is “moving the goalposts” a bit of the overall claim of the concept validity). No such exotic scenario is necessary. A large, slow force can be converted into a smaller, faster one. It’s what gearboxes, levers, inclined planes etc do all the time, quite routinely. Unless a gearbox is what you mean by the category of ‘heat pump’ ---
**Author:** ![ziploc](https://avatars.discourse-cdn.com/v4/letter/z/bbe5ce/32.png) [@ziploc](https://boards.straightdope.com/u/ziploc)\ **Post date:** [November 13, 2010, 12:01am UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/94 "2010-11-13T00:01:05Z")
> [@GargoyleWB](#): > > Your lego bar is only as sustainable as the potential m_g_h of your body. Now you’re just messing with us - right? Do you actually believe that his pushing the bar has anything to do with his gravitational potential energy!? > [@](#): > > I think a firm concept also requires any “heat pump” equipment to also be traveling with the car faster than the wind speed. We’ve specified all along that this is wind powered. I think it definitely counts as moving the goal posts if you now require our cart to drag the sun along with it. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 13, 2010, 10:40am UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/95 "2010-11-13T10:40:25Z")
> [@ziploc](#): > > Now you’re just messing with us - right? Do you actually believe that his pushing the bar has anything to do with his gravitational potential energy!? I’m wondering if **GargoyleWB** is thinking the Lego vehicle is driven forward by the downward force of the rack on the gear (like a pip being squeezed out) It isn’t - it’s the forward push that makes the thing move. ---
**Author:** ![ThinAirDesigns](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@ThinAirDesigns](https://boards.straightdope.com/u/ThinAirDesigns)\ **Post date:** [November 13, 2010, 4:36pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/96 "2010-11-13T16:36:38Z")
> [@Mangetout](#): > > I’m wondering if **GargoyleWB** is thinking the Lego vehicle is driven forward by the downward force of the rack on the gear (like a pip being squeezed out) It isn’t - it’s the forward push that makes the thing move. Just in case he _is_ thinking that, here is a video which was made by someone speficially to show that this isn’t true. [![](https://i.ytimg.com/vi/bbF8jtej8jw/hqdefault.jpg?sqp=-oaymwEmCOADEOgC8quKqQMa8AEB-AH-BIAC4AOKAgwIABABGHIgYChDMA8=&rs=AOn4CLDGja9-ft6nWzDDA-LsgEfZcEc5EA "Under the ruler 3: tilting the ruler") ](https://www.youtube.com/watch?v=bbF8jtej8jw) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 13, 2010, 5:09pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/97 "2010-11-13T17:09:12Z")
Excellent - I was going to do something like that myself, but that one is so clear, there’s no need. (That vehicle is operating on exactly the same principles, for anyone else watching). Really, anyone still suspicious that these vehicles (including the Blackbird) are claiming to do something forbidden by physics also needs to direct their suspicion at ordinary bicycles, or at least those models that include gearing. It’s absolutely as absurd to say the Blackbird can’t travel faster than the wind as it is to say that I can’t make a bicycle go faster than my fastest running speed. That the power source for a bicycle is onboard vs the external/envronmental power source of the Blackbird is actually irrelevant. That it exploits mechanical advantage via a classical machine is the whole point. ---
**Author:** ![GargoyleWB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gargoylewb/32/199_2.png) [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)\ **Post date:** [November 13, 2010, 7:05pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/98 "2010-11-13T19:05:55Z")
> [@Mangetout](#): > > I’m wondering if **GargoyleWB** is thinking the Lego vehicle is driven forward by the downward force of the rack on the gear (like a pip being squeezed out) It isn’t - it’s the forward push that makes the thing move. Correct, my mistake, I thought your lego car was using the bar as a lever and I wasn’t getting your vibe, I can see the bar moving forward against your tablecloth pattern and see your concept now. Very cool. 🙂 I’m still wrapped up on wind car though…help me out here, where is the car’s energy coming from in these two regimes… Below wind speed: I assume the car is building and storing energy from the rotation of the fan blades? Then it regears itself to boost itself past wind speed? Over wind speed: The car is using it’s stored energy? But how does it sustain itself if the wind is no longer sufficient to impart force to the fan blades? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 13, 2010, 7:51pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/99 "2010-11-13T19:51:26Z")
At all speeds, the wind is pushing the _whole system_. At all speeds, the propeller, driven by the motion of the vehicle, is pushing back against the wind. At the speed builds, the ‘system’ comprises the vehicle, plus a big cushion of air it’s blowing out behind it. Let’s imagine a desk fan on a rollerskate - and when it’s switched on, the rollerskate starts to move. If you blow against the air that the fan is blowing out, the rollerskate will move faster - because the system includes the air the fan is blowing out. That’s how the wind continues to exert influence on the vehicle after it exceeds the wind speed - it’s then blowing against the stream of moving air being squirted out of the back of the propeller (or, if you prefer, increasing the overall pressure in that region) It’s actually the same as the geared version - even when the vehicle is moving faster than the rod pushing it (which, because it’s solidly, rather than fluidly coupled, is right away), the force can still affect the system, because part of the system (the little gear on top) is now moving backwards in opposition, pushing against the force driving it ---
**Author:** ![ziploc](https://avatars.discourse-cdn.com/v4/letter/z/bbe5ce/32.png) [@ziploc](https://boards.straightdope.com/u/ziploc)\ **Post date:** [November 13, 2010, 8:02pm UTC](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778/100 "2010-11-13T20:02:58Z")
The “air cushion” theory is a common (and sort of understandable) misconception. When the vehicle is traveling faster than the wind there’s no difference at all between the flow all around that vehicle vs. the flow around an aircraft in flight. It’s not a matter of two air masses converging - but rather a propeller pulling itself through an airmass that happens to be moving. If you imagine an airplane flying on a no-wind day vs. an airplane flying downwind, there’s nothing at all different about the airflow in either case. This cart is similar to the plane that’s flying downwind. In both cases the vehicle is fully immersed in a fluid that just happens to be moving in the same direction. [Previous page](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778.md?page=4) [Next page](https://boards.straightdope.com/t/forget-planes-on-treadmills-heres-a-sail-cart-out-sailing-the-wind/559778.md?page=6)